Structure of Vector Mesons in Holographic Model with Linear Confinement
Anatoly Radyushkin; Hovhannes Grigoryan
2007-11-01
We investigate wave functions and form factors of vector mesons in the holographic dual model of QCD with oscillator-like infrared cutoff. We introduce wave functions conjugate to solutions of the 5D equation of motion and develop a formalism based on these wave functions, which are very similar to those of a quantum-mechanical oscillator. For the lowest bound state (rho-meson), we show that all its elastic form factors can be built from the basic form factor which, in this model, exhibits a perfect vector meson dominance, i.e., is given by the rho-pole contribution alone. We calculate the electric radius of the rho-meson and find the value _C = 0.655 fm, which is larger than in the case of the hard-wall cutoff. We calculate the coupling constant f_rho and find that the experimental value is in the middle between the values given by the oscillator and hard-wall models.
Vector-meson-dominance model for radiative decays involving light scalar mesons.
Black, Deirdre; Harada, Masayasu; Schechter, Joseph
2002-05-06
We study a vector-dominance model which predicts quite a large number of currently interesting decay amplitudes of the types S-->gammagamma, V-->Sgamma, and S-->Vgamma, where S and V denote scalar and vector mesons, in terms of three parameters. As an application, the model makes it easy to study in detail a recent proposal to boost the ratio Gamma(phi-->f(0)gamma)/Gamma(phi-->a(0)(0)gamma) by including the isospin violating a(0)(0)-f(0) mixing. However, we find that this effect is actually small in our model.
Study of Chiral Confining Model with Vector Mesons
NASA Astrophysics Data System (ADS)
Ren, Ching-Yun
1991-02-01
This dissertation consists of two parts, the study of the chiral confining model and the investigation of vacuum instability. In the first part we present a chiral confining model in which a bag is formed dynamically. The major topics addressed are: construction of the model, mean-field solution, anomalously large rho nucleon tensor coupling, and a projection method including the quantum effects of mesons. Two features of QCD, namely, chiral invariance and vacuum condensates, are crucial ingredients of our chiral confining model. The interaction of the valence quarks with the quark condensate is described via the sigma field. It generates the quark dynamical mass. The interaction of the quarks with the gluon condensate is described in our model through the color dielectric function, epsilon. This interaction generates the bag within which quarks are absolutely confined. The introduction of the color dielectric function epsilon modifies the quark-meson interaction by multiplying a factor epsilon ^{-1/2}. Thus the quark part of the rho meson source current is structurally different from the isovector part of the electromagnetic current. Thus the chiral confining model provides a natural explanation why the tensor coupling of the rho meson, kappa_rho, is larger than the isovector part of the anomalous magnetic moment of the nucleon, kappa_upsilon . We have improved a simple method of calculating expectation values of operators in states of good angular momentum projected from a hedgehog baryon state. We have included the contributions of quantum mesons. The symmetry of the hedgehog state under grand-reversal introduces remarkable simplification in the calculation of matrix elements of operators which do not contain time derivatives of meson fields. The quantum meson contributions turn out to be (3/2)/< B|{bf J }^2| B> times the classical meson fields contributions, with | B> being the hedgehog state. In the second part we show that the perturbative vacuum of model
Decays of heavy vector mesons in the quark confinement model
NASA Astrophysics Data System (ADS)
Ivanov, M. A.; Valit, Yu. M.
1995-12-01
We analyze the radiative and hadronic decays of vector heavy mesons within the relativistic quark model with confined light quarks. The only adjustable parameters in this approach are the values of constituent masses of heavy quarks ( M c and M b). We adjust them using the available experimental data from CLEO and ARGUS-collaborations for the D *→ Dγ and D *→ Dπ branching ratios. It is found that the value of M c varies approximately in the interval 1.3 GeV< M c<1.65 GeV. We give the predictions for the absolute values of decay widths and compare our results with those obtained in other approaches. Also we consider the heavy quark limit M Q→∞ with E=M H-MQ=const for the decay amplitudes.
Chiral bag plus skyrmion hybrid model with vector mesons for nucleon
NASA Astrophysics Data System (ADS)
Takashita, H.; Yoro, S.; Toki, H.
1988-08-01
The chiral bag plus skyrmion hybrid model (CSH) is extended to include the vector mesons (ω and ϱ mesons) following the hidden local symmetry prescription for nucleon. The hedgehog ansatz is taken for π, ω and ϱ meson fields and the coupled differential equations for quarks and mesons are solved numerically. It is found that the magnitude of the rho-meson field drops suddenly at R ≈ 0.2 fm as the bag radius increases. The hedgehog masses and the axial coupling gA are calculated as a function of the bag radius. It is found that gA behaves non-monotonically with the bag radius.
Scalar mesons in a linear sigma model with (axial-)vector mesons
Parganlija, D.; Kovacs, P.; Wolf, Gy.; Giacosa, F.; Rischke, D. H.
2013-03-25
The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for qq states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar qq states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as qq states.
Scalar mesons in a linear sigma model with (axial-)vector mesons
NASA Astrophysics Data System (ADS)
Parganlija, D.; Kovács, P.; Wolf, Gy.; Giacosa, F.; Rischke, D. H.
2013-03-01
The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for qq states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar qq states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as qq states.
Chiral Quark-Meson model of N and DELTA with vector mesons
Broniowski, W.; Banerjee, M.K.
1985-10-01
Vector mesons rho, A/sub 1/ and ..omega.. are introduced in the Chiral Quark-Meson Theory (CQMT) of N and ..delta... We propose a new viewpoint for developing CQMT from QCD at the mean-field level. The SU(2) x SU(2) chiral Lagrangian incorporates universal coupling. Accordingly, rho is coupled to the conserved isospin current, A to the partially conserved axial-vector current (PCAC), and ..omega.. to the conserved baryon current. As a result the only parameter of the model not directly related to experiment is the quark-pion coupling constant. A fully self-consistent mean-field solution to the model is found for fields in the hedgehog ansatz. The vector mesons play a very important role in the system. They contribute significantly to the values of observables and produce a high-quality fit to many data. The classical stability of the system with respect to hedgehog excitations is analyzed through the use of the Quark-Meson RPA equations (QMRPA).
Ablakulov, Kh. Narzikulov, Z.
2015-01-15
A phenomenological model is developed in terms of bilocal meson fields in order to describe a vector meson and its leptonic decays. A new Salpeter equation for this particle and the Schwinger-Dyson equation allowing for the presence of an arbitrary potential and for a modification associated with the renormalization of the quark (antiquark ) wave function within the meson are given. An expression for the constant of the leptonic decay of the charged rho meson is obtained from an analysis of the decay process τ → ρν via parametrizing in it the hadronization of intermediate charged weak W bosons into a bilocal vector meson. The potential is chosen in the form of the sum of harmonic-oscillator and Coulomb potentials, and the respective boundary-value problem is formulated. It is shown that the solutions to this problem describe both the mass spectrum of vector mesons and their leptonic-decay constants.
Deeply Virtual Compton Scattering on nucleons and nuclei in generalized vector meson dominance model
Vadim Guzey; Klaus Goeke; Marat Siddikov
2008-02-01
We consider Deeply Virtual Compton Scattering (DVCS) on nucleons and nuclei in the framework of generalized vector meson dominance (GVMD) model. We demonstrate that the GVMD model provides a good description of the HERA data on the dependence of the proton DVCS cross section on $Q^2$, $W$ (at $Q^2=4$ GeV$^2$) and $t$. At $Q^2 = 8$ GeV$^2$, the soft $W$-behavior of the GVMD model somewhat underestimates the $W$-dependence of the DVCS cross section due to the hard contribution not present in the GVMD model. We estimate $1/Q^2$ power-suppressed corrections to the DVCS amplitude and the DVCS cross section and find them large. We also make predictions for the nuclear DVCS amplitude and cross section in the kinematics of the future Electron-Ion Collider. We predict significant nuclear shadowing, which matches well predictions of the leading-twist nuclear shadowing in DIS on nuclei.
Meson vacuum phenomenology in a three-flavor linear sigma model with (axial-)vector mesons
NASA Astrophysics Data System (ADS)
Parganlija, D.; Kovács, P.; Wolf, Gy.; Giacosa, F.; Rischke, D. H.
2013-01-01
We study scalar, pseudoscalar, vector, and axial-vector mesons with nonstrange and strange quantum numbers in the framework of a linear sigma model with global chiral U(Nf)L×U(Nf)R symmetry. We perform a global fit of meson masses, decay widths, as well as decay amplitudes. The quality of the fit is, for a hadronic model that does not consider isospin-breaking effects, surprisingly good. We also investigate the question whether the scalar q¯q states lie below or above 1 GeV and find the scalar states above 1 GeV to be preferred as q¯q states. Additionally, we also describe the axial-vector resonances as q¯q states.
NASA Astrophysics Data System (ADS)
Chen, Kan; Pang, Cheng-Qun; Liu, Xiang; Matsuki, Takayuki
2015-04-01
Inspired by the abundant experimental observation of axial-vector states, we study whether the observed axial-vector states can be categorized into the conventional axial-vector meson family. In this paper we carry out an analysis based on the mass spectra and two-body Okubo-Zweig-Iizuka-allowed decays. Besides testing the possible axial-vector meson assignments, we also predict abundant information for their decays and the properties of some missing axial-vector mesons, which are valuable for further experimental exploration of the observed and predicted axial-vector mesons.
NASA Astrophysics Data System (ADS)
Hosaka, A.; Toki, H.; Weise, W.
1990-01-01
We investigate nucleon structure in a (non-linear) chiral bag model with vector mesons. The model incorporates two different degrees of freedom: mesons outside the bag at long and intermediate ranges, and quarks inside the bag at short distances. The ρ, a 1 and ω mesons outside the bag are included in a chiral effective lagrangian based on the non-linear sigma model. The classical solution is obtained using the hedgehog ansatz, and the cranking method is applied to construct the physical nucleon states. Static properties of the nucleon such as its mass, axial vector coupling constant, magnetic moments and charge radii are studied in detail as functions of the bag radius. Quark and meson contributions to these quantities are calculated separately. In particular, we discuss the extent to which the vector-meson dominance picture holds in the chiral bag.
Medium Modification of Vector Mesons
Chaden Djalali, Michael Paolone, Dennis Weygand, Michael H. Wood, Rakhsha Nasseripour
2011-03-01
The theory of the strong interaction, Quantum Chromodynamics (QCD), has been remarkably successful in describing high-energy and short-distance-scale experiments involving quarks and gluons. However, applying QCD to low energy and large-distance scale experiments has been a major challenge. Various QCD-inspired models predict a partial restoration of chiral symmetry in nuclear matter with modifications of the properties of hadrons from their free-space values. Measurable changes such as a shift in mass and/or a change of width are predicted at normal nuclear density. Photoproduction of vector mesons off nuclei have been performed at different laboratories. The properties of the ρ, ω and φ mesons are investigated either directly by measuring their mass spectra or indirectly through transparency ratios. The latest results regarding medium modifications of the vector mesons in the nuclear medium will be discussed.
Vector meson electroproduction in QCD
NASA Astrophysics Data System (ADS)
Lu, Juan; Cai, Xian-Hao; Zhou, Li-Juan
2012-08-01
Based on the generalized QCD vector meson dominance model, we study the electroproduction of a vector meson off a proton in the QCD inspired eikonalized model. Numerical calculations for the total cross section σtot and differential cross section dσ/dt are performed for ρ, ω and varphi meson electroproduction in this paper. Since gluons interact among themselves (self-interaction), two gluons can form a glueball with quantum numbers IG, JPC = 0+,2++, decay width Γt ≈ 100 MeV, and mass of mG = 2.23 GeV. The three gluons can form a three-gluon colorless bound state with charge conjugation quantum number C = -1, called the Odderon. The mediators of interactions between projectiles (the quark and antiquark pair fluctuated from the virtual photon) and the proton target (a three-quark system) are the tensor glueball and the Odderon. Our calculated results in the tensor glueball and Odderon exchange model fit to the existing data successfully, which evidently shows that our present QCD mechanism is a good description of meson electroproduction off a proton. It should be emphasized that our mechanism is different from the theoretical framework of Block et al. We also believe that the present study and its success are important for the investigation of other vector meson electro- and photoproduction at high energies, as well as for searching for new particles such as tensor glueballs and Odderons, which have been predicted by QCD and the color glass condensate model (CGC). Therefore, in return, it can test the validity of QCD and the CGC model.
Vector mesons as a Higgs phenomenon
Hajuj, O. )
1990-07-01
We propose an approach to couple vector mesons to the Skyrme model. We show that classically the model exhibits stable hedgehog baryons. The classically stable solutions are quantized. The nucleon-{Delta} splitting is found to be in good agreement with experimental results.
Vector meson dominance and the {rho} meson
Benayoun, M.; OConnell, H.B.; Williams, A.G.
1999-04-01
We discuss the properties of vector mesons, in particular the {rho}{sup 0}, in the context of the hidden local symmetry (HLS) model. This provides a unified framework to study several aspects of the low energy QCD sector. First, we show that in the HLS model the physical photon is massless, without requiring off field diagonalization. We then demonstrate the equivalence of HLS and the two existing representations of vector meson dominance, VMD1 and VMD2, at both the tree level and one loop order. Finally the S matrix pole position is shown to provide a model and process independent means of specifying the {rho} mass and width, in contrast with the real axis prescription currently used in the Particle Data Group tables. {copyright} {ital 1999} {ital The American Physical Society}
Light Vector Mesons in the Nuclear Medium
Wood, Michael; Nasseripour, Rakhsha; Weygand, Dennis; Djalali, Chaden; Tur, Clarisse; Mosel, Ulrich; Muehlich, Pascal; Adams, Gary; Amaryan, Moscov; Amaryan, Moskov; Ambrozewicz, Pawel; Anghinolfi, Marco; Asryan, Gegham; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Baillie, Nathan; Ball, James; Baltzell, Nathan; Barrow, Steve; Battaglieri, Marco; Bedlinskiy, Ivan; Bektasoglu, Mehmet; Bellis, Matthew; Benmouna, Nawal; Berman, Barry; Biselli, Angela; Blaszczyk, Lukasz; Bouchigny, Sylvain; Boyarinov, Sergey; Bradford, Robert; Branford, Derek; Briscoe, William; Brooks, William; Burkert, Volker; Butuceanu, Cornel; Calarco, John; Careccia, Sharon; Carman, Daniel; Carnahan, Bryan; Casey, Liam; Chen, Shifeng; Cheng, Lu; Cole, Philip; Collins, Patrick; Coltharp, Philip; Crabb, Donald; Crannell, Hall; Crede, Volker; Cummings, John; Dashyan, Natalya; De Vita, Raffaella; De Sanctis, Enzo; Degtiarenko, Pavel; Denizli, Haluk; Dennis, Lawrence; Deur, Alexandre; Dharmawardane, Kahanawita; Dickson, Richard; Dodge, Gail; Doughty, David; Dugger, Michael; Dytman, Steven; Dzyubak, Oleksandr; Egiyan, Hovanes; Egiyan, Kim; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fedotov, Gleb; Feldman, Gerald; Feuerbach, Robert; Fradi, Ahmed; Funsten, Herbert; Garcon, Michel; Gavalian, Gagik; Gilfoyle, Gerard; Giovanetti, Kevin; Girod, Francois-Xavier; Goetz, John; Gordon, Christopher; Gothe, Ralf; Griffioen, Keith; Guidal, Michel; Guler, Nevzat; Guo, Lei; Gyurjyan, Vardan; Hadjidakis, Cynthia; Hafidi, Kawtar; Hakobyan, Hayk; Hakobyan, Rafael; Hanretty, Charles; Hardie, John; Hassall, Neil; Hersman, F.; Hicks, Kenneth; Hleiqawi, Ishaq; Holtrop, Maurik; Hyde, Charles; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Ito, Mark; Jenkins, David; Jo, Hyon-Suk; Johnstone, John; Joo, Kyungseon; Juengst, Henry; Kalantarians, Narbe; Kellie, James; Khandaker, Mahbubul; Khetarpal, Puneet; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Klimenko, Alexei; Kossov, Mikhail; Krahn, Zebulun; Kramer, Laird; Kubarovsky, Valery; Kuhn, Joachim; Kuhn, Sebastian; Kuleshov, Sergey; Lachniet, Jeff; Laget, Jean; Langheinrich, Jorn; Lawrence, David; Li, Ji; Livingston, Kenneth; Lu, Haiyun; MacCormick, Marion; Markov, Nikolai; Mattione, Paul; McAleer, Simeon; McKinnon, Bryan; McNabb, John; Mecking, Bernhard; Mehrabyan, Surik; Melone, Joseph; Mestayer, Mac; Meyer, Curtis; Mibe, Tsutomu; Mikhaylov, Konstantin; Minehart, Ralph; Mirazita, Marco; Miskimen, Rory; Mokeev, Viktor; Moriya, Kei; Morrow, Steven; Moteabbed, Maryam; Mueller, James; Munevar Espitia, Edwin; Mutchler, Gordon; Nadel-Turonski, Pawel; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Niczyporuk, Bogdan; Niroula, Megh; Niyazov, Rustam; Nozar, Mina; Osipenko, Mikhail; Ostrovidov, Alexander; Park, Kijun; Pasyuk, Evgueni; Paterson, Craig; Pereira, Sergio; Pierce, Joshua; Pivnyuk, Nikolay; Pocanic, Dinko; Pogorelko, Oleg; Pozdnyakov, Sergey; Preedom, Barry; Price, John; Prok, Yelena; Protopopescu, Dan; Raue, Brian; Riccardi, Gregory; Ricco, Giovanni; Ripani, Marco; Ritchie, Barry; Ronchetti, Federico; Rosner, Guenther; Rossi, Patrizia; Sabatie, Franck; Salamanca, Julian; Salgado, Carlos; Santoro, Joseph; Sapunenko, Vladimir; Schumacher, Reinhard; Serov, Vladimir; Sharabian, Youri; Sharov, Dmitri; Shvedunov, Nikolay; Smith, Elton; Smith, Lee; Sober, Daniel; Sokhan, Daria; Stavinsky, Aleksey; Stepanyan, Stepan; Stepanyan, Samuel; Stokes, Burnham; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Taiuti, Mauro; Tedeschi, David; Tkabladze, Avtandil; Tkachenko, Svyatoslav; Todor, Luminita; Ungaro, Maurizio; Vineyard, Michael; Vlassov, Alexander; Watts, Daniel; Weinstein, Lawrence; Williams, Michael; Wolin, Elliott; Yegneswaran, Amrit; Zana, Lorenzo; Zhang, Bin; Zhang, Jixie; Zhao, Bo; Zhao, Zhiwen
2008-07-01
The light vector mesons ($\\rho$, $\\omega$, and $\\phi$) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the $\\rho$ meson at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to $e^{+}e^{-}$. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The $\\rho$ meson mass spectrum was extracted after the $\\omega$ and $\\phi$ signals were removed in a nearly model-independent way. Comparisons were made between the $\\rho$ mass spectra from the heavy targets ($A > 2$) with the mass spectrum extracted from the deuterium target. With respect to the $\\rho$-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body eff
Vector Meson Form Factors and Wave Functions from Holographic QCD
Hovhannes Grigoryan; Anatoly Radyushkin
2007-10-10
Based on the holographic dual model of QCD, we study 2- and 3-point functions of vector currents and derive form factors as well as wave functions for the vector mesons. As a result, generalized vector-meson dominance representation for form factors is obtained with a very specific VMD pattern. The calculated electric radius of the rho-meson is shown to be in a good agreement with predictions from lattice QCD.
NASA Astrophysics Data System (ADS)
Yu, Byung-Geel; Kim, Hungchong; Kong, Kook-Jin
2017-01-01
We investigate the role driven by the scalar meson σ exchange in the photoproduction of the vector meson ϕ (1020 ) off a proton by using a Reggeized model. Based on the π0(135 )+σ (500 )+f2(1270 ) +Pomeron exchanges, we demonstrate that the σ exchange plays the role to reproduce the bump structure at the forward angle in the differential cross section as well as the peaking behavior in the total cross section observed in the CLAS Collaboration. We also discuss the possible observation of the scaled cross section s7d σ /d t at the production angle θ =9 0 ° from the CLAS data. It is found that the axial vector meson f1(1285 ) exchange with the trajectory αf 1(t )=0.028 t +0.9 ±0.2 arising from the axial anomaly of the QCD vacuum plays the role to clarify the scaling up to 5 GeV.
Quantum electrodynamics for vector mesons.
Djukanovic, Dalibor; Schindler, Matthias R; Gegelia, Jambul; Scherer, Stefan
2005-07-01
Quantum electrodynamics for rho mesons is considered. It is shown that, at the tree level, the value of the gyromagnetic ratio of the rho+ is fixed to 2 in a self-consistent effective quantum field theory. Further, the mixing parameter of the photon and the neutral vector meson is equal to the ratio of electromagnetic and strong couplings, leading to the mass difference M(rho0)-M(rho+/-) approximately 1 MeV at tree order.
Holographic picture of heavy vector meson melting
NASA Astrophysics Data System (ADS)
Braga, Nelson R. F.; Martin Contreras, Miguel Angel; Diles, Saulo
2016-11-01
The fraction of heavy vector mesons produced in a heavy ion collision, as compared to a proton-proton collision, serves as an important indication of the formation of a thermal medium, the quark-gluon plasma. This sort of analysis strongly depends on understanding the thermal effects of a medium like the plasma on the states of heavy mesons. In particular, it is crucial to know the temperature ranges where they undergo a thermal dissociation, or melting. AdS/QCD models are know to provide an important tool for the calculation of hadronic masses, but in general are not consistent with the observation that decay constants of heavy vector mesons decrease with excitation level. It has recently been shown that this problem can be overcome using a soft wall background and introducing an extra energy parameter, through the calculation of correlation functions at a finite position of anti-de Sitter space. This approach leads to the evaluation of masses and decay constants of S wave quarkonium states with just one flavor dependent and one flavor independent parameter. Here we extend this more realistic model to finite temperatures and analyze the thermal behavior of the states 1 S, 2 S and 3 S of bottomonium and charmonium. The corresponding spectral function exhibits a consistent picture for the melting of the states where, for each flavor, the higher excitations melt at lower temperatures. We estimate for these six states the energy ranges in which the heavy vector mesons undergo a transition from a well-defined peak in the spectral function to complete melting in the thermal medium. A very clear distinction between the heavy flavors emerges, with the bottomonium state Υ (1S) surviving a deconfinement transition at temperatures much larger than the critical deconfinement temperature of the medium.
Hard Exclusive Vector Meson Leptoproduction At HERMES
Golembiovskaya, M.
2011-07-15
The HERMES experiment at DESY, Hamburg collected a set of data on hard exclusive vector meson ({rho}{sup 0}{phi},{omega}) leptoproduction using the 27.6 GeV longitudinally polarized lepton beam of HERA accelerator and longitudinally or transversely polarized or unpolarized gas targets. Measurements of exclusive vector meson production provide access to the structure of the nucleon since the process can be described in terms of Generalized Parton Distributions (GPDs). An overview of the HERMES results on exclusive vector mesons production is presented.
Skyrmions with vector mesons in the hidden local symmetry approach
NASA Astrophysics Data System (ADS)
Ma, Yong-Liang; Yang, Ghil-Seok; Oh, Yongseok; Harada, Masayasu
2013-02-01
The roles of light ρ and ω vector mesons in the Skyrmion are investigated in a chiral Lagrangian derived from the hidden local symmetry (HLS) up to O(p4) including the homogeneous Wess-Zumino terms. We write a general “master formula” that allows us to determine the parameters of the HLS Lagrangian from a class of holographic QCD models valid at the large-Nc and -λ (’t Hooft constant) limit by integrating out the infinite towers of vector and axial-vector mesons other than the lowest ρ and ω mesons. Within this approach we find that the physical properties of the Skyrmion as the solitonic description of baryons are independent of the HLS parameter a. Therefore the only parameters of the model are the pion decay constant and the vector-meson mass. Once determined in the meson sector, we have a totally parameter-free theory that allows us to study unequivocally the role of light vector mesons in the Skyrmion structure. We find, as suggested by Sutcliffe, that the inclusion of the ρ meson reduces the soliton mass, which makes the Skyrmion come closer to the Bogomol’nyi-Prasad-Sommerfield soliton, but the role of the ω meson is found to increase the soliton mass. In stark contrast, the Δ-N mass difference, which is determined by the moment of inertia in the adiabatic collective quantization of the Skyrmion, is increased by the ρ vector meson, while it is reduced by the inclusion of the ω meson. All these observations show the importance of the ω meson in the properties of the nucleon and nuclear matter in the Skyrme model.
Diffractive vector meson photoproduction from dual string theory
Freund, Peter G. O.; Nastase, Horatiu
2009-04-15
We study diffractive vector-meson photoproduction using string theory via AdS/CFT. The large s behavior of the cross sections for the scattering of the vector meson V on a proton is dominated by the soft Pomeron, {sigma}{sub V}{approx}s{sup 2{epsilon}}{sup -2{alpha}{sub P}{sup '}}{sup /B}, where from the string theory model of [arXiv:hep-th/0501039], {epsilon} is approximately 1/7 below 10 GeV, and 1/11 for higher, but still sub-Froissart, energies. This is due to the production of black holes in the dual gravity. In {phi} photoproduction the mesonic Regge poles do not contribute, so that we deal with a pure Pomeron contribution. This allows for an experimental test. At the gauge theory 'Planck scale' of about 1-2 GeV, the ratios of the soft Pomeron contributions to the photoproduction cross sections of different vector mesons involve not only the obvious quark model factors, but also the Boltzmann factors e{sup -4M{}sub V}{sup /T{}sub 0}, with T{sub 0} the temperature of the dual black hole. The presence of these factors is confirmed in the experimental data for {rho}, {omega}, {phi}, J/{psi}, and {psi}(2S) photoproduction and is compatible with the meager {upsilon} photoproduction data. Throughout, we use vector-meson dominance, and from the data we obtain T{sub 0} of about 1.3 GeV, i.e. the gauge theory ''Planck scale,'' as expected. The ratio of the experimental soft Pomeron onset scale E-circumflex{sub R}{approx}9 GeV and of the gauge theory Planck scale, T{sub 0}{approx}1.3 GeV, conforms to the theoretical prediction of N{sub c}{sup 2}/N{sub c}{sup 1/4}.
Asymmetric vector mesons produced in nuclear collisions
NASA Astrophysics Data System (ADS)
Dremin, I. M.; Nechitailo, V. A.
2016-09-01
It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high-energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further described in quantum mechanics as the interference of direct and continuum states in the Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with ρ-meson data and admit reasonable explanation.
Holographic correspondence applied to vector meson emission from a heavy accelerated nucleus
Hoodbhoy, Pervez
2008-12-01
We consider a classical source, moving on the 4D boundary of a 5D anti-de Sitter space, that is coupled to quantum fields residing in the bulk. Bremsstrahlung-like radiation of the corresponding quanta is shown to occur and the S matrix is derived assuming that the source is sufficiently massive so that recoil effects are negligible. As an illustrative example, using the anti-de Sitter hard-wall model, we consider vector mesons coupled to a heavy nucleus that is moved around at high speed in an accelerator ring. The meson radiation rate is found to be finite but small. Much higher accelerations, such as when a pair of heavy ions suffer an ultra peripheral collision, cause substantial emission of various excited vector mesons. Predictions are made for the spectrum of this radiation. A comparison is made against existing photon-pomeron fusion calculations for the transverse momentum spectra of rho mesons. These have the same overall shape as the recently measured transverse momentum distributions at RHIC.
Vector Meson Property in Covariant Classification Scheme
NASA Astrophysics Data System (ADS)
Oda, Masuho
2004-08-01
Recently our collaboration group has proposed the covariant classification shceme of hadrons, leading to possible existence of two ground state vector mesons. One is corresponding to ordinary ρ nonet and the other is extra ρ nonet. We investigate the decay property of ω(1250) and ρ(1250) in the covariant classification scheme. And it is shown that ω(1250) is promising candidate of our extra ω meson.
Dilepton production in heavy-ion collisions with in-medium spectral functions of vector mesons
Santini, E.; Faessler, Amand; Fuchs, C.; Cozma, M. D.; Krivoruchenko, M. I.; Martemyanov, B.
2008-09-15
The in-medium spectral functions of {rho} and {omega} mesons and the broadening of nucleon resonances at finite baryon density are calculated self-consistently by combining a resonance dominance model for the vector meson production with an extended vector meson dominance model. The influence of the in-medium modifications of the vector meson properties on the dilepton spectrum in heavy-ion collisions is investigated. The dilepton spectrum is generated for the C+C reaction at 2.0A GeV and compared with recent HADES Collaboration data. The collision dynamics is then described by the Tuebingen relativistic quantum molecular dynamics transport model. We find that an iterative calculation of the vector meson spectral functions that takes into account the broadening of the nucleon resonances due to their increased in-medium decay branchings is convergent and provides a reasonable description of the experimental data in the mass region 0.45{<=}M{<=}0.75 GeV. On the other side, the theoretical calculations slightly underestimate the region m{sub {pi}}{<=}M{<=}0.4 GeV. Popular in-medium scenarios such as a schematic collisional broadening and dropping vector mesons masses are discussed as well.
Exclusive vector meson production at HERA from QCD with saturation
Marquet, C.; Peschanski, R.; Soyez, G.
2007-08-01
Following recent predictions that the geometric scaling properties of deep inelastic scattering data in inclusive {gamma}*p collisions are expected also in exclusive diffractive processes, we investigate the diffractive production of vector mesons. Using analytic results in the framework of the Balitsky-Kovchegov (BK) equation at nonzero momentum transfer, we extend to the nonforward amplitude a QCD-inspired forward saturation model including charm, following the theoretical predictions for the momentum transfer dependence of the saturation scale. We obtain a good fit to the available HERA data and make predictions for deeply virtual Compton scattering measurements.
Multisolitons with vector mesons on the two-sphere
NASA Astrophysics Data System (ADS)
Carrasco, F. L.; Reula, Oscar A.
2014-08-01
Recent studies have suggested a strong connection between the static solutions of the 3D Skyrme model and those corresponding to its low-dimensional analog (baby-Skyrme model) on a two-sphere. We have found almost identical solutions considering an alternative two-dimensional model in which a vector meson field is introduced and coupled to the system, instead of the usual Skyrme term. It has been known that including this vector meson field in three dimensions stabilizes the nonlinear sigma model without the need for a term that is quartic on derivatives of the pion fields (Skyrme term). The resulting model has proven to share many of the features that the usual Skyrme theory has, but with a better mathematical formulation in terms of the well posedness of its evolution equations. In the present work, we have numerically searched for static multisolitonic solutions of this alternative stabilization, for the case in which the base space is a two-sphere. Moreover, we analyze the stability of these solutions under small perturbations in a fully dynamical setting. We have also considered the inclusion of a particular potential term in the Lagrangian and explored the low- and high-density phases of solitons for different ranges of the parameter space, achieving solitons localized enough, which allows for a comparison with planar (two-dimensional) studies.
Incoherent vector mesons production in PbPb ultraperipheral collisions at the LHC
NASA Astrophysics Data System (ADS)
Xie, Ya-Ping; Chen, Xurong
2017-03-01
The incoherent rapidity distributions of vector mesons are computed in dipole model in PbPb ultraperipheral collisions at the CERN Large Hadron Collider (LHC). The IIM model fitted from newer data is employed in the dipole amplitude. The Boosted Gaussian and Gaus-LC wave functions for vector mesons are implemented in the calculations as well. Predictions for the J / ψ, ψ (2 s), ρ and ϕ incoherent rapidity distributions are evaluated and compared with experimental data and other theoretical predictions in this paper. We obtain closer predictions of the incoherent rapidity distributions for J / ψ than previous calculations in the IIM model.
Spin alignment of vector mesons in heavy ion and proton-proton collisions
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Cuautle, Eleazar; Corral, G. Herrera; Magnin, J.; Montaño, Luis Manuel
2010-01-01
The spin alignment matrix element ρ00 for the vector mesons K and ϕ(1020) has been measured in RHIC at central rapidities. These measurements are consistent with the absence of polarization with respect to the reaction plane in mid-central Au+Au collisions whereas, when measured with respect to the production plane in the same reactions and in p+p collisions, a non-vanishing and p⊥-dependent ρ00 is found. We show that this behavior can be understood in a simple model of vector meson production where the spin of their constituent quarks is oriented during hadronization as the result of Thomas precession.
Vector meson production in ultra-peripheral collisions
NASA Astrophysics Data System (ADS)
Thomas, James O.
Charged ions moving at relativistic speeds generate strong electromagnetic fields (E/M) that, at regions outside the source (important when the E/M sources are nuclei), behave like the fields from a beam of real photons. These equivalent, or virtual photons, can induce an excitation in another nucleus as the source flies by. Existing theories attempt to explain such processes and predict their outcome. One way to study such Ultra-Peripheral Collisions (UPCs) is to simulate them using a Monte-Carlo Multi-Collisional (MCMC) model based on nucleon degrees of freedom. The CRISP (acronym for Collaboration Rio-Illheus-Sao Paulo) model is one such theory. It is basically at the stage of a well-documented software package that implements the MCMC. This model has successfully predicted observables, such as neutron multiplicity, from central collisions and also in UPCs with relativistic heavy ions. However, the photoproduction of vector mesons has only recently been added to the CRISP model. A completely different approach to study UPCs focuses on the role of Parton Distribution Functions (PDFs) in the excitation process. Here, instead of nucleons, the degrees of freedom are quarks and gluons (generically known as partons). Several distinct PDFs exist in the literature and are continually being updated. This work used experimental results released from the ALICE collaboration at the Large Hadron Collider (LHC) facility located at the international particle physics laboratory CERN in Switzerland. Our outputs from the CRISP model, and from the sub-nucleon degrees of freedom model, were photonuclear cross sections for vector meson production. A comparison of our results with the experimental data allowed us to constrain different PDFs, as well as the effect of multiple collisions on the production of mesons with nucleons in the final channel. Upon completion of the calculations, it was seen that the hadronic models could accurately predict the production of the J/psi meson, but
Glueballs and vector mesons at NICA
NASA Astrophysics Data System (ADS)
Parganlija, Denis
2016-08-01
Two interconnected fields of interest are suggested for NICA. Firstly, existence of glueballs is predicted by the theory of strong interaction but --even after decades of research-- glueball identification in the physical spectrum is still unclear. NICA can help to ascertain experimental glueball candidates via J/Ψ decays whose yield is expected to be large. Importance of glueballs is not limited to vacuum: since they couple to other meson states, glueballs can also be expected to influence signatures of chiral-symmetry restoration in the high-energy phase of strong dynamics. Mass shifting or in-medium broadening of vector and axial-vector mesons may occur there but the extent of such phenomena is still uncertain. Additionally, glueball properties could also be modified in medium. Exploration of these issues is the second suggested field of interest that can be pursued at NICA.
Electromagnetic form factors of heavy flavored vector mesons
NASA Astrophysics Data System (ADS)
Priyadarsini, M.; Dash, P. C.; Kar, Susmita; Patra, Sweta P.; Barik, N.
2016-12-01
We study the electromagnetic form factors of heavy flavored vector mesons such as (D*,Ds*,J /Ψ ) , (B*,Bs*,ϒ ) via one photon radiative decays (V →P γ ) in the relativistic independent quark (RIQ) model based on a flavor independent average interaction potential in the scalar vector harmonic form. The momentum dependent spacelike (q2<0 ) form factors calculated in this model are analytically continued to the physical timelike region 0 ≤q2≤(MV-MP)2 . The predicted coupling constant gV P γ=FV P(q2=0 ) for real photon case in the limit q2→0 and decay widths Γ (V →P γ ) are found in reasonable agreement with experimental data and other model predictions.
Vector meson production and nuclear effects in FNAL E866
Leitch, M.J.; Brooks, M.L.; Awes, T.C.
1999-02-01
Fermilab E866/NUSEA is a fixed-target experiment which has made a number of measurements of the production of vector mesons by 800 GeV protons. These include the nuclear dependence of J/{psi}, {psi}{prime} and {phi} over very broad ranges in x{sub F} and p{sub T}, and the J/{psi} decay angular distribution at very large x{sub F}. Preliminary results from measurements on Be, Fe and W targets are presented and discussed in the context of nuclear effects such as energy loss and multiple scattering of the partons, absorption of the produced c{anti c} pairs, and shadowing. Production mechanisms involving color-singlet or color-octet states for the c{anti c} pair which eventually forms a J{psi} or {psi}{prime} have implications on the strength of absorption in the nucleus and on the angular distribution of the decay muons. Preliminary results on the angular distributions versus x{sub F} and p{sub T} indicate some transverse polarization of the J/{psi} as predicted by models of production through the color octet state. Measurements of dimuons in the 1 to 3 GeV region explore the nuclear dependence of the {phi} meson and also the composition of the continuum between the {phi} and the J/{psi}. These studies of vector meson production and its nuclear dependence are critical in furthering their understanding of these processes towards future measurements at RHIC and new results from NA50 at CERN, where J/{psi} suppression is predicted to be an important signature of the creation of quark-gluon plasma in heavy-ion collisions.
Vector meson modification in nuclear matter at CLAS
Djalali, Chaden; Wood, Michael; Nasseripour, Rakhsha; Weygand, Dennis
2008-09-01
Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The properties of the A vector mesons were investigated via their rare leptonic decay to e+e . After subtracting the combinatorial background, the A meson mass distributions were extracted for each of the targets. We observe no effects on the mass of the A meson, some widening in titanium and iron is observed consistent with the collisional broadening.
Vector meson production in ultra-peripheral collisions at the LHC
Fiore, R.; Jenkovszky, L.; Salii, A.; Libov, V.; Machado, M. V. T.
2015-04-10
By using a Regge-pole model for vector meson production (VMP), that successfully describes the HERA data, we analyse the connection of VMP cross sections in photon-induced reactions at HERA with those in ultra-peripheral collisions at the Large Hadron Collider (LHC). The role of the low-energy behaviour of VMP cross sections in γp collisions is scrutinized.
NASA Astrophysics Data System (ADS)
Gonçalves, V. P.; Moreira, B. D.; Navarra, F. S.
2017-03-01
In this paper, we update the predictions for exclusive J /Ψ , Ψ (2 S ), and ϒ photoproduction in proton-proton and nucleus-nucleus collisions at the Run 2 LHC energies obtained with the color dipole formalism and considering the impact-parameter color glass condensate model (bCGC) for the forward dipole-target scattering amplitude. The impact of the charm mass on the predictions is investigated, and a comparison with the LHCb data on rapidity distributions and photon-hadron cross sections is presented. Our results demonstrate that the current data can be quite well described by the bCGC model, which takes into account nonlinear effects in the QCD dynamics and reproduces the very precise HERA data, without introducing any additional effect or free parameter.
In-medium properties of light vector mesons
C. Djalali; R. Nasseripour; D. P. Weygand; M. H. Wood
2007-08-01
The photoproduction of vector mesons on various nuclei has been studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. All three vector mesons ρ, ω and phi are observed via their decay to e+e-. The possible in-medium effects on the properties of the ρ meson are of particular interest. The ρ spectral function is extracted from the data on carbon, iron and titanium, and compared to the spectrum from liquid deuterium, which is relatively free of nuclear effects. We observe no effects on the mass of the ρ meson, some widening in titanium and iron is observed consistent with the collisional broadening.
Beauty vector meson decay constants from QCD sum rules
Lucha, Wolfgang; Melikhov, Dmitri; Simula, Silvano
2016-01-22
We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.
Medium Modification of the Light Vector Mesons in Nuclei
Nasseripour, R.; Djalali, C.; Wood, M.; Weygand, D.
2008-10-13
Theoretical calculations predict the modification of properties of vector mesons, such as a shift in their masses and/or broadening of their widths in dense nuclear matter. These effects can be related to partial restoration of chiral symmetry at high density or temperature. Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The data were taken with a beam of tagged photons with energies up to 4 GeV on various nuclear targets. The properties of the {rho} vector mesons were investigated via their rare leptonic decay to e+e{sup -}. This decay channel is preferred over hadronic modes in order to eliminate final state interactions in the nuclear matter. The combinatorial background in the mass spectrum was removed by a self-normalizing mixed-event technique. The {rho} meson mass distributions were extracted for each of the targets. Statistically significant results regarding medium modification of the rho meson in the nuclear medium rule out large medium effects. Transparency studies of the {omega} and {phi} vector mesons allows a determination of their widths in the medium.
Beauty vector meson decay constants from QCD sum rules
NASA Astrophysics Data System (ADS)
Lucha, Wolfgang; Melikhov, Dmitri; Simula, Silvano
2016-01-01
We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.
A fresh look at exclusive electroproduction of light vector mesons
NASA Astrophysics Data System (ADS)
Meškauskas, M.; Müller, D.
2014-02-01
Relying on the collinear factorization approach, we demonstrate that H1 and ZEUS measurements of exclusive light vector meson and photon electroproduction cross sections can be simultaneously described for photon virtualities of . Our findings reveal that quark exchanges are important in this small region and that in leading order approximation the gluonic component is suppressed, e.g., the skewness ratio can be much smaller than one.
The coherent cross section of vector mesons in ultraperipheral PbPb collisions at the LHC
NASA Astrophysics Data System (ADS)
Xie, Ya-ping; Chen, Xurong
2016-06-01
The coherent cross section of J/ψ , ρ , and φ are computed in the dipole model in the ultraperipheral PbPb collisions. The IP-Sat and IIM model are applied in the calculation of the differential cross section of the dipole scattering off the nucleon, and three kinds of forward vector meson wave functions are used in the overlap. The prediction of J/ψ and ρ is compared with the experimental data of the ALICE collaboration, and the prediction of φ is also given in this paper.
Electroproduction of the Φ(1020) Vector Meson at 4 GeV
Loukachine, Konstantin
2000-02-01
We studied the reaction ep → e'p'Φ with a 4.2 GeV incident electron beam in the region of the electroproduction variables Q^{2} from 0.7 to 2.2 GeV^{2} and W from 2.0 to 2.6 GeV. The data were taken and analyzed at the Thomas Jefferson National Accelerator Facility. For the first time, we observe the expected t-slope dependence on Q^{2} and Δτ in Φ vector meson production. We find that the width of the forward Φ-meson diffraction peak increases rapidly as the interaction time decreases below cΔτ of 1 fm. Within a simple optical model framework, the data show that Φ meson has a smaller size than the ρ. The measured Φ cross-section dependence on Q^{2} is in a good agreement with previous measurements and well-described by the phenomenological Pomeron exchange model. Our cross-section data do not favor the standard Vector Meson Dominance and s$\\bar{s}$-knockout model predictions. From the angular distribution of the decay Φ → K^{+} K^{-}, assuming the s-channel helicity conservation, we extracted the longitudinal-to-transverse cross-section ratio, R, and Vector Meson Dominance scaling parameter, ζ^{2}, which are consistent with the previous measurements and the model expectations.
Dilepton yields from brown-rho scaled vector mesons including memory effects.
Schenke, Björn; Greiner, Carsten
2007-01-12
Scenarios with dropping vector meson masses, motivated by the work of Brown and Rho, have been strongly discussed after recent NA60 Collaboration data were presented. In this Letter they are investigated within a nonequilibrium field theoretical description that includes quantum mechanical memory. Dimuon yields are calculated by application of a model for the fireball, and strong modifications are found in the comparison to quasiequilibrium calculations, which assume instantaneous adjustment of all meson properties to the surrounding medium. In addition, results for the situation of very broad excitations are presented.
Leading-Twist Distribution Amplitudes of Scalar- and Vector-Mesons
Li, B.-L.; Chang, L.; Ding, M.; Roberts, C. D.; Zong, H.-S.
2016-11-15
A symmetry-preserving truncation of the two-body light-quark bound-state problem in relativistic quantum field theory is used to calculate the leading-twist parton distribution amplitudes (PDAs) of scalar systems, both ground-state and radial excitations, and the radial excitations of vector mesons. Owing to the fact that the scale-independent leptonic decay constant of a scalar meson constituted from equal-mass valence-constituents vanishes, it is found that the PDA of a given scalar system possesses one more zero than that of an analogous vector meson. Consequently, whereas the mean light-front relative momentum of the valence-constituents within a vector meson is zero, that within a scalar meson is large, an outcome which hints at a greater role for light-front angular momentum in systems classified as P-wave in quantum mechanical models. Values for the scale-dependent decay constants of ground-state scalar and vector systems are a by-product of this analysis, and they turn out to be roughly equal, viz. ≃ 0.2 GeV at an hadronic scale. In addition, it is confirmed that the dilation characterising ground-state PDAs is manifest in the PDAs of radial excitations too. The impact of SU(3)-flavour symmetry breaking is also considered. When compared with pseudoscalar states, it is a little stronger in scalar systems, but the size is nevertheless determined by the flavour-dependence of dynamical chiral symmetry breaking and the PDAs are still skewed toward the heavier valence-quark in asymmetric systems.
Vector meson condensation in a pion superfluid
NASA Astrophysics Data System (ADS)
Brauner, Tomáš; Huang, Xu-Guang
2016-11-01
We revisit the suggestion that charged ρ -mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that ρ -meson condensation is either avoided or postponed to isospin chemical potentials much higher than the ρ -meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and ρ -mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.
Hidden local symmetry and infinite tower of vector mesons for baryons
NASA Astrophysics Data System (ADS)
Ma, Yong-Liang; Oh, Yongseok; Yang, Ghil-Seok; Harada, Masayasu; Lee, Hyun Kyu; Park, Byung-Yoon; Rho, Mannque
2012-10-01
In an effort to access dense baryonic matter relevant for compact stars in a unified framework that handles both single baryon and multibaryon systems on the same footing, we first address a holographic dual action for a single baryon focusing on the role of the infinite tower of vector mesons deconstructed from five dimensions. To leading order in ’t Hooft coupling λ=NcgYM2, one has the Bogomol’nyi-Prasad-Sommerfield (BPS) Skyrmion that results when the warping of the bulk background and the Chern-Simons term in the Sakai-Sugimoto (SS) D4/D8-D8¯ model are ignored. The infinite tower was found by Sutcliffe to induce flow to a conformal theory, i.e., the BPS. We compare this structure to that of the SS model consisting of a 5D Yang-Mills action in warped space and the Chern-Simons term in which higher vector mesons are integrated out while preserving hidden local symmetry and valid to O(λ0) and O(p4) in the chiral counting. We point out the surprisingly important role of the ω meson that figures in the Chern-Simons term that encodes chiral anomaly in the baryon structure and that may be closely tied to short-range repulsion in nuclear interactions.
Electro- and Photoproduction of Vector Mesons at Jefferson Lab
Marco Battaglieri
2002-09-01
The total and differential cross section for exclusive electro- and photoproduction of vector mesons in the resonance region and above (1.6 < W < 2.9 GeV) was measured at Jefferson Laboratory in a wide kinematic range (0 < Q2 < 4 GeV2 and 0< -t < 5 GeV2). The measurement of the total and differential cross section down to 100 pb/GeV2 with the full kinematic coverage, was possible for the first time thanks to the combination of the 100% duty cycle of CEBAF and the large acceptance of the CLAS detector. The main results from the CLAS Collaboration activity in this field will be presented and discussed.
Form Factors and Wave Functions of Vector Mesons in Holographic QCD
Hovhannes R. Grigoryan; Anatoly V. Radyushkin
2007-07-01
Within the framework of a holographic dual model of QCD, we develop a formalism for calculating form factors of vector mesons. We show that the holographic bound states can be described not only in terms of eigenfunctions of the equation of motion, but also in terms of conjugate wave functions that are close analogues of quantum-mechanical bound state wave functions. We derive a generalized VMD representation for form factors, and find a very specific VMD pattern, in which form factors are essentially given by contributions due to the first two bound states in the Q^2-channel. We calculate electric radius of the \\rho-meson, finding the value < r_\\rho^2>_C = 0.53 fm^2.
Vector meson J/Ψ,phi electro-production in QCD
NASA Astrophysics Data System (ADS)
Lu, Juan; Zhou, Li-Juan
2010-04-01
We study the vector meson electro-production off the proton in a QCD inspired model. A calculation of the differential cross section is performed for the J/Ψ,phi meson off the proton. The theoretical results are consistent with the experimental data, and remind us to consider the contribution from the tensor glueball and Odderon to the differential cross section. Since gluons interact among themselves via self-interaction, the gluons can form a glueball with quantum numbers IG, JPC = 0+, 2++, with a decay width Γt = 100 MeV and mass of mG = 2.23 GeV. The three gluons can form a three gluon color bound state with charge conjugation quantum number C = -1. This study is quite important to verify the validity of QCD and to search for new particles (tensor glueball and Odderon) as well as quest for new physics.
Realizing vector meson dominance with transverse charge densities
Gerald Miller, Mark Strikman, Christian Weiss
2011-10-01
The transverse charge density in a fast-moving nucleon is represented as a dispersion integral of the imaginary part of the Dirac form factor in the timelike region (spectral function). At a given transverse distance b the integration effectively extends over energies in a range {radical}t {approx}< 1/b, with exponential suppression of larger values. The transverse charge density at peripheral distances thus acts as a low-pass filter for the spectral function and allows one to select energy regions dominated by specific t-channel states, corresponding to definite exchange mechanisms in the spacelike form factor. We show that distances b {approx} 0.5 - 1.5 fm in the isovector density are maximally sensitive to the {rho} meson region, with only a {approx}10% contribution from higher-mass states. Soft-pion exchange governed by chiral dynamics becomes relevant only at larger distances. In the isoscalar density higher-mass states beyond the {omega} are comparatively more important. The dispersion approach suggests that the positive transverse charge density in the neutron at b {approx} 1 fm, found previously in a Fourier analysis of spacelike form factor data, could serve as a sensitive test of the isoscalar strength in the {approx}1 GeV mass region. In terms of partonic structure, the transverse densities in the vector meson region b {approx} 1 fm support an approximate mean-field picture of the motion of valence quarks in the nucleon.
Chaden Djalali
2011-12-01
Recent studies of light vector meson production in heavy nuclear targets has generated interest in {rho}-{omega} interference in the leptonic e{sup +}e{sup -} decay channel. An experimental study of the elementary process provides valuable input for theoretical models and calculations. In experiment E04-005 (g12), high statistics photoproduction data has been taken in Jefferson Lab's Hall B with the Cebaf Large Acceptance Spectrometer (CLAS). The invariant mass spectrum is fitted with two interfering relativistic Breit-Wigner functions to determine the interference phase. Preliminary analysis indicate a measurable {rho}-{omega} interference.
Baryon-number-induced Chern-Simons couplings of vector and axial-vector mesons in holographic QCD.
Domokos, Sophia K; Harvey, Jeffrey A
2007-10-05
We show that holographic models of QCD predict the presence of a Chern-Simons coupling between vector and axial-vector mesons at finite baryon density. In the Anti de Sitter/Conformal Field Theory dictionary, the coefficient of this coupling is proportional to the baryon number density and is fixed uniquely in the five-dimensional holographic dual by anomalies in the flavor currents. For the lightest mesons, the coupling mixes transverse rho and a1 polarization states. At sufficiently large baryon number densities, it produces an instability, which causes the rho and a1 mesons to condense in a state breaking both rotational and translational invariance.
K* vector meson resonance dynamics in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Ilner, Andrej; Cabrera, Daniel; Markert, Christina; Bratkovskaya, Elena
2017-01-01
We study the strange vector meson (K*,K¯* ) dynamics in relativistic heavy-ion collisions based on the microscopic parton-hadron-string dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees of freedom, a phase transition from hadronic to partonic matter—quark-gluon-plasma (QGP)—and a dynamical hadronization of quarks and antiquarks as well as final hadronic interactions. We investigate the role of in-medium effects on the K*,K¯* meson dynamics by employing Breit-Wigner spectral functions for the K* with self-energies obtained from a self-consistent coupled-channel G -matrix approach. Furthermore, we confront the PHSD calculations with experimental data for p +p , Cu+Cu , and Au+Au collisions at energies up to √{sN N}=200 GeV. Our analysis shows that, at relativistic energies, most of the final K* (observed experimentally) are produced during the late hadronic phase, dominantly by the K +π →K* channel, such that the fraction of the K* from the QGP is small and can hardly be reconstructed from the final observables. The influence of the in-medium effects on the K* dynamics at energies typical of the BNL Relativistic Heavy Ion Collider is rather modest due to their dominant production at low baryon densities (but high meson densities); however, it increases with decreasing beam energy. Moreover, we find that the additional cut on the invariant-mass region of the K* further influences the shape and the height of the final spectra. This imposes severe constraints on the interpretation of the experimental results.
Broz, Michal
2015-04-10
Vector mesons are copiously produced in ultra-peripheral collisions. In these collisions, the impact parameter is larger than the sum of the radii of the two projectiles, implying that electromagnetic processes become dominant. The cross section of production of vector mesons is expected to be sensitive to the gluon distribution and can therefore probe nuclear gluon shadowing (Pb–Pb) and the gluon structure function in the nucleon (p-Pb). The ALICE Collaboration has performed the first measurements of the production of ρ{sup 0}, J/ψ and ψ/(2S) in Pb–Pb ultra-peripheral collision as well as the cross section for exclusive J/ψ photoproduction off protons in ultra-peripheral proton-lead collisions at the LHC. The results are compared to the STARLIGHT Monte Carlo and to QCD based models.
Glueball enhancements in p(gamma,VV)p through vector meson dominance
Stephen R. Cotanch; Robert A. Williams
2004-03-01
Double vector meson photoproduction, p(gamma, G {yields} VV)p, mediated by a scalar glueball G is investigated. Using vector meson dominance (VMD) and Regge/pomeron phenomenology, a measureable glueball enhancement is predicted in the invariant VV = rho rho and omega omega mass spectra. The scalar glueball is assumed to be the lightest physical state on the daughter pomeron trajectory governing diffractive vector meson photoproduction. In addition to cross sections, calculations for hadronic and electromagnetic glueball decays, G -> V V' (V,V'= rho, omega, phi, gamma), and gamma{sub v} V {yields} G transition form factors are presented based upon flavor universality, VMD and phenomenological couplings from phi photoproduction analyses. The predicted glueball decay widths are similar to an independent theoretical study. A novel signature for glueball detection is also discussed.
Vector meson masses from a hidden local symmetry in a constant magnetic field
NASA Astrophysics Data System (ADS)
Kawaguchi, Mamiya; Matsuzaki, Shinya
2016-06-01
We discuss the magnetic responses of vector meson masses based on the hidden local symmetry (HLS) model in a constant magnetic field, described by the lightest two-flavor system including the pion, rho and omega mesons in the spectrum. The effective masses influenced under the magnetic field are evaluated according to the derivative or chiral expansion established in the HLS model. At the leading order O (p2), the g factor of the charged rho meson is fixed to be 2, implying that the rho meson at this order is treated just like a pointlike spin-1 particle. Beyond the leading order, one finds anomalous magnetic interactions of the charged rho meson, involving the anomalous magnetic moment, which give corrections to the effective mass. It is then suggested that up to O (p4) the charged rho meson tends to become massless. Of interest is that nontrivial magnetic dependence of neutral mesons emerges to give rise to the significant mixing among neutral mesons. Consequently, it leads to the dramatic enhancement of the omega meson mass, which is testable in future lattice simulations. Corrections from terms beyond O (p4) are also addressed.
Mass spectrum and decay constants of radially excited vector mesons
NASA Astrophysics Data System (ADS)
Mojica, Fredy F.; Vera, Carlos E.; Rojas, Eduardo; El-Bennich, Bruno
2017-07-01
We calculate the masses and weak decay constants of flavorless and flavored ground and radially excited JP=1- mesons within a Poincaré covariant continuum framework based on the Bethe-Salpeter equation. We use in both the quark's gap equation and the meson bound-state equation an infrared massive and finite interaction in the leading symmetry-preserving truncation. While our numerical results are in rather good agreement with experimental values where they are available, no single parametrization of the QCD inspired interaction reproduces simultaneously the ground and excited mass spectrum, which confirms earlier work on pseudoscalar mesons. This feature being a consequence of the lowest truncation, we pin down the range and strength of the interaction in both cases to identify common qualitative features that may help to tune future interaction models beyond the rainbow-ladder approximation.
Holographic vector mesons from spectral functions at finite baryon or isospin density
Erdmenger, Johanna; Kaminski, Matthias; Rust, Felix
2008-02-15
We consider gauge/gravity duality with flavor for the finite-temperature field theory dual of the AdS-Schwarzschild black hole background with embedded D7-brane probes. In particular, we investigate spectral functions at finite baryon density in the black hole phase. We determine the resonance frequencies corresponding to meson-mass peaks as function of the quark mass over temperature ratio. We find that these frequencies have a minimum for a finite value of the quark mass. If the quotient of quark mass and temperature is increased further, the peaks move to larger frequencies. At the same time the peaks narrow, in agreement with the formation of nearly stable vector meson states which exactly reproduce the meson-mass spectrum found at zero temperature. We also calculate the diffusion coefficient, which has finite value for all quark mass to temperature ratios, and exhibits a first-order phase transition. Finally we consider an isospin chemical potential and find that the spectral functions display a resonance peak splitting, similar to the isospin meson-mass splitting observed in effective QCD models.
On pseudosupersymmetric oscillators and reality of relativistic energies for vector mesons
NASA Technical Reports Server (NTRS)
Beckers, Jules; Debergh, Nathalie
1995-01-01
Specific oscillators - hereafter called pseudosupersymmetric oscillators - appear as interesting nonrelativistic concepts in connection with the study of relativistic vector mesons interacting with an external constant magnetic field when the real character of the energy eigenvalues is required as expected. A new pseudosupersymmetric quantum mechanics can then be developed and the corresponding pseudosupersymmetries can be pointed out.
Vector meson production at 3.67 GeV/c
NASA Astrophysics Data System (ADS)
Maggiora, M.; Disto Collaboration
2003-06-01
We present the latest results from the DISTO collaboration on vector meson production ( overlinepp → ppV ) with a polarised proton beam of 3.67 GeV/c: the total and the differential cross sections for ω, θ and ϱ 0 production; the preliminary analysing power A y for θ production.
An effective approach to VMD at one loop order and the departure from ideal mixing vector mesons
O'Connell, H.B.
2000-03-28
The authors examine the mechanisms producing departures from ideal mixing for vector mesons within the context of the Hidden Local Symmetry (HLS) model. The authors show that kaon loop transitions between the ideal combinations of the {omega} and {phi} mesons necessitate a field transformation in order to get the mass eigenstates. It is shown that this transformation is close to a rotation for processes involving, like meson decays, on-shell {omega} and {phi} mesons. The HLS model predicts a momentum dependent, slowly varying mixing angle between the ideal states. The authors examine numerically the consequences of this for radiative and leptonic decays of light mesons. The mean {omega}--{phi} mixing angle is found smaller than its ideal value; this is exhibited separately in radiative and in leptonic decays. Effects of nonet symmetry breaking in the vector sector are compared to those produced by the field rotation implied by the HLS model.
NASA Astrophysics Data System (ADS)
Jung, Christopher; Rennecke, Fabian; Tripolt, Ralf-Arno; von Smekal, Lorenz; Wambach, Jochen
2017-02-01
In this work, we present the first results on vector- and axial-vector meson spectral functions as obtained by applying the nonperturbative functional renormalization group approach to an effective low-energy theory motivated by the gauged linear sigma model. By using a recently proposed analytic continuation method, we study the in-medium behavior of the spectral functions of the ρ and a1 mesons in different regimes of the phase diagram. In particular, we demonstrate explicitly how these spectral functions degenerate at high temperatures as well as at large chemical potentials, as a consequence of the restoration of chiral symmetry. In addition, we also compute the momentum dependence of the ρ and a1 spectral functions and discuss the various timelike and spacelike processes that can occur.
Nonleptonic two-body B decays including axial-vector mesons in the final state
Calderon, G.; Munoz, J. H.; Vera, C. E.
2007-11-01
We present a systematic study of exclusive charmless nonleptonic two-body B decays including axial-vector mesons in the final state. We calculate branching ratios of B{yields}PA, VA, and AA decays, where A, V, and P denote an axial vector, a vector, and a pseudoscalar meson, respectively. We assume a naive factorization hypothesis and use the improved version of the nonrelativistic Isgur-Scora-Grinstein-Wise quark model for form factors in B{yields}A transitions. We include contributions that arise from the effective {delta}B=1 weak Hamiltonian H{sub eff}. The respective factorized amplitudes of these decays are explicitly shown and their penguin contributions are classified. We find that decays B{sup -}{yields}a{sub 1}{sup 0}{pi}{sup -}, B{sup 0}{yields}a{sub 1}{sup {+-}}{pi}{sup {+-}}, B{sup -}{yields}a{sub 1}{sup -}K{sup 0}, B{sup 0}{yields}a{sub 1}{sup +}K{sup -}, B{sup 0}{yields}f{sub 1}K{sup 0}, B{sup -}{yields}f{sub 1}K{sup -}, B{sup -}{yields}K{sub 1}{sup -}(1400){eta}{sup (')}, B{sup -}{yields}b{sub 1}{sup -}K{sup 0}, and B{sup 0}{yields}b{sub 1}{sup +}{pi}{sup -}(K{sup -}) have branching ratios of the order of 10{sup -5}. We also study the dependence of branching ratios for B{yields}K{sub 1}P(V,A) decays [K{sub 1}=K{sub 1}(1270), K{sub 1}(1400)] with respect to the mixing angle between K{sub 1A} and K{sub 1B}.
Hencken, Kai; Baur, Gerhard; Trautmann, Dirk
2006-01-13
We study the transverse momentum distribution of vector mesons produced in ultraperipheral relativistic heavy ion collisions (UPCs). In UPCs there is no strong interaction between the nuclei, and the vector mesons are produced in photon-nucleus collisions where the (quasireal) photon is emitted from the other nucleus. Exchanging the role of both ions leads to interference effects. A detailed study of the transverse momentum distribution, which is determined by the transverse momentum of the emitted photon, the production process on the target, and the interference effect, is done. We study the unrestricted cross section and the one with an additional electromagnetic excitation of one or both ions; in the latter case small impact parameters are emphasized.
The In-medium Mass and Widths of Light Vector Mesons
C. Djalali, M. Paolone, D. Weygand, M. H. Wood, R. Nasseripour
2011-05-01
Partial restoration of chiral symmetry in ordinary nuclear matter suggests the modification of properties of vector mesons, such as a shift in mass and/or a change of width. Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The properties of the rho, omega and [cursive phi] mesons were investigated via their rare leptonic decay to e+e-. This decay channel has an advantage over hadronic modes as it eliminates final state interactions in the nuclear matter. After subtracting the combinatorial background, the meson mass distributions were extracted for each of the nuclear targets. No significant mass shift is observed, however substantial increase in the widths of the mesons is reported.
On parasupersymmetric oscillators and relativistic vector mesons in constant magnetic fields
NASA Technical Reports Server (NTRS)
Debergh, Nathalie; Beckers, Jules
1995-01-01
Johnson-Lippmann considerations on oscillators and their connection with the minimal coupling schemes are visited in order to introduce a new Sakata-Taketani equation describing vector mesons in interaction with a constant magnetic field. This new proposal, based on a specific parasupersymmetric oscillator-like system, is characterized by real energies as opposed to previously pointed out relativistic equations corresponding to this interacting context.
Rotation-invariant relations in vector meson decays into fermion pairs.
Faccioli, Pietro; Lourenço, Carlos; Seixas, João
2010-08-06
The covariance properties of angular momentum eigenstates imply the existence of a rotation-invariant relation among the parameters of the difermion decay distribution of inclusively observed vector mesons. This relation is a generalization of the Lam-Tung identity, a result specific to Drell-Yan production in perturbative QCD, here shown to be equivalent to the dynamical condition that the dilepton is always produced transversely polarized with respect to quantization axes belonging to the production plane.
Lappi, T.; Venugopalan, R.; Mantysaari, H.
2015-02-25
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application, we examine the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
Lappi, T; Mäntysaari, H; Venugopalan, R
2015-02-27
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
NASA Astrophysics Data System (ADS)
Tang, A. H.; Wang, G.
2016-08-01
The electromagnetic (EM) field pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system and causes photons emitted in upper and lower hemispheres to have different preferences in the circular polarization. Similar helicity separation for massive particles, owing to the global vorticity, is also possible. In this paper, we lay out a procedure to measure the variation of the circular polarization with respect to the reaction plane in relativistic heavy-ion collisions for massless photons, as well as similar polarization patterns for vector mesons decaying into two daughters. We propose to study the yield differentially and compare the yield between upper and lower hemispheres to identify and quantify such effects.
Tang, A. H.; Wang, G.
2016-08-30
The electromagnetic (EM) eld pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system, and causes photons emitted in upper- and lower-hemispheres to have different preferences in the circular polarization. Similar helicity separation for massive particles, due to the global vorticity, is also possible. In this paper, we lay down a procedure to measure the variation of the circular polarization w.r.t the reaction plane in relativistic heavy-ion collisions for massless photons, as well as similar polarization patterns for vector mesons decaying into two daughters. We propose to study the yield differentially and compare the yield between upper- and lower-hemispheres in order to identify and quantify such effects.
Tang, A. H.; Wang, G.
2016-08-30
The electromagnetic (EM) eld pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system, and causes photons emitted in upper- and lower-hemispheres to have different preferences in the circular polarization. Similar helicity separation for massive particles, due to the global vorticity, is also possible. In this paper, we lay down a procedure to measure the variation of the circular polarization w.r.t the reaction plane in relativistic heavy-ion collisions formore » massless photons, as well as similar polarization patterns for vector mesons decaying into two daughters. We propose to study the yield differentially and compare the yield between upper- and lower-hemispheres in order to identify and quantify such effects.« less
Tang, A. H.; Wang, G.
2016-08-30
The electromagnetic (EM) eld pattern created by spectators in relativistic heavy-ion collisions plants a seed of positive (negative) magnetic helicity in the hemisphere above (below) the reaction plane. Owing to the chiral anomaly, the magnetic helicity interacts with the fermionic helicity of the collision system, and causes photons emitted in upper- and lower-hemispheres to have different preferences in the circular polarization. Similar helicity separation for massive particles, due to the global vorticity, is also possible. In this paper, we lay down a procedure to measure the variation of the circular polarization w.r.t the reaction plane in relativistic heavy-ion collisions for massless photons, as well as similar polarization patterns for vector mesons decaying into two daughters. We propose to study the yield differentially and compare the yield between upper- and lower-hemispheres in order to identify and quantify such effects.
Exclusive central diffractive production of scalar, pseudoscalar and vector mesons
NASA Astrophysics Data System (ADS)
Lebiedowicz, P.; Nachtmann, O.; Szczurek, A.
2014-11-01
We discuss exclusive central diffractive production of scalar (ƒ0(980), ƒ0(1370), ƒ0(1500)), pseudoscalar (η, η'(958)), and vector (ρ0) mesons in proton-proton collisions. The amplitudes are formulated in terms of effective vertices required to respect standard rules of Quantum Field Theory and propagators for the exchanged pomeron and reggeons. Different pomeron-pomeron-meson tensorial (vectorial) coupling structures are possible in general. In most cases two lowest orbital angular momentum - spin couplings are necessary to describe experimental differential distributions. For the ƒ0(980) and η production the reggeon-pomeron, pomeron-reggeon, and reggeon-reggeon exchanges are included in addition, which seems to be necessary at relatively low energies. The theoretical results are compared with the WA102 experimental data, in order to determine the model parameters. For the ρ0 production the photon-pomeron and pomeron-photon exchanges are considered. The coupling parameters of tensor pomeron and/or reggeon are fixed from the H1 and ZEUS experimental data of the γp → ρ0 p reaction. We present first predictions of this mechanism for pp → ppπ+π- reaction being studied at COMPASS, RHIC, Tevatron, and LHC. Correlation in azimuthal angle between outgoing protons and distribution in pion rapidities at √s = 7 TeV are presented. We show that high-energy central production of mesons could provide crucial information on the spin structure of the soft pomeron.
Vector meson-baryon interaction to study dynamical generation of resonances
Khemchandani, K. P.; Hosaka, A.; Kaneko, H.; Nagahiro, H.
2011-10-21
With the motivation to find dynamical generation of resonances, we study vector-meson baryon interaction by taking s-,t-,u-channel diagrams and a contact interaction into account. A comparison of the different contributions obtained from these diagrams is done in the SU(2) limit, which shows that these diagrams could be equally important. We find it worthwhile to pay attention to the structure of the total interaction between the two non-zero spin particles which possess similar masses and find spin dependent interaction similar to the nucleon-nucleon case.
Measuring nuclear transparency from exclusive vector meson production in lepton-nucleus scattering
Fang, G.Y.
1994-04-01
Preliminary results on the measurement of nuclear transparencies from exclusive {rho}{sup 0} meson production from E665 at Fermilab are reported. The data were collected on hydrogen, deuterium, carbon, calcium, and lead targets with a mean beam energy of 470 GeV. Increases in the transparencies are observed in both coherent and incoherent production channels as the virtuality of the photon increases, as expected of color transparency. Ideas of systematic studies of color transparency in exclusive vector meson production at CEBAF are discussed.
NASA Astrophysics Data System (ADS)
Ben, F. G.; Machado, M. V. T.; Sauter, W. K.
2017-09-01
We provide a universal expression of cross sections for the exclusive vector meson production and deeply virtual Compton scattering (DVCS) in photon-proton and photon-nucleus interactions based on the geometric scaling phenomenon. The theoretical parametrization based on the scaling property depends only on the single variable τA=Q2/Qsat2, where the saturation scale, Qsat, drives the energy dependence and the corresponding nuclear effects. This phenomenological result describes all available data from DESY-HERA for ρ ,ϕ ,J /ψ production and DVCS measurements. A discussion is also carried out on the size of nuclear shadowing corrections on photon-nucleus interaction.
Inclusive production of vector mesons in e/sup +/e/sup minus/ annihilation at. sqrt. s = 29 GeV
Edberg, T.K.
1988-08-01
This thesis describes the measurement of multiplicities and differential cross-sections of the /rho//sup 0/, K*/sup 0/, and /phi/ in e/sup +/e/sup -/ annihilation at ..sqrt..s = 29 GeV, using data collected by the TPC/2..gamma.. Detector Facility at PEP. The number of vector mesons per event is determined to be N(/rho//sup 0/) = 0.77 +- 0.08 +- 0.15, N(K*/sup 0/ + /bar K/*/sup 0/) = 0.58 +- 0.05 +- 0.11, and N(/phi/) = 0.076 +- 0.010 +- 0.012. These multiplicities are used to find that the ratio of strange quarks to up quarks produced in the hadronization process is 0.30 +- 0.07, and that the ratio of light vector mesons to all light mesons produced in the hadronization process is 0.45 +- 0.08. All results agree with previous measurements. Measurements are compared with predictions of the Lund and Webber hadronization models, neither model is particularly favored nor disfavored. 60 refs., 32 figs., 24 tabs.
Measurement of Vector Meson Decays in Nuclei at J-PARC
NASA Astrophysics Data System (ADS)
Morino, Y.; Aoki, K.; Aramaki, Y.; En'yo, H.; Hamagaki, H.; Kanaya, J.; Kanno, K.; Kawama, D.; Kiyomichi, A.; Komatsu, Y.; Masumoto, S.; Murakami, H.; Muto, R.; Nakai, W.; Naruki, M.; Obara, Y.; Ozawa, K.; Sakuma, F.; Sawada, S.; Sekimoto, M.; Shibukawa, T.; Shigaki, K.; Takahashi, T. N.; Watanabe, Y. S.; Yokkaichi, S.
Mass modification of vector meson has been studied in order to investigate the restoration of the chiral symmetry in hot and/or dense matter. Systematical measurement is necessary to confirm the mass modification due to the chiral symmetry restoration. For this purpose, E16 experiment at J-PARC will detect the vector mesons via e + e - decay. A goal of the E16 experiment is to reveal the target mass dependence and the meson velocity dependence of the mass modification through systematic measurement. For that purpose, it is aimed to collect slowly moving φ with typical β γ < 1.25 via di-electron decay as many as possible. The experiment will be performed at the high momentum beam line at J-PARC hadron hall, which supplies a 30-GeV proton beam with an intensity of 2 × 1010 protons per pulse. To cope with the high particle-rate environment, GEMs are used in the E16 spectrometer as the main detectors. To observe a possible second peak due to the modified mass of the φ inside nuclei, 5 MeV/c2 is our goal for the mass resolution. Preparation of the spectrometer construction is now in progress for the first beam time planned at 2016.
Photoproduction of vector mesons: from ultraperipheral to semi-central heavy ion collisions
NASA Astrophysics Data System (ADS)
Kłusek-Gawenda, Mariola; Szczurek, Antoni
2016-11-01
We discuss nuclear cross sections for AA → AAV and AA → AAVV reactions with one or two vector mesons in the final state. Our analysis is done in the impact parameter space equivalent photon approximation. This approach allows to consider the above processes taking into account distance between colliding nuclei. We consider both ultraperipheral and semi-central collisions. We are a first group which undertook a study of single J/ψ photoproduction for different centrality bins. We show that one can describe new ALICE experimental data by including geometrical effects of collisions in the flux factor. Next, total and differential cross section for double-scattering mechanism in the exclusive AA → AAVV reaction in ultrarelativistic ultraperipheral heavy ion collisions is presented. In this context we consider double photoproduction and photon-photon processes. Simultaneously, we get very good agreement of our results with STAR (RHIC), CMS and ALICE (LHC) experimental data for single ρ0 and J/ψ vector meson production. A comparison of our predictions for exclusive four charged pions production is also presented.
Production rates of strange vector mesons at the Z^{0} resonance
Dima, Mihai O.
1997-05-01
This dissertation presents a study of strange vector meson production, "leading particle" effect and a first direct measurement of the strangeness suppression parameter in hadronic decays of the neutral electroweak boson, Z. The measurements were performed in e^{+}e^{-} collisions at the Stanford Linear Accelerator Center (SLAC) with the SLC Large Detector (SLD) experiment. A new generation particle ID system, the SLD Cerenkov Ring Imaging Detector (CRID) is used to discriminate kaons from pions, enabling the reconstruction of the vector mesons over a wide momentum range. The inclusive production rates of ρ and K*^{0} and the differential rates versus momentum were measured and are compared with those of other experiments and theoretical predictions. The high longitudinal polarisation of the SLC electron beam is used in conjunction with the electroweak quark production asymmetries to separate quark jets from antiquark jets. K*^{0} production is studied separately in these samples, and the results show evidence for the "leading particle" effect. The difference between K*^{0} production rates at high momentum in quark and antiquark jets yields a first direct measurement of strangeness suppression in jet fragmentation.
Exclusive production of vector mesons in pp and pp-bar collisions
Cisek, Anna; Schaefer, Wolfgang; Szczurek, Antoni
2011-07-15
Protons and antiprotons at collider energies are a source of high energy Weizsaecker-Williams photons. This opens up a possibility to study at the LHC exclusive photoproduction of heavy vector mesons at energies much larger than possible at the HERA accelerator.We present selected results on the production of vector mesons {rho}, {omega}, {phi}, J/{Psi} and {Upsilon}. We show distributions in rapidity, transverse momentum of mesons and azimuthal angle between outgoing protons for RHIC, Tevatron and LHC energies. The absorption effects are discussed.The amplitude for {gamma}p{yields}Vp is calculated in a pQCD k{sub T}-factorization approach with an unintegrated gluon distribution constrained by inclusive deep-inelastic structure function. The total cross section for diffractive meson (virtual) photo-production as a function of energy and photon virtuality is calculated and compared to HERA data. We also discuss the ratio of the first radial excitation state (2S) to the ground state (1S) in diffractive J/{Psi} and {Upsilon} production.
Observation of chicJ radiative decays to light vector mesons.
Bennett, J V; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Zweber, P; Dobbs, S; Metreveli, Z; Seth, K K; Tan, B J Y; Tomaradze, A; Libby, J; Martin, L; Powell, A; Wilkinson, G; Ecklund, K M; Love, W; Savinov, V; Mendez, H; Ge, J Y; Miller, D H; Shipsey, I P J; Xin, B; Adams, G S; Hu, D; Moziak, B; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F; Artuso, M; Blusk, S; Khalil, S; Li, J; Mountain, R; Nisar, S; Randrianarivony, K; Sultana, N; Skwarnicki, T; Stone, S; Wang, J C; Zhang, L M; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Naik, P; Rademacker, J; Asner, D M; Edwards, K W; Reed, J; Briere, R A; Tatishvili, G; Vogel, H; Rosner, J L; Alexander, J P; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Hunt, J M; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Ledoux, J; Mahlke-Krüger, H; Mohapatra, D; Onyisi, P U E; Patterson, J R; Peterson, D; Riley, D; Ryd, A; Sadoff, A J; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Athar, S B; Patel, R; Yelton, J; Rubin, P; Eisenstein, B I; Karliner, I; Mehrabyan, S; Lowrey, N; Selen, M; White, E J; Wiss, J
2008-10-10
Using a total of 2.74 x 10(7) decays of the psi(2S) collected with the CLEO-c detector, we present a study of chi(cJ)-->gammaV, where V=rho(0), omega, phi. The transitions chi(c1)-->gammarho(0 and chi(c1)-->gammaomega are observed with B(chi(c1)-->gammarho(0))=(2.43+/-0.19+/-0.22) x 10(-4) and B(chi(c1)-->gammaomega)=(8.3+/-1.5+/-1.2) x 10(-5). In the chi(c1)-->gammarho(0) transition, the final state meson is dominantly longitudinally polarized. Upper limits on the branching fractions of other chi(cJ) states to light vector mesons are presented.
Sarsour, Murad
2015-05-01
The data collected over the past decade have demonstrated that the Relativistic Heavy Collider (RHIC) at BNL has created the Quark Gluon Plasma (QGP). A major objective of heavy ion physics nowadays is to study and quantify the fundamental properties of the QGP. One of the crucial probes of this matter is di-lepton measurement in the low mass region. Di-leptons are not affected by the strong interaction once produced; therefore, they can probe the whole evolution of the collision. The planned study will focus on the low mass vector mesons (p, ω, and Φ) through their di-lepton decay channel. The low mass vector mesons are especially good probes to study the properties of this matter created in heavy-ion collisions. Due to their short lifetimes, considerable fraction of them decays inside the hot and dense media. Knowledge of their production rates and spectral properties provides insights into the medium properties; they provide information about in-medium modifications of their spectral shape. The low mass vector mesons also allow understanding the nature of the chiral symmetry restoration in hot and/or dense matter. Generally, there are array of effects due to QGP which can contribute to the modification of the spectra and the true relative contribution is difficult to disentangle. Therefore, studying different colliding systems and wide range of observables at different kinematics will allow disentangling the modification effects and better understand the properties of QGP and the low mass vector mesons will provide very valuable information. In addition, this measurement offers a unique and critical look at QGP where we focus on the low mass vector mesons at forward rapidities which has not been done at RHIC.
NASA Astrophysics Data System (ADS)
da Silveira, G. Gil; Gonçalves, V. P.; Jaime, M. M.
2017-02-01
Over the past years, the LHC experiments have reported experimental evidence for processes associated to photon-photon and photon-hadron interactions, showing their potential to investigate the production of low- and high-mass systems in exclusive events. In the particular case of the photoproduction of vector mesons, the experimental study of this final state is expected to shed light on the description of the QCD dynamics at small values of the Bjorken-x variable. In this paper, we extend previous studies for the exclusive J /Ψ and ϒ photoproduction in p p collisions based on the nonlinear QCD dynamics by performing a detailed study of the final-state distributions that can be measured experimentally at the LHC and at a future circular collider. Predictions for the rapidity and transverse momentum distributions of the vector mesons and of final-state dimuons are presented for p p collisions at √{s }=7 , 13, and 100 TeV.
Comparison of isoscalar vector meson production cross sections in proton-proton collisions
NASA Astrophysics Data System (ADS)
Abdel-Bary, M.; Abdel-Samad, S.; Brinkmann, K.-Th.; Clement, H.; Dietrich, J.; Doroshkevich, E.; Dshemuchadse, S.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Gillitzer, A.; Hesselbarth, D.; Jä, R.; Karsch, L.; Kilian, K.; Kuhlmann, E.; Marcello, S.; Michel, P.; Mö, K.; Morsch, H. P.; Pizzolotto, C.; Plettner, Ch.; Ritman, J.; Roderburg, E.; Schö, P.; Schroeder, W.; Schulte-Wissermann, M.; Steinke, M.; Sun, G. J.; Ullrich, W.; Wenzel, R.; Wintz, P.; Wagner, M.; Wilms, A.; Wirth, S.; Zupranski, P.; COSY-TOF Collaboration
2007-04-01
The reaction pp → ppω was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum Jülich, Germany). Total as well as differential cross sections were determined at an excess energy of 93 MeV (pbeam = 2950 MeV / c). Using the total cross section of (9.0 ± 0.7 ± 1.1) μb for the reaction pp → ppω determined here and existing data for the reaction pp → ppϕ, the ratio Rϕ / ω =σϕ /σω turns out to be significantly larger than expected by the Okubo-Zweig-Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the ω production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for ω production to published distributions for ϕ production at 83 MeV shows that the data are consistent with an identical production mechanism for both vector mesons.
Comparison of isoscalar vector meson production cross sections in proton proton collisions
NASA Astrophysics Data System (ADS)
Cosy-Tof Collaboration; Abdel-Bary, M.; Abdel-Samad, S.; Brinkmann, K.-Th.; Clement, H.; Dietrich, J.; Doroshkevich, E.; Dshemuchadse, S.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Gillitzer, A.; Hesselbarth, D.; Jä, R.; Karsch, L.; Kilian, K.; Kuhlmann, E.; Marcello, S.; Michel, P.; Mö, K.; Morsch, H. P.; Pizzolotto, C.; Plettner, Ch.; Ritman, J.; Roderburg, E.; Schö, P.; Schroeder, W.; Schulte-Wissermann, M.; Steinke, M.; Sun, G. J.; Ullrich, W.; Wenzel, R.; Wintz, P.; Wagner, M.; Wilms, A.; Wirth, S.; Zupranski, P.
2007-04-01
The reaction pp→ppω was investigated with the TOF spectrometer, which is an external experiment at the accelerator COSY (Forschungszentrum Jülich, Germany). Total as well as differential cross sections were determined at an excess energy of 93 MeV (p=2950 MeV/c). Using the total cross section of (9.0±0.7±1.1) μb for the reaction pp→ppω determined here and existing data for the reaction pp→ppϕ, the ratio R=σ/σ turns out to be significantly larger than expected by the Okubo Zweig Iizuka (OZI) rule. The uncertainty of this ratio is considerably smaller than in previous determinations. The differential distributions show that the ω production is still dominated by S-wave production at this excess energy, however higher partial waves clearly contribute. A comparison of the measured angular distributions for ω production to published distributions for ϕ production at 83 MeV shows that the data are consistent with an identical production mechanism for both vector mesons.
Test of the OZI rule in vector meson production with the COMPASS experiment
NASA Astrophysics Data System (ADS)
Bernhard, Johannes; Compass Collaboration
2012-09-01
The COMPASS experiment at CERN collected a large set of data with hadron beams (p, π K) and different targets (H2, Pb, Ni, W) in the years 2008 and 2009. The main goal is the search for exotic bound states of quarks and gluons (glueballs, hybrids) and several preliminary results from the ongoing analysis have already emerged. The production of exotic states is known to be favoured in glue-rich environments, e.g. so-called OZI-forbidden processes. The Okubo-Zweig-Iizuka (OZI) rule states that processes with disconnected quark line diagrams are suppressed. As a consequence, states with an sbar s component should be suppressed with respect to states containing mainly u and d quarks. The numerous reported violations of the OZI rule show that the underlying physics is more complicated. By studying the degree of OZI violation a lot can learned about the production mechanism and possibly also about the nucleon structure itself. The uniquely large COMPASS data sample allows for detailed studies with respect to kinematic variables (e.g. xF). Results from the ongoing analysis on the comparison of ω and phi vector mesons production in pp → pp (ω/phi) are presented and an outlook on the prospect of spin alignment measurements with COMPASS is given.
Beyond gauge theory: positivity and causal localization in the presence of vector mesons
NASA Astrophysics Data System (ADS)
Schroer, Bert
2016-07-01
The Hilbert space formulation of interacting s=1 vector-potentials stands is an interesting contrast with the point-local Krein space setting of gauge theory. Already in the absence of interactions the Wilson loop in a Hilbert space setting has a topological property which is missing in the gauge-theoretic description (Haag duality, Aharonov-Bohm effect); the conceptual differences increase in the presence of interactions. The Hilbert space positivity weakens the causal localization properties of interacting fields, which results in the replacement of the gauge-variant point-local matter fields in Krein space by string-local physical fields in Hilbert space. The gauge invariance of the perturbative S-matrix corresponds to its independence of the space-like string direction of its interpolating fields. In contrast to gauge theory, whose direct physical range is limited to a gauge-invariant perturbative S-matrix and local observables, its Hilbert space string-local counterpart is a full-fledged quantum field theory (QFT). The new setting reveals that the Lie structure of self-coupled vector mesons results from perturbative implementation of the causal localization principles of QFT.
Philip L. Cole
2004-09-01
The set of experiments forming the g8a run took place in the summer of 2001 in Hall B of Jefferson Lab. The g8a run was the commissioning experiment for the linearly-polarized photon beam at CLAS. The aim of these experiments is to improve the understanding of the underlying symmetry of the quark degrees of freedom in the nucleon, the nature of the parity exchange between the incident photon and the target nucleon, and the mechanism of associated strangeness production in electromagnetic reactions. A beam of tagged and collimated linearly polarized photons (energy range 1.8-2.2 GeV) in conjunction with the large solid angle coverage of CLAS make possible the extraction of the differential cross-sections and polarization observables for the photoproduction of vector mesons and kaons. The reaction channels are under investigation to search for possibly missing nucleon resonances. An overview of the experiment and preliminary results on the measurement of the photon asymmetries of the aforementioned reactions will be presented in this paper.
Inclusive vector meson production in nu_{µ}D charged current interactions
Chang, C. C.; Mann, W. A.; Napier, A.
1980-01-01
From hadronic systems induced in 3571 charged-current neutrino-deuterium interactions in the FNAL 15-foot diameter bubble chamber, invariant mass distributions (..pi../sup +/..pi../sup -/) and (K/sub s//sup 0/..pi../sup + -/) have been used to study inclusive production of vector meson resonances. Inclusive rates from a pure isoscalar target are determined to be 0.05 +- 0.01 K*/sup +/(890) per charged-current event and 0.19 +- 0.04 rho/sup 0/ per charged-current event. Inclusive K*(890)/sup + -/ production is found to be predominantly K*/sup +/(890) in the current fragmentation region. The ratios (rho/sup 0//event) from neutron targets and from proton targets separately are, respectively, 0.18 +- 0.06 and 0.21 +- 0.08. For deuteron targets, trends in the dependence of (rho/sup 0//event) on variables Y/sub R/, W, p/sub T/, and Q/sup 2/ are found to be similar to those observed in rho/sup 0/ production from anti ..nu../sub ..mu../p collisions.
Study of χcJ radiative decays into a vector meson
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Alberto, D.; An, L.; An, Q.; An, Z. H.; Bai, J. Z.; Baldini, R.; Ban, Y.; Becker, J.; Berger, N.; Bertani, M.; Bian, J. M.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Cao, G. F.; Cao, X. X.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, Y.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denysenko, I.; Destefanis, M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fan, R. R.; Fang, J.; Fang, S. S.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Greco, M.; Grishin, S.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, B.; Huang, G. M.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jia, L. K.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Komamiya, S.; Kuehn, W.; Lange, J. S.; Leung, J. K. C.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, Lei; Li, N. B.; Li, Q. J.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Liao, X. T.; Liu, B. J.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, G. C.; Liu, H.; Liu, H. B.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K.; Liu, K. Y.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. H.; Liu, Y. B.; Liu, Y. W.; Liu, Yong; Liu, Z. A.; Liu, Z. Q.; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, T.; Ma, X.; Ma, X. Y.; Maggiora, M.; Malik, Q. A.; Mao, H.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Mitchell, R. E.; Mo, X. H.; Muchnoi, N. Yu.; Nefedov, Y.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pelizaeus, M.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pun, C. S. J.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Sonoda, S.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. D.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tang, X. F.; Tian, H. L.; Toth, D.; Varner, G. S.; Wan, X.; Wang, B. Q.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xiao, Z. J.; Xie, Y. G.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Y.; Xu, Z. R.; Xu, Z. Z.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, M.; Yang, T.; Yang, Y.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, L.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, S. H.; Zhang, T. R.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhao, Z. L.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zheng, Z. P.; Zhong, B.; Zhong, J.; Zhong, L.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, X. W.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Zuo, J. X.; Zweber, P.
2011-06-01
The decays χcJ→γV (V=ϕ, ρ0, ω) are studied with a sample of radiative ψ'→γχcJ events in a sample of (1.06±0.04)×108ψ' events collected with the BESIII detector. The branching fractions are determined to be: B(χc1→γϕ)=(25.8±5.2±2.3)×10-6, B(χc1→γρ0)=(228±13±22)×10-6, and B(χc1→γω)=(69.7±7.2±6.6)×10-6. The decay χc1→γϕ is observed for the first time. Upper limits at the 90% confidence level on the branching fractions for χc0 and χc2 decays into these final states are determined. In addition, the fractions of the transverse polarization component of the vector meson in χc1→γV decays are measured to be 0.29-0.12-0.09+0.13+0.10 for χc1→γϕ, 0.158±0.034-0.014+0.015 for χc1→γρ0, and 0.247-0.087-0.026+0.090+0.044 for χc1→γω, respectively. The first errors are statistical and the second ones are systematic.
LETTER TO THE EDITOR: Massive, topologically massive, models
NASA Astrophysics Data System (ADS)
Deser, S.; Tekin, Bayram
2002-06-01
In three dimensions, there are two distinct mass-generating mechanisms for gauge fields: adding the usual Proca/Pauli-Fierz, or the more esoteric Chern-Simons (CS), terms. Here, we analyse the three-term models where both types are present and their various limits. Surprisingly, in the tensor case, these seemingly innocuous systems are physically unacceptable. If the sign of the Einstein term is 'wrong', as is in fact required in the CS theory, then the excitation masses are always complex; with the usual sign, there is a (known) region of the two mass parameters where reality is restored, but instead a ghost problem arises, while for the 'pure mass' two-term system without an Einstein action, complex masses are unavoidable. This contrasts with the smooth behaviour of the corresponding vector models. Separately, we show that the 'partial masslessness' exhibited by (plain) massive spin-2 models in de Sitter backgrounds is shared by the three-term system: it also enjoys a reduced local gauge invariance when this mass parameter is tuned to the cosmological constant.
Simulations for an experiment to probe the in-medium properties of photoproduced vector mesons
Tur, Clarisse
2003-01-01
The g7 experiment has been devised to measure the modifications of the vector meson properties, such as mass or width, inside nuclear medium, based on the ideas presented in the numerous papers published during the fifteen years that preceded its run. It consisted in sending a bremstrahlung photon beam on a target that contained elements with different densities, a liquid deuterium cell, and seven solid foils: carbon, iron, carbon, lead, carbon, titanium, carbon. The goal of the experiment is to examine the inclusive e^{+}e^{-} photoproduction in the incoherent region. The reaction of interest to g7 is γA → VA' → e^{+}e^{-}A' where V could be a ρ an ω or a Ψ meson. The goal of the present thesis was to present the simulation work done prior to the g7 run in the fall of 2002 at Jlab, essential for the choice of the ideal experimental setup and conditions, as well as the test run of June 2002. The simulations needed a particular attention, given the many experimental challenges that awaited the g7 team. First, one had to prove that the resolution of the CLAS detector was sufficient to properly locate the vertices of the events given the multi-segmented target, and the simulations proved that fact. They also provided a rough idea of the systematic errors that one had to expect. Using nuclei bigger than carbon was a first time for CLAS. Given the very small branching ratio for ρ → e^{+}e^{-}, a very intense beam had to be sent on the target containing high-Z material. Thus, a huge background, formed of low energy e^{+}e^{-} pairs, was expected around the target and the region I of the drift chambers and which one had to reduce in an efficient way. The simulations showed that using the mini torus with its current set to 75% of its maximum value would give a reduction of about a factor of 3 in the number of hits in the region I of the drift chambers, compared to the case with no mini torus in
Placing Observational Constraints on Massive Star Models
NASA Astrophysics Data System (ADS)
Rosenfield, Philip
2011-10-01
The lives and deaths of massive stars are intricately linked to the evolution of galaxies. Yet, despite their integral importance to understanding galaxy evolution, models of massive stars are inconsistent with observations. These uncertainties can be traced to limited observational constraints available for improving massive star models. A sensitive test of the underlying physics of massive stars, e.g., convection, rotation, and mass loss is to measure the ratio of blue core helium burning stars {BHeB} to red core helium burning stars {RHeB}, 5-20Msun stars in the stage evolution immediately following the main sequence. Even the most sophisticated models cannot accurately predict the observed ratio over a range of metallicities, suggesting an insufficient understanding of the underlying physics. However, observational measurements of this ratio over a wide range of environments would provide substantial constraints on the physical parameters governing the evolution of all stars >5 Msun.We propose to place stringent observational constraints on the physics of massive star evolution by uniformly measuring the B/R HeB ratio in a wide range of galaxies. The HST archive contains high quality optical imaging of resolved stellar populations of dozens of nearby galaxies. From the ANGST program, we identified 38 galaxies, spanning 2 dex in metallicity that have significant BHeB and RHeB populations. Using this sample, we will empirically characterize the colors of the BHeB and RHeB sequences as a function of luminosity and metallicity, measure the B/R ratio, and constrain the lifetimes of the BHeB and RHeBs in the Padova stellar evolution models and the Cambridge STARS code.
Modeling populations of rotationally mixed massive stars
NASA Astrophysics Data System (ADS)
Brott, I.
2011-02-01
Massive stars can be considered as cosmic engines. With their high luminosities, strong stellar winds and violent deaths they drive the evolution of galaxies through-out the history of the universe. Despite the importance of massive stars, their evolution is still poorly understood. Two major issues have plagued evolutionary models of massive stars until today: mixing and mass loss On the main sequence, the effects of mass loss remain limited in the considered mass and metallicity range, this thesis concentrates on the role of mixing in massive stars. This thesis approaches this problem just on the cross road between observations and simulations. The main question: Do evolutionary models of single stars, accounting for the effects of rotation, reproduce the observed properties of real stars. In particular we are interested if the evolutionary models can reproduce the surface abundance changes during the main-sequence phase. To constrain our models we build a population synthesis model for the sample of the VLT-FLAMES Survey of Massive stars, for which star-formation history and rotational velocity distribution are well constrained. We consider the four main regions of the Hunter diagram. Nitrogen un-enriched slow rotators and nitrogen enriched fast rotators that are predicted by theory. Nitrogen enriched slow rotators and nitrogen unenriched fast rotators that are not predicted by our model. We conclude that currently these comparisons are not sufficient to verify the theory of rotational mixing. Physical processes in addition to rotational mixing appear necessary to explain the stars in the later two regions. The chapters of this Thesis have been published in the following Journals: Ch. 2: ``Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones'', I. Brott, S. E. de Mink, M. Cantiello, N. Langer, A. de Koter, C. J. Evans, I. Hunter, C. Trundle, J.S. Vink submitted to Astronomy & Astrop hysics Ch. 3: ``The VLT-FLAMES Survey of Massive
Masses of Axial-Vector Resonances in a Linear Sigma Model with N{sub f} = 3
Parganlija, Denis; Giacosa, Francesco; Kovacs, Peter; Wolf, Gyoergy
2011-05-23
We discuss an N{sub f} = 3 linear sigma model with vector and axial-vector mesons (extended Linear Sigma Model-eLSM). We present first results regarding the masses of axial-vector mesons determined from the extended model.
Towards Realistic Modeling of Massive Star Clusters
NASA Astrophysics Data System (ADS)
Gnedin, O.; Li, H.
2016-06-01
Cosmological simulations of galaxy formation are rapidly advancing towards smaller scales. Current models can now resolve giant molecular clouds in galaxies and predict basic properties of star clusters forming within them. I will describe new theoretical simulations of the formation of the Milky Way throughout cosmic time, with the adaptive mesh refinement code ART. However, many challenges - physical and numerical - still remain. I will discuss how observations of massive star clusters and star forming regions can help us overcome some of them. Video of the talk is available at https://goo.gl/ZoZOfX
NASA Astrophysics Data System (ADS)
Guzey, V.; Strikman, M.; Zhalov, M.
2017-02-01
By using the theoretical approaches that describe well the available data on t -integrated coherent photoproduction of light and heavy vector mesons in Pb-Pb ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) in Run 1, we calculate the momentum transfer distributions for this process for ρ and J /ψ vector mesons in the kinematics of Run 2 at the LHC. We demonstrate that nuclear shadowing not only suppresses the absolute value of the cross sections but also shifts the momentum transfer distributions toward smaller values of the momentum transfer |t | . This result can be interpreted as a broadening in the impact parameter space of the effective nucleon density in nuclei by 14% in the case of ρ and the nuclear gluon distribution by 5%-11% in the case of J /ψ .
Vector Meson Mass Corrections at O(a{sup 2}) in PQChPT with Wilson and Ginsparg-Wilson quarks
Hovhannes R. Grigoryan; Anthony W. Thomas
2005-07-01
We derive the mixed as well as unmixed lattice heavy meson chiral Lagrangian up to order O(a{sup 2}), with Wilson and Ginsparg-Wilson fermions. We consider two flavor partially quenched theory and calculate vector meson mass corrections up to order O(a{sup 2}), including the corrections associated with the violation of O(4) rotational symmetry down to hypercubic group. The chiral extrapolation formula is then compared with that used in numerical simulations.
Massive Stars: Input Physics and Stellar Models
NASA Astrophysics Data System (ADS)
El Eid, M. F.; The, L.-S.; Meyer, B. S.
2009-10-01
We present a general overview of the structure and evolution of massive stars of masses ≥12 M ⊙ during their pre-supernova stages. We think it is worth reviewing this topic owing to the crucial role of massive stars in astrophysics, especially in the evolution of galaxies and the universe. We have performed several test computations with the aim to analyze and discuss many physical uncertainties still encountered in massive-star evolution. In particular, we explore the effects of mass loss, convection, rotation, 12C( α, γ)16O reaction and initial metallicity. We also compare and analyze the similarities and differences among various works and ours. Finally, we present useful comments on the nucleosynthesis from massive stars concerning the s-process and the yields for 26Al and 60Fe.
Observation of a New Narrow Axial-Vector Meson a1(1420).
Adolph, C; Akhunzyanov, R; Alexeev, M G; Alexeev, G D; Amoroso, A; Andrieux, V; Anosov, V; Austregesilo, A; Azevedo, C; Badełek, B; Balestra, F; Barth, J; Beck, R; Bedfer, Y; Bernhard, J; Bicker, K; Bielert, E R; Birsa, R; Bisplinghoff, J; Bodlak, M; Boer, M; Bordalo, P; Bradamante, F; Braun, C; Bressan, A; Büchele, M; Burtin, E; Chang, W-C; Chiosso, M; Choi, I; Chung, S U; Cicuttin, A; Crespo, M L; Curiel, Q; Dalla Torre, S; Dasgupta, S S; Dasgupta, S; Denisov, O Yu; Dhara, L; Donskov, S V; Doshita, N; Dünnweber, W; Duic, V; Dziewiecki, M; Efremov, A; Eversheim, P D; Eyrich, W; Faessler, M; Ferrero, A; Finger, M; Finger, M; Fischer, H; Franco, C; du Fresne von Hohenesche, N; Friedrich, J M; Frolov, V; Gautheron, F; Gavrichtchouk, O P; Gerassimov, S; Gnesi, I; Gorzellik, M; Grabmüller, S; Grasso, A; Grosse-Perdekamp, M; Grube, B; Grussenmeyer, T; Guskov, A; Haas, F; Hahne, D; von Harrach, D; Hashimoto, R; Heinsius, F H; Herrmann, F; Hinterberger, F; Horikawa, N; d'Hose, N; Hsieh, C-Yu; Huber, S; Ishimoto, S; Ivanov, A; Ivanshin, Yu; Iwata, T; Jahn, R; Jary, V; Jörg, P; Joosten, R; Kabuß, E; Ketzer, B; Khaustov, G V; Khokhlov, Yu A; Kisselev, Yu; Klein, F; Klimaszewski, K; Koivuniemi, J H; Kolosov, V N; Kondo, K; Königsmann, K; Konorov, I; Konstantinov, V F; Kotzinian, A M; Kouznetsov, O; Krämer, M; Kremser, P; Krinner, F; Kroumchtein, Z V; Kuchinski, N; Kunne, F; Kurek, K; Kurjata, R P; Lednev, A A; Lehmann, A; Levillain, M; Levorato, S; Lichtenstadt, J; Maggiora, A; Magnon, A; Makins, N; Makke, N; Mallot, G K; Marchand, C; Martin, A; Marzec, J; Matousek, J; Matsuda, H; Matsuda, T; Meshcheryakov, G; Meyer, W; Michigami, T; Mikhailov, Yu V; Miyachi, Y; Nagaytsev, A; Nagel, T; Nerling, F; Neyret, D; Nikolaenko, V I; Novy, J; Nowak, W-D; Nunes, A S; Olshevsky, A G; Orlov, I; Ostrick, M; Panzieri, D; Parsamyan, B; Paul, S; Peng, J-C; Pereira, F; Pesek, M; Peshekhonov, D V; Platchkov, S; Pochodzalla, J; Polyakov, V A; Pretz, J; Quaresma, M; Quintans, C; Ramos, S; Regali, C; Reicherz, G; Riedl, C; Rocco, E; Rossiyskaya, N S; Ryabchikov, D I; Rychter, A; Samoylenko, V D; Sandacz, A; Santos, C; Sarkar, S; Savin, I A; Sbrizzai, G; Schiavon, P; Schmeing, S; Schmidt, K; Schmieden, H; Schönning, K; Schopferer, S; Schlüter, T; Selyunin, A; Shevchenko, O Yu; Silva, L; Sinha, L; Sirtl, S; Slunecka, M; Sozzi, F; Srnka, A; Stolarski, M; Sulc, M; Suzuki, H; Szabelski, A; Szameitat, T; Sznajder, P; Takekawa, S; Ter Wolbeek, J; Tessaro, S; Tessarotto, F; Thibaud, F; Tskhay, V; Uhl, S; Veloso, J; Virius, M; Wallner, S; Weisrock, T; Wilfert, M; Zaremba, K; Zavertyaev, M; Zemlyanichkina, E; Ziembicki, M; Zink, A
2015-08-21
The COMPASS Collaboration at CERN has measured diffractive dissociation of 190 GeV/c pions into the π(-)π(-)π(+) final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers J(PC)=1(++). We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with J(PC)=2(++) and 4(++) decaying into ρ(770)π and with J(PC)=1(++) decaying into f0(980)π. We identify a new a1 meson with mass (1414(-13)(+15)) MeV/c2 and width (153(-23)(+8)) MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.
Light vector meson production in pp collisions at √{ s} = 7 TeV
NASA Astrophysics Data System (ADS)
Abelev, B.; Abrahantes Quintana, A.; Adamová, D.; Adare, A. M.; Aggarwal, M. M.; Aglieri Rinella, G.; Agocs, A. G.; Agostinelli, A.; Aguilar Salazar, S.; Ahammed, Z.; Ahmad, N.; Ahmad Masoodi, A.; Ahn, S. U.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Almaráz Aviña, E.; Alt, T.; Altini, V.; Altinpinar, S.; Altsybeev, I.; Andrei, C.; Andronic, A.; Anguelov, V.; Anson, C.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arbor, N.; Arcelli, S.; Arend, A.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Asryan, A.; Augustinus, A.; Averbeck, R.; Awes, T. C.; Äystö, J.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bailhache, R.; Bala, R.; Baldini Ferroli, R.; Baldisseri, A.; Baldit, A.; Baltasar Dos Santos Pedrosa, F.; Bán, J.; Baral, R. C.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Bathen, B.; Batigne, G.; Batyunya, B.; Baumann, C.; Bearden, I. G.; Beck, H.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bergmann, C.; Berzano, D.; Betev, L.; Bhasin, A.; Bhati, A. K.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Blanco, F.; Blanco, F.; Blau, D.; Blume, C.; Boccioli, M.; Bock, N.; Bogdanov, A.; Bøggild, H.; Bogolyubsky, M.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Bortolin, C.; Bose, S.; Bossú, F.; Botje, M.; Böttger, S.; Boyer, B.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broz, M.; Brun, R.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Bugaiev, K.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Calvo Villar, E.; Camerini, P.; Canoa Roman, V.; Cara Romeo, G.; Carena, W.; Carena, F.; Carlin Filho, N.; Carminati, F.; Carrillo Montoya, C. A.; Casanova Díaz, A.; Caselle, M.; Castillo Castellanos, J.; Castillo Hernandez, J. F.; Casula, E. A. R.; Catanescu, V.; Cavicchioli, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chiavassa, E.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Chojnacki, M.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Coccetti, F.; Coffin, J.-P.; Colamaria, F.; Colella, D.; Conesa Balbastre, G.; Conesa Del Valle, Z.; Constantin, P.; Contin, G.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortese, P.; Cortés Maldonado, I.; Cosentino, M. R.; Costa, F.; Cotallo, M. E.; Crescio, E.; Crochet, P.; Cruz Alaniz, E.; Cuautle, E.; Cunqueiro, L.; Dainese, A.; Dalsgaard, H. H.; Danu, A.; Das, K.; Das, D.; Das, I.; Dash, S.; Dash, A.; de, S.; de Azevedo Moregula, A.; de Barros, G. O. V.; de Caro, A.; de Cataldo, G.; de Cuveland, J.; de Falco, A.; de Gruttola, D.; Delagrange, H.; Del Castillo Sanchez, E.; Deloff, A.; Demanov, V.; De Marco, N.; Dénes, E.; de Pasquale, S.; Deppman, A.; D Erasmo, G.; de Rooij, R.; di Bari, D.; Dietel, T.; di Giglio, C.; di Liberto, S.; di Mauro, A.; di Nezza, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domínguez, I.; Dönigus, B.; Dordic, O.; Driga, O.; Dubey, A. K.; Ducroux, L.; Dupieux, P.; Dutta Majumdar, A. K.; Dutta Majumdar, M. R.; Elia, D.; Emschermann, D.; Engel, H.; Erdal, H. A.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Eyyubova, G.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fearick, R.; Fedunov, A.; Fehlker, D.; Feldkamp, L.; Felea, D.; Feofilov, G.; Fernández Téllez, A.; Ferretti, A.; Ferretti, R.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Fini, R.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Fragkiadakis, M.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Garabatos, C.; Garcia-Solis, E.; Garishvili, I.; Gerhard, J.; Germain, M.; Geuna, C.; Gheata, M.; Gheata, A.; Ghidini, B.; Ghosh, P.; Gianotti, P.; Girard, M. R.; Giubellino, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez, R.; Ferreiro, E. G.; González-Trueba, L. H.; González-Zamora, P.; Gorbunov, S.; Goswami, A.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Grajcarek, R.; Grelli, A.; Grigoras, C.; Grigoras, A.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gros, P.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerra Gutierrez, C.; Guerzoni, B.; Guilbaud, M.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Gutbrod, H.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Han, B. H.; Hanratty, L. D.; Hansen, A.; Harmanova, Z.; Harris, J. W.; Hartig, M.; Hasegan, D.; Hatzifotiadou, D.; Hayrapetyan, A.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Herrmann, N.; Hetland, K. F.; Hicks, B.; Hille, P. T.; Hippolyte, B.; Horaguchi, T.; Hori, Y.; Hristov, P.; Hřivnáčová, I.; Huang, M.; Huber, S.; Humanic, T. J.; Hwang, D. S.; Ichou, R.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Incani, E.; Innocenti, G. M.; Innocenti, P. G.; Ippolitov, M.; Irfan, M.; Ivan, C.; Ivanov, M.; Ivanov, A.; Ivanov, V.; Ivanytskyi, O.; Jachołkowski, A.; Jacobs, P. M.; Jancurová, L.; Jang, H. J.; Jangal, S.; Janik, R.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, S.; Jimenez Bustamante, R. T.; Jirden, L.; Jones, P. G.; Jung, W.; Jung, H.; Jusko, A.; Kaidalov, A. B.; Kakoyan, V.; Kalcher, S.; Kaliňák, P.; Kalisky, M.; Kalliokoski, T.; Kalweit, A.; Kanaki, K.; Kang, J. H.; Kaplin, V.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kazantsev, A.; Kebschull, U.; Keidel, R.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, D. W.; Kim, M.; Kim, J. H.; Kim, S. H.; Kim, S.; Kim, B.; Kim, T.; Kim, D. J.; Kim, J. S.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Klay, J. L.; Klein, J.; Klein-Bösing, C.; Kliemant, M.; Kluge, A.; Knichel, M. L.; Koch, K.; Köhler, M. K.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Konevskikh, A.; Korneev, A.; Kottachchi Kankanamge Don, C.; Kour, R.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kramer, F.; Kraus, I.; Krawutschke, T.; Kretz, M.; Krivda, M.; Krizek, F.; Krus, M.; Kryshen, E.; Krzewicki, M.; Kucheriaev, Y.; Kuhn, C.; Kuijer, P. G.; Kurashvili, P.; Kurepin, A. B.; Kurepin, A.; Kuryakin, A.; Kushpil, V.; Kushpil, S.; Kvaerno, H.; Kweon, M. J.; Kwon, Y.; Ladrón de Guevara, P.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; La Rocca, P.; Lazzeroni, C.; Lea, R.; Le Bornec, Y.; Lee, K. S.; Lee, S. C.; Lefèvre, F.; Lehnert, J.; Leistam, L.; Lenhardt, M.; Lenti, V.; León, H.; León Monzón, I.; León Vargas, H.; Lévai, P.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Liu, L.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Lohn, S.; Lohner, D.; Loizides, C.; Loo, K. K.; Lopez, X.; López Torres, E.; Løvhøiden, G.; Lu, X.-G.; Luettig, P.; Lunardon, M.; Luo, J.; Luparello, G.; Luquin, L.; Luzzi, C.; Ma, R.; Ma, K.; Madagodahettige-Don, D. M.; Maevskaya, A.; Mager, M.; Mahapatra, D. P.; Maire, A.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Mangotra, L.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Marín, A.; Markert, C.; Martashvili, I.; Martinengo, P.; Martínez, M. I.; Martínez Davalos, A.; Martínez García, G.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastromarco, M.; Mastroserio, A.; Matthews, Z. L.; Matyja, A.; Mayani, D.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Meddi, F.; Menchaca-Rocha, A.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Michalon, A.; Midori, J.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitu, C.; Mlynarz, J.; Mohanty, A. K.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Monteno, M.; Montes, E.; Moon, T.; Morando, M.; Moreira de Godoy, D. A.; Moretto, S.; Morsch, A.; Muccifora, V.; Mudnic, E.; Muhuri, S.; Müller, H.; Munhoz, M. G.; Musa, L.; Musso, A.; Nandi, B. K.; Nania, R.; Nappi, E.; Nattrass, C.; Naumov, N. P.; Navin, S.; Nayak, T. K.; Nazarenko, S.; Nazarov, G.; Nedosekin, A.; Nicassio, M.; Nielsen, B. S.; Niida, T.; Nikolaev, S.; Nikolic, V.; Nikulin, S.; Nikulin, V.; Nilsen, B. S.; Nilsson, M. S.; Noferini, F.; Nomokonov, P.; Nooren, G.; Novitzky, N.; Nyanin, A.; Nyatha, A.; Nygaard, C.; Nystrand, J.; Obayashi, H.; Ochirov, A.; Oeschler, H.; Oh, S. K.; Oh, S.; Oleniacz, J.; Oppedisano, C.; Ortiz Velasquez, A.; Ortona, G.; Oskarsson, A.; Ostrowski, P.; Otterlund, I.; Otwinowski, J.; Oyama, K.; Ozawa, K.; Pachmayer, Y.; Pachr, M.; Padilla, F.; Pagano, P.; Paić, G.; Painke, F.; Pajares, C.; Pal, S.; Pal, S. K.; Palaha, A.; Palmeri, A.; Papikyan, V.; Pappalardo, G. S.; Park, W. J.; Passfeld, A.; Pastirčák, B.; Patalakha, D. I.; Paticchio, V.; Pavlinov, A.; Pawlak, T.; Peitzmann, T.; Perales, M.; Pereira de Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Perez Lezama, E.; Perini, D.; Perrino, D.; Peryt, W.; Pesci, A.; Peskov, V.; Pestov, Y.; Petráček, V.; Petran, M.; Petris, M.; Petrov, P.; Petrovici, M.; Petta, C.; Piano, S.; Piccotti, A.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Pitz, N.; Piuz, F.; Piyarathna, D. B.; Płoskoń, M.; Pluta, J.; Pocheptsov, T.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polák, K.; Polichtchouk, B.; Pop, A.; Porteboeuf-Houssais, S.; Pospíšil, V.; Potukuchi, B.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puchagin, S.; Puddu, G.; Pulvirenti, A.; Punin, V.; Putiš, M.; Putschke, J.; Quercigh, E.; Qvigstad, H.; Rachevski, A.; Rademakers, A.; Radomski, S.; Räihä, T. S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Ramírez Reyes, A.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Read, K. F.; Real, J. S.; Redlich, K.; Reichelt, P.; Reicher, M.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riccati, L.; Ricci, R. A.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Rodríguez Cahuantzi, M.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Rosnet, P.; Rossegger, S.; Rossi, A.; Roukoutakis, F.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Ryabinkin, E.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahu, P. K.; Saini, J.; Sakaguchi, H.; Sakai, S.; Sakata, D.; Salgado, C. A.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Šándor, L.; Sandoval, A.; Sano, M.; Sano, S.; Santo, R.; Santoro, R.; Sarkamo, J.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schreiner, S.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, P. A.; Scott, R.; Segato, G.; Selyuzhenkov, I.; Senyukov, S.; Seo, J.; Serci, S.; Serradilla, E.; Sevcenco, A.; Sgura, I.; Shabetai, A.; Shabratova, G.; Shahoyan, R.; Sharma, N.; Sharma, S.; Shigaki, K.; Shimomura, M.; Shtejer, K.; Sibiriak, Y.; Siciliano, M.; Sicking, E.; Siddhanta, S.; Siemiarczuk, T.; Silvermyr, D.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Skjerdal, K.; Smakal, R.; Smirnov, N.; Snellings, R.; Søgaard, C.; Soltz, R.; Son, H.; Song, M.; Song, J.; Soos, C.; Soramel, F.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stan, I.; Stefanek, G.; Stefanini, G.; Steinbeck, T.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stocco, D.; Stolpovskiy, M.; Strabykin, K.; Strmen, P.; Suaide, A. A. P.; Subieta Vásquez, M. A.; Sugitate, T.; Suire, C.; Sukhorukov, M.; Sultanov, R.; Šumbera, M.; Susa, T.; Szanto de Toledo, A.; Szarka, I.; Szostak, A.; Tagridis, C.; Takahashi, J.; Tapia Takaki, J. D.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terrevoli, C.; Thäder, J.; Thomas, D.; Thomas, J. H.; Tieulent, R.; Timmins, A. R.; Tlusty, D.; Toia, A.; Torii, H.; Toscano, L.; Tosello, F.; Traczyk, T.; Truesdale, D.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ulery, J.; Ullaland, K.; Ulrich, J.; Uras, A.; Urbán, J.; Urciuoli, G. M.; Usai, G. L.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; van der Kolk, N.; Vande Vyvre, P.; van Leeuwen, M.; Vannucci, L.; Vargas, A.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vechernin, V.; Veldhoen, M.; Venaruzzo, M.; Vercellin, E.; Vergara, S.; Vernekohl, D. C.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Vikhlyantsev, O.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, L.; Vinogradov, A.; Vinogradov, Y.; Virgili, T.; Viyogi, Y. P.; Vodopyanov, A.; Voloshin, S.; Voloshin, K.; Volpe, G.; von Haller, B.; Vranic, D.; Øvrebekk, G.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, V.; Wagner, B.; Wan, R.; Wang, Y.; Wang, M.; Wang, Y.; Wang, D.; Watanabe, K.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, A.; Wilk, G.; Williams, M. C. S.; Windelband, B.; Xaplanteris Karampatsos, L.; Yang, S.; Yang, H.; Yano, S.; Yasnopolskiy, S.; Yi, J.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J.; Yu, W.; Yuan, X.; Yushmanov, I.; Zach, C.; Zampolli, C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zelnicek, P.; Zgura, I.; Zhalov, M.; Zhang, X.; Zhou, D.; Zhou, Y.; Zhou, F.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zinovjev, G.; Zoccarato, Y.; Zynovyev, M.; Alice Collaboration
2012-04-01
The ALICE experiment has measured low-mass dimuon production in pp collisions at √{ s} = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (η , ρ , ω ,η‧ , ϕ) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for ω and ϕ are σω (1
Observation of χc1 Decays into Vector Meson Pairs ΦΦ, ωω and, ωΦ
Ablikim, M.; Achasov, M. N.; An, L.; ...
2011-08-22
Using (106±4)×10⁶ ψ(3686) events accumulated with the BESIII detector at the BEPCII e⁺e⁻ collider, we present the first measurement of decays of χc1 to vector meson pairs ΦΦ, ωω, and ωΦ. The branching fractions are measured to be (4.4±0.3±0.5)×10⁻⁴, (6.0±0.3±0.7)×10⁻⁴, and (2.2±0.6±0.2)×10⁻⁵, for χc1 →ΦΦ, ωω, and ωΦ, respectively, which indicates that the hadron helicity selection rule is significantly violated in χcJ decays. In addition, the measurement of χcJ→ωΦ provides the first indication of the rate of doubly OZI-suppressed χcJ decay. Finally, we present improved measurements for the branching fractions of χc0 and χc2 to vector meson pairs.
Observation of χ(c1) decays into vector meson pairs φφ, ωω, and ωφ.
Ablikim, M; Achasov, M N; An, L; An, Q; An, Z H; Bai, J Z; Baldini, R; Ban, Y; Becker, J; Berger, N; Bertani, M; Bian, J M; Bondarenko, O; Boyko, I; Briere, R A; Bytev, V; Cai, X; Cao, G F; Cao, X X; Chang, J F; Chelkov, G; Chen, G; Chen, H S; Chen, J C; Chen, M L; Chen, S J; Chen, Y; Chen, Y B; Cheng, H P; Chu, Y P; Cronin-Hennessy, D; Dai, H L; Dai, J P; Dedovich, D; Deng, Z Y; Denysenko, I; Destefanis, M; Ding, Y; Dong, L Y; Dong, M Y; Du, S X; Duan, M Y; Fan, R R; Fang, J; Fang, S S; Feng, C Q; Fu, C D; Fu, J L; Gao, Y; Geng, C; Goetzen, K; Gong, W X; Greco, M; Grishin, S; Gu, M H; Gu, Y T; Guan, Y H; Guo, A Q; Guo, L B; Guo, Y P; Hao, X Q; Harris, F A; He, K L; He, M; He, Z Y; Heng, Y K; Hou, Z L; Hu, H M; Hu, J F; Hu, T; Huang, B; Huang, G M; Huang, J S; Huang, X T; Huang, Y P; Hussain, T; Ji, C S; Ji, Q; Ji, X B; Ji, X L; Jia, L K; Jiang, L L; Jiang, X S; Jiao, J B; Jiao, Z; Jin, D P; Jin, S; Jing, F F; Kavatsyuk, M; Komamiya, S; Kuehn, W; Lange, J S; Leung, J K C; Li, Cheng; Li, Cui; Li, D M; Li, F; Li, G; Li, H B; Li, J C; Li, Lei; Li, N B; Li, Q J; Li, W D; Li, W G; Li, X L; Li, X N; Li, X Q; Li, X R; Li, Z B; Liang, H; Liang, Y F; Liang, Y T; Liao, G R; Liao, X T; Liu, B J; Liu, B J; Liu, C L; Liu, C X; Liu, C Y; Liu, F H; Liu, Fang; Liu, Feng; Liu, G C; Liu, H; Liu, H B; Liu, H M; Liu, H W; Liu, J P; Liu, K; Liu, K Y; Liu, Q; Liu, S B; Liu, X; Liu, X H; Liu, Y B; Liu, Y W; Liu, Yong; Liu, Z A; Liu, Z Q; Loehner, H; Lu, G R; Lu, H J; Lu, J G; Lu, Q W; Lu, X R; Lu, Y P; Luo, C L; Luo, M X; Luo, T; Luo, X L; Ma, C L; Ma, F C; Ma, H L; Ma, Q M; Ma, T; Ma, X; Ma, X Y; Maggiora, M; Malik, Q A; Mao, H; Mao, Y J; Mao, Z P; Messchendorp, J G; Min, J; Mitchell, R E; Mo, X H; Muchnoi, N Yu; Nefedov, Y; Ning, Z; Olsen, S L; Ouyang, Q; Pacetti, S; Pelizaeus, M; Peters, K; Ping, J L; Ping, R G; Poling, R; Pun, C S J; Qi, M; Qian, S; Qiao, C F; Qin, X S; Qiu, J F; Rashid, K H; Rong, G; Ruan, X D; Sarantsev, A; Schulze, J; Shao, M; Shen, C P; Shen, X Y; Sheng, H Y; Shepherd, M R; Song, X Y; Sonoda, S; Spataro, S; Spruck, B; Sun, D H; Sun, G X; Sun, J F; Sun, S S; Sun, X D; Sun, Y J; Sun, Y Z; Sun, Z J; Sun, Z T; Tang, C J; Tang, X; Tang, X F; Tian, H L; Toth, D; Varner, G S; Wan, X; Wang, B Q; Wang, K; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, Q; Wang, S G; Wang, X L; Wang, Y D; Wang, Y F; Wang, Y Q; Wang, Z; Wang, Z G; Wang, Z Y; Wei, D H; Wen, Q G; Wen, S P; Wiedner, U; Wu, L H; Wu, N; Wu, W; Wu, Z; Xiao, Z J; Xie, Y G; Xu, G F; Xu, G M; Xu, H; Xu, Y; Xu, Z R; Xu, Z Z; Xue, Z; Yan, L; Yan, W B; Yan, Y H; Yang, H X; Yang, M; Yang, T; Yang, Y; Yang, Y X; Ye, M; Ye, M H; Yu, B X; Yu, C X; Yu, L; Yuan, C Z; Yuan, W L; Yuan, Y; Zafar, A A; Zallo, A; Zeng, Y; Zhang, B X; Zhang, B Y; Zhang, C C; Zhang, D H; Zhang, H H; Zhang, H Y; Zhang, J; Zhang, J W; Zhang, J Y; Zhang, J Z; Zhang, L; Zhang, S H; Zhang, T R; Zhang, X J; Zhang, X Y; Zhang, Y; Zhang, Y H; Zhang, Z P; Zhang, Z Y; Zhao, G; Zhao, H S; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M G; Zhao, Q; Zhao, S J; Zhao, T C; Zhao, X H; Zhao, Y B; Zhao, Z G; Zhao, Z L; Zhemchugov, A; Zheng, B; Zheng, J P; Zheng, Y H; Zheng, Z P; Zhong, B; Zhong, J; Zhong, L; Zhou, L; Zhou, X K; Zhou, X R; Zhu, C; Zhu, K; Zhu, K J; Zhu, S H; Zhu, X L; Zhu, X W; Zhu, Y S; Zhu, Z A; Zhuang, J; Zou, B S; Zou, J H; Zuo, J X; Zweber, P
2011-08-26
Using (106±4)×10⁻⁶ ψ(3686) events accumulated with the BESIII detector at the BEPCII e⁺e⁻ collider, we present the first measurement of decays of χ(c1) to vector meson pairs φφ, ωω, and ωφ. The branching fractions are measured to be (4.4±0.3±0.5)×10⁻⁴, (6.0±0.3±0.7)×10⁻⁴, and (2.2±0.6±0.2)×10⁻⁵, for χ(c1)→φφ, ωω, and ωφ, respectively, which indicates that the hadron helicity selection rule is significantly violated in χ(cJ) decays. In addition, the measurement of χ(cJ)→ωφ provides the first indication of the rate of doubly OZI-suppressed χ(cJ) decay. Finally, we present improved measurements for the branching fractions of χ(c0) and χ(c2) to vector meson pairs.
Ablikim, M.; An, Z. H.; Bai, J. Z.; Berger, N.; Bian, J. M.; Cai, X.; Cao, G. F.; Cao, X. X.; Chang, J. F.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, Y.; Chen, Y. B.; Chu, Y. P.; Dai, H. L.; Dai, J. P.; Deng, Z. Y.; Dong, L. Y.
2011-08-26
Using (106{+-}4)x10{sup 6} {psi}(3686) events accumulated with the BESIII detector at the BEPCII e{sup +}e{sup -} collider, we present the first measurement of decays of {chi}{sub c1} to vector meson pairs {phi}{phi}, {omega}{omega}, and {omega}{phi}. The branching fractions are measured to be (4.4{+-}0.3{+-}0.5)x10{sup -4}, (6.0{+-}0.3{+-}0.7)x10{sup -4}, and (2.2{+-}0.6{+-}0.2)x10{sup -5}, for {chi}{sub c1}{yields}{phi}{phi}, {omega}{omega}, and {omega}{phi}, respectively, which indicates that the hadron helicity selection rule is significantly violated in {chi}{sub cJ} decays. In addition, the measurement of {chi}{sub cJ}{yields}{omega}{phi} provides the first indication of the rate of doubly OZI-suppressed {chi}{sub cJ} decay. Finally, we present improved measurements for the branching fractions of {chi}{sub c0} and {chi}{sub c2} to vector meson pairs.
Observation of χ_{c1} Decays into Vector Meson Pairs ΦΦ, ωω and, ωΦ
Ablikim, M.; Achasov, M. N.; An, L.; An, Q.; An, Z. H.; Bai, J. Z.; Baldini, R.; Ban, Y.; Becker, J.; Berger, N.; Bertani, M.; Bian, J. M.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Cao, G. F.; Cao, X. X.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, Y.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denysenko, I.; Destefanis, M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Duan, M. Y.; Fan, R. R.; Fang, J.; Fang, S. S.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Greco, M.; Grishin, S.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, B.; Huang, G. M.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jia, L. K.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kavatsyuk, M.; Komamiya, S.; Kuehn, W.; Lange, J. S.; Leung, J. K. C.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, Lei; Li, N. B.; Li, Q. J.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Liao, X. T.; Liu, B. J.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, G. C.; Liu, H.; Liu, H. B.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K. Y.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. H.; Liu, Y. B.; Liu, Y. W.; Liu, Yong; Liu, Z. A.; Liu, Z. Q.; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, T.; Ma, X.; Ma, X. Y.; Maggiora, M.; Malik, Q. A.; Mao, H.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Mitchell, R. E.; Mo, X. H.; Muchnoi, N. Yu.; Nefedov, Y.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pelizaeus, M.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pun, C. S. J.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Sonoda, S.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. D.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tang, X. F.; Tian, H. L.; Toth, D.; Varner, G. S.; Wan, X.; Wang, B. Q.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xiao, Z. J.; Xie, Y. G.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Y.; Xu, Z. R.; Xu, Z. Z.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, M.; Yang, T.; Yang, Y.; Yang, Y. X.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, L.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, S. H.; Zhang, T. R.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhao, Z. L.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zheng, Z. P.; Zhong, B.; Zhong, J.; Zhong, L.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, X. W.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Zuo, J. X.; Zweber, P.
2011-08-22
Using (106±4)×10⁶ ψ(3686) events accumulated with the BESIII detector at the BEPCII e⁺e⁻ collider, we present the first measurement of decays of χ_{c1} to vector meson pairs ΦΦ, ωω, and ωΦ. The branching fractions are measured to be (4.4±0.3±0.5)×10⁻⁴, (6.0±0.3±0.7)×10⁻⁴, and (2.2±0.6±0.2)×10⁻⁵, for χ_{c1} →ΦΦ, ωω, and ωΦ, respectively, which indicates that the hadron helicity selection rule is significantly violated in χ_{cJ} decays. In addition, the measurement of χ_{cJ}→ωΦ provides the first indication of the rate of doubly OZI-suppressed χ_{cJ} decay. Finally, we present improved measurements for the branching fractions of χ_{c0} and χ_{c2} to vector meson pairs.
Periodic ground state for the charged massive Schwinger model
Nagy, S.; Sailer, K.; Polonyi, J.
2004-11-15
It is shown that the charged massive Schwinger model supports a periodic vacuum structure for arbitrary charge density, similar to the common crystalline layout known in solid state physics. The dynamical origin of the inhomogeneity is identified in the framework of the bosonized model and in terms of the original fermionic variables.
Generalized universality in the massive sine-Gordon model
Nagy, S.; Sailer, K.; Nandori, I.; Polonyi, J.
2008-01-15
A nontrivial interplay of the UV and IR scaling laws, a generalization of the universality is demonstrated in the framework of the massive sine-Gordon model, as a result of a detailed study of the global behavior of the renormalization group flow and the phase structure.
Modeling groundwater flow on massively parallel computers
Ashby, S.F.; Falgout, R.D.; Fogwell, T.W.; Tompson, A.F.B.
1994-12-31
The authors will explore the numerical simulation of groundwater flow in three-dimensional heterogeneous porous media. An interdisciplinary team of mathematicians, computer scientists, hydrologists, and environmental engineers is developing a sophisticated simulation code for use on workstation clusters and MPPs. To date, they have concentrated on modeling flow in the saturated zone (single phase), which requires the solution of a large linear system. they will discuss their implementation of preconditioned conjugate gradient solvers. The preconditioners under consideration include simple diagonal scaling, s-step Jacobi, adaptive Chebyshev polynomial preconditioning, and multigrid. They will present some preliminary numerical results, including simulations of groundwater flow at the LLNL site. They also will demonstrate the code`s scalability.
The halo model in a massive neutrino cosmology
Massara, Elena; Villaescusa-Navarro, Francisco; Viel, Matteo E-mail: villaescusa@oats.inaf.it
2014-12-01
We provide a quantitative analysis of the halo model in the context of massive neutrino cosmologies. We discuss all the ingredients necessary to model the non-linear matter and cold dark matter power spectra and compare with the results of N-body simulations that incorporate massive neutrinos. Our neutrino halo model is able to capture the non-linear behavior of matter clustering with a ∼20% accuracy up to very non-linear scales of k = 10 h/Mpc (which would be affected by baryon physics). The largest discrepancies arise in the range k = 0.5 – 1 h/Mpc where the 1-halo and 2-halo terms are comparable and are present also in a massless neutrino cosmology. However, at scales k < 0.2 h/Mpc our neutrino halo model agrees with the results of N-body simulations at the level of 8% for total neutrino masses of < 0.3 eV. We also model the neutrino non-linear density field as a sum of a linear and clustered component and predict the neutrino power spectrum and the cold dark matter-neutrino cross-power spectrum up to k = 1 h/Mpc with ∼30% accuracy. For masses below 0.15 eV the neutrino halo model captures the neutrino induced suppression, casted in terms of matter power ratios between massive and massless scenarios, with a 2% agreement with the results of N-body/neutrino simulations. Finally, we provide a simple application of the halo model: the computation of the clustering of galaxies, in massless and massive neutrinos cosmologies, using a simple Halo Occupation Distribution scheme and our halo model extension.
de Rham, Claudia
2014-01-01
We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alternative and related models of massive gravity such as new massive gravity, Lorentz-violating massive gravity and non-local massive gravity.
A symmetric approach to the massive nonlinear sigma model
Ferrari, Ruggero
2011-09-28
In the present study we extend to the massive case the procedure of divergences subtraction, previously introduced for the massless nonlinear sigma model (D = 4). Perturbative expansion in the number of loops is successfully constructed. The resulting theory depends on the Spontaneous Symmetry Breaking parameter v, on the mass m and on the radiative correction parameter Λ. Fermions are not considered in the present work. SU(2) Ⓧ SU(2) is the group used.
Massive dark photons in a Higgs portal model
Hadjimichef, Dimiter
2015-12-17
An extension of the Standard Model with a hidden sector which consists of gauge singlets (a Dirac fermion χ and a scalar S) plus a vector boson V{sub μ} (dark massive photon) is studied. The singlet scalar interacts with the Standard Model sector through the triple and quartic scalar interactions, while the singlet fermion and vector boson field interact with the Standard Model only via the singlet scalar. The scalar field generates the vector boson’s mass. Perspectives for future e{sup −}e{sup +} colliders is considered.
Chiral Lagrangians for Baryons Coupled to Massive SPIN-1 Fields
NASA Astrophysics Data System (ADS)
Borasoy, B.; Meißner, Ulf-G.
We analyze the effective low energy field theory of Goldstone bosons and baryons chirally coupled to massive spin-1 fields. We use the electromagnetic baryon form factors to demonstrate the formal equivalence between the vector and the tensor field formulation for the spin-1 fields. We also discuss the origin of the so-called Weinberg term in pion-nucleon scattering and the role of ρ meson exchange. Chirally coupled vector mesons do not give rise to this two-pion nucleon seagull interaction but rather to higher order corrections. Some problems of the formal equivalence arising in higher orders and related to loops are touched upon.
Quantum superposition of massive objects and collapse models
Romero-Isart, Oriol
2011-11-15
We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.
Massive-Scale Tree Modelling from Tls Data
NASA Astrophysics Data System (ADS)
Raumonen, P.; Casella, E.; Calders, K.; Murphy, S.; Åkerbloma, , M.; Kaasalainen, M.
2015-03-01
This paper presents a method for reconstructing automatically the quantitative structure model of every tree in a forest plot from terrestrial laser scanner data. A new feature is the automatic extraction of individual trees from the point cloud. The method is tested with a 30-m diameter English oak plot and a 80-m diameter Australian eucalyptus plot. For the oak plot the total biomass was overestimated by about 17 %, when compared to allometry (N = 15), and the modelling time was about 100 min with a laptop. For the eucalyptus plot the total biomass was overestimated by about 8.5 %, when compared to a destructive reference (N = 27), and the modelling time was about 160 min. The method provides accurate and fast tree modelling abilities for, e.g., biomass estimation and ground truth data for airborne measurements at a massive ground scale.
Monte Carlo shell model studies with massively parallel supercomputers
NASA Astrophysics Data System (ADS)
Shimizu, Noritaka; Abe, Takashi; Honma, Michio; Otsuka, Takaharu; Togashi, Tomoaki; Tsunoda, Yusuke; Utsuno, Yutaka; Yoshida, Tooru
2017-06-01
We present an overview of the advanced Monte Carlo shell model (MCSM), including its recent applications to no-core shell-model calculations and to large-scale shell-model calculations (LSSM) in the usual sense. For the ab initio no-core MCSM we show recent methodological developments, which include the evaluation of energy eigenvalues in an infinitely large model space by an extrapolation method. As an example of the application of the no-core MCSM, the cluster structure of Be isotopes is discussed. Regarding LSSM applications, the triple shape coexistence in 68Ni and 70Ni and the shape transition of Zr isotopes are clarified with the visualization of the intrinsic deformation of the MCSM wave function. General aspects of the code development of the MCSM on massively parallel computers are also briefly described.
Massively parallel forward modeling of scalar and tensor gravimetry data
NASA Astrophysics Data System (ADS)
Moorkamp, M.; Jegen, M.; Roberts, A.; Hobbs, R.
2010-05-01
We present an approach to calculate scalar and tensor gravity utilizing the massively parallel architecture of consumer graphics cards. Our parametrization is based on rectilinear blocks with constant density within each blocks. This type of parametrization is well suited for inversion of gravity data or joint inversion with other datasets, but requires the calculation of a large number of model blocks for complex geometries. For models exceeding 10,000 cells we achieve an acceleration of a factor of 40 for scalar data and 30 for tensor data compared to a single thread on the CPU. This significant acceleration allows fast computation of large models exceeding 10 6 model parameters and thousands of measurement sites.
Higher derivative massive spin-3 models in D =2 +1
NASA Astrophysics Data System (ADS)
Dalmazi, D.; Mendonça, E. L.
2016-07-01
We find new higher derivative models describing a parity doublet of massive spin-3 modes in D =2 +1 dimensions. One of them is of fourth order in derivatives while the other one is of sixth order. They are complete, in the sense that they contain the auxiliary scalar field required to remove spurious degrees of freedom. Both of them are obtained through the master action technique starting with the usual (second-order) spin-3 Singh-Hagen model, which guarantees that they are ghost free. The fourth- and sixth-order terms are both invariant under (transverse) Weyl transformations, quite similarly to the fourth-order K -term of the "new massive gravity." The sixth-order term slightly differs from the product of the Schouten by the Einstein tensor, both of third order in derivatives. It is also possible to write down the fourth-order term as a product of a Schouten-like by an Einstein-like tensor (both of second order in derivatives) in close analogy with the K -term.
The Influence of the Enhanced Vector Meson Sector on the Properties of the Matter of Neutron Stars
Bednarek, Ilona; Manka, Ryszard; Pienkos, Monika
2014-01-01
This paper gives an overview of the model of a neutron star with non-zero strangeness constructed within the framework of the nonlinear realization of the chiral symmetry. The emphasis is put on the physical properties of the matter of a neutron star as well as on its internal structure. The obtained solution is particularly aimed at the problem of the construction of a theoretical model of a neutron star matter with hyperons that will give high value of the maximum mass. PMID:25188304
The influence of the enhanced vector meson sector on the properties of the matter of neutron stars.
Bednarek, Ilona; Manka, Ryszard; Pienkos, Monika
2014-01-01
This paper gives an overview of the model of a neutron star with non-zero strangeness constructed within the framework of the nonlinear realization of the chiral SU(3)L x SU(3)R symmetry. The emphasis is put on the physical properties of the matter of a neutron star as well as on its internal structure. The obtained solution is particularly aimed at the problem of the construction of a theoretical model of a neutron star matter with hyperons that will give high value of the maximum mass.
Comprehensive climate system modeling on massively parallel computers
Wehner, M.F.; Eltgroth, P.G.; Mirin, A.A.; Duffy, P.B.; Caldeira, K.G.; Bolstad, J.H.; Wang, H.; Matarazzo, C.M.; Creach, U,E.
1996-10-01
A better understanding of both natural and human induced changes to the Earth`s climate is necessary for policy makers to make informed decisions regarding energy usage and other greenhouse gas producing activities. To achieve this, substantial increases in the sophistication of climate models are required. Coupling between the climate subsystems of the atmosphere, oceans, cryosphere and biosphere is only now beginning to be explored in global models. the enormous computational expenses of such models is one significant factor limiting progress. A comprehensive climate system model targeted to distributed memory massively parallel processing (MPP) computers is under development at Lawrence Livermore National Laboratory. This class of computers promises the computational power to permit the timely execution of climate models of substantially more sophistication than current generation models. Our strategy for achieving high performance on large numbers of processors is to exploit the multiple layers of parallelism naturally contained within highly coupled global climate models. The centerpiece of this strategy is the concurrent execution of multiple independently parallelized components of the climate system model. This methodology allows the assignment of an arbitrary number of processors to each of the major climate subsystems. Hence, a higher total number of processors may be efficiently used. Furthermore, load imbalances arising from the coupling of submodels may be minimized by adjusting the distribution of processors among the submodels.
Abelev, B. I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, B. D.; Arkhipkin, D.; Krueger, K.; Spinka, H. M.; Underwood, D. G.; STAR Collaboration; High Energy Physics; Univ. of Illinois; Panjab Univ.; Variable Energy Cyclotron Centre; Kent State Univ.; Particle Physic Lab.
2008-01-01
We present the first spin alignment measurements for the K*{sup 0}(892) and (1020) vector mesons produced at midrapidity with transverse momenta up to 5 GeV/c at {radical}s{sub NN} = 200 GeV at RHIC. The diagonal spin-density matrix elements with respect to the reaction plane in Au+Au collisions are {rho}{sub 00} = 0.32 {+-} 0.04 (stat) {+-} 0.09 (syst) for the K*{sup 0} (0.8 < p{sub T} < 5.0 GeV/c) and {rho}{sub 00} = 0.34 {+-} 0.02 (stat) {+-} 0.03 (syst) for the {phi} (0.4 < p{sub T} < 5.0 GeV/c) and are constant with transverse momentum and collision centrality. The data are consistent with the unpolarized expectation of 1/3 and thus no evidence is found for the transfer of the orbital angular momentum of the colliding system to the vector-meson spins. Spin alignments for K*{sup 0} and {phi} in Au+Au collisions were also measured with respect to the particle's production plane. The {phi} result, {rho}{sub 00} = 0.41 {+-} 0.02 (stat) {+-} 0.04 (syst), is consistent with that in p+p collisions, {rho}{sub 00} = 0.39 {+-} 0.03 (stat) {+-} 0.06 (syst), also measured in this work. The measurements thus constrain the possible size of polarization phenomena in the production dynamics of vector mesons.
Massive Yang-Mills for vector and axial-vector spectral functions at finite temperature
NASA Astrophysics Data System (ADS)
Hohler, Paul M.; Rapp, Ralf
2016-05-01
The hadronic mechanism which leads to chiral symmetry restoration is explored in the context of the ρπa1 system using Massive Yang-Mills, a hadronic effective theory which governs their microscopic interactions. In this approach, vector and axial-vector mesons are implemented as gauge bosons of a local chiral gauge group. We have previously shown that this model can describe the experimentally measured vector and axial-vector spectral functions in vacuum. Here, we carry the analysis to finite temperatures by evaluating medium effects in a pion gas and calculating thermal spectral functions. We find that the spectral peaks in both channels broaden along with a noticeable downward mass shift in the a1 spectral peak and negligible movement of the ρ peak. The approach toward spectral function degeneracy is accompanied by a reduction of chiral order parameters, i.e., the pion decay constant and scalar condensate. Our findings suggest a mechanism where the chiral mass splitting induced in vacuum is burned off. We explore this mechanism and identify future investigations which can further test it.
Modeling the Asymmetric Wind of Massive LBV Binary MWC 314
NASA Astrophysics Data System (ADS)
Lobel, A.; Groh, J.; Torres Dozinel, K.; Gorlova, N.; Martayan, C.; Raskin, G.; Van Winckel, H.; Prins, S.; Pessemier, W.; Waelkens, C.; Frémat, Y.; Hensberge, H.; Dummortier, L.; Jorissen, A.; Van Eck, S.; Lehmann, H.
2012-12-01
Spectroscopic monitoring with Mercator-HERMES over the past two years reveals that MWC 314 is a massive binary system composed of an early B-type primary LBV star and a less-luminous supergiant companion. We determine an orbital period Porb of 60.85 d from optical S II and Ne I absorption lines observed in this single-lined spectroscopic binary. We find an orbital eccentricity of e = 0.26, and a large amplitude of the radial velocity curve of 80.6 km s-1. The ASAS V light-curve during our spectroscopic monitoring reveals two brightness minima (ΔV = 0.1 mag) over the orbital period due to partial eclipses at an orbital inclination angle of ˜ 70°. We find a clear correlation between the orbital phases and the detailed shapes of optical and near-IR P Cygni-type line profiles of He I, Si II, and double- or triple-peaked stationary cores of prominent Fe II emission lines. A preliminary 3-D radiative transfer model computed with Wind3D shows that the periodic P Cygni line profile variability results from an asymmetric common-envelope wind with enhanced density (or line opacity) in the vicinity of the LBV primary. The variable orientation of the inner LBV wind region due to the orbital motion produces variable P Cygni line profiles (with wind velocities of ˜ 200 km s-1) between orbital phases φ = 0.65 to 0.85, while weak inverse P Cygni profiles are observed half an orbital period later around φ = 0.15 to 0.35. We do not observe optical or near-IR He II, C III, and Si III lines, signaling that the LBV's spectral type is later than B0. Detailed modeling of the asymmetrical wind properties of massive binary MWC 314 provides important new physical information about the most luminous hot (binary) stars such as η Carinae.
Modeling Broadband X-Ray Absorption of Massive Star Winds
NASA Technical Reports Server (NTRS)
Leutenegger, Maurice A.; Cohen,David H.; Zsargo, Janos; Martell, Erin M.; MacArthur, James P.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John
2010-01-01
We present a method for computing the net transition of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral ISM tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype cars largely be understood as a wind absorption effect.
MODELING BROADBAND X-RAY ABSORPTION OF MASSIVE STAR WINDS
Leutenegger, Maurice A.; Zsargo, Janos; Martell, Erin M.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John
2010-08-20
We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength-dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral interstellar medium (ISM) tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype can largely be understood as a wind absorption effect.
1-D Modeling of Massive Particle Injection (MPI) in Tokamaks
NASA Astrophysics Data System (ADS)
Wu, W.; Parks, P. B.; Izzo, V. A.
2008-11-01
A 1-D Fast Current Quench (FCQ) model is developed to study current evolution and runaway electron suppression under massive density increase. The model consists of coupled toroidal electric field and energy equations, and it is solved numerically for DIII-D and ITER operating conditions. Simulation results suggest that fast shutdown by D2 liquid jet/pellet injection is in principle achievable for the desired plasma cooling time (˜15 ms for DIII-D and ˜50 ms for ITER) under ˜150x or higher densification. The current density and pressure profile are practically unaltered during the initial phase of jet propagation when dilution cooling dominates. With subsequent radiation cooling, the densified discharge enters the strongly collisional regime where Pfirsch-Schluter thermal diffusion can inhibit current contraction on the magnetic axis. Often the 1/1 kink instability, addressed by Kadomtsev's magnetic reconnection model, can be prevented. Our results are compared with NIMROD simulations in which the plasma is suddenly densified by ˜100x and experiences instantaneous dilution cooling, allowing for use of actual (lower) Lundquist numbers.
mpdcm: A toolbox for massively parallel dynamic causal modeling.
Aponte, Eduardo A; Raman, Sudhir; Sengupta, Biswa; Penny, Will D; Stephan, Klaas E; Heinzle, Jakob
2016-01-15
Dynamic causal modeling (DCM) for fMRI is an established method for Bayesian system identification and inference on effective brain connectivity. DCM relies on a biophysical model that links hidden neuronal activity to measurable BOLD signals. Currently, biophysical simulations from DCM constitute a serious computational hindrance. Here, we present Massively Parallel Dynamic Causal Modeling (mpdcm), a toolbox designed to address this bottleneck. mpdcm delegates the generation of simulations from DCM's biophysical model to graphical processing units (GPUs). Simulations are generated in parallel by implementing a low storage explicit Runge-Kutta's scheme on a GPU architecture. mpdcm is publicly available under the GPLv3 license. We found that mpdcm efficiently generates large number of simulations without compromising their accuracy. As applications of mpdcm, we suggest two computationally expensive sampling algorithms: thermodynamic integration and parallel tempering. mpdcm is up to two orders of magnitude more efficient than the standard implementation in the software package SPM. Parallel tempering increases the mixing properties of the traditional Metropolis-Hastings algorithm at low computational cost given efficient, parallel simulations of a model. Future applications of DCM will likely require increasingly large computational resources, for example, when the likelihood landscape of a model is multimodal, or when implementing sampling methods for multi-subject analysis. Due to the wide availability of GPUs, algorithmic advances can be readily available in the absence of access to large computer grids, or when there is a lack of expertise to implement algorithms in such grids. Copyright © 2015 Elsevier B.V. All rights reserved.
Efficiently modeling neural networks on massively parallel computers
NASA Technical Reports Server (NTRS)
Farber, Robert M.
1993-01-01
Neural networks are a very useful tool for analyzing and modeling complex real world systems. Applying neural network simulations to real world problems generally involves large amounts of data and massive amounts of computation. To efficiently handle the computational requirements of large problems, we have implemented at Los Alamos a highly efficient neural network compiler for serial computers, vector computers, vector parallel computers, and fine grain SIMD computers such as the CM-2 connection machine. This paper describes the mapping used by the compiler to implement feed-forward backpropagation neural networks for a SIMD (Single Instruction Multiple Data) architecture parallel computer. Thinking Machines Corporation has benchmarked our code at 1.3 billion interconnects per second (approximately 3 gigaflops) on a 64,000 processor CM-2 connection machine (Singer 1990). This mapping is applicable to other SIMD computers and can be implemented on MIMD computers such as the CM-5 connection machine. Our mapping has virtually no communications overhead with the exception of the communications required for a global summation across the processors (which has a sub-linear runtime growth on the order of O(log(number of processors)). We can efficiently model very large neural networks which have many neurons and interconnects and our mapping can extend to arbitrarily large networks (within memory limitations) by merging the memory space of separate processors with fast adjacent processor interprocessor communications. This paper will consider the simulation of only feed forward neural network although this method is extendable to recurrent networks.
cellGPU: Massively parallel simulations of dynamic vertex models
NASA Astrophysics Data System (ADS)
Sussman, Daniel M.
2017-10-01
Vertex models represent confluent tissue by polygonal or polyhedral tilings of space, with the individual cells interacting via force laws that depend on both the geometry of the cells and the topology of the tessellation. This dependence on the connectivity of the cellular network introduces several complications to performing molecular-dynamics-like simulations of vertex models, and in particular makes parallelizing the simulations difficult. cellGPU addresses this difficulty and lays the foundation for massively parallelized, GPU-based simulations of these models. This article discusses its implementation for a pair of two-dimensional models, and compares the typical performance that can be expected between running cellGPU entirely on the CPU versus its performance when running on a range of commercial and server-grade graphics cards. By implementing the calculation of topological changes and forces on cells in a highly parallelizable fashion, cellGPU enables researchers to simulate time- and length-scales previously inaccessible via existing single-threaded CPU implementations. Program Files doi:http://dx.doi.org/10.17632/6j2cj29t3r.1 Licensing provisions: MIT Programming language: CUDA/C++ Nature of problem: Simulations of off-lattice "vertex models" of cells, in which the interaction forces depend on both the geometry and the topology of the cellular aggregate. Solution method: Highly parallelized GPU-accelerated dynamical simulations in which the force calculations and the topological features can be handled on either the CPU or GPU. Additional comments: The code is hosted at https://gitlab.com/dmsussman/cellGPU, with documentation additionally maintained at http://dmsussman.gitlab.io/cellGPUdocumentation
Chronology protection in Galileon models and massive gravity
Burrage, Clare; Rham, Claudia de; Heisenberg, Lavinia; Tolley, Andrew J. E-mail: claudia.deRham@case.edu E-mail: andrew.j.tolley@case.edu
2012-07-01
Galileon models are a class of effective field theories that have recently received much attention. They arise in the decoupling limit of theories of massive gravity, and in some cases they have been treated in their own right as scalar field theories with a specific nonlinearly realized global symmetry (Galilean transformation). It is well known that in the presence of a source, these Galileon theories admit superluminal propagating solutions, implying that as quantum field theories they must admit a different notion of causality than standard local Lorentz invariant theories. We show that in these theories it is easy to construct closed timelike curves (CTCs) within the naive regime of validity of the effective field theory. However, on closer inspection we see that the CTCs could never arise since the Galileon inevitably becomes infinitely strongly coupled at the onset of the formation of a CTC. This implies an infinite amount of backreaction, first on the background for the Galileon field, signaling the break down of the effective field theory, and subsequently on the spacetime geometry, forbidding the formation of the CTC. Furthermore the background solution required to create CTCs becomes unstable with an arbitrarily fast decay time. Thus Galileon theories satisfy a direct analogue of Hawking's chronology protection conjecture.
Modeling and analysing massive star spectra: recent advances
NASA Astrophysics Data System (ADS)
Hamann, Wolf-Rainer; Todt, Helge; Sander, Andreas; Hainich, Rainer; Shenar, Tomer; Oskinova, Lidia
2013-06-01
Depending on their mass-loss rate, the spectra of massive stars are more or less formed in the expanding parts of their atmosphere, i.e. in the stellar wind. Over decades we have developed a sophisticated non-LTE code for modeling such spectra adequately. Originally, the "Potsdam WR PoWR" code aimed at Wolf-Rayet stars with their emission-line dominated spectra. Meanwhile we have added a more detailed treatment of the lower, nearly static parts of the atmosphere, including pressure broadening of lines. This extends the applicability of the models to spectra showing both, photospheric absorption lines and stellar wind features, e.g. from O and B-type stars. The ionizing effect of X-rays, which are intrinsically produced in stellar winds, can be taken into account. Instead of a one-temperature plasma, a power-law distribution of the X-ray emission measure can be chosen and gives the best fit of the EUV spectral energy distribution. The effect of rotation on the emergent spectrum can be simulated under suitable assumptions on the angular motions in the wind. When clumping is accounted for in the approximation of optically thin structures, this leads to a reduction of empirical mass-loss rates when determined from recombination lines. A more general, but not fully consistent formalism has been incorporated to account for the effect of "macroclumping" on resonance lines. PoWR calculations were also combined with a 3-D Monte Carlo code for resonance line scattering in a structured stellar wind. A formalism has been developed to establish the hydrodynamically consistent solution for radiation-driven winds, including all multiple-scattering effects that are essential e.g. for WR stars, but this branch of the code is not ready yet for routinely use. PoWR models have been used extensively for analyzing WR stars in the Galaxy and the Magellanic Clouds, and for a couple of OB-type stars and LBVs. An increasing number of models is made available via internet.
Properties of young massive clusters obtained with different massive-star evolutionary models
NASA Astrophysics Data System (ADS)
Wofford, Aida; Charlot, Stéphane
We undertake a comprehensive comparative test of seven widely-used spectral synthesis models using multi-band HST photometry of a sample of eight YMCs in two galaxies. We provide a first quantitative estimate of the accuracies and uncertainties of new models, show the good progress of models in fitting high-quality observations, and highlight the need of further comprehensive comparative tests.
Massive quiver matrix models for massive charged particles in AdS
Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric
2016-01-11
Here, we present a new class of N = 4 supersymmetric quiver matrix models and argue that it describes the stringy low-energy dynamics of internally wrapped D-branes in four-dimensional anti-de Sitter (AdS) flux compactifications. The Lagrangians of these models differ from previously studied quiver matrix models by the presence of mass terms, associated with the AdS gravitational potential, as well as additional terms dictated by supersymmetry. These give rise to dynamical phenomena typically associated with the presence of fluxes, such as fuzzy membranes, internal cyclotron motion and the appearance of confining strings. We also show how these models can bemore » obtained by dimensional reduction of four-dimensional supersymmetric quiver gauge theories on a three-sphere.« less
Massive quiver matrix models for massive charged particles in AdS
Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric
2016-01-11
Here, we present a new class of N = 4 supersymmetric quiver matrix models and argue that it describes the stringy low-energy dynamics of internally wrapped D-branes in four-dimensional anti-de Sitter (AdS) flux compactifications. The Lagrangians of these models differ from previously studied quiver matrix models by the presence of mass terms, associated with the AdS gravitational potential, as well as additional terms dictated by supersymmetry. These give rise to dynamical phenomena typically associated with the presence of fluxes, such as fuzzy membranes, internal cyclotron motion and the appearance of confining strings. We also show how these models can be obtained by dimensional reduction of four-dimensional supersymmetric quiver gauge theories on a three-sphere.
NASA Astrophysics Data System (ADS)
Frisullo, Valeria
This thesis is a study of the photoproduction of light and charmed-anticharmed mesons, using data collected by the FOCUS experiment. FOCUS is a fixed target photoproduction experiment at Fermi National Accelerator Laboratory (Fermi-lab), that collected data during 1996-1997. The experiment had a dimuon trigger which allowed us to obtain a very large sample of dimuon events. The first analysis focuses on the study of the low mass vector mesons rho, o and φ, and provides the first high statistics measurement of the rho -- φ and rho -- o interference phases using muons. Attempts to determine such parameters, necessary for a better understanding of the production mechanisms of these vector mesons, date back to the end of the '60's, but a consistent analysis using leptonic final states ( e+e- or mu +mu-) is still missing. Our results are: frf=-31.2+/- 26.8∘a ndfrw= 184.5+/-3.5+/-3.1∘ . Our second analysis studies the psi' charmonium state and determines its branching fraction (BF) into the mu+mu- decay channel. The technique used to extract the BFpsi'→mu +mu- consists of measuring the yield of the psi' → mu+mu- decay (Y2b) relative to the yield of psi' → J/psipi+pi -, where the J/psi decays in mu +mu- (Y4 b). Fitting the psi' peak in the mu+mu - and mu+mu- pi +pi- mass plots, we report signal event yields of Y2b = 563 +/- 35 and Y4b = 1262 +/- 39. These measurements allow us to evaluate the psi' branching fraction as: BFy'→m+m-= 7.51+/-0.55stat+/- 0.55sys x10-3. This result significantly improves the precision of the world average value.
NASA Astrophysics Data System (ADS)
Wofford, Aida; Charlot, Stéphane; Eldridge, John
2015-08-01
We compute libraries of stellar + nebular spectra of populations of coeval stars with ages of <100 Myr and metallicities of Z=0.001 to 0.040, using different sets of massive-star evolution tracks, i.e., new Padova tracks for single non-rotating stars, the Geneva tracks for single non-rotating and rotating stars, and the Auckland tracks for single non-rotating and binary stars. For the stellar component, we use population synthesis codes galaxev, starburst99, and BPASS, depending on the set of tracks. For the nebular component we use photoionization code cloudy. From these spectra, we obtain magnitudes in filters F275W, F336W, F438W, F547M, F555W, F657N, and F814W of the Hubble Space Telescope (HST) Wide Field Camera Three. We use i) our computed magnitudes, ii) new multi-band photometry of massive-star clusters in nearby (<11 Mpc) galaxies spanning the metallicity range 12+log(O/H)=7.2-9.2, observed as part of HST programs 13364 (PI Calzetti) and 13773 (PI Chandar), and iii) Bayesian inference to a) establish how well the different models are able to constrain the metallicities, extinctions, ages, and masses of the star clusters, b) quantify differences in the cluster properties obtained with the different models, and c) assess how properties of lower-mass clusters are affected by the stochastic sampling of the IMF. In our models, the stellar evolution tracks, stellar atmospheres, and nebulae have similar chemical compositions. Different metallicities are available with different sets of tracks and we compare results from models of similar metallicities. Our results have implications for studies of the formation and evolution of star clusters, the cluster age and mass functions, and the star formation histories of galaxies.
Network-oriented massive spatio-temporal data model and its applications
NASA Astrophysics Data System (ADS)
Liu, Renyi; Liu, Nan; Bao, Weizheng; Zhu, Yan
2006-10-01
It is foundation and key of developing GIS platforms of new generation to study the network-oriented massive spatial and spatio-temporal data model. But the research has met many difficulties. The paper combines two models of massive spatial data and spatio-temporal data seemed to be independent to study together in theory and technique. On the base of analyzing the limitations of present geographical spatial data model and spatio-temporal data model, a new model with characteristics of new generation's GIS platform, that is, Feature-Oriented Massive Spatio-temporal Object Tree (FOMSOT) with four-tier architectures is presented. The FOMSOT breaks down the constraint of map layer. It can deal with the massive spatio-temporal data better. The dynamic multi-base state with amendment (DMSA), fast index of base state with amendment in section, storage factors of variable granularity (SFVG) are used in FOMSOT which can manage the massive spatio-temporal data in high efficiency. A prototype "LyranMap" of new generation's GIS platform with the theory and technical method of FOMSOT has been realized, and it has been used in some application systems, for example, the land planning system "LandPlanner", land investigation system "LandExplorer" and land cadastral system "LandReGIS". These verify the correctness and effectiveness of the FOMSOT.
Hypernuclei and massive neutron stars
NASA Astrophysics Data System (ADS)
Fortin, M.; Avancini, S. S.; Providência, C.; Vidaña, I.
2017-06-01
V at saturation for the gω Λ coupling given by the SU(6) symmetry, being of the order of the values generally used in the literature. On the other hand, the Λ potential in Λ matter varies between -14 and -8 MeV, taking for vector mesons couplings the SU(6) values, at variance with generally employed values between -1 and -5 MeV. If the SU(6) constraint is relaxed and the vector meson couplings to hyperons are kept to values not larger than those of nucleons, then values between -13 and +9 MeV are obtained.
A new interpretation of Bethe ansatz solutions for massive Thirring model
Fujita, T.; Sekiguchi, Y.; Yamamoto, K.
1997-04-01
We reexamine Bethe ansatz solutions of the massive Thirring model. We solve equations of periodic boundary conditions numerically without referring to the density of states. It is found that there is only one bound state in the massive Thirring model. The bound state spectrum obtained here is consistent with Fujita-Ogura{close_quote}s solutions of the infinite momentum frame prescription. Further, it turns out that there exist no solutions for {ital string}-like configurations. Instead, we find boson-boson scattering states in two-particle two-hole configurations where all the rapidity variables turn out to be real. {copyright} 1997 Academic Press, Inc.
Singularity-free RW viscous fluid cosmological models in presence of massive scalar fields
NASA Astrophysics Data System (ADS)
Roy, A. R.; Maiti, P. K.
1994-09-01
Singularity-free Robertson-Walker cosmological models (RWCM) are developed by considering the cosmic matter as composed of an interacting viscous fluid (with zero bulk viscosity) and a massive scalar (meson) field. Solutions are obtained for two different cases, viz., when the Hubble's parameter H is epoch independent and when H is epoch dependent. A solution corresponding to RWCM with only the massive scalar field as the matter content is also presented. The essential physical behavior of the models developed are discussed in detail.
Scientific development of a massively parallel ocean climate model. Final report
Semtner, A.J.; Chervin, R.M.
1996-09-01
Over the last three years, very significant advances have been made in refining the grid resolution of ocean models and in improving the physical and numerical treatments of ocean hydrodynamics. Some of these advances have occurred as a result of the successful transition of ocean models onto massively parallel computers, which has been led by Los Alamos investigators. Major progress has been made in simulating global ocean circulation and in understanding various ocean climatic aspects such as the effect of wind driving on heat and freshwater transports. These steps have demonstrated the capability to conduct realistic decadal to century ocean integrations at high resolution on massively parallel computers.
Ocean Modeling and Visualization on Massively Parallel Computer
NASA Technical Reports Server (NTRS)
Chao, Yi; Li, P. Peggy; Wang, Ping; Katz, Daniel S.; Cheng, Benny N.
1997-01-01
Climate modeling is one of the grand challenges of computational science, and ocean modeling plays an important role in both understanding the current climatic conditions and predicting future climate change.
Ocean Modeling and Visualization on Massively Parallel Computer
NASA Technical Reports Server (NTRS)
Chao, Yi; Li, P. Peggy; Wang, Ping; Katz, Daniel S.; Cheng, Benny N.
1997-01-01
Climate modeling is one of the grand challenges of computational science, and ocean modeling plays an important role in both understanding the current climatic conditions and predicting future climate change.
Self-consistent Models of Strong Interaction with Chiral Symmetry
DOE R&D Accomplishments Database
Nambu, Y.; Pascual, P.
1963-04-01
Some simple models of (renormalizable) meson-nucleon interaction are examined in which the nucleon mass is entirely due to interaction and the chiral ( gamma {sub 5}) symmetry is "broken'' to become a hidden symmetry. It is found that such a scheme is possible provided that a vector meson is introduced as an elementary field. (auth)
Main sequence models for massive zero-metal stars
NASA Technical Reports Server (NTRS)
Cary, N.
1974-01-01
Zero-age main-sequence models for stars of 20, 10, 5, and 2 solar masses with no heavy elements are constructed for three different possible primordial helium abundances: Y=0.00, Y=0.23, and Y=0.30. The latter two values of Y bracket the range of primordial helium abundances cited by Wagoner. With the exceptions of the two 20 solar mass models that contain helium, these models are found to be self-consistent in the sense that the formation of carbon through the triple-alpha process during premain sequence contraction is not sufficient to bring the CN cycle into competition with the proton-proton chain on the ZAMS. The zero-metal models of the present study have higher surface and central temperatures, higher central densities, smaller radii, and smaller convective cores than do the population I models with the same masses.
Main sequence models for massive zero-metal stars
NASA Technical Reports Server (NTRS)
Cary, N.
1974-01-01
Zero-age main-sequence models for stars of 20, 10, 5, and 2 solar masses with no heavy elements are constructed for three different possible primordial helium abundances: Y=0.00, Y=0.23, and Y=0.30. The latter two values of Y bracket the range of primordial helium abundances cited by Wagoner. With the exceptions of the two 20 solar mass models that contain helium, these models are found to be self-consistent in the sense that the formation of carbon through the triple-alpha process during premain sequence contraction is not sufficient to bring the CN cycle into competition with the proton-proton chain on the ZAMS. The zero-metal models of the present study have higher surface and central temperatures, higher central densities, smaller radii, and smaller convective cores than do the population I models with the same masses.
Massively parallel implementation of a high order domain decomposition equatorial ocean model
Ma, H.; McCaffrey, J.W.; Piacsek, S.
1999-06-01
The present work is about the algorithms and parallel constructs of a spectral element equatorial ocean model. It shows that high order domain decomposition ocean models can be efficiently implemented on massively parallel architectures, such as the Connection Machine Model CM5. The optimized computational efficiency of the parallel spectral element ocean model comes not only from the exponential convergence of the numerical solution, but also from the work-intensive, medium-grained, geometry-based data parallelism. The data parallelism is created to efficiently implement the spectral element ocean model on the distributed-memory massively parallel computer, which minimizes communication among processing nodes. Computational complexity analysis is given for the parallel algorithm of the spectral element ocean model, and the model's parallel performance on the CM5 is evaluated. Lastly, results from a simulation of wind-driven circulation in low-latitude Atlantic Ocean are described.
MASSIVELY PARALLEL IMPLEMENTATION OF A HIGH ORDER DOMAIN DECOMPOSITION EQUATORIAL OCEAN MODEL
MA,H.; MCCAFFREY,J.W.; PIACSEK,S.
1998-07-15
The present work is about the algorithms and parallel constructs of a spectral element equatorial ocean model. It shows that high order domain decomposition ocean models can be efficiently implemented on massively parallel architectures, such as the Connection Machine Model CM5. The optimized computational efficiency of the parallel spectral element ocean model comes not only from the exponential convergence of the numerical solution, but also from the work-intensive, medium-grained, geometry-based data parallelism. The data parallelism is created to efficiently implement the spectral element ocean model on the distributed-memory massively parallel computer, which minimizes communication among processing nodes. Computational complexity analysis is given for the parallel algorithm of the spectral element ocean model, and the model's parallel performance on the CM5 is evaluated. Lastly, results from a simulation of wind-driven circulation in low-latitude Atlantic ocean are described.
Magnetic Models of Circumstellar Clouds around Massive Stars
NASA Astrophysics Data System (ADS)
Owocki, S.; Townsend, R.; Ud-Doula, A.
2008-08-01
This talk reviewed recent efforts to develop dynamical models for the effects of a surface dipole field on radiatively driven wind outflows. One particular project applies magnetohydrodynamic (MHD) simulations of a Magnetically Confined Wind Shock (MCWS) model (originally developed by Babel & Montmerle 1997) to explain X-ray emission observed by Rosat (Gagné et al. 1997) from the magnetic O7V star θ^{1 Ori C.
Biomimetic Models for An Ecological Approach to Massively-Deployed Sensor Networks
NASA Technical Reports Server (NTRS)
Jones, Kennie H.; Lodding, Kenneth N.; Olariu, Stephan; Wilson, Larry; Xin, Chunsheng
2005-01-01
Promises of ubiquitous control of the physical environment by massively-deployed wireless sensor networks open avenues for new applications that will redefine the way we live and work. Due to small size and low cost of sensor devices, visionaries promise systems enabled by deployment of massive numbers of sensors ubiquitous throughout our environment working in concert. Recent research has concentrated on developing techniques for performing relatively simple tasks with minimal energy expense, assuming some form of centralized control. Unfortunately, centralized control is not conducive to parallel activities and does not scale to massive size networks. Execution of simple tasks in sparse networks will not lead to the sophisticated applications predicted. We propose a new way of looking at massively-deployed sensor networks, motivated by lessons learned from the way biological ecosystems are organized. We demonstrate that in such a model, fully distributed data aggregation can be performed in a scalable fashion in massively deployed sensor networks, where motes operate on local information, making local decisions that are aggregated across the network to achieve globally-meaningful effects. We show that such architectures may be used to facilitate communication and synchronization in a fault-tolerant manner, while balancing workload and required energy expenditure throughout the network.
Biomimetic Models for An Ecological Approach to Massively-Deployed Sensor Networks
NASA Technical Reports Server (NTRS)
Jones, Kennie H.; Lodding, Kenneth N.; Olariu, Stephan; Wilson, Larry; Xin, Chunsheng
2005-01-01
Promises of ubiquitous control of the physical environment by massively-deployed wireless sensor networks open avenues for new applications that will redefine the way we live and work. Due to small size and low cost of sensor devices, visionaries promise systems enabled by deployment of massive numbers of sensors ubiquitous throughout our environment working in concert. Recent research has concentrated on developing techniques for performing relatively simple tasks with minimal energy expense, assuming some form of centralized control. Unfortunately, centralized control is not conducive to parallel activities and does not scale to massive size networks. Execution of simple tasks in sparse networks will not lead to the sophisticated applications predicted. We propose a new way of looking at massively-deployed sensor networks, motivated by lessons learned from the way biological ecosystems are organized. We demonstrate that in such a model, fully distributed data aggregation can be performed in a scalable fashion in massively deployed sensor networks, where motes operate on local information, making local decisions that are aggregated across the network to achieve globally-meaningful effects. We show that such architectures may be used to facilitate communication and synchronization in a fault-tolerant manner, while balancing workload and required energy expenditure throughout the network.
LOW MACH NUMBER MODELING OF CORE CONVECTION IN MASSIVE STARS
Gilet, C.; Almgren, A. S.; Bell, J. B.; Nonaka, A.; Woosley, S. E.; Zingale, M.
2013-08-20
This work presents three-dimensional simulations of core convection in a 15 M{sub Sun} star halfway through its main sequence lifetime. To perform the necessary long-time calculations, we use the low Mach number code MAESTRO, with initial conditions taken from a one-dimensional stellar model. We first identify several key factors that the one-dimensional initial model must satisfy to ensure efficient simulation of the convection process. We then use the three-dimensional simulations to examine the effects of two common modeling choices on the resulting convective flow: using a fixed composition approximation and using a reduced domain size. We find that using a fixed composition model actually increases the computational cost relative to using the full multi-species model because the fixed composition system takes longer to reach convection that is in a quasi-static state. Using a reduced (octant rather than full sphere) simulation domain yields flow with statistical properties that are within a factor of two of the full sphere simulation values. Both the octant and full sphere simulations show similar mixing across the convection zone boundary that is consistent with the turbulent entrainment model. However, the global character of the flow is distinctly different in the octant simulation, showing more rapid changes in the large-scale structure of the flow and thus a more isotropic flow on average.
Low Mach Number Modeling of Core Convection in Massive Stars
NASA Astrophysics Data System (ADS)
Gilet, C.; Almgren, A. S.; Bell, J. B.; Nonaka, A.; Woosley, S. E.; Zingale, M.
2013-08-01
This work presents three-dimensional simulations of core convection in a 15 M ⊙ star halfway through its main sequence lifetime. To perform the necessary long-time calculations, we use the low Mach number code MAESTRO, with initial conditions taken from a one-dimensional stellar model. We first identify several key factors that the one-dimensional initial model must satisfy to ensure efficient simulation of the convection process. We then use the three-dimensional simulations to examine the effects of two common modeling choices on the resulting convective flow: using a fixed composition approximation and using a reduced domain size. We find that using a fixed composition model actually increases the computational cost relative to using the full multi-species model because the fixed composition system takes longer to reach convection that is in a quasi-static state. Using a reduced (octant rather than full sphere) simulation domain yields flow with statistical properties that are within a factor of two of the full sphere simulation values. Both the octant and full sphere simulations show similar mixing across the convection zone boundary that is consistent with the turbulent entrainment model. However, the global character of the flow is distinctly different in the octant simulation, showing more rapid changes in the large-scale structure of the flow and thus a more isotropic flow on average.
Spatially flat R-W cosmological model with massive scalar field
NASA Astrophysics Data System (ADS)
Varma, M. N.
1989-11-01
An exact solution for the spatially flat Robertson-Walker (R-W) cosmological model with massive scalar field is obtained, using Einstein's field equations in the presence of a cosmological constant. This solution varies in the sense that the Hubble parameter is epoch-dependent while it is epoch-independent in the solution obtained by Rao et al. (1976).
Analytical model of massive Pulsar J0348+0432
NASA Astrophysics Data System (ADS)
Kayum Jafry, M. Abdul; Molla, Sajahan; Islam, Rabiul; Kalam, Mehedi
2017-10-01
In this article we propose a model for the Pulsar J0348+0432 (Antoniadis et al. in Science 340:1233232, 2013) in a compact relativistic binary. Here we investigate the physical properties of the Pulsar J0348+0432 by using the Finch and Skea (Class. Quantum Gravity 4:467, 1989) metric. Using our model, we evaluate central density (ρ0), surface density (ρb), central pressure (p 0), surface redshift (Z s) and probable radius of the above mentioned compact object, which is very much consistent with reported data. We also obtain a possible equation of state (EoS) of the pulsar which is physically acceptable.
Wall-layer model for LES with massive separation
NASA Astrophysics Data System (ADS)
Fakhari, Ahmad; Armenio, Vincenzo; Roman, Federico
2016-11-01
Currently, Wall Functions (WF) work well under specific conditions, mostly exhibit drawbacks specially in flows with separation beyond curvatures. In this work, we propose a more general WF which works well in attached and detached flows, in presence and absence of Immersed Boundaries (IB). First we modified an equilibrium stress WF for boundary-fitted geometry making dynamic the computation of the k (von Karman constant) of the log-law; the model was first applied to a periodic open channel flow, and then to the flow over a 2D single hill using uniform coarse grids; the model captured separation with reasonable accuracy. Thereafter IB Method by Roman et al. was improved to avoid momentum loss at the interface between the fluid-solid regions. This required calibration of interfacial eddy viscosity; also a random stochastic forcing was used in wall-normal direction to increase Reynolds stresses and improve mean velocity profile. Finally, to reproduce flow separation, a simplified boundary layer equation was applied to construct velocity at near wall computational nodes. The new scheme was tested on the 2D single hill and periodic hills applying Cartesian and curvilinear grids; good agreement with references was obtained with reduction in cost and complexity. Financial support from project COSMO "CFD open source per opera morta" PAR FSC 2007-2013, Friuli Venezia Giulia.
A model for the massive binary V340 Muscae
NASA Astrophysics Data System (ADS)
Hauck, Norbert
2016-02-01
A synthetic light curve has been fitted to photometric data from the ASAS-3 database. The parameters of the best solution are well consistent with those derived from stellar models for both components for an initial metallicity Z=0.020 and a common age of 5 Myr. Therefore, we can reliably estimate the absolute dimensions of this close eclipsing binary system. Apparently, the O-type primary star has a mass of about 22.65 Msun and a radius of 10.35 Rsun. For the secondary star, likely a late B-type dwarf, we obtain about 3.1 Msun and 2.1 Rsun. Their mass ratio of about 0.138 might be the lowest found so far in O-type binaries. [English and German online-version of this paper available under www.bav-astro.eu/rb/rb2016-2/1.html].
Constructing Neuronal Network Models in Massively Parallel Environments.
Ippen, Tammo; Eppler, Jochen M; Plesser, Hans E; Diesmann, Markus
2017-01-01
Recent advances in the development of data structures to represent spiking neuron network models enable us to exploit the complete memory of petascale computers for a single brain-scale network simulation. In this work, we investigate how well we can exploit the computing power of such supercomputers for the creation of neuronal networks. Using an established benchmark, we divide the runtime of simulation code into the phase of network construction and the phase during which the dynamical state is advanced in time. We find that on multi-core compute nodes network creation scales well with process-parallel code but exhibits a prohibitively large memory consumption. Thread-parallel network creation, in contrast, exhibits speedup only up to a small number of threads but has little overhead in terms of memory. We further observe that the algorithms creating instances of model neurons and their connections scale well for networks of ten thousand neurons, but do not show the same speedup for networks of millions of neurons. Our work uncovers that the lack of scaling of thread-parallel network creation is due to inadequate memory allocation strategies and demonstrates that thread-optimized memory allocators recover excellent scaling. An analysis of the loop order used for network construction reveals that more complex tests on the locality of operations significantly improve scaling and reduce runtime by allowing construction algorithms to step through large networks more efficiently than in existing code. The combination of these techniques increases performance by an order of magnitude and harnesses the increasingly parallel compute power of the compute nodes in high-performance clusters and supercomputers.
Constructing Neuronal Network Models in Massively Parallel Environments
Ippen, Tammo; Eppler, Jochen M.; Plesser, Hans E.; Diesmann, Markus
2017-01-01
Recent advances in the development of data structures to represent spiking neuron network models enable us to exploit the complete memory of petascale computers for a single brain-scale network simulation. In this work, we investigate how well we can exploit the computing power of such supercomputers for the creation of neuronal networks. Using an established benchmark, we divide the runtime of simulation code into the phase of network construction and the phase during which the dynamical state is advanced in time. We find that on multi-core compute nodes network creation scales well with process-parallel code but exhibits a prohibitively large memory consumption. Thread-parallel network creation, in contrast, exhibits speedup only up to a small number of threads but has little overhead in terms of memory. We further observe that the algorithms creating instances of model neurons and their connections scale well for networks of ten thousand neurons, but do not show the same speedup for networks of millions of neurons. Our work uncovers that the lack of scaling of thread-parallel network creation is due to inadequate memory allocation strategies and demonstrates that thread-optimized memory allocators recover excellent scaling. An analysis of the loop order used for network construction reveals that more complex tests on the locality of operations significantly improve scaling and reduce runtime by allowing construction algorithms to step through large networks more efficiently than in existing code. The combination of these techniques increases performance by an order of magnitude and harnesses the increasingly parallel compute power of the compute nodes in high-performance clusters and supercomputers. PMID:28559808
NASA Astrophysics Data System (ADS)
Mead, A. J.; Heymans, C.; Lombriser, L.; Peacock, J. A.; Steele, O. I.; Winther, H. A.
2016-06-01
We present an accurate non-linear matter power spectrum prediction scheme for a variety of extensions to the standard cosmological paradigm, which uses the tuned halo model previously developed in Mead et al. We consider dark energy models that are both minimally and non-minimally coupled, massive neutrinos and modified gravitational forces with chameleon and Vainshtein screening mechanisms. In all cases, we compare halo-model power spectra to measurements from high-resolution simulations. We show that the tuned halo-model method can predict the non-linear matter power spectrum measured from simulations of parametrized w(a) dark energy models at the few per cent level for k < 10 h Mpc-1, and we present theoretically motivated extensions to cover non-minimally coupled scalar fields, massive neutrinos and Vainshtein screened modified gravity models that result in few per cent accurate power spectra for k < 10 h Mpc-1. For chameleon screened models, we achieve only 10 per cent accuracy for the same range of scales. Finally, we use our halo model to investigate degeneracies between different extensions to the standard cosmological model, finding that the impact of baryonic feedback on the non-linear matter power spectrum can be considered independently of modified gravity or massive neutrino extensions. In contrast, considering the impact of modified gravity and massive neutrinos independently results in biased estimates of power at the level of 5 per cent at scales k > 0.5 h Mpc-1. An updated version of our publicly available HMCODE can be found at https://github.com/alexander-mead/hmcode.
Massive neutrinos in the standard model and beyond
NASA Astrophysics Data System (ADS)
Thalapillil, Arun Madhav
The generation of the fermion mass hierarchy in the standard model of particle physics is a long-standing puzzle. The recent discoveries from neutrino physics suggests that the mixing in the lepton sector is large compared to the quark mixings. To understand this asymmetry between the quark and lepton mixings is an important aim for particle physics. In this regard, two promising approaches from the theoretical side are grand unified theories and family symmetries. In the first part of my thesis we try to understand certain general features of grand unified theories with Abelian family symmetries by taking the simplest SU(5) grand unified theory as a prototype. We construct an SU(5) toy model with U(1) F ⊗Z'2 ⊗Z'' 2⊗Z''' 2 family symmetry that, in a natural way, duplicates the observed mass hierarchy and mixing matrices to lowest approximation. The system for generating the mass hierarchy is through a Froggatt-Nielsen type mechanism. One idea that we use in the model is that the quark and charged lepton sectors are hierarchical with small mixing angles while the light neutrino sector is democratic with larger mixing angles. We also discuss some of the difficulties in incorporating finer details into the model without making further assumptions or adding a large scalar sector. In the second part of my thesis, the interaction of high energy neutrinos with weak gravitational fields is explored. The form of the graviton-neutrino vertex is motivated from Lorentz and gauge invariance and the non-relativistic interpretations of the neutrino gravitational form factors are obtained. We comment on the renormalization conditions, the preservation of the weak equivalence principle and the definition of the neutrino mass radius. We associate the neutrino gravitational form factors with specific angular momentum states. Based on Feynman diagrams, spin-statistics, CP invariance and symmetries of the angular momentum states in the neutrino-graviton vertex, we deduce
Numerical model of massive hydraulic fracture. Final report. [SYMFRAC1
Palmer, I.D.; Craig, H.R.; Luiskutty, C.T.
1985-03-01
This project has involved development of a hydraulic fracture simulator which calculates fracture height as a function of distance from the wellbore in a situation in which a payzone is bounded by two zones in which the minimum in-situ stress is higher (the fracture is vertical). The fracture must be highly elongated (length/height ratio approximately greater than 4) and variations in elastic modulus across zones are ignored. First, we describe the leakoff and spurt loss calculations employed in the modeling. Second, we discuss a revised version of the vertically symmetric simulator (bounding zone stresses equal). The addition of non-Newtonian flow and leakoff (including spurt loss) is described in detail. An illustrative result is given. Third, we describe in detail the vertically asymmetric simulator (bounding zone stresses not equal). To illustrate the last results, we present design calculations for a 30,000 gallon fracture, which was the first stimulation in the Multi-Well Experiment. The 80 ft fracture interval in the Paludal zone has at its upper edge a 520 psi stress contrast, and at its lower edge a 1195 psi contrast. Computed fracture height growth above and below the perforated interval, bottomhole pressure, and width profiles in vertical sections are displayed. Comparison is made with diagnostic measurements of fracture length, height, and bottomhole pressure. The appropriate computer codes are included in this report. 21 references, 11 figures, 4 tables.
VizieR Online Data Catalog: Models for massive low-Z single stars (Szecsi+, 2015)
NASA Astrophysics Data System (ADS)
Szecsi, D.; Langer, N.; Yoon, S.-C.; Sanyal, D.; de Mink, S. E.; Evans, C. J.; Dermine, T.
2015-07-01
Massive rotating single stars with an initial metal composition appropriate for the dwarf galaxy I Zw 18 ([Fe/H]=-1.7) are modelled during hydrogen burning for initial masses of 9-300M⊙ and rotational velocities of 0-900km/s. Internal mixing processes in these models were calibrated based on an observed sample of OB-type stars in the Magellanic Clouds. (4 data files).
Local Hamiltonian Monte Carlo study of the massive schwinger model, the decoupling of heavy flavours
NASA Astrophysics Data System (ADS)
Ranft, J.
1983-12-01
The massive Schwinger model with two flavours is studied using the local hamiltonian lattice Monte Carlo method. Chiral symmetry breaking is studied using the fermion condensate as order parameter. For a small ratio of the two fermion masses, degeneracy of the two flavours is found. For a large ratio of the masses, the heavy flavour decouples and the light fermion behaves like in the one flavour Schwinger model. On leave from Sektion Physik, Karl-Marx-Universität, Leipzig, GDR.
Effect of Turbulence Models on Two Massively-Separated Benchmark Flow Cases
NASA Technical Reports Server (NTRS)
Rumsey, Christopher L.
2003-01-01
Two massively-separated flow cases (the 2-D hill and the 3-D Ahmed body) were computed with several different turbulence models in the Reynolds-averaged Navier-Stokes code CFL3D as part of participation in a turbulence modeling workshop held in Poitiers, France in October, 2002. Overall, results were disappointing, but were consistent with results from other RANS codes and other turbulence models at the workshop. For the 2-D hill case, those turbulence models that predicted separation location accurately ended up yielding a too-long separation extent downstream. The one model that predicted a shorter separation extent in better agreement with LES data did so only by coincidence: its prediction of earlier reattachment was due to a too-late prediction of the separation location. For the Ahmed body, two slant angles were computed, and CFD performed fairly well for one of the cases (the larger slant angle). Both turbulence models tested in this case were very similar to each other. For the smaller slant angle, CFD predicted massive separation, whereas the experiment showed reattachment about half-way down the center of the face. These test cases serve as reminders that state- of-the-art CFD is currently not a reliable predictor of massively-separated flow physics, and that further validation studies in this area would be beneficial.
Sharma, Neelesh; Verma, R. C.; Dhir, Rohit
2011-01-01
In this paper, we investigate phenomenologically two-body weak decays of the bottom mesons emitting pseudoscalar/vector meson and a tensor meson. Form factors are obtained using the improved Isgur-Scora-Grinstein-Wise II model. Consequently, branching ratios for the Cabibbo-Kobayashi-Maskawa-favored and Cabibbo-Kobayashi-Maskawa-suppressed decays are calculated.
NASA Astrophysics Data System (ADS)
Dybalski, Wojciech; Møller, Jacob Schach
2015-11-01
We show asymptotic completeness of two-body scattering for a class of translation invariant models describing a single quantum particle (the electron) linearly coupled to a massive scalar field (bosons). Our proof is based on a recently established Mourre estimate for these models. In contrast to previous approaches, it requires no number cutoff, no restriction on the particle-field coupling strength, and no restriction on the magnitude of total momentum. Energy, however, is restricted by the two-boson threshold, admitting only scattering of a dressed electron and a single asymptotic boson. The class of models we consider include the UV-cutoff Nelson and polaron models.
Massive lepton pair production: what has QCD done to the classical Drell-Yan model
Berger, E.L.
1982-11-01
A report is presented of recent experimental and theoretical progress in studies of the production of massive lepton pairs in hadronic collisions. Among the topics discussed are deviations from scaling, the status of the proofs of factorization in the parton model, higher-order terms in the QCD expansion, the discrepancy between measured and predicted yields (K factor), high-twist terms, soft gluon effects, and transverse momentum distributions.
Regression models tolerant to massively missing data: a case study in solar-radiation nowcasting
NASA Astrophysics Data System (ADS)
Žliobaitė, I.; Hollmén, J.; Junninen, H.
2014-12-01
Statistical models for environmental monitoring strongly rely on automatic data acquisition systems that use various physical sensors. Often, sensor readings are missing for extended periods of time, while model outputs need to be continuously available in real time. With a case study in solar-radiation nowcasting, we investigate how to deal with massively missing data (around 50% of the time some data are unavailable) in such situations. Our goal is to analyze characteristics of missing data and recommend a strategy for deploying regression models which would be robust to missing data in situations where data are massively missing. We are after one model that performs well at all times, with and without data gaps. Due to the need to provide instantaneous outputs with minimum energy consumption for computing in the data streaming setting, we dismiss computationally demanding data imputation methods and resort to a mean replacement, accompanied with a robust regression model. We use an established strategy for assessing different regression models and for determining how many missing sensor readings can be tolerated before model outputs become obsolete. We experimentally analyze the accuracies and robustness to missing data of seven linear regression models. We recommend using the regularized PCA regression with our established guideline in training regression models, which themselves are robust to missing data.
Extended Nambu-Jona-Lasinio model and hidden local symmetry of low energy QCD
NASA Astrophysics Data System (ADS)
Wakamatsu, M.
1996-11-01
Using the standard auxiliary field method, we derive from the extended Nambu-Jona-Lasinio model an effective meson action containing vector and axial-vector mesons in addition to Goldstone bosons. The vector and axial-vector mesons in this effective action transform as gauge fields of hidden local symmetry Glocal=[U(n)L×U(n)R]local. Here, the realization of enlarged hidden local symmetry is accomplished via the introduction of two kinds of ``compensating'' fields. For obtaining the intrinsic-parity-violating part of the action, we generalize the standard gauged Wess-Zumino-Witten action such that it also contains two kinds of ``compensators'' in addition to the usual Goldstone bosons as well as the vector and axial-vector mesons. This generalized gauged Wess-Zumino-Witten action turns out to have Gglobal×Glocal symmetry, where Gglobal is the usual U(n)L×U(n)R global chiral symmetry while Glocal is the U(n)L×U(n)R hidden local symmetry. This means that Glocal has no gauge anomaly and its associated vector and axial-vector mesons can be regarded as gauge bosons of Glocal. The introduction of the coupling with the external electroweak fields requires us to gauge some appropriate subgroup of Gglobal. To make it consistent with the anomaly structure of QCD is a nontrivial problem. We explain how this can be done, following the recent suggestion by several authors.
Nonlinear cosmological matter power spectrum with massive neutrinos: The halo model
Abazajian, Kevork; Habib, Salman; Switzer, Eric R.; Dodelson, Scott; Heitmann, Katrin
2005-02-15
Measurements of the linear power spectrum of galaxies have placed tight constraints on neutrino masses. We extend the framework of the halo model of cosmological nonlinear matter clustering to include the effect of massive neutrino infall into cold dark matter (CDM) halos. The magnitude of the effect of neutrino clustering for three degenerate mass neutrinos with m{sub {nu}{sub i}}=0.9 eV is of order {approx}1%, within the potential sensitivity of upcoming weak lensing surveys. In order to use these measurements to further constrain--or eventually detect--neutrino masses, accurate theoretical predictions of the nonlinear power spectrum in the presence of massive neutrinos will be needed, likely only possible through high-resolution multiple particle (neutrino, CDM and baryon) simulations.
The Nonlinear cosmological matter power spectrum with massive neutrinos. 1. The Halo model
Abazajian, Kevork; Switzer, Eric R.; Dodelson, Scott; Heitmann, Katrin; Habib, Salman; /Los Alamos
2004-11-01
Measurements of the linear power spectrum of galaxies have placed tight constraints on neutrino masses. We extend the framework of the halo model of cosmological nonlinear matter clustering to include the effect of massive neutrino infall into cold dark matter (CDM) halos. The magnitude of the effect of neutrino clustering for three degenerate mass neutrinos with m{sub v{sub 1}} = 0.9 eV is of order {approx}1%, within the potential sensitivity of upcoming weak lensing surveys. In order to use these measurements to further constrain--or eventually detect--neutrino masses, accurate theoretical predictions of the nonlinear power spectrum in the presence of massive neutrinos will be needed, likely only possible through high-resolution multiple particle (neutrino, CDM and baryon) simulations.
Using numerical models of bow shocks to investigate the circumstellar medium of massive stars
NASA Astrophysics Data System (ADS)
van Marle, A. J.; Decin, L.; Cox, N. L. J.; Meliani, Z.
2015-01-01
Many massive stars travel through the interstellar medium at supersonic speeds. As a result they form bow shocks at the interface between the stellar wind. We use numerical hydrodynamics to reproduce such bow shocks numerically, creating models that can be compared to observations. In this paper we discuss the influence of two physical phenomena, interstellar magnetic fields and the presence of interstellar dust grains on the observable shape of the bow shocks of massive stars. We find that the interstellar magnetic field, though too weak to restrict the general shape of the bow shock, reduces the size of the instabilities that would otherwise be observed in the bow shock of a red supergiant. The interstellar dust grains, due to their inertia can penetrate deep into the bow shock structure of a main sequence O-supergiant, crossing over from the ISM into the stellar wind. Therefore, the dust distribution may not always reflect the morphology of the gas. This is an important consideration for infrared observations, which are dominated by dust emission. Our models clearly show, that the bow shocks of massive stars are useful diagnostic tools that can used to investigate the properties of both the stellar wind as well as the interstellar medium.
Regression models tolerant to massively missing data: a case study in solar radiation nowcasting
NASA Astrophysics Data System (ADS)
Žliobaitė, I.; Hollmén, J.; Junninen, H.
2014-07-01
Statistical models for environmental monitoring strongly rely on automatic data acquisition systems, using various physical sensors. Often, sensor readings are missing for extended periods of time while model outputs need to be continuously available in real time. With a case study in solar radiation nowcasting, we investigate how to deal with massively missing data (around 50% of the time some data are unavailable) in such situations. Our goal is to analyze the characteristics of missing data and recommend a strategy for deploying regression models, which would be robust to missing data in situations, where data are massively missing. We are after one model that performs well at all times, with and without data gaps. Due to the need to provide instantaneous outputs with minimum energy consumption for computing in the data streaming setting, we dismiss computationally demanding data imputation methods, and resort to a simple mean replacement. We use an established strategy for comparing different regression models, with the possibility of determining how many missing sensor readings can be tolerated before model outputs become obsolete. We experimentally analyze accuracies and robustness to missing data of seven linear regression models and recommend using regularized PCA regression. We recommend using our established guideline in training regression models, which themselves are robust to missing data.
Low-metallicity massive single stars with rotation. Evolutionary models applicable to I Zwicky 18
NASA Astrophysics Data System (ADS)
Szécsi, Dorottya; Langer, Norbert; Yoon, Sung-Chul; Sanyal, Debashis; de Mink, Selma; Evans, Christopher J.; Dermine, Tyl
2015-09-01
Context. Low-metallicity environments such as the early Universe and compact star-forming dwarf galaxies contain many massive stars. These stars influence their surroundings through intense UV radiation, strong winds and explosive deaths. A good understanding of low-metallicity environments requires a detailed theoretical comprehension of the evolution of their massive stars. Aims: We aim to investigate the role of metallicity and rotation in shaping the evolutionary paths of massive stars and to provide theoretical predictions that can be tested by observations of metal-poor environments. Methods: Massive rotating single stars with an initial metal composition appropriate for the dwarf galaxy I Zw 18 ([Fe/H] = -1.7) are modelled during hydrogen burning for initial masses of 9-300 M⊙ and rotational velocities of 0-900 km s-1. Internal mixing processes in these models were calibrated based on an observed sample of OB-type stars in the Magellanic Clouds. Results: Even moderately fast rotators, which may be abundant at this metallicity, are found to undergo efficient mixing induced by rotation resulting in quasi chemically-homogeneous evolution. These homogeneously-evolving models reach effective temperatures of up to 90 kK during core hydrogen burning. This, together with their moderate mass-loss rates, make them transparent wind ultraviolet intense stars (TWUIN star), and their expected numbers might explain the observed He II ionising photon flux in I Zw 18 and other low-metallicity He II galaxies. Our slowly rotating stars above ~80 M⊙ evolve into late B- to M-type supergiants during core hydrogen burning, with visual magnitudes up to 19m at the distance of I Zw 18. Both types of stars, TWUIN stars and luminous late-type supergiants, are only predicted at low metallicity. Conclusions: Massive star evolution at low metallicity is shown to differ qualitatively from that in metal-rich environments. Our grid can be used to interpret observations of local star
3-D Radiative Transfer Modeling of Structured Winds in Massive Hot Stars with Wind3D
NASA Astrophysics Data System (ADS)
Lobel, A.; Toalá, J. A.; Blomme, R.
2011-01-01
We develop 3-D models of the structured winds of massive hot stars with the Wind3D radiative transfer (RT) code. We investigate the physical properties of large-scale structures observed in the wind of the B-type supergiant HD 64760 with detailed line profile fits to Discrete Absorption Components (DACs) and rotational modulations observed with IUE in Si IV λ1395. We develop parameterized input models for Wind3D with large-scale equatorial wind density- and velocity-structures, or so-called `Co-rotating Interaction Regions' (CIRs) and `Rotational Modulation Regions' (RMRs). The parameterized models offer important advantages for high-performance RT calculations over ab-initio hydrodynamic input models. The acceleration of the input model calculations permits us to simulate and investigate a wide variety of physical conditions in the extended winds of massive hot stars. The new modeling method is very flexible for constraining the dynamic and geometric wind properties of RMRs in HD 64760. We compute that the modulations are produced by a regular pattern of radial density enhancements that protrude almost linearly into the equatorial wind. We find that the modulations are caused by narrow `spoke-like' wind regions. We present a hydrodynamic model showing that the linearly shaped radial wind pattern can be caused by mechanical wave action at the base of the stellar wind from the blue supergiant.
Janecky, D.R.
1986-01-01
Incremental reaction path modeling of chemical and sulfur isotopic reactions occurring in active hydrothermal vents on the seafloor, in combination with chemical and petrographic data from sulfide samples from the seafloor and massive sulfide ore deposits, allows a detailed examination of the processes involved. This paper presents theoretical models of reactions of two types: (1) adiabatic mixing between hydrothermal solution and seawater, and (2) reaction of hydrothermal solution with sulfide deposit materials. In addition, reaction of hydrothermal solution with sulfide deposit minerals and basalt in feeder zones is discussed.
Massive scalar field interacting with viscous fluid distribution in cosmological models
NASA Astrophysics Data System (ADS)
Tarachand Singh, R. K.; Ibotombi Singh, N.
1988-12-01
The study of Einstein's field equations describing Robertson-Walker cosmological models with massive scalar field and viscous fluid representing the matter has been made. The problem has been investigated with and without the source density in the wave equation. Corresponding exact solutions of the field equations have been obtained under different physical equations of state, including dust distribution, Zeldovich fluid distribution, disordered distribution of radiation subject to physically realistic conditions. It has been found that physically realistic solutions have been obtained for closed cosmological models only.
Evidence against the Sciama Model of Radiative Decay of Massive Neutrinos
NASA Astrophysics Data System (ADS)
Bowyer, Stuart; Korpela, Eric J.; Edelstein, Jerry; Lampton, Michael; Morales, Carmen; Pérez-Mercader, Juan; Gómez, José F.; Trapero, Joaquín
1999-11-01
We report on spectral observations of the night sky in the band around 900 Å where the emission line in the Sciama model of radiatively decaying massive neutrinos would be present. The data were obtained with a high-resolution, high-sensitivity spectrometer flown on the Spanish satellite MINISAT. The observed emission is far less intense than that expected in the Sciama model. Based on the development and utilization of the Espectrógrafo Ultravioleta de Radiación Difusa, a collaboration of the Spanish Instituto Nacional de Tecnica Aeroespacial and the Center for EUV Astrophysics, University of California, Berkeley.
Cao, Renzhi; Bhattacharya, Debswapna; Adhikari, Badri; Li, Jilong; Cheng, Jianlin
2016-09-01
Model evaluation and selection is an important step and a big challenge in template-based protein structure prediction. Individual model quality assessment methods designed for recognizing some specific properties of protein structures often fail to consistently select good models from a model pool because of their limitations. Therefore, combining multiple complimentary quality assessment methods is useful for improving model ranking and consequently tertiary structure prediction. Here, we report the performance and analysis of our human tertiary structure predictor (MULTICOM) based on the massive integration of 14 diverse complementary quality assessment methods that was successfully benchmarked in the 11th Critical Assessment of Techniques of Protein Structure prediction (CASP11). The predictions of MULTICOM for 39 template-based domains were rigorously assessed by six scoring metrics covering global topology of Cα trace, local all-atom fitness, side chain quality, and physical reasonableness of the model. The results show that the massive integration of complementary, diverse single-model and multi-model quality assessment methods can effectively leverage the strength of single-model methods in distinguishing quality variation among similar good models and the advantage of multi-model quality assessment methods of identifying reasonable average-quality models. The overall excellent performance of the MULTICOM predictor demonstrates that integrating a large number of model quality assessment methods in conjunction with model clustering is a useful approach to improve the accuracy, diversity, and consequently robustness of template-based protein structure prediction. Proteins 2016; 84(Suppl 1):247-259. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.
Design and Performance Analysis of a Massively Parallel Atmospheric General Circulation Model
NASA Technical Reports Server (NTRS)
Schaffer, Daniel S.; Suarez, Max J.
1998-01-01
In the 1990's computer manufacturers are increasingly turning to the development of parallel processor machines to meet the high performance needs of their customers. Simultaneously, atmospheric scientists study weather and climate phenomena ranging from hurricanes to El Nino to global warming that require increasingly fine resolution models. Here, implementation of a parallel atmospheric general circulation model (GCM) which exploits the power of massively parallel machines is described. Using the horizontal data domain decomposition methodology, this FORTRAN 90 model is able to integrate a 0.6 deg. longitude by 0.5 deg. latitude problem at a rate of 19 Gigaflops on 512 processors of a Cray T3E 600; corresponding to 280 seconds of wall-clock time per simulated model day. At this resolution, the model has 64 times as many degrees of freedom and performs 400 times as many floating point operations per simulated day as the model it replaces.
γ-Ray emission signals in the massive graviton mediated dark matter model
NASA Astrophysics Data System (ADS)
Zhang, Cun; Cui, Ming-Yang; Feng, Lei; Fan, Yi-Zhong; Ren, Zhong-Zhou
2017-03-01
Dark matter may interact with Standard Model (SM) particle through the exchange of a massive spin-2 graviton producing signals that can be detected. In this work we examine the γ-ray emission signals, including the line emission and the continuous spectrum component in such a massive graviton-mediated dark matter model. The constraints of LHC data, dark matter relic density as well as the dark matter indirect detection data have been applied to narrow down the parameter space. We focus on the vector dark matter model which could produce detectable γ-ray line signal. It is found that the γ-ray line data is effective on constraining the model parameters and the ongoing and upcoming space or ground-based γ-ray experiments can constrain the model further. As for the continuous γ-ray emission, the total effective annihilation cross section is ∼10-26 cm3s-1 except at the region where dark matter mass is around the graviton mass or half of it, which is consistent with current observational data and will be reliably probed by the upcoming CTA.
RADIATION TRANSFER OF MODELS OF MASSIVE STAR FORMATION. I. DEPENDENCE ON BASIC CORE PROPERTIES
Zhang Yichen; Tan, Jonathan C. E-mail: jt@astro.ufl.edu
2011-05-20
Radiative transfer calculations of massive star formation are presented. These are based on the Turbulent Core Model of McKee and Tan and self-consistently included a hydrostatic core, an inside-out expansion wave, a zone of free-falling rotating collapse, wide-angle dust-free outflow cavities, an active accretion disk, and a massive protostar. For the first time for such models, an optically thick inner gas disk extends inside the dust destruction front. This is important to conserve the accretion energy naturally and for its shielding effect on the outer region of the disk and envelope. The simulation of radiation transfer is performed with the Monte Carlo code of Whitney, yielding spectral energy distributions (SEDs) for the model series, from the simplest spherical model to the fiducial one, with the above components each added step by step. Images are also presented in different wavebands of various telescope cameras, including Spitzer IRAC and MIPS, SOFIA FORCAST, and Herschel PACS and SPIRE. The existence of the optically thick inner disk produces higher optical wavelength fluxes but reduces near- and mid-IR emission. The presence of outflow cavities, the inclination angle to the line of sight, and the thickness of the disk all affect the SEDs and images significantly. For the high-mass surface density cores considered here, the mid-IR emission can be dominated by the outflow cavity walls, as has been suggested by De Buizer. The effect of varying the pressure of the environment bounding the surface of the massive core is also studied. With lower surface pressures, the core is larger, has lower extinction and accretion rates, and the observed mid-IR flux from the disk can then be relatively high even though the accretion luminosity is lower. In this case the silicate absorption feature becomes prominent, in contrast to higher density cores forming under higher pressures.
Steady-State Models of X-ray Emission from Massive-Star Magnetospheres
NASA Astrophysics Data System (ADS)
Bard, Christopher; Townsend, Richard D.
2016-01-01
In the subset of OB stars with large-scale, organized magnetic fields, the stellar wind is forced to flow along magnetic field lines and is trapped within a magnetosphere corotating with its host star. As the wind turns on itself, shocks heat the plasma to millions of degrees and produce X-ray emission. Such magnetospheres are typically classified with the "wind magnetic confinement parameter", a simplified ratio between the magnetic energy density and the wind kinetic energy density. This parameter is often used to estimate magnetosphere properties, such as size, mass-loss rate, and spin-down time. Unfortunately, the strong magnetic fields in magnetospheres (polar strength: 100 G - 10 kG) and resulting Alfven velocities make magnetohydrodynamics simulations computationally difficult due to very small timesteps. To get around this issue, we approximate a massive-star magnetosphere as a series of one-dimensional flows along magnetic dipole field lines and develop a steady-state model from the resulting hydrodynamic equations. With this model, we derive scaling relations for the stellar mass-loss rate as a function of surface colatitude and find agreement with previous scaling results derived from simulations. These relations are further extended to include the effects of rigid-body rotation within the magnetosphere. Additionally, we develop an X-ray emission model from this steady-state analysis and compare it against both the "XADM" model for X-ray emission from massive star magnetospheres and observations of massive magnetic stars. Finally, we discuss improvements to the traditional wind magnetic confinement parameter to take into account the effect of a magnetic field on the wind kinetic energy density.
Radiation Transfer of Models of Massive Star Formation. I. Dependence on Basic Core Properties
NASA Astrophysics Data System (ADS)
Zhang, Yichen; Tan, Jonathan C.
2011-05-01
Radiative transfer calculations of massive star formation are presented. These are based on the Turbulent Core Model of McKee & Tan and self-consistently included a hydrostatic core, an inside-out expansion wave, a zone of free-falling rotating collapse, wide-angle dust-free outflow cavities, an active accretion disk, and a massive protostar. For the first time for such models, an optically thick inner gas disk extends inside the dust destruction front. This is important to conserve the accretion energy naturally and for its shielding effect on the outer region of the disk and envelope. The simulation of radiation transfer is performed with the Monte Carlo code of Whitney, yielding spectral energy distributions (SEDs) for the model series, from the simplest spherical model to the fiducial one, with the above components each added step by step. Images are also presented in different wavebands of various telescope cameras, including Spitzer IRAC and MIPS, SOFIA FORCAST, and Herschel PACS and SPIRE. The existence of the optically thick inner disk produces higher optical wavelength fluxes but reduces near- and mid-IR emission. The presence of outflow cavities, the inclination angle to the line of sight, and the thickness of the disk all affect the SEDs and images significantly. For the high-mass surface density cores considered here, the mid-IR emission can be dominated by the outflow cavity walls, as has been suggested by De Buizer. The effect of varying the pressure of the environment bounding the surface of the massive core is also studied. With lower surface pressures, the core is larger, has lower extinction and accretion rates, and the observed mid-IR flux from the disk can then be relatively high even though the accretion luminosity is lower. In this case the silicate absorption feature becomes prominent, in contrast to higher density cores forming under higher pressures.
Bauerle, Matthew
2014-08-01
This project utilizes Graphics Processing Units (GPUs) to compute radiograph simulations for arbitrary objects. The generation of radiographs, also known as the forward projection imaging model, is computationally intensive and not widely utilized. The goal of this research is to develop a massively parallel algorithm that can compute forward projections for objects with a trillion voxels (3D pixels). To achieve this end, the data are divided into blocks that can each t into GPU memory. The forward projected image is also divided into segments to allow for future parallelization and to avoid needless computations.
Modeling multi-nucleon transfer in symmetric collisions of massive nuclei
NASA Astrophysics Data System (ADS)
Welsh, T.; Loveland, W.; Yanez, R.; Barrett, J. S.; McCutchan, E. A.; Sonzogni, A. A.; Johnson, T.; Zhu, S.; Greene, J. P.; Ayangeakaa, A. D.; Carpenter, M. P.; Lauritsen, T.; Harker, J. L.; Walters, W. B.; Amro, B. M. S.; Copp, P.
2017-08-01
Symmetric collisions of massive nuclei, such as 238U + 248Cm, have been proposed as ways to make new n-rich heavy nuclei via multi-nucleon transfer (MNT) reactions. We have measured the yields of several projectile-like and target-like fragments from the reaction of 1360 MeV 204Hg + 198Pt. We find that current models for this symmetric collision (GRAZING, DNS, ImQMD) significantly underestimate the yields of these transfer products, even for small transfers.
Modeling multi-nucleon transfer in symmetric collisions of massive nuclei
Welsh, T.; Loveland, W.; Yanez, R.; ...
2017-05-18
We propose symmetric collisions of massive nuclei, such as 238U + 248Cm, as ways to make new n-rich heavy nuclei via multi-nucleon transfer (MNT) reactions. We have measured the yields of several projectile-like and target-like fragments from the reaction of 1360 MeV 204Hg + 198Pt. We also find that current models for this symmetric collision (GRAZING, DNS, ImQMD) significantly underestimate the yields of these transfer products, even for small transfers.
Shanks, W.C. Pat; Koski, Randolph A.; Mosier, Dan L.; Schulz, Klaus J.; Morgan, Lisa A.; Slack, John F.; Ridley, W. Ian; Dusel-Bacon, Cynthia; Seal, Robert R.; Piatak, Nadine M.; Shanks, W.C. Pat; Thurston, Roland
2012-01-01
An unusual feature of VMS deposits is the common association of stratiform "exhalative" deposits precipitated from hydrothermal fluids emanating into bottom waters. These deposits may extend well beyond the margins of massive sulfide and are typically composed of silica, iron, and manganese oxides, carbonates, sulfates, sulfides, and tourmaline.
A scalable approach to modeling groundwater flow on massively parallel computers
Ashby, S.F.; Falgout, R.D.; Tompson, A.F.B.
1995-12-01
We describe a fully scalable approach to the simulation of groundwater flow on a hierarchy of computing platforms, ranging from workstations to massively parallel computers. Specifically, we advocate the use of scalable conceptual models in which the subsurface model is defined independently of the computational grid on which the simulation takes place. We also describe a scalable multigrid algorithm for computing the groundwater flow velocities. We axe thus able to leverage both the engineer`s time spent developing the conceptual model and the computing resources used in the numerical simulation. We have successfully employed this approach at the LLNL site, where we have run simulations ranging in size from just a few thousand spatial zones (on workstations) to more than eight million spatial zones (on the CRAY T3D)-all using the same conceptual model.
Radiation Transfer of Models of Massive Star Formation. III. The Evolutionary Sequence
NASA Astrophysics Data System (ADS)
Zhang, Yichen; Tan, Jonathan C.; Hosokawa, Takashi
2014-06-01
We present radiation transfer simulations of evolutionary sequences of massive protostars forming from massive dense cores in environments of high mass surface densities, based on the Turbulent Core Model. The protostellar evolution is calculated with a multi-zone numerical model, with the accretion rate regulated by feedback from an evolving disk wind outflow cavity. The disk evolution is calculated assuming a fixed ratio of disk to protostellar mass, while the core envelope evolution assumes an inside-out collapse of the core with a fixed outer radius. In this framework, an evolutionary track is determined by three environmental initial conditions: the core mass Mc , the mass surface density of the ambient clump Σcl, and the ratio of the core's initial rotational to gravitational energy β c . Evolutionary sequences with various Mc , Σcl, and β c are constructed. We find that in a fiducial model with Mc = 60 M ⊙, Σcl = 1 g cm-2, and β c = 0.02, the final mass of the protostar reaches at least ~26 M ⊙, making the final star formation efficiency >~ 0.43. For each of the evolutionary tracks, radiation transfer simulations are performed at selected stages, with temperature profiles, spectral energy distributions (SEDs), and multiwavelength images produced. At a given stage, the envelope temperature depends strongly on Σcl, with higher temperatures in a higher Σcl core, but only weakly on Mc . The SED and MIR images depend sensitively on the evolving outflow cavity, which gradually widens as the protostar grows. The fluxes at <~ 100 μm increase dramatically, and the far-IR peaks move to shorter wavelengths. The influence of Σcl and β c (which determines disk size) are discussed. We find that, despite scatter caused by different Mc , Σcl, β c , and inclinations, sources at a given evolutionary stage appear in similar regions of color-color diagrams, especially when using colors with fluxes at >~ 70 μm, where scatter due to inclination is minimized
R-LODs: fast LOD-based ray tracing of massive models
Yoon, Sung-Eui; Lauterbach, Christian; Manocha, Dinesh
2006-08-25
We present a novel LOD (level-of-detail) algorithm to accelerate ray tracing of massive models. Our approach computes drastic simplifications of the model and the LODs are well integrated with the kd-tree data structure. We introduce a simple and efficient LOD metric to bound the error for primary and secondary rays. The LOD representation has small runtime overhead and our algorithm can be combined with ray coherence techniques and cache-coherent layouts to improve the performance. In practice, the use of LODs can alleviate aliasing artifacts and improve memory coherence. We implement our algorithm on both 32bit and 64bit machines and able to achieve up to 2.20 times improvement in frame rate of rendering models consisting of tens or hundreds of millions of triangles with little loss in image quality.
BPS and non-BPS kinks in a massive nonlinear S{sup 2}-sigma model
Alonso-Izquierdo, A.; Leon, M. A. Gonzalez; Guilarte, J. Mateos
2009-06-15
The stability of the topological kinks of the nonlinear S{sup 2}-sigma model discovered by Alonso Izquierdo et al. is discussed by means of a direct estimation of the spectra of the second-order fluctuation operators around topological kinks. The one-loop mass shifts caused by quantum fluctuations around these kinks are computed using the Cahill-Comtet-Glauber formula. The (lack of) stability of the nontopological kinks is unveiled by application of the Morse index theorem. These kinks are identified as non-BPS states. There are two types of topological kinks coming from the twofold embedding of the sine-Gordon model in the massive nonlinear sigma model. It is shown that sine-Gordon kinks of only one type satisfy first-order equations and are accordingly BPS classical solutions. Finally, the interplay between instability and supersymmetry is explored.
A New Occurrence Model for National Assessment of Undiscovered Volcanogenic Massive Sulfide Deposits
Shanks, W.C. Pat; Dusel-Bacon, Cynthia; Koski, Randolph; Morgan, Lisa A.; Mosier, Dan; Piatak, Nadine M.; Ridley, Ian; Seal, Robert R., II; Schulz, Klaus J.; Slack, John F.; Thurston, Roland
2009-01-01
Volcanogenic massive sulfide (VMS) deposits are very significant current and historical resources of Cu-Pb-Zn-Au-Ag, are active exploration targets in several areas of the United States and potentially have significant environmental effects. This new USGS VMS deposit model provides a comprehensive review of deposit occurrence and ore genesis, and fully integrates recent advances in the understanding of active seafloor VMS-forming environments, and integrates consideration of geoenvironmental consequences of mining VMS deposits. Because VMS deposits exhibit a broad range of geological and geochemical characteristics, a suitable classification system is required to incorporate these variations into the mineral deposit model. We classify VMS deposits based on compositional variations in volcanic and sedimentary host rocks. The advantage of the classification method is that it provides a closer linkage between tectonic setting and lithostratigraphic assemblages, and an increased predictive capability during field-based studies.
Lattice approach to finite volume form-factors of the Massive Thirring (Sine-Gordon) model
NASA Astrophysics Data System (ADS)
Hegedűs, Árpád
2017-08-01
In this paper we demonstrate, that the light-cone lattice approach for the Massive-Thirring (sine-Gordon) model, through the quantum inverse scattering method, admits an appropriate framework for computing the finite volume form-factors of local operators of the model. In this work we compute the finite volume diagonal matrix elements of the U(1) conserved current in the pure soliton sector of the theory. Based on the systematic large volume expansion of our results, we conjecture an exact expression for the finite volume expectation values of local operators in pure soliton states. At large volume in leading order these expectation values have the same form as in purely elastic scattering theories, but exponentially small corrections differ from previous Thermodynamic Bethe Ansatz conjectures of purely elastic scattering theories.
Asteroseismological Study of Massive ZZ Ceti Stars with Fully Evolutionary Models
NASA Astrophysics Data System (ADS)
Romero, A. D.; Kepler, S. O.; Córsico, A. H.; Althaus, L. G.; Fraga, L.
2013-12-01
We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon-oxygen core DA white dwarf models characterized by a detailed and consistent chemical inner profile for the core and the envelope. Our sample comprises all of the ZZ Ceti stars with spectroscopic stellar masses between 0.72 and 1.05 M ⊙ known to date. The asteroseismological analysis of a set of 42 stars enables study of the ensemble properties of the massive, pulsating white dwarf stars with carbon-oxygen cores, in particular the thickness of the hydrogen envelope and the stellar mass. A significant fraction of stars in our sample have stellar mass that is high enough to crystallize at the effective temperatures of the ZZ Ceti instability strip, which enables us to study the effects of crystallization on the pulsation properties of these stars. Our results show that the phase diagram presented in Horowitz et al. seems to be a good representation of the crystallization process inside white dwarf stars, in agreement with the results from white dwarf luminosity function in globular clusters.
Asteroseismological study of massive ZZ Ceti stars with fully evolutionary models
Romero, A. D.; Kepler, S. O.; Córsico, A. H.; Althaus, L. G.
2013-12-10
We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon-oxygen core DA white dwarf models characterized by a detailed and consistent chemical inner profile for the core and the envelope. Our sample comprises all of the ZZ Ceti stars with spectroscopic stellar masses between 0.72 and 1.05 M {sub ☉} known to date. The asteroseismological analysis of a set of 42 stars enables study of the ensemble properties of the massive, pulsating white dwarf stars with carbon-oxygen cores, in particular the thickness of the hydrogen envelope and the stellar mass. A significant fraction of stars in our sample have stellar mass that is high enough to crystallize at the effective temperatures of the ZZ Ceti instability strip, which enables us to study the effects of crystallization on the pulsation properties of these stars. Our results show that the phase diagram presented in Horowitz et al. seems to be a good representation of the crystallization process inside white dwarf stars, in agreement with the results from white dwarf luminosity function in globular clusters.
NASA Astrophysics Data System (ADS)
Shin, Min-Su; Sekora, Michael; Byun, Yong-Ik
2009-12-01
We present a new framework to detect various types of variable objects within massive astronomical time series data. Assuming that the dominant population of objects is non-variable, we find outliers from this population by using a non-parametric Bayesian clustering algorithm based on an infinite Gaussian mixture model (GMM) and the Dirichlet process. The algorithm extracts information from a given data set, which is described by six variability indices. The GMM uses those variability indices to recover clusters that are described by six-dimensional multivariate Gaussian distributions, allowing our approach to consider the sampling pattern of time series data, systematic biases, the number of data points for each light curve and photometric quality. Using the Northern Sky Variability Survey data, we test our approach and prove that the infinite GMM is useful at detecting variable objects, while providing statistical inference estimation that suppresses false detection. The proposed approach will be effective in the exploration of future surveys such as Gaia, Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) and Large Synoptic Survey Telescope (LSST), which will produce massive time series data.
RADIATION TRANSFER OF MODELS OF MASSIVE STAR FORMATION. II. EFFECTS OF THE OUTFLOW
Zhang, Yichen; Tan, Jonathan C.; McKee, Christopher F. E-mail: jt@astro.ufl.edu
2013-04-01
We present radiation transfer simulations of a massive (8 M{sub Sun }) protostar forming from a massive (M{sub c} = 60 M{sub Sun }) protostellar core, extending the model developed by Zhang and Tan. The two principal improvements are (1) developing a model for the density and velocity structure of a disk wind that fills the bipolar outflow cavities, based in part on the disk-wind model of Blandford and Payne; and (2) solving for the radially varying accretion rate in the disk due to a supply of mass and angular momentum from the infall envelope and their loss to the disk wind. One consequence of the launching of the disk wind is a reduction in the amount of accretion power that is radiated by the disk. We also include a non-Keplerian potential appropriate for a growing, massive disk. For the transition from dusty to dust-free conditions where gas opacities dominate, we now implement a gradual change as a more realistic approximation of dust destruction. We study how the above effects, especially the outflow, influence the spectral energy distributions (SEDs) and the synthetic images of the protostar. Dust in the outflow cavity significantly affects the SEDs at most viewing angles. It further attenuates the short-wavelength flux from the protostar, controlling how the accretion disk may be viewed, and contributes a significant part of the near- and mid-IR fluxes. These fluxes warm the disk, boosting the mid- and far-IR emission. We find that for near face-on views, i.e., looking down the outflow cavity (although not too close to the axis), the SED from the near-IR to about 60 {mu}m is very flat, which may be used to identify such systems. We show that the near-facing outflow cavity and its walls are still the most significant features in images up to 70 {mu}m, dominating the mid-IR emission and determining its morphology. The thermal emission from the dusty outflow itself dominates the flux at {approx}20 {mu}m. The detailed distribution of the dust in the outflow
NASA Astrophysics Data System (ADS)
Lobel, A.
2010-06-01
We present modeling research work of the winds and circumstellar environments of a variety of prototypical hot and cool massive stars using advanced radiative-transfer calculations. This research aims at unraveling the detailed physics of various mass-loss mechanisms of luminous stars in the upper portion of the H-R diagram. Very recent 3D radiative-transfer calculations, combined with hydrodynamic simulations, show that radiatively-driven winds of OB supergiants are structured due to large-scale density and velocity fields caused by rotating bright spots at the stellar equator. The mass-loss rates computed from matching Discrete Absorption Components (DACs) in IUE observations of HD 64760 (B Ib) do not reveal appreciable changes from the rates of unstructured (smooth) wind models. Intermediate yellow supergiants (such as the yellow hypergiant ρ Cas, F-G Ia0), on the other hand, show prominent spectroscopic signatures of strongly increased mass-loss rates during episodic outbursts that cause dramatic changes of the stellar photospheric conditions. Long-term high-resolution spectroscopic monitoring of cool hypergiants near the Yellow Evolutionary Void reveals that their mass-loss rates and wind-structure are dominated by photospheric eruptions and large-amplitude pulsations that impart mechanical momentum to the circumstellar environment by propagating acoustic (shock) waves. In massive red supergiants, however, clear evidence for mechanical wave propagation from the sub-photospheric convection zones is lacking, despite their frequently observed spectroscopic and photometric variability. Recent spatially resolved HST-STIS observations inside Betelgeuse's (M Iab) very extended chromosphere and dust envelope show evidence of warm chromospheric gas far beyond the dust-condensation radius of radiative-transfer models. Models for these long-term spectroscopic observations demonstrate that the chromospheric pulsations are not spherically symmetric. The STIS observations
Mass loss from evolved massive stars: self-consistent modeling of the wind and photosphere
NASA Astrophysics Data System (ADS)
Groh, J. H.
2007-03-01
This work analyzes the mass loss phenomenon in evolved massive stars through self-consistent modeling of the wind and photosphere of such stars, using the radiative transfer code CMFGEN. In the first part, fundamental physical parameters of Wolf-Rayet stars of spectral types WN3-w (WR 46 e WR 152) and WN6-s (WR 136) were obtained. The results clearly indicate that hydrogen is present on the surface of those stars in a considerable fraction, defying current evolutionary models. For both WN subtypes, significant difference between the physical parameters obtained here and in previous works were noticed. The 20-year evolution of the luminous blue variable (LBV) AG Carinae was analyzed in detail in the second part of this work. The results indicate unexpected changes in the current paradigm of massive star evolution during the S Dor cycle. In this work, the high rotational velocity obtained during the hot phases, and the transition between the bistability regimes of line-driven winds were detected for the first time in LBVs. Those results need to be considered in future analysis of such massive stars. This Thesis also presents a pioneering study about the impact of the time variability effects on the analysis of the winds of LBVs. The results achieved here are valid for the whole LBV class, and show that the mass-loss rates derived from Hα and radio free-free emission are affected by time-dependent effects. The mass-loss rate evolution during the S Dor cycle, derived using time-dependent models, implies that LBV eruptions begin well before the maximum in the visual lightcurve during this phase. The analysis of the full S Dor cycle of AG Car rule out that the S Dor variability is caused exclusively by an expanding pseudo-photosphere. The AG Car hydrostatic radius was found to vary by a factor of six between cool and hot phases, while the bolometric luminosity is 50% higher during the hot phase. Both results provide observational contraints for the physical mechanism
Wehner, W.F.; Mirin, A.A.; Bolstad, J.H.
1996-09-01
A comprehensive climate system model is under development at Lawrence Livermore National Laboratory. The basis for this model is a consistent coupling of multiple complex subsystem models, each describing a major component of the Earth`s climate. Among these are general circulation models of the atmosphere and ocean, a dynamic and thermodynamic sea ice model, and models of the chemical processes occurring in the air, sea water, and near-surface land. The computational resources necessary to carry out simulations at adequate spatial resolutions for durations of climatic time scales exceed those currently available. Distributed memory massively parallel processing (MPP) computers promise to affordably scale to the computational rates required by directing large numbers of relatively inexpensive processors onto a single problem. We have developed a suite of routines designed to exploit current generation MPP architectures via domain and functional decomposition strategies. These message passing techniques have been implemented in each of the component models and in their coupling interfaces. Production runs of the atmospheric and oceanic components performed on the National Environmental Supercomputing Center (NESC) Cray T3D are described.
Modeling the evolution of galaxies and massive black holes across cosmic time
NASA Astrophysics Data System (ADS)
Angles-Alcazar, Daniel
I use cosmological hydrodynamic simulations to investigate different aspects of the evolution of galaxies and massive black holes across cosmic time. First, I present high resolution "zoom-in" simulations including various prescriptions for galactic outflows designed to explore the impact of star-formation driven winds on the morphological, dynamical, and structural properties of individual galaxies from early times down to z = 2. Simulations without winds produce massive, compact galaxies with low gas fractions, super-solar metallicities, high bulge fractions, and much of the star formation concentrated within the inner kpc. I show that strong winds are required to suppress early star formation, maintain high gas fractions, redistribute star-forming gas and metals over larger scales, and increase the velocity dispersion of simulated galaxies, more in agreement with the large, extended, turbulent disks typical of high-redshift star-forming galaxies. Next, I combine cosmological simulations with analytic models of black hole growth to investigate the physical mechanisms driving the observed connection between massive black holes and their host galaxies. I describe a plausible model consistent with available observations in which black hole growth is limited by galaxy-scale torques. In this torque-limited growth scenario, black holes and host galaxies evolve on average toward the observed scaling relations, regardless of the initial conditions, and with no need for mass averaging through mergers or additional self-regulation processes. Outflows from the accretion disk play a key role by providing significant mass loss, but there is no need for strong interaction with the inflowing gas in order to regulate black holes in a non-linear feedback loop. I discuss some of the main implications of this scenario in the context of current observations, including the distribution and evolution of Eddington ratios, the connection between major galaxy mergers, star formation, and
NASA Technical Reports Server (NTRS)
Treinish, Lloyd A.; Gough, Michael L.; Wildenhain, W. David
1987-01-01
The capability was developed of rapidly producing visual representations of large, complex, multi-dimensional space and earth sciences data sets via the implementation of computer graphics modeling techniques on the Massively Parallel Processor (MPP) by employing techniques recently developed for typically non-scientific applications. Such capabilities can provide a new and valuable tool for the understanding of complex scientific data, and a new application of parallel computing via the MPP. A prototype system with such capabilities was developed and integrated into the National Space Science Data Center's (NSSDC) Pilot Climate Data System (PCDS) data-independent environment for computer graphics data display to provide easy access to users. While developing these capabilities, several problems had to be solved independently of the actual use of the MPP, all of which are outlined.
Modeling Massive Cluster Formation with Stellar Feedback using Flash and AMUSE
NASA Astrophysics Data System (ADS)
McMillan, Stephen; Wall, Joshua; Mac Low, Mordecai-Mark
2015-08-01
Star cluster formation is a complex astrophysical problem combining multiple competing physical processes in a challenging computational environment, placing stringent demands on both software and hardware. Current simulations still fall short of a realistic description of the physical processes at work in star-forming regions. We are developing a hybrid simulation code to explore the formation and assembly of massive star clusters by combining the magnetohydrodynamics code Flash and the AMUSE software environment. Flash handles gas dynamics and star formation through cloud collapse, while AMUSE manages the dynamics and evolution of stars and binary systems. The gravitational interaction between the gas and the stars is treated via a symplectic gravity bridge between the codes in AMUSE. Radiative, wind, and supernova feedback are followed in FLASH based on information provided by the AMUSE system. We present some early results of this work, focusing on cluster formation and assembly, and including simplified models of feedback to study gas expulsion and cluster survival.
The massive O(N) non-linear sigma model at high orders
NASA Astrophysics Data System (ADS)
Bijnens, Johan; Carloni, Lisa
2011-02-01
We extend our earlier work on the massive O(N) non-linear sigma model to other observables. We derive expressions at leading order in the large N expansion at all orders in the loop expansion for the decay constant, vacuum expectation value, meson-meson scattering and the scalar and vector form factors. This is done using cactus diagram resummation using a generalized gap equation and other recursion relations. For general N we derive the expressions for the n-th-loop-order leading logarithms (M/Flog (/M))n, up to five loops for the decay constant and vacuum expectation value (VEV) and up to four loops for meson-meson scattering, the scalar and vector form factors. We also quote our earlier result for the mass. The large N results do not give a good approximation for the case N=3. We use our results to study the convergence of the perturbative series and compare with elastic unitarity.
Polarimetric modeling of corotating interaction regions threading massive-star winds
NASA Astrophysics Data System (ADS)
Ignace, Richard; St-Louis, Nicole; Proulx-Giraldeau, Félix
2015-03-01
Context. Massive star winds are complex radiation-hydrodynamic (sometimes magnetohydrodynamic) outflows that are propelled by their enormously strong luminosities. The winds are often found to be structured and variable, but can also display periodic or quasi-periodic behavior in a variety of wind diagnostics. Aims: The regular variations observed in putatively single stars, especially in UV wind lines, have often been attributed to corotating interaction regions (CIRs) like those seen in the solar wind. We present light curves for variable polarization from winds with CIR structures. Methods: We develop a model for a time-independent CIR based on a kinematical description. Assuming optically thin electron scattering, we explore the range of polarimetric light curves that result as the curvature, latitude, and number of CIRs are varied. Results: We find that a diverse array of variable polarizations result from an exploration of cases. The net polarization from an unresolved source is weighted more toward the inner radii of the wind. Given that most massive stars have relatively fast winds compared to their rotation speeds, CIRs tend to be conical at inner radii, transitioning to a spiral shape at a few to several stellar radii in the wind. Conclusions: Winds with a single CIR structure lead to easily identifiable polarization signatures. By contrast allowing for multiple CIRs, all emerging from a range of azimuth and latitude positions at the star, can yield complex polarimetric behavior. Although our model is based on some simplifying assumptions, it produces qualitative behavior that we expect to be robust, and this has allowed us to explore a wide range of CIR configurations that will prove useful for interpreting polarimetric data. Appendix A is available in electronic form at http://www.aanda.org
Strong Lens Models for Massive Galaxy Clusters in the Reionization Lensing Cluster Survey
NASA Astrophysics Data System (ADS)
Cerny, Catherine; Sharon, Keren; Coe, Dan A.; Paterno-Mahler, Rachel; Jones, Christine; Czakon, Nicole G.; Umetsu, Keiichi; Stark, Daniel; Bradley, Larry D.; Trenti, Michele; Johnson, Traci; Bradac, Marusa; Dawson, William; Rodney, Steven A.; Strolger, Louis-Gregory; RELICS Team
2017-01-01
We present strong lensing models for five galaxy clusters from the Planck SZ cluster catalog as a part of the Reionization Lensing Cluster Survey (RELICS), a program that seeks to constrain the galaxy luminosity function past z~9 by conducting a wide field survey of massive galaxy clusters with HST (GO-14096, PI: Coe). The strong gravitational lensing effects of these clusters significantly magnify background galaxies, which enhances our ability to discover the large numbers of high redshift galaxies at z~9-12 needed to create a representative sample. We use strong lensing models for these clusters to study their mass distribution and magnification, which allows us to quantify the lensing effect on the background galaxies. These models can then be utilized in the RELICS survey in order to identify high redshift galaxy candidates that may be lensed by the clusters. The intrinsic properties of these galaxy candidates can be derived by removing the lensing effect as predicted by our models, which will meet the science goals of the RELICS survey. We use HST WFC3 and ACS imaging to create lensing models for the clusters RXC J0142.9+4438, ACO-2537, ACO-2163, RXCJ2211.7-0349, and ACT-CLJ0102-49151.
Globular clusters kinematics and dynamical models of the massive early-type galaxy NGC 1399
NASA Astrophysics Data System (ADS)
Samurović, S.
2016-06-01
We analyze the dynamical models of the massive early-type galaxy NGC 1399, the central galaxy of the Fornax cluster. We use the sample of 790 globular clusters as tracers of gravitational potential and we first extract the kinematics, which is then dynamically modeled. We find that the velocity dispersion remains high and approximately constant throughout the whole galaxy and that the departures from the Gaussian distribution of the orbits are not large. We use the spherical Jeans equation in both Newtonian and MOND approaches, assuming three cases of orbital anisotropies: we study isotropic, tangentially and radially anisotropic models in order to establish the best-fitting values of the mass-to-light ratios. We found that in the Newtonian approximation a significant amount of dark matter is needed and that Navarro-Frenk-White (NFW) model with a dark halo provides a satisfactory description of the kinematics of NGC 1399. We tested three MOND models (standard, simple and toy) and found that none of them can provide a fit of the velocity dispersion profile without the inclusion of dark matter. Finally, using our findings, we placed the galaxy NGC 1399 within the context of other observed early-type galaxies and discuss its location among them.
RADIATION-HYDRODYNAMIC MODELS OF THE EVOLVING CIRCUMSTELLAR MEDIUM AROUND MASSIVE STARS
Toala, J. A.; Arthur, S. J.
2011-08-20
We study the evolution of the interstellar and circumstellar media around massive stars (M {>=} 40 M{sub sun}) from the main sequence (MS) through to the Wolf-Rayet (WR) stage by means of radiation-hydrodynamic simulations. We use publicly available stellar evolution models to investigate the different possible structures that can form in the stellar wind bubbles around WR stars. We find significant differences between models with and without stellar rotation, and between models from different authors. More specifically, we find that the main ingredients in the formation of structures in the WR wind bubbles are the duration of the red supergiant (or luminous blue variable) phase, the amount of mass lost, and the wind velocity during this phase, in agreement with previous authors. Thermal conduction is also included in our models. We find that MS bubbles with thermal conduction are slightly smaller, due to extra cooling which reduces the pressure in the hot, shocked bubble, but that thermal conduction does not appear to significantly influence the formation of structures in post-MS bubbles. Finally, we study the predicted X-ray emission from the models and compare our results with observations of the WR bubbles S 308, NGC 6888, and RCW 58. We find that bubbles composed primarily of clumps have reduced X-ray luminosity and very soft spectra, while bubbles with shells correspond more closely to observations.
NASA Astrophysics Data System (ADS)
Armenio, Vincenzo; Fakhari, Ahmad; Petronio, Andrea; Padovan, Roberta; Pittaluga, Chiara; Caprino, Giovanni
2015-11-01
Massive flow separation is ubiquitous in industrial applications, ruling drag and hydrodynamic noise. In spite of considerable efforts, its numerical prediction still represents a challenge for CFD models in use in engineering. Aside commercial software, over the latter years the opensource software OpenFOAMR (OF) has emerged as a valid tool for prediction of complex industrial flows. In the present work, we simulate two flows representative of a class of situations occurring in industrial problems: the flow around sphere and that around a wall-mounted square cylinder at Re = 10000 . We compare the performance two different tools, namely OF and ANSYS CFX 15.0 (CFX) using different unstructured grids and turbulence models. The grids have been generated using SNAPPYHEXMESH and ANSYS ICEM CFD 15.0 with different near wall resolutions. The codes have been run in a RANS mode using k - ɛ model (OF) and SST - k - ω (CFX) with and without wall-layer models. OF has been also used in LES, WMLES and DES mode. Regarding the sphere, RANS models were not able to catch separation, while good prediction of separation and distribution of stresses over the surface were obtained using LES, WMLES and DES. Results for the second test case are currently under analysis. Financial support from COSMO ``cfd open source per opera mortta'' PAR FSC 2007-2013, Friuli Venezia Giulia.
Raining on black holes and massive galaxies: the top-down multiphase condensation model
NASA Astrophysics Data System (ADS)
Gaspari, M.; Temi, P.; Brighenti, F.
2017-04-01
The plasma haloes filling massive galaxies, groups and clusters are shaped by active galactic nucleus (AGN) heating and subsonic turbulence (σv ∼ 150 km s-1), as probed by Hitomi. Novel 3D high-resolution simulations show the soft X-ray, keV hot plasma cools rapidly via radiative emission at the high-density interface of the turbulent eddies, stimulating a top-down condensation cascade of warm 104 K filaments. The kpc-scale ionized (optical/ultraviolet) filaments form a skin enveloping the neutral filaments (optical/infrared/21 cm). The peaks of the warm filaments further condense into cold molecular clouds (<50 K; radio) with total mass of several 107 M⊙ and inheriting the turbulent kinematics. In the core, the clouds collide inelastically, mixing angular momentum and leading to Chaotic Cold Accretion (CCA). The black hole accretion rate (BHAR) can be modelled via quasi-spherical viscous accretion, dot{M}_bullet ∝ ν _c, with clump collisional viscosity νc ≡ λc σv and λc ∼ 100 pc. Beyond the core, pressure torques shape the angular momentum transport. In CCA, the BHAR is recurrently boosted up to 2 dex compared with the disc evolution, which arises as turbulence becomes subdominant. With negligible rotation too, compressional heating inhibits the molecular phase. The CCA BHAR distribution is lognormal with pink noise, f-1 power spectrum characteristic of fractal phenomena. Such chaotic fluctuations can explain the rapid luminosity variability of AGN and high-mass X-ray binaries. An improved criterium to trace non-linear condensation is proposed: σv/vcool ≲ 1. The three-phase CCA reproduces key observations of cospatial multiphase gas in massive galaxies, including Chandra X-ray images, SOAR Hα filaments and kinematics, Herschel [C+] emission and ALMA molecular associations. CCA plays important role in AGN feedback and unification, the evolution of BHs, galaxies and clusters.
Volcanogenic Massive Sulfide Deposits of the World - Database and Grade and Tonnage Models
Mosier, Dan L.; Berger, Vladimir I.; Singer, Donald A.
2009-01-01
Grade and tonnage models are useful in quantitative mineral-resource assessments. The models and database presented in this report are an update of earlier publications about volcanogenic massive sulfide (VMS) deposits. These VMS deposits include what were formerly classified as kuroko, Cyprus, and Besshi deposits. The update was necessary because of new information about some deposits, changes in information in some deposits, such as grades, tonnages, or ages, revised locations of some deposits, and reclassification of subtypes. In this report we have added new VMS deposits and removed a few incorrectly classified deposits. This global compilation of VMS deposits contains 1,090 deposits; however, it was not our intent to include every known deposit in the world. The data was recently used for mineral-deposit density models (Mosier and others, 2007; Singer, 2008). In this paper, 867 deposits were used to construct revised grade and tonnage models. Our new models are based on a reclassification of deposits based on host lithologies: Felsic, Bimodal-Mafic, and Mafic volcanogenic massive sulfide deposits. Mineral-deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types vary significantly, and (2) deposits of different types occur in distinct geologic settings that can be identified from geologic maps. Mineral-deposit models combine the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Globally based deposit models allow recognition of important features and demonstrate how common different features are. Well-designed deposit models allow geologists to deduce possible mineral-deposit types in a given geologic environment and economists to determine the possible economic viability of these resources. Thus, mineral-deposit models play a central role in presenting geoscience
Multi-dimensional models of circumstellar shells around evolved massive stars
NASA Astrophysics Data System (ADS)
van Marle, A. J.; Keppens, R.
2012-11-01
Context. Massive stars shape their surrounding medium through the force of their stellar winds, which collide with the circumstellar medium. Because the characteristics of these stellar winds vary over the course of the evolution of the star, the circumstellar matter becomes a reflection of the stellar evolution and can be used to determine the characteristics of the progenitor star. In particular, whenever a fast wind phase follows a slow wind phase, the fast wind sweeps up its predecessor in a shell, which is observed as a circumstellar nebula. Aims: We make 2D and 3D numerical simulations of fast stellar winds sweeping up their slow predecessors to investigate whether numerical models of these shells have to be 3D, or whether 2D models are sufficient to reproduce the shells correctly. Methods: We use the MPI-AMRVAC code, using hydrodynamics with optically thin radiative losses included, to make numerical models of circumstellar shells around massive stars in 2D and 3D and compare the results. We focus on those situations where a fast Wolf-Rayet star wind sweeps up the slower wind emitted by its predecessor, being either a red supergiant or a luminous blue variable. Results: As the fast Wolf-Rayet wind expands, it creates a dense shell of swept up material that expands outward, driven by the high pressure of the shocked Wolf-Rayet wind. These shells are subject to a fair variety of hydrodynamic-radiative instabilities. If the Wolf-Rayet wind is expanding into the wind of a luminous blue variable phase, the instabilities will tend to form a fairly small-scale, regular filamentary lattice with thin filaments connecting knotty features. If the Wolf-Rayet wind is sweeping up a red supergiant wind, the instabilities will form larger interconnected structures with less regularity. The numerical resolution must be high enough to resolve the compressed, swept-up shell and the evolving instabilities, which otherwise may not even form. Conclusions: Our results show that 3D
NASA Astrophysics Data System (ADS)
Cazorla, Constantin; Nazé, Yaël; Morel, Thierry; Georgy, Cyril; Godart, Mélanie; Langer, Norbert
2017-08-01
Aims: Past observations of fast-rotating massive stars exhibiting normal nitrogen abundances at their surface have raised questions about the rotational mixing paradigm. We revisit this question thanks to a spectroscopic analysis of a sample of bright fast-rotating OB stars, with the goal of quantifying the efficiency of rotational mixing at high rotation rates. Methods: Our sample consists of 40 fast rotators on the main sequence, with spectral types comprised between B0.5 and O4. We compare the abundances of some key element indicators of mixing (He, CNO) with the predictions of evolutionary models for single objects and for stars in interacting binary systems. Results: The properties of half of the sample stars can be reproduced by single evolutionary models, even in the case of probable or confirmed binaries that can therefore be true single stars in a pre-interaction configuration. The main problem for the rest of the sample is a mismatch for the [N/O] abundance ratio (we confirm the existence of fast rotators with a lack of nitrogen enrichment) and/or a high helium abundance that cannot be accounted for by models. Modifying the diffusion coefficient implemented in single-star models does not solve the problem as it cannot simultaneously reproduce the helium abundances and [N/O] abundance ratios of our targets. Since part of them actually are binaries, we also compared their chemical properties with predictions for post-mass transfer systems. We found that these models can explain the abundances measured for a majority of our targets, including some of the most helium-enriched, but fail to reproduce them in other cases. Our study thus reveals that some physical ingredients are still missing in current models.
Integration and management of massive remote-sensing data based on GeoSOT subdivision model
NASA Astrophysics Data System (ADS)
Li, Shuang; Cheng, Chengqi; Chen, Bo; Meng, Li
2016-07-01
Owing to the rapid development of earth observation technology, the volume of spatial information is growing rapidly; therefore, improving query retrieval speed from large, rich data sources for remote-sensing data management systems is quite urgent. A global subdivision model, geographic coordinate subdivision grid with one-dimension integer coding on 2n-tree, which we propose as a solution, has been used in data management organizations. However, because a spatial object may cover several grids, ample data redundancy will occur when data are stored in relational databases. To solve this redundancy problem, we first combined the subdivision model with the spatial array database containing the inverted index. We proposed an improved approach for integrating and managing massive remote-sensing data. By adding a spatial code column in an array format in a database, spatial information in remote-sensing metadata can be stored and logically subdivided. We implemented our method in a Kingbase Enterprise Server database system and compared the results with the Oracle platform by simulating worldwide image data. Experimental results showed that our approach performed better than Oracle in terms of data integration and time and space efficiency. Our approach also offers an efficient storage management system for existing storage centers and management systems.
The evolution of massive stars including mass loss - Presupernova models and explosion
NASA Technical Reports Server (NTRS)
Woosley, S. E.; Langer, Norbert; Weaver, Thomas A.
1993-01-01
The evolution of massive stars of 35, 40, 60, and 85 solar masses is followed through all stages of nuclear burning to the point of Fe core collapse. Critical nuclear reaction and mass-loss rates are varied. Efficient mass loss during the Wolf-Rayet (WR) stage is likely to lead to final masses as small as 4 solar masses. For a reasonable parameterization of the mass loss, there may be convergence of all WR stars, both single and in binaries, to a narrow band of small final masses. Our representative model, a 4.25 solar-mass WR presupernova derived from a 60 solar mass star, is followed through a simulated explosion, and its explosive nucleosynthesis and light curve are determined. Its properties are similar to those observed in Type Ib supernovae. The effects of the initial mass and mass loss on the presupernova structure of small mass WR models is also explored. Important properties of the presupernova star and its explosion can only be obtained by following the complete evolution starting on the main sequence.
Exploring Bias and Uncertainty in Gaussian Mixture Models of Young, Massive Star Clusters
NASA Astrophysics Data System (ADS)
Elrod, Aunna; Clarkson, William I.
2016-06-01
Mixture models are important for studies of star clusters observed against a foreground or background field population. By directly estimating both the distribution parameters of the components and the component fractions (and thus the formal membership probabilities), the populations of interest can be fit directly without recourse to binning. Gaussian Mixtures are a highly popular choice when modeling star clusters, and their determination using the Expectation Maximization algorithm, or its extension to cases with strongly varying measurement uncertainty (e.g. Bovy et al.’s Extreme Deconvolution) now appears in some statistics textbooks.Here we describe our Monte Carlo study to estimate the effect of the choice of instrumental setup, particularly different field of views, on parameter recovery for simulated star clusters under a variety of situations. We simulate observations of a Young, Massive Cluster like those near the Galactic Center, focusing mainly on scenarios where the same cluster is observed from ground and from space. We characterize the bias and uncertainty that might be introduced when using this fairly recent yet increasingly popular technique across heterogenous instrumental setups.
The evolution of massive stars including mass loss - Presupernova models and explosion
NASA Technical Reports Server (NTRS)
Woosley, S. E.; Langer, Norbert; Weaver, Thomas A.
1993-01-01
The evolution of massive stars of 35, 40, 60, and 85 solar masses is followed through all stages of nuclear burning to the point of Fe core collapse. Critical nuclear reaction and mass-loss rates are varied. Efficient mass loss during the Wolf-Rayet (WR) stage is likely to lead to final masses as small as 4 solar masses. For a reasonable parameterization of the mass loss, there may be convergence of all WR stars, both single and in binaries, to a narrow band of small final masses. Our representative model, a 4.25 solar-mass WR presupernova derived from a 60 solar mass star, is followed through a simulated explosion, and its explosive nucleosynthesis and light curve are determined. Its properties are similar to those observed in Type Ib supernovae. The effects of the initial mass and mass loss on the presupernova structure of small mass WR models is also explored. Important properties of the presupernova star and its explosion can only be obtained by following the complete evolution starting on the main sequence.
Galactic models with massive coronae. V. The spiral SAB galaxy M 81
NASA Astrophysics Data System (ADS)
Tenjes, P.; Haud, U.; Einasto, J.
1998-07-01
Stellar populations in spiral galaxy M 81 are studied by using modelling. The galaxy is assumed to be stationary and consisting of a superposition of several subsystems. Each subsystem corresponds to a certain stellar/gas/dark matter population with a certain density distribution, chemical composition and kinematical characteristics. We presume that equidensity surfaces of the galactic populations are similar concentric ellipsoids or can be represented as sums of such ellipsoids. The input observational data base consists of surface photometry along the minor and major axis in UBVRI colours, rotation velocities of gas, stellar velocity dispersions, distribution and kinematics of globular clusters, distribution of the young stellar component and gas, kinematics of M 81 satellite galaxies. These data are used to decompose the galaxy into a central nucleus, a metal-rich core and a bulge, a metal-poor halo, an old stellar disk, a young gaseous-stellar disk and a massive dark matter component. Each population is characterized by its ellipticity, radius, mass, luminosity, structure parameter and colour indices. These population parameters are found using the least-squares algorithm. The algorithm minimizes the sum of squares of relative deviations of the model from observations. The values of the parameters were calculated in several steps from a preliminary crude model to the final model. The sensitivity of the population parameters to various observational data is analysed. Particular attention is devoted to the dark matter problem. In the final model the mean mass-to-luminosity ratio of the optically visible parts of the galaxy is found to be M/L_B = 5.4+/- 2.4 M_{sun/Lsun, and the ratio of the total mass to the visible one M_T/M_vis = 44. In the inner regions the best fit with observations is obtained when a central point mass 2.7* 10(8) M_{sun is added to the nucleus.
Three-dimensional electromagnetic modeling and inversion on massively parallel computers
Newman, G.A.; Alumbaugh, D.L.
1996-03-01
This report has demonstrated techniques that can be used to construct solutions to the 3-D electromagnetic inverse problem using full wave equation modeling. To this point great progress has been made in developing an inverse solution using the method of conjugate gradients which employs a 3-D finite difference solver to construct model sensitivities and predicted data. The forward modeling code has been developed to incorporate absorbing boundary conditions for high frequency solutions (radar), as well as complex electrical properties, including electrical conductivity, dielectric permittivity and magnetic permeability. In addition both forward and inverse codes have been ported to a massively parallel computer architecture which allows for more realistic solutions that can be achieved with serial machines. While the inversion code has been demonstrated on field data collected at the Richmond field site, techniques for appraising the quality of the reconstructions still need to be developed. Here it is suggested that rather than employing direct matrix inversion to construct the model covariance matrix which would be impossible because of the size of the problem, one can linearize about the 3-D model achieved in the inverse and use Monte-Carlo simulations to construct it. Using these appraisal and construction tools, it is now necessary to demonstrate 3-D inversion for a variety of EM data sets that span the frequency range from induction sounding to radar: below 100 kHz to 100 MHz. Appraised 3-D images of the earth`s electrical properties can provide researchers opportunities to infer the flow paths, flow rates and perhaps the chemistry of fluids in geologic mediums. It also offers a means to study the frequency dependence behavior of the properties in situ. This is of significant relevance to the Department of Energy, paramount to characterizing and monitoring of environmental waste sites and oil and gas exploration.
NASA Technical Reports Server (NTRS)
Juang, Hann-Ming Henry; Tao, Wei-Kuo; Zeng, Xi-Ping; Shie, Chung-Lin; Simpson, Joanne; Lang, Steve
2004-01-01
The capability for massively parallel programming (MPP) using a message passing interface (MPI) has been implemented into a three-dimensional version of the Goddard Cumulus Ensemble (GCE) model. The design for the MPP with MPI uses the concept of maintaining similar code structure between the whole domain as well as the portions after decomposition. Hence the model follows the same integration for single and multiple tasks (CPUs). Also, it provides for minimal changes to the original code, so it is easily modified and/or managed by the model developers and users who have little knowledge of MPP. The entire model domain could be sliced into one- or two-dimensional decomposition with a halo regime, which is overlaid on partial domains. The halo regime requires that no data be fetched across tasks during the computational stage, but it must be updated before the next computational stage through data exchange via MPI. For reproducible purposes, transposing data among tasks is required for spectral transform (Fast Fourier Transform, FFT), which is used in the anelastic version of the model for solving the pressure equation. The performance of the MPI-implemented codes (i.e., the compressible and anelastic versions) was tested on three different computing platforms. The major results are: 1) both versions have speedups of about 99% up to 256 tasks but not for 512 tasks; 2) the anelastic version has better speedup and efficiency because it requires more computations than that of the compressible version; 3) equal or approximately-equal numbers of slices between the x- and y- directions provide the fastest integration due to fewer data exchanges; and 4) one-dimensional slices in the x-direction result in the slowest integration due to the need for more memory relocation for computation.
Climate system modeling on massively parallel systems: LDRD Project 95-ERP-47 final report
Mirin, A.A.; Dannevik, W.P.; Chan, B.; Duffy, P.B.; Eltgroth, P.G.; Wehner, M.F.
1996-12-01
Global warming, acid rain, ozone depletion, and biodiversity loss are some of the major climate-related issues presently being addressed by climate and environmental scientists. Because unexpected changes in the climate could have significant effect on our economy, it is vitally important to improve the scientific basis for understanding and predicting the earth`s climate. The impracticality of modeling the earth experimentally in the laboratory together with the fact that the model equations are highly nonlinear has created a unique and vital role for computer-based climate experiments. However, today`s computer models, when run at desired spatial and temporal resolution and physical complexity, severely overtax the capabilities of our most powerful computers. Parallel processing offers significant potential for attaining increased performance and making tractable simulations that cannot be performed today. The principal goals of this project have been to develop and demonstrate the capability to perform large-scale climate simulations on high-performance computing systems (using methodology that scales to the systems of tomorrow), and to carry out leading-edge scientific calculations using parallelized models. The demonstration platform for these studies has been the 256-processor Cray-T3D located at Lawrence Livermore National Laboratory. Our plan was to undertake an ambitious program in optimization, proof-of-principle and scientific study. These goals have been met. We are now regularly using massively parallel processors for scientific study of the ocean and atmosphere, and preliminary parallel coupled ocean/atmosphere calculations are being carried out as well. Furthermore, our work suggests that it should be possible to develop an advanced comprehensive climate system model with performance scalable to the teraflops range. 9 refs., 3 figs.
Modeling and Observations of Massive Binaries with the B[e] Phenomenon
NASA Astrophysics Data System (ADS)
Lobel, A.; Martayan, C.; Mehner, A.; Groh, J. H.
2017-02-01
We report a long-term high-resolution spectroscopic monitoring program of LBVs and candidate LBVs with Mercator-HERMES. Based on 7 years of data, we recently showed that supergiant MWC 314 is a (Galactic) semi-detached eccentric binary with stationary permitted and forbidden emission lines in the optical and near-IR region. MWC 314 is a luminous and massive probable LBV star showing a strongly orbitally-modulated wind variability. We observe discrete absorption components in P Cyg He I lines signaling large-scale wind structures. In 2014 XMM observed X-rays indicating strong wind-wind collision in the close binary system (a ≃1 AU). A VLT-NACO imaging survey recently revealed that MWC 314 is a triple hierarchical system. We present a 3-D non-LTE radiative transfer model of the extended asymmetric wind structure around the primary B0 supergiant for modeling the orbital variability of P Cyg absorption (v∞˜1200 km s-1) in He I lines. An analysis of the HERMES monitoring spectra of the Galactic LBV star MWC 930 however does not show clear indications of a spectroscopic binary. The detailed long-term spectroscopic variability of this massive B[e] star is very similar to the spectroscopic variability of the prototypical blue hypergiant S Dor in the LMC. We observe prominent P Cyg line shapes in MWC 930 that temporarily transform into split absorption line cores during variability phases of its S Dor cycle over the past decade with a brightening in V of ˜ 1.2 mag. The line splitting phenomenon is very similar to the split metal line cores observed in pulsating Yellow Hypergiants ρ Cas (F-K Ia+) and HR 8752 (A-K Ia+) with [Ca II] and [N II] emission lines. We propose the line core splitting in MWC 930 is due to optically thick central line emission produced in the inner ionized wind region becoming mechanically shock-excited with the increase of R* and decrease of Teff of the LBV.
Connecting real-time properties of the massless Schwinger model to the massive case
NASA Astrophysics Data System (ADS)
Hebenstreit, F.; Berges, J.
2014-08-01
Quantum electrodynamics in 1+1 space-time dimensions is analytically solvable for massless fermions, while no solution is known for massive fermions. Employing the classical-statistical approach, we simulate the real-time dynamics on a lattice using Wilson fermions with mass m at gauge coupling g. It is shown that quantitative properties of the massless Schwinger model are emerging in the limit of large g/m. We investigate two scenarios corresponding to opposite charges which are either held fixed or moving back-to-back along the light cone, as employed in effective descriptions for jet energy loss and photon production in the context of heavy-ion collisions. Remarkably, we find that the dynamics is rather well described by the massless limit for a wide range of mass values at fixed coupling. Moreover, our study shows that previous approximate scenarios with external charges on the light cone rather accurately capture the self-consistent dynamics of the energy conserving simulation.
On the Vainshtein mechanism in the minimal model of massive gravity
Renaux-Petel, Sébastien
2014-03-01
We reinvestigate the fate of the Vainhstein mechanism in the minimal model of dRGT massive gravity. As the latter is characterised by the complete absence of interactions in the decoupling limit, we study their structure at higher energies. We show that in static spherically symmetric configurations, the lowest energy scale of interactions is pushed up to the Planck mass. This fact points towards an absence of Vainshtein mechanism in this framework, but does not prove it. By resorting to the exact vacuum equations of motion, we show that there is indeed an obstruction that precludes any recovery of General Relativity under the conditions of stationarity and spherical symmetry. However, we argue that the latter are too restrictive and might miss some important physical phenomena. Indeed, we point out that in generic non spherically symmetric or time-dependent situations, interactions arising at energies arbitrarily close to the energy scale of the decoupling limit reappear. This leads us to question whether the small degree of spherical symmetry breaking in the solar system can be sufficient to give rise to a successful Vainshtein mechanism.
Galaxy clustering, CMB and supernova data constraints on ϕCDM model with massive neutrinos
NASA Astrophysics Data System (ADS)
Chen, Yun; Xu, Lixin
2016-01-01
We investigate a scalar field dark energy model (i.e., ϕCDM model) with massive neutrinos, where the scalar field possesses an inverse power-law potential, i.e., V (ϕ) ∝ϕ-α (α > 0). We find that the sum of neutrino masses Σmν has significant impacts on the CMB temperature power spectrum and on the matter power spectrum. In addition, the parameter α also has slight impacts on the spectra. A joint sample, including CMB data from Planck 2013 and WMAP9, galaxy clustering data from WiggleZ and BOSS DR11, and JLA compilation of Type Ia supernova observations, is adopted to confine the parameters. Within the context of the ϕCDM model under consideration, the joint sample determines the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the Thomson scattering optical depth due to reionization, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be θ* = (1.0415-0.0011+0.0012) ×10-2, τ =0.0914-0.0242+0.0266, Ωbh2 = 0.0222 ± 0.0005, Ωch2 = 0.1177 ± 0.0036, and ns =0.9644-0.0119+0.0118, respectively, at 95% confidence level (CL). It turns out that α < 4.995 at 95% CL for the ϕCDM model. And yet, the ΛCDM scenario corresponding to α = 0 is not ruled out at 95% CL. Moreover, we get Σmν < 0.262 eV at 95% CL for the ϕCDM model, while the corresponding one for the ΛCDM model is Σmν < 0.293 eV. The allowed scale of Σmν in the ϕCDM model is a bit smaller than that in the ΛCDM model. It is consistent with the qualitative analysis, which reveals that the increases of α and Σmν both can result in the suppression of the matter power spectrum. As a consequence, when α is larger, in order to avoid suppressing the matter power spectrum too much, the value of Σmν should be smaller.
NASA Astrophysics Data System (ADS)
Livio, Mario; Villaver, Eva
2009-11-01
Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.
Modeling GRB 050904: Autopsy of a Massive Stellar Explosion at z=6.29
NASA Astrophysics Data System (ADS)
Gou, L.-J.; Fox, D. B.; Mészáros, P.
2007-10-01
GRB 050904, at redshift z=6.29, was discovered and observed by Swift, and, with a spectroscopic redshift from the Subaru Telescope, is the first gamma-ray burst to be identified from beyond the epoch of reionization. Since the progenitors of long GRBs have been identified as massive stars, this event offers a unique opportunity to investigate star formation environments at this epoch. Apart from its record redshift, the burst is remarkable in two respects: first, it exhibits fast-evolving X-ray and optical flares that peak simultaneously at t~470 s in the observer's frame and may thus originate in the same emission region; second, its afterglow exhibits an accelerated decay in the near-infrared (NIR) from t~104 s to t~3×104 s after the burst, coincident with repeated and energetic X-ray flaring activity. We perform a complete analysis of available X-ray, NIR, and radio observations, utilizing afterglow models that incorporate a range of physical effects not previously considered for this or any other GRB afterglow and quantifying our model uncertainties in detail with Markov chain Monte Carlo analysis. We explore the possibility that the early optical and X-ray flare is due to synchrotron and inverse Compton emission from the reverse-shock regions of the outflow. We suggest that the period of accelerated decay in the NIR may be due to suppression of synchrotron radiation by inverse Compton interaction of X-ray flare photons with electrons in the forward shock; a subsequent interval of slow decay would then be due to a progressive decline in this suppression. The range of acceptable models demonstrates that the kinetic energy and circumburst density of GRB 050904 are well above the typical values for low-redshift GRBs.
Extended soft wall model with background related to features of QCD thermodynamics
NASA Astrophysics Data System (ADS)
Zöllner, R.; Kämpfer, B.
2017-06-01
The soft wall model is extended to accommodate at the same time i) approximately linear ρ meson Regge trajectories at zero temperature T, ii) various options for the thermodynamics with reference to QCD (cross-over or second-order transition or first-order transition at Tc, and iii) the appearance of vector meson states at T ≲ Tc. While the vector meson masses display some modest model dependence very near to Tc, they stay below Tc to good accuracy independent of the temperature, that is nearly as at T=0, thus being very consistent with the thermo-statistical models widely employed in analyses of the hadron yields in relativistic heavy-ion collisions in a region where baryon densitiy effects can be neglected and the vacuum hadron masses are used.
NASA Astrophysics Data System (ADS)
Klähn, T.; Łastowiecki, R.; Blaschke, D.
2013-10-01
The precise measurements of the high masses of the pulsars PSR J1614-2230 (M1614=1.97±0.04M⊙) and PSR J0348-0432 (M0348=2.01±0.04M⊙) provide an important constraint for the equation of state of cold, dense matter and are suited to give interesting insights regarding the nature and existence of the possible phase transition to deconfined quark matter in the cores of neutron stars. We analyze the stability and composition of compact star sequences for a class of hybrid nuclear-quark-matter equations of state. The quark matter phase is described in the framework of a standard color superconducting 3-flavor Nambu-Jona-Lasinio model, and the hadronic phase is given by the Dirac-Brueckner-Hartree-Fock equation of state for the Bonn-A potential. The phase transition is obtained by a Maxwell construction. Within this model setup, we aim to constrain otherwise not strictly fixed parameters of the Nambu-Jona-Lasinio model, namely, the coupling strengths in the vector meson and diquark interaction channels. We perform this investigation for two different parametrizations characterized by a different scalar coupling constant. The analysis of flow data obtained in heavy-ion collisions resulted in a further constraint that we account for in our discussion. Massive hybrid stars with extended quark matter cores can be obtained in accordance with all of the considered constraints.
Modeling the NIR-silhouette massive disk candidate in M 17
NASA Astrophysics Data System (ADS)
Steinacker, J.; Chini, R.; Nielbock, M.; Nürnberger, D.; Hoffmeister, V.; Huré, J.-M.; Semenov, D.
2006-09-01
Aims.The physical properties of the massive disk candidate in the star-forming region M 17 are analyzed. Methods: .Making use of the rare configuration in which the gas and dust structure is seen in silhouette against the background radiation at λ=2.2~μm, we determine the column density distribution from a high-resolution NAOS/CONICA image. The influence of scattered light on the mass determination is analyzed using 3D radiative transfer calculations. Further upper flux limits derived from observations with the Spitzer telescope at MIR wavelengths are used together with the NACO image to estimate the flux from the central object. For a range of stellar radii, stellar surface temperatures, and dust grain sizes, we apply three different models to account for the observed fluxes. The stability of the disk against self-gravitational forces is analyzed calculating the ratio of the gravitational acceleration by the central object and the disk, and the deviations from a Keplerian profile. Results: .We find that the column density is consistent with a central source surrounded by a rotationally symmetric distribution of gas and dust. The extent of the symmetric disk part is about 3000 AU, with a warped point-symmetrical extension beyond that radius, and therefore larger than any circumstellar disk yet detected. The modeling yields a radial density powerlaw exponent of -1.1 indicating a flat radial density distribution, and a large e-folding scale height ratio H/R of about 0.5. The mass of the entire disk estimated from the column density is discussed depending on the assumed distance and the dust model and ranges between 0.02 and 5 M⊙. We conclude that unless a star is located close to the disk in the foreground, scattered light will have little influence on the mass determination. We present a Spitzer image taken at λ=7.8~μm with the disk seen in emission and identify polycyclic aromatic hydrocarbon (PAH) emission on the disk surface excited by the nearby massive
A generic Froude scale model study of massive bedload deposition in a debris basin
NASA Astrophysics Data System (ADS)
Piton, Guillaume; Recking, Alain
2017-04-01
Sediment trapping structures, such as gravel deposition basins, are regularly implemented in mountainous context for flood hazard mitigation. These structures should ultimately trap gravels when their excess may aggravate the downstream flood hazard, while, the remaining time, allowing a suitable background sediment continuity. Such optimized designs require a sufficient knowledge of the flow features and geomorphic processes implied in gravel trapping. A generic Froude scale model of a 10%-steep, bedload deposition basin, with a slit dam and without outlet structure, is presented in this work. Accurate photogrammetry and large scale particle image velocimetry (LS-PIV) were combined to study the geomorphic patterns and to reconstruct the flows. The emergence of self induced cycles of braided and channelized flows, with intense grain size sorting, is described. It sheds light on the similarity of bedload trapping with alluvial fan formation or fluvial delta development. The deposition slope, a key parameter in the structure design, is more precisely studied. The measurements are correctly estimated by a new simple equation, which is developed from prior works dedicated to steep slope stream hydraulics and bedload transport. The analysis demonstrates additionally that, despite the steepness of the studied conditions, most flows are subcritical due to roughness adjustment. We finally highlight that morphologically-active flows, i.e., with dimensionless shear stress higher than the threshold for motion, have Froude number ≈ 1; i.e., that a critical flow hypothesis seems reasonable, as a first approximation, to describe flows over massive bedload depositions. This new dataset, with complete geomorphic and flow measurements, in diverse conditions, may be used as reference to try and test numerical approaches of the phenomena.
Seismic waves modeling with the Fourier pseudo-spectral method on massively parallel machines.
NASA Astrophysics Data System (ADS)
Klin, Peter
2015-04-01
The Fourier pseudo-spectral method (FPSM) is an approach for the 3D numerical modeling of the wave propagation, which is based on the discretization of the spatial domain in a structured grid and relies on global spatial differential operators for the solution of the wave equation. This last peculiarity is advantageous from the accuracy point of view but poses difficulties for an efficient implementation of the method to be run on parallel computers with distributed memory architecture. The 1D spatial domain decomposition approach has been so far commonly adopted in the parallel implementations of the FPSM, but it implies an intensive data exchange among all the processors involved in the computation, which can degrade the performance because of communication latencies. Moreover, the scalability of the 1D domain decomposition is limited, since the number of processors can not exceed the number of grid points along the directions in which the domain is partitioned. This limitation inhibits an efficient exploitation of the computational environments with a very large number of processors. In order to overcome the limitations of the 1D domain decomposition we implemented a parallel version of the FPSM based on a 2D domain decomposition, which allows to achieve a higher degree of parallelism and scalability on massively parallel machines with several thousands of processing elements. The parallel programming is essentially achieved using the MPI protocol but OpenMP parts are also included in order to exploit the single processor multi - threading capabilities, when available. The developed tool is aimed at the numerical simulation of the seismic waves propagation and in particular is intended for earthquake ground motion research. We show the scalability tests performed up to 16k processing elements on the IBM Blue Gene/Q computer at CINECA (Italy), as well as the application to the simulation of the earthquake ground motion in the alluvial plain of the Po river (Italy).
NASA Astrophysics Data System (ADS)
Larour, E.; Rignot, E.; Morlighem, M.; Seroussi, H.
2008-12-01
We implemented a fully-three-dimensional, thermo-mechanical, finite element model of the Antarctic Ice Sheet with a spatial resolution varying from 10 km inland to 2 km along the coast on a massively-parallelized architecture named CIELO and developed at JPL. The model is based on a "Pattyn" type formulation for ice sheets, and a "MacAyeal shelf-stream" formulation for ice shelves. Both types of formulations are coupled using penalty methods, which enables a considerable reduction of the computational load. Using a simple law of basal friction (based on locally computed balanced velocities), the model is able to replicate the location and order-magnitude speed of major ice streams and ice shelves. We then coupled the model with observations of ice motion from SAR interferometry to refine the pattern of basal friction using an inverse control method (MacAyeal 1993). The result provides an excellent agreement with observations and a first complete mapping of the pattern of basal friction along the coast of Antarctica at a resolution compatible with the size of its glaciers and ice streams.
Rali, Parth; Gandhi, Viral; Tariq, Cheema
2016-01-01
Hemoptysis, or coughing of blood, oftentimes triggers anxiety and fear for patients. The etiology of hemoptysis will determine the clinical course, which includes watchful waiting or intensive care admission. Any amount of hemoptysis that compromises the patient's respiratory status is considered massive hemoptysis and should be considered a medical emergency. In this article, we review introduction, definition, bronchial circulation anatomy, etiology, and management of massive hemoptysis.
Disks Surrounding Massive Stars: When Computational Models are Confronted by Observations
2010-01-01
frecuentemente, ĺıneas de emisión de metales una vez ionizados, debido a la presencia del disco. Hemos calculado modelos teóricos computacionales de...parámetros libres del modelo para estos sistemas estrella-disco. ABSTRACT Many massive stars are embedded within gaseous circumstellar matter; sometimes dust
Signatures of massive collisions in debris discs. A self-consistent numerical model
NASA Astrophysics Data System (ADS)
Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.
2015-01-01
Context. Violent stochastic collisional events have been invoked as a possible explanation for some debris discs displaying pronounced azimuthal asymmetries or having a luminosity excess exceeding that expected for systems at collisional steady-state. So far, no thorough modelling of the consequences of such stochastic events has been carried out, mainly because of the extreme numerical challenge of coupling the dynamical and collisional evolution of the released dust. Aims: We perform the first fully self-consistent modelling of the aftermath of massive breakups in debris discs. We follow the collisional and dynamical evolution of dust released after the breakup of a Ceres-sized body at 6 AU from its central star. We investigate the duration, magnitude, and spatial structure of the signature left by such a violent event, as well as its observational detectability. Methods: We use the recently developed LIDT-DD code, which handles the coupled collisional and dynamical evolution of debris discs. The main focus is placed on the complex interplay between destructive collisions, Keplerian dynamics, and radiation pressure forces. We use the GRaTer package to estimate the system's luminosity at different wavelengths. Results: The breakup of a Ceres-sized body at 6 AU creates an asymmetric dust disc that is homogenized by the coupled action of collisions and dynamics on a timescale of a few 105 years. After a transient period where it is very steep, the particle size distribution in the system relaxes to a collisional steady-state law after ~104 years. The luminosity excess in the breakup's aftermath should be detectable by mid-IR photometry, from a 30 pc distance, over a period of ~106 years that exceeds the duration of the asymmetric phase of the disc (a few 105 years). As for the asymmetric structures, we derive synthetic images for the VLT/SPHERE and JWST/MIRI instruments, showing that they should be clearly visible and resolved from a 10 pc distance. Images at 1.6
Constraining massive star evolution from massive clusters
NASA Astrophysics Data System (ADS)
Chene, Andre-Nicolas; Herve, Anthony; Martins, Fabrice; Bouret, Jean-Claude; Borissova, Jordanka; Ramirez, Sebastian; Kurtev, Radostin; Kumar, Nanda; Amigo, Pia; Fierro, Celia
2013-06-01
The exact evolution of massive stars is not accurately known at present. The general trend is that stars with masses above 40 - 60 Mo go from O-type stars to H-rich WN stars, and Luminous Blue Variables (?), before turning into H-poor WN stars and finally WC stars. At lower masses, the H-rich WN and LBV phases are replaced by a blue and a red supergiant phases, respectively. However, what are the details of such evolutionary sequences? The study of massive clusters is a golden opportunity to establish this. Indeed, the turn-off mass of massive clusters can be directly translated into the mass, and hence the nature, of the progenitors of their evolved objects contents. So far, only the Arches, Quintuplet, NGC3603, NGC2244 and central clusters have been studied this way. But 6 newly discovered heavily-obscured clusters in the large survey â"VISTA Variables in the Via Lactea" (VVV) have been found to have Wolf-Rayet stars as well as blue and/or red supergiants, together with many main sequence OB stars. This poster presents our efforts to model the massive star components of these clusters using CMFGEN, bringing new blocks to the pavement of massive stellar evolution and more than doubling the number of clusters in which such evolutionary sequence are established.
Kamada, Ayuki; Yoshida, Naoki; Kohri, Kazunori; Takahashi, Tomo E-mail: naoki.yoshida@phys.s.u-tokyo.ac.jp E-mail: tomot@cc.saga-u.ac.jp
2013-03-01
We study the formation of non-linear structures in warm dark matter (WDM) models and in a long-lived charged massive particle (CHAMP) model. CHAMPs with a decay lifetime of about 1 yr induce characteristic suppression in the matter power spectrum at subgalactic scales through acoustic oscillations in the thermal background. We explore structure formation in such a model. We also study three WDM models, where the dark matter particles are produced through the following mechanisms: i) WDM particles are produced in the thermal background and then kinematically decoupled; ii) WDM particles are fermions produced by the decay of thermal heavy bosons; and iii) WDM particles are produced by the decay of non-relativistic heavy particles. We show that the linear matter power spectra for the three models are all characterised by the comoving Jeans scale at the matter-radiation equality. Furthermore, we can also describe the linear matter power spectrum for the long-lived CHAMP model in terms of a suitably defined characteristic cut-off scale k{sub Ch}, similarly to the WDM models. We perform large cosmological N-body simulations to study the non-linear growth of structures in these four models. We compare the halo mass functions, the subhalo mass functions, and the radial distributions of subhalos in simulated Milky Way-size halos. For the characteristic cut-off scale k{sub cut} = 51 h Mpc{sup −1}, the subhalo abundance ( ∼ 10{sup 9}M{sub sun}) is suppressed by a factor of ∼ 10 compared with the standard ΛCDM model. We then study the models with k{sub cut} ≅ 51, 410, 820 h Mpc{sup −1}, and confirm that the halo and the subhalo abundances and the radial distributions of subhalos are indeed similar between the different WDM models and the long-lived CHAMP model. The result suggests that the cut-off scale k{sub cut} not only characterises the linear power spectra but also can be used to predict the non-linear clustering properties. The radial distribution of subhalos
Quark Model Estimate of ω NN and ρ NN Coupling Constants.
NASA Astrophysics Data System (ADS)
Qian, L.; Banerjee, S.; Tandy, P. C.
1996-10-01
Approximate Bethe-Salpeter solutions for ρ and ω mesons are used to estimate the vector and tensor coupling constants for these mesons with the nucleon. The meson-quark amplitudes are coupled to the valence quarks of a mean field chiral quark-meson model of the nucleon. The meson description used here is based upon a finite range barqq interaction which in turn is constrained only by pion physics. The vector meson properties here are therefore predictions. In this respect, and others, the present results are compared to recent estimates(S.-F. Gao, L.S. Celenza, C.M. Shakin, W.-D. Sun and J. Szweda, Phys. Rev. C53), 1936 (1996). of vector meson coupling constants based upon the zero-range Nambu-Jona-Lasinio (NJL) model. In particular, we find a ratio f_ρ / g_ρ agreeing better with the empirical value than with the vector meson dominance value inherent in the NJL model. The absolute values of the vector coupling constants are found to be very similar to the empirical values; the magnitudes of the meson barqq substructure amplitudes are crucial to this result.
Mapping and Modeling the Extended Winds of the Massive Interacting Binary, Eta Carinae
NASA Technical Reports Server (NTRS)
Gull, Ted
2010-01-01
The combination HST/STIS high spatial and moderate spectral resolutions have revealed the massive interacting wind structure of Eta Carinae by forbidden lines of singly and doubly ionized elements. Throughout the 5.54-year period, lines of Fe++, Ne++, Ar++, S++ and N+ reveal the interacting wind structures, near critical electron densities of 10(exp 5) to 3 x 10(exp 7)cu cm, photoionized by the hot secondary, Eta Car B, Lines of Fe+ and Ni+ trace the denser (>10(exp 7)cu cm. less-ionized (< 8 eV) primary wind of Eta Car A as it wraps around the interacting binary stars. For 5 years of the 5.54 year period, the FUV radiation from Eta Car B escapes the orbital region, ionizing the boundaries of the expanding wind structures. But for three to six months, Eta Car B plunges into the primary wind approaching to within 1 to 2 AU, leading to cutoff of FUV and X-ray fluxes. The interacting wind structure, resolved out to 0.8", drops io ionization and then rebuilds as Eta Car B emerges from the primary wind envelope. Solid Particle Hydrodynamical(SPH) models have been developed extending out to 2000 AU and adapted to include FUV radiation effects of the winds. In turn, synthetic spectroimages of selected forbidden lines have been constructed and compared to the spectroimages recorded by the HST/STIS throughout 1998.0 to 2004.3, extending across the 1998 and 2003.5 minima. By this method, we show that the orbital axis of the binary system must bc within 15 degrees of the Homunculus axis of symmetry and that periastron occurs with Eta Car B passing on the far side of Eta Car B. This result ties the current binary orbit with the bipolar ejection with intervening skirt and leads to implications that the binary system influenced the mass ejection of the l840s and the lesser ejection of the 1890s.
Mapping and Modeling the Extended Winds of the Massive Interacting Binary, Eta Carinae
NASA Technical Reports Server (NTRS)
Gull, Ted
2010-01-01
The combination HST/STIS high spatial and moderate spectral resolutions have revealed the massive interacting wind structure of Eta Carinae by forbidden lines of singly and doubly ionized elements. Throughout the 5.54-year period, lines of Fe++, Ne++, Ar++, S++ and N+ reveal the interacting wind structures, near critical electron densities of 10(exp 5) to 3 x 10(exp 7)cu cm, photoionized by the hot secondary, Eta Car B, Lines of Fe+ and Ni+ trace the denser (>10(exp 7)cu cm. less-ionized (< 8 eV) primary wind of Eta Car A as it wraps around the interacting binary stars. For 5 years of the 5.54 year period, the FUV radiation from Eta Car B escapes the orbital region, ionizing the boundaries of the expanding wind structures. But for three to six months, Eta Car B plunges into the primary wind approaching to within 1 to 2 AU, leading to cutoff of FUV and X-ray fluxes. The interacting wind structure, resolved out to 0.8", drops io ionization and then rebuilds as Eta Car B emerges from the primary wind envelope. Solid Particle Hydrodynamical(SPH) models have been developed extending out to 2000 AU and adapted to include FUV radiation effects of the winds. In turn, synthetic spectroimages of selected forbidden lines have been constructed and compared to the spectroimages recorded by the HST/STIS throughout 1998.0 to 2004.3, extending across the 1998 and 2003.5 minima. By this method, we show that the orbital axis of the binary system must bc within 15 degrees of the Homunculus axis of symmetry and that periastron occurs with Eta Car B passing on the far side of Eta Car B. This result ties the current binary orbit with the bipolar ejection with intervening skirt and leads to implications that the binary system influenced the mass ejection of the l840s and the lesser ejection of the 1890s.
Eliasberg, Claire D; Dar, Ayelet; Jensen, Andrew R; Murray, Iain R; Hardy, Winters R; Kowalski, Tomasz J; Garagozlo, Cameron A; Natsuhara, Kyle M; Khan, Adam Z; McBride, Owen J; Cha, Peter I; Kelley, Benjamin V; Evseenko, Denis; Feeley, Brian T; McAllister, David R; Péault, Bruno; Petrigliano, Frank A
2017-02-15
Rotator cuff tears are a common cause of shoulder pain and often necessitate operative repair. Muscle atrophy, fibrosis, and fatty infiltration can develop after rotator cuff tears, which may compromise surgical outcomes. This study investigated the regenerative potential of 2 human adipose-derived progenitor cell lineages in a murine model of massive rotator cuff tears. Ninety immunodeficient mice were used (15 groups of 6 mice). Mice were assigned to 1 of 3 surgical procedures: sham, supraspinatus and infraspinatus tendon transection (TT), or TT and denervation via suprascapular nerve transection (TT + DN). Perivascular stem cells (PSCs) were harvested from human lipoaspirate and sorted using fluorescence-activated cell sorting into pericytes (CD146 CD34 CD45 CD31) and adventitial cells (CD146 CD34 CD45 CD31). Mice received no injection, injection with saline solution, or injection with pericytes or adventitial cells either at the time of the index procedure ("prophylactic") or at 2 weeks following the index surgery ("therapeutic"). Muscles were harvested 6 weeks following the index procedure. Wet muscle weight, muscle fiber cross-sectional area, fibrosis, and fatty infiltration were analyzed. PSC treatment after TT (prophylactic or therapeutic injections) and after TT + DN (therapeutic injections) resulted in less muscle weight loss and greater muscle fiber cross-sectional area than was demonstrated for controls (p < 0.05). The TT + DN groups treated with pericytes at either time point or with adventitial cells at 2 weeks postoperatively had less fibrosis than the TT + DN controls. There was less fatty infiltration in the TT groups treated with pericytes at either time point or with adventitial cells at the time of surgery compared with controls. Our findings demonstrated significantly less muscle atrophy in the groups treated with PSCs compared with controls. This suggests that the use of PSCs may have a role in the prevention of muscle atrophy without leading
Quantum cosmological Friedman models with a massive Yang-Mills field
NASA Astrophysics Data System (ADS)
Gerhardt, Claus
2009-07-01
We prove the existence of a spectral resolution of the Wheeler-DeWitt equation when the matter field is provided by a massive Yang-Mills field. The resolution is achieved by first solving the free eigenvalue problem for the gravitational field and then the constrained eigenvalue problem for the Yang-Mills field. In the latter case, the mass of the Yang-Mills field assumes the role of the eigenvalue.
The evolution of massive stars
NASA Technical Reports Server (NTRS)
1982-01-01
The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.
NASA Astrophysics Data System (ADS)
Rong, Yu; Jing, Yingjie; Gao, Liang; Guo, Qi; Wang, Jie; Sun, Shuangpeng; Wang, Lin; Pan, Jun
2017-10-01
We take advantage of the statistical power of the large-volume dark-matter-only Millennium simulation, combined with a sophisticated semi-analytic galaxy formation model, to explore whether the recently reported $z=3.7$ quiescent galaxy ZF-COSMOS-20115 (ZF; Glazebrook et al. 2017) can be accommodated in current galaxy formation models. In our model, a population of quiescent galaxies (QGs) with stellar masses and star formation rates comparable to those of ZF naturally emerges at redshifts $z<4$. There are two and five ZF analogues at the redshift $3.86$ and $3.58$ in the Millennium simulation volume, respectively. We demonstrate that, while the $z>3.5$ massive QGs are rare (about 2\\% of the galaxies with the similar stellar masses), the existing AGN feedback model implemented in the semi-analytic galaxy formation model can successfully explain the formation of the high-redshift QGs as it does on their lower redshift counterparts.
Quark-Novae in massive binaries: a model for double-humped, hydrogen-poor, superluminous Supernovae
NASA Astrophysics Data System (ADS)
Ouyed, Rachid; Leahy, Denis; Koning, Nico
2015-12-01
LSQ14bdq and SN 2006oz are superluminous, hydrogen-poor, SNe with double-humped light curves. We show that a Quark-Nova (QN; explosive transition of the Neutron Star - NS - to a quark star -QS) occurring in a massive binary, experiencing two Common Envelope (CE) phases, can quantitatively explain the light curves of LSQ14bdq and SN 2006oz. The more massive component (A) explodes first as a normal SN, yielding a NS which ejects the hydrogen envelope of the companion when the system enters its first CE phase. During the second CE phase, the NS spirals into and inflates the second He-rich CE. In the process it gains mass and triggers a QN, outside of the CO core, leaving behind a QS. The first hump in our model is the QN shock re-energizing the expanded He-rich CE. The QN occurs when the He-rich envelope is near maximum size (˜1000 R⊙) and imparts enough energy to unbind and eject the envelope. Subsequent merging of the QS with the CO core of component B, driven by gravitational radiation, turns the QS to a black hole. The ensuing black hole accretion provides sufficient power for the second brighter and long lasting hump. Our model suggests a possible connection between SLSNe-I and type Ic-BL SNe which occur when the QN is triggered inside the CO core. We estimate the rate of QNe in massive binaries during the second CE phase to be ˜5 × 10-5 of that of core-collapse SNe.
NASA Astrophysics Data System (ADS)
LeFloch, Philippe G.; Ma, Yue
2016-09-01
The Hyperboloidal Foliation Method (introduced by the authors in 2014) is extended here and applied to the Einstein equations of general relativity. Specifically, we establish the nonlinear stability of Minkowski spacetime for self-gravitating massive scalar fields, while existing methods only apply to massless scalar fields. First of all, by analyzing the structure of the Einstein equations in wave coordinates, we exhibit a nonlinear wave-Klein-Gordon model defined on a curved background, which is the focus of the present paper. For this model, we prove here the existence of global-in-time solutions to the Cauchy problem, when the initial data have sufficiently small Sobolev norms. A major difficulty comes from the fact that the class of conformal Killing fields of Minkowski space is significantly reduced in the presence of a massive scalar field, since the scaling vector field is not conformal Killing for the Klein-Gordon operator. Our method relies on the foliation (of the interior of the light cone) of Minkowski spacetime by hyperboloidal hypersurfaces and uses Lorentz-invariant energy norms. We introduce a frame of vector fields adapted to the hyperboloidal foliation and we establish several key properties: Sobolev and Hardy-type inequalities on hyperboloids, as well as sup-norm estimates, which correspond to the sharp time decay for the wave and the Klein-Gordon equations. These estimates allow us to control interaction terms associated with the curved geometry and the massive field by distinguishing between two levels of regularity and energy growth and by a successive use of our key estimates in order to close a bootstrap argument.
Inconsistency of topologically massive hypergravity
NASA Technical Reports Server (NTRS)
Aragone, C.; Deser, S.
1985-01-01
The coupled topologically massive spin-5/2 gravity system in D = 3 dimensions whose kinematics represents dynamical propagating gauge invariant massive spin-5/2 and spin-2 excitations, is shown to be inconsistent, or equivalently, not locally hypersymmetric. In contrast to D = 4, the local constraints on the system arising from failure of the fermionic Bianchi identities do not involve the 'highest spin' components of the field, but rather the auxiliary spinor required to construct a consistent massive model.
Villaescusa-Navarro, Francisco; Viel, Matteo; Marulli, Federico; Castorina, Emanuele; Sefusatti, Emiliano; Saito, Shun E-mail: federico.marulli3@unibo.it E-mail: branchin@fis.uniroma3.it E-mail: esefusat@ictp.it
2014-03-01
By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the
NASA Astrophysics Data System (ADS)
Hervías, C.; Bronfman, L.; Merello, M.; Ake-Nyman, L.; Lo, N.; Garay, G.
2015-12-01
We present observations and analysis of the massive molecular outflow G331.512-0.103, obtained with ALMA band 7, preliminary presented in Merello et al. (2013a). The lines can be classified into two groups: with narrow velocity emission, tracing the systemic velocity ambient medium and the sub-structures within; and with broad velocity wings, tracing the outflow and shocked gas emission. The physical conditions are calculated. The ambient medium core has a mean density of ˜5×106 cm-3 and a temperature of ˜ 70 K. The interpretation of the molecular emission suggest an expanding cavity geometry powered by stellar winds from a new-born UCHII region, alongside a massive and high-velocity molecular outflow. Also, the presence of sub-structures is made evident by the emission of narrow lines such as CH3OH and CH3CCH. This scenario, along with the estimated physical conditions, is modeled through a 3D geometry radiative transfer code: MOLLIE; in the SiO(J=8-7) molecular line. The main features of the the outflow and the expanding cavity are reproduced by the model.
Hsu, Jason E; Reuther, Katherine E; Sarver, Joseph J; Lee, Chang Soo; Thomas, Stephen J; Glaser, David L; Soslowsky, Louis J
2011-07-01
The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff "force couple," is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior-posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two-tendon rotator cuff tears in a rat model. Forty-eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two-tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two-tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two-tendon tear may be sufficient to restore adequate function. An in vivo model system for two-tendon repair of massive rotator cuff tears is presented. Copyright © 2011 Orthopaedic Research Society.
Hsu, Jason E.; Reuther, Katherine E.; Sarver, Joseph J.; Lee, Chang Soo; Thomas, Stephen J.; Glaser, David L.; Soslowsky, Louis J.
2011-01-01
The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff “force couple,” is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior-posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two-tendon rotator cuff tears in a rat model. Forty-eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two-tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two-tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two tendon tear may be sufficient to restore adequate function. An in vivo model system for two-tendon repair of massive rotator cuff tears is presented. PMID:21308755
A model for the non-thermal emission of the very massive colliding-wind binary HD 93129A
NASA Astrophysics Data System (ADS)
del Palacio, S.; Romero, G. E.; Bosch-Ramon, V.; Benaglia, P.
2016-08-01
Recently, the wind collision region of the system HD 93129A was resolved for the first time using very large baseline interferometry. This system is one of the most massive known binaries in our Galaxy. In this work we develop a broadband radiative model for the wind collision region. The model takes into account the evolution of accelerated particles streaming along the shocked region, their emission through different radiative processes, and the attenuation of the radiation while it propagates across all local fields. We reproduce the available radio data, and analyze the consequent detectability of the source in hard X/gamma-rays. We predict how the emission from the system will evolve in the forthcoming years when the stars come closer, and we also provide synthetic radio maps that allow to interpret the future observations with very large baseline interferometry in 2.3 GHz and 8.6 GHz. According to our results, the non-thermal emission from this system will enhance in the near future. With instruments such as NuSTAR, Fermi, and CTA, it will be possible to determine whether the relativistic particle content is hadron or lepton dominated, and other parameters such as the strength of the magnetic field in the wind collision region and, indirectly, the magnetic field in the surface of the very massive stars.
Model for Thermal Relic Dark Matter of Strongly Interacting Massive Particles.
Hochberg, Yonit; Kuflik, Eric; Murayama, Hitoshi; Volansky, Tomer; Wacker, Jay G
2015-07-10
A recent proposal is that dark matter could be a thermal relic of 3→2 scatterings in a strongly coupled hidden sector. We present explicit classes of strongly coupled gauge theories that admit this behavior. These are QCD-like theories of dynamical chiral symmetry breaking, where the pions play the role of dark matter. The number-changing 3→2 process, which sets the dark matter relic abundance, arises from the Wess-Zumino-Witten term. The theories give an explicit relationship between the 3→2 annihilation rate and the 2→2 self-scattering rate, which alters predictions for structure formation. This is a simple calculable realization of the strongly interacting massive-particle mechanism.
NASA Astrophysics Data System (ADS)
Fil, A.; Nardon, E.; Hoelzl, M.; Huijsmans, G. T. A.; Orain, F.; Becoulet, M.; Beyer, P.; Dif-Pradalier, G.; Guirlet, R.; Koslowski, H. R.; Lehnen, M.; Morales, J.; Pamela, S.; Passeron, C.; Reux, C.; Saint-Laurent, F.
2015-06-01
JOREK 3D non-linear MHD simulations of a D2 Massive Gas Injection (MGI) triggered disruption in JET are presented and compared in detail to experimental data. The MGI creates an overdensity that rapidly expands in the direction parallel to the magnetic field. It also causes the growth of magnetic islands ( m / n = 2 / 1 and 3/2 mainly) and seeds the 1/1 internal kink mode. O-points of all island chains (including 1/1) are located in front of the MGI, consistently with experimental observations. A burst of MHD activity and a peak in plasma current take place at the same time as in the experiment. However, the magnitude of these two effects is much smaller than in the experiment. The simulated radiation is also much below the experimental level. As a consequence, the thermal quench is not fully reproduced. Directions for progress are identified. Radiation from impurities is a good candidate.
Modeling gas-phase H2O between 5 μ m and 540 μ m toward massive protostars
NASA Astrophysics Data System (ADS)
Boonman, A. M. S.; Doty, S. D.; van Dishoeck, E. F.; Bergin, E. A.; Melnick, G. J.; Wright, C. M.; Stark, R.
2003-08-01
We present models and observations of gas-phase H2O lines between 5 and 540 mu m toward deeply embedded massive protostars, involving both pure rotational and ro-vibrational transitions. The data have been obtained for 6 sources with both the Short and Long Wavelength Spectrometers (SWS and LWS) on board the Infrared Space Observatory (ISO) and with the Submillimeter Wave Astronomy Satellite (SWAS). For comparison, CO J=7-6 spectra have been observed with the MPIfR/SRON 800 GHz heterodyne spectrometer at the James Clerk Maxwell Telescope (JCMT). A radiative transfer model in combination with different physical/chemical scenarios has been used to model these H2O lines for 4 sources to probe the chemical structure of these massive protostars. The results indicate that pure gas-phase production of H2O cannot explain the observed spectra. Ice evaporation in the warm inner envelope and freeze-out in the cold outer part are important for most of our sources and occur at T ~ 90-110 K. The ISO-SWS data are particularly sensitive to ice evaporation in the inner part whereas the ISO-LWS data are good diagnostics of freeze-out in the outer region. The modeling suggests that the 557 GHz SWAS line includes contributions from both the cold and the warm H2O gas. The SWAS line profiles indicate that for some of the sources a fraction of up to 50% of the total flux may originate in the outflow. Shocks do not seem to contribute significantly to the observed emission in other H2O lines, however, in contrast with the case for Orion. The results show that three of the observed and modeled H2O lines, the 303-212, 212-101, and 110-101 lines, are good candidates to observe with the Herschel Space Observatory in order to further investigate the physical and chemical conditions in massive star-forming regions. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and UK) and with the
Massive Supergravity and Deconstruction
Gregoire, Thomas; Schwartz, Matthew D.; Shadmi, Yael
2004-03-23
We present a simple superfield Lagrangian for massive supergravity. It comprises the minimal supergravity Lagrangian with interactions as well as mass terms for the metric superfield and the chiral compensator. This is the natural generalization of the Fierz-Pauli Lagrangian for massive gravity which comprises mass terms for the metric and its trace. We show that the on-shell bosonic and fermionic fields are degenerate and have the appropriate spins: 2, 3/2, 3/2 and 1. We then study this interacting Lagrangian using goldstone superfields. We find that achiral multiplet of goldstones gets a kinetic term through mixing, just as the scalar goldstone does in the non-supersymmetric case. This produces Planck scale (Mpl) interactions with matter and all the discontinuities and unitarity bounds associated with massive gravity. In particular, the scale of strong coupling is (Mpl m^4)^1/5, where m is the multiplet's mass. Next, we consider applications of massive supergravity to deconstruction. We estimate various quantum effects which generate non-local operators in theory space. As an example, we show that the single massive supergravity multiplet in a 2-site model can serve the function of an extra dimension in anomaly mediation.
NASA Astrophysics Data System (ADS)
Weber, J. A.; Pauldrach, A. W. A.; Hoffmann, T. L.
2015-11-01
Context. H II regions play a crucial role in the measurement of the chemical composition of the interstellar medium and provide fundamental data about element abundances that constrain models of galactic chemical evolution. Discrepancies that still exist between observed emission line strengths and those predicted by nebular models can be partly attributed to the spectral energy distributions (SEDs) of the sources of ionizing radiation used in the models as well as to simplifying assumptions made in nebular modeling. Aims: One of the main influences on the nebular spectra is the metallicity, both nebular and stellar, which shows large variations even among nearby galaxies. Although nebular modeling often involves testing of different nebular metallicities against their influence on the predicted spectra, adequate grids of stellar atmospheres and realistic SEDs for different metallicities are still lacking. This is unfortunate because the influence of stellar metallicity on nebular line strength ratios, via its effect on the SEDs, is of similar importance as variations in the nebular metallicity. To overcome this deficiency we have computed a grid of model atmosphere SEDs for massive and very massive O-type stars covering a range of metallicities from significantly subsolar (0.1 Z⊙) to supersolar (2 Z⊙). Methods: The SEDs have been computed using a state-of-the-art model atmosphere code that takes into account the attenuation of the ionizing flux by the spectral lines of all important elements and the hydrodynamics of the radiatively driven winds and their influence on the SEDs. For the assessment of the SEDs in nebular simulations we have developed a (heretofore not available) 3D radiative transfer code that includes a time-dependent treatment of the metal ionization. Results: Using the SEDs in both 1D and 3D nebular models we explore the relative influence of stellar metallicity, gas metallicity, and inhomogeneity of the gas on the nebular ionization structure
Resummation of Massive Gravity
Rham, Claudia de; Gabadadze, Gregory; Tolley, Andrew J.
2011-06-10
We construct four-dimensional covariant nonlinear theories of massive gravity which are ghost-free in the decoupling limit to all orders. These theories resume explicitly all the nonlinear terms of an effective field theory of massive gravity. We show that away from the decoupling limit the Hamiltonian constraint is maintained at least up to and including quartic order in nonlinearities, hence excluding the possibility of the Boulware-Deser ghost up to this order. We also show that the same remains true to all orders in a similar toy model.
ERIC Educational Resources Information Center
Fasimpaur, Karen
2013-01-01
MOOCs--massive open online courses--are all the rage these days, with hundreds of thousands of participants signing up and investors plunking down millions to get a piece of the pie. Why is there so much excitement about this new disruptive form of online learning, and how does this model apply to professional learning for teachers? Traditional…
Pustavoitau, Aliaksei; Lesley, Maggie; Ariyo, Promise; Latif, Asad; Villamayor, April J; Frank, Steven M; Rizkalla, Nicole; Merritt, William; Cameron, Andrew; Dagher, Nabil; Philosophe, Benjamin; Gurakar, Ahmet; Gottschalk, Allan
2017-05-01
Patients undergoing liver transplantation frequently but inconsistently require massive blood transfusion. The ability to predict massive transfusion (MT) could reduce the impact on blood bank resources through customization of the blood order schedule. Current predictive models of MT for blood product utilization during liver transplantation are not generally applicable to individual institutions owing to variability in patient population, intraoperative management, and definitions of MT. Moreover, existing models may be limited by not incorporating cirrhosis stage or thromboelastography (TEG) parameters. This retrospective cohort study included all patients who underwent deceased-donor liver transplantation at the Johns Hopkins Hospital between 2010 and 2014. We defined MT as intraoperative transfusion of > 10 units of packed red blood cells (pRBCs) and developed a multivariable predictive model of MT that incorporated cirrhosis stage and TEG parameters. The accuracy of the model was assessed with the goodness-of-fit test, receiver operating characteristic analysis, and bootstrap resampling. The distribution of correct patient classification was then determined as we varied the model threshold for classifying MT. Finally, the potential impact of these predictions on blood bank resources was examined. Two hundred three patients were included in the study. Sixty (29.6%) patients met the definition for MT and received a median (interquartile range) of 19.0 (14.0-27.0) pRBC units intraoperatively compared with 4.0 units (1.0-6.0) for those who did not satisfy the criterion for MT. The multivariable model for predicting MT included Model for End-stage Liver Disease score, whether simultaneous liver and kidney transplant was performed, cirrhosis stage, hemoglobin concentration, platelet concentration, and TEG R interval and angle. This model demonstrated good calibration (Hosmer-Lemeshow goodness-of-fit test P = .45) and good discrimination (c statistic: 0.835; 95
A model for the non-thermal emission of the very massive colliding-wind binary HD 93129A
NASA Astrophysics Data System (ADS)
del Palacio, Santiago; Bosch-Ramon, Valentí; Romero, Gustavo E.; Benaglia, Paula
2016-06-01
Context. Recently, the colliding-wind region of the binary stellar system HD 93129A was resolved for the first time using Very Large Baseline Interferometry. This system, one of the most massive known binaries in our Galaxy, presents non-thermal emission in the radio band, which can be used to infer the physical conditions in the system, and make predictions for the high-energy band. Aims: We intend to constrain some of the unknown parameters of HD 93129A through modeling the non-thermal emitter. We also aim to analyse the detectability of this source in hard X-rays and γ-rays. Finally, we want to predict how the non-thermal emission will evolve in the future, when the stars approach periastron. Methods: A broadband radiative model for the wind-collision region (WCR) has been developed taking into account the evolution of the accelerated particles streaming along the shocked region, the emission by different radiative processes, and the attenuation of the emission propagating through the local matter and radiation fields. We reproduce the available radio data, and make predictions of the emission in hard X-rays and γ-rays under different assumptions. Results: From the analysis of the radio emission, we find that the binary HD 93129A is more likely to have a low inclination and a high eccentricity, with the more massive star being currently closer to the observer. The minimum energy of the non-thermal electrons seems to be between ~20-100 MeV, depending on the intensity of the magnetic field in the WCR. The latter can be in the range ~20-1500 mG. Conclusions: Our model is able to reproduce the observed radio emission, and predicts that the non-thermal radiation from HD 93129A will increase in the near future. With instruments such as NuSTAR, Fermi, and CTA, it will be possible to constrain the relativistic particle content of the source, and other parameters such as the magnetic field strength in the WCR which, in turn, can be used to obtain upper-limits of the
Sesana, Alberto
2010-08-10
We construct evolutionary tracks for massive black hole binaries (MBHBs) embedded in a surrounding distribution of stars. The dynamics of the binary is evolved by taking into account the erosion of the central stellar cusp bound to the massive black holes, the scattering of unbound stars feeding the binary loss cone, and the emission of gravitational waves (GWs). Stellar dynamics is treated in a hybrid fashion by coupling the results of numerical three-body scattering experiments of bound and unbound stars to an analytical framework for the evolution of the stellar density distribution and for the efficiency of the binary loss-cone refilling. Our main focus is on the behavior of the binary eccentricity, in the attempt of addressing its importance in the merger process and its possible impact for GW detection with the planned Laser Interferometer Space Antenna (LISA), and ongoing and forthcoming pulsar timing array (PTA) campaigns. We produce a family of evolutionary tracks extensively sampling the relevant parameters of the system which are the binary mass, mass ratio and initial eccentricity, the slope of the stellar density distribution, its normalization and the efficiency of loss-cone refilling. We find that, in general, stellar dynamics causes a dramatic increase of the MBHB eccentricity, especially for initially already mildly eccentric and/or unequal mass binaries. This affects the overall system dynamics; high eccentricities enhance the efficiency of GW emission, accelerating the final coalescence process. When applied to standard MBHB population models, our results predict eccentricities in the ranges 10{sup -3}-0.2 and 0.03-0.3 for sources detectable by LISA and PTA, respectively. Such figures may have a significant impact on the signal modeling, on source detection, and on the development of parameter estimation algorithms.
NASA Astrophysics Data System (ADS)
Pouliasis, E.; Di Matteo, P.; Haywood, M.
2017-02-01
In this work, two new axisymmetric models for the Galactic mass distribution are presented. Motivated by recent results, these two models include the contribution of a stellar thin disc and of a thick disc, as massive as the thin counterpart but with a shorter scale-length. Both models satisfy a number of observational constraints: stellar densities at the solar vicinity, thin and thick disc scale lengths and heights, rotation curve(s), and the absolute value of the perpendicular force Kz as a function of distance to the Galactic centre. We numerically integrate into these new models the motion of all Galactic globular clusters for which distances, proper motions, and radial velocities are available, and the orbits of about one thousand stars in the solar vicinity. The retrieved orbital characteristics are compared to those obtained by integrating the clusters and stellar orbits in pure thin disc models. We find that, due to the possible presence of a thick disc, the computed orbital parameters of disc stars can vary by as much as 30-40%. We also show that the systematic uncertainties that affect the rotation curve still plague computed orbital parameters of globular clusters by similar amounts.
Simulation of the world ocean climate with a massively parallel numerical model
NASA Astrophysics Data System (ADS)
Ushakov, K. V.; Ibrayev, R. A.; Kalmykov, V. V.
2015-07-01
The INM-IO numerical World Ocean model is verified through the calculation of the model ocean climate. The numerical experiment was conducted for a period of 500 years following the CORE-I protocol. We analyze some basic elements of the large-scale ocean circulation and local and integral characteristics of the model solution. The model limitations and ways they are overcome are described. The results generally fit the level of leading models. This experiment is a necessary step preceding the transition to high-resolution diagnostic and prognostic calculations of the state of the World Ocean and its individual basins.
NASA Astrophysics Data System (ADS)
Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.
2014-12-01
LIDT-DD is a new hybrid model coupling the collisional and dynamical evolution in debris discs in a self-consistent way. It has been developed in a way that allows to treat a large number of different astrophysical cases where collisions and dynamics have an important role. This interplay was often totally neglected in previous studies whereas, even for the simplest configurations, the real physics of debris discs imposes strong constraints and interactions between dynamics and collisions. After presenting the LIDT-DD model, we will describe the evolution of violent stochastic collisional events with this model. These massive impacts have been invoked as a possible explanation for some debris discs displaying pronounced azimuthal asymmetries or having a luminosity excess exceeding that expected for systems at collisional steady-state. So far, no thorough modelling of the consequences of such stochastic events has been carried out, mainly because of the extreme numerical challenge of coupling the dynamical and collisional evolution of the released dust. We follow the collisional and dynamical evolution of dust released after the breakup of a Ceres-sized body at 6 AU from its central star. We investigate the duration, magnitude and spatial structure of the signature left by such a violent event, as well as its observational detectability. We use the GRaTer package to estimate the system's luminosity at different wavelengths and derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments.
Volcanogenic Massive Sulfide Deposit Density
Mosier, Dan L.; Singer, Donald A.; Berger, Vladimir I.
2007-01-01
A mineral-deposit density model for volcanogenic massive sulfide deposits was constructed from 38 well-explored control areas from around the world. Control areas contain at least one exposed volcanogenic massive sulfide deposit. The control areas used in this study contain 150 kuroko, 14 Urals, and 25 Cyprus massive sulfide subtypes of volcanogenic massive sulfide deposits. For each control area, extent of permissive rock, number of exposed volcanogenic massive sulfide deposits, map scale, deposit age, and deposit density were determined. The frequency distribution of deposit densities in these 38 control areas provides probabilistic estimates of the number of deposits for tracts that are permissive for volcanogenic massive sulfide deposits-90 percent of the control areas have densities of 100 or more deposits per 100,000 square kilometers, 50 percent of the control areas have densities of 700 or more deposits per 100,000 square kilometers, and 10 percent of the control areas have densities of 3,700 or more deposits per 100,000 square kilometers. Both map scale and the size of the control area are shown to be predictors of deposit density. Probabilistic estimates of the number of volcanogenic massive sulfide deposits can be made by conditioning the estimates on sizes of permissive area. The model constructed for this study provides a powerful tool for estimating the number of undiscovered volcanogenic massive sulfide deposits when conducting resource assessments. The value of these deposit densities is due to the consistency of these models with the grade and tonnage and the descriptive models. Mineral-deposit density models combined with grade and tonnage models allow reasonable estimates of the number, size, and grades of volcanogenic massive sulfide deposits to be made.
Madhusudhan, Nikku; Burrows, Adam; Currie, Thayne E-mail: burrows@astro.princeton.edu
2011-08-10
We have generated an extensive new suite of massive giant planet atmosphere models and used it to obtain fits to photometric data for the planets HR 8799b, c, and d. We consider a wide range of cloudy and cloud-free models. The cloudy models incorporate different geometrical and optical thicknesses, modal particle sizes, and metallicities. For each planet and set of cloud parameters, we explore grids in gravity and effective temperature, with which we determine constraints on the planet's mass and age. Our new models yield statistically significant fits to the data, and conclusively confirm that the HR 8799 planets have much thicker clouds than those required to explain data for typical L and T dwarfs. Both models with (1) physically thick forsterite clouds and a 60 {mu}m modal particle size and (2) clouds made of 1 {mu}m sized pure iron droplets and 1% supersaturation fit the data. Current data are insufficient to accurately constrain the microscopic cloud properties, such as composition and particle size. The range of best-estimated masses for HR 8799b, HR 8799c, and HR 8799d conservatively span 2-12 M{sub J} , 6-13 M{sub J} , and 3-11 M{sub J} , respectively, and imply coeval ages between {approx}10 and {approx}150 Myr, consistent with previously reported stellar ages. The best-fit temperatures and gravities are slightly lower than values obtained by Currie et al. using even thicker cloud models. Finally, we use these models to predict the near-to-mid-IR colors of soon-to-be imaged planets. Our models predict that planet-mass objects follow a locus in some near-to-mid-IR color-magnitude diagrams that is clearly separable from the standard L/T dwarf locus for field brown dwarfs.
Interactive analysis and visualization of massive earth system models using VAPOR
NASA Astrophysics Data System (ADS)
Norton, Alan; Clyne, John
2013-04-01
Recent trends in earth system modeling are leading to a dramatic increase in the size of simulation outputs; however current visualization and analysis capabilities do not readily scale with the increased simulation size. VAPOR is a visualization and analysis package that was designed to enable interactive visualization and analysis of these large datasets, using a wavelet-based multiscale data model. VAPOR runs on Mac, Windows and Linux desktops, exploiting the power of modern graphics cards. VAPOR includes several features to facilitate interactive analysis of earth system data, such as built-in support for Python/NumPy scripting, streamlines, particle tracing and geo-referencing. In this presentation the capabilities of VAPOR will be described and applied to various earth system models. We shall show how to use VAPOR to interactively browse and analyze these large datasets, such as the results of the POP ocean model and the WRF-ARW weather model.
Shear-free axial model in massive Brans-Dicke gravity
NASA Astrophysics Data System (ADS)
Sharif, M.; Manzoor, Rubab
2017-01-01
This paper explores the influences of dark energy on the shear-free axially symmetric evolution by considering self-interacting Brans-Dicke gravity as a dark energy candidate. We describe energy source of the model and derive all the effective dynamical variables as well as effective structure scalars. It is found that scalar field is one of the sources of anisotropy and dissipation. The resulting effective structure scalars help to study the dynamics associated with dark energy in any axial configuration. In order to investigate shear-free evolution, we formulate a set of governing equations along with heat transport equation. We discuss consequences of shear-free condition upon different SBD fluid models like dissipative non-geodesic and geodesic models. For dissipative non-geodesic case, the rotational distribution turns out to be the necessary and sufficient condition for radiating model. The dissipation depends upon inhomogeneous expansion. The geodesic model is found to be irrotational and non-radiating. The non-dissipative geodesic model leads to FRW model for positive values of the expansion parameter.
NASA Astrophysics Data System (ADS)
Glover, Simon C. O.
2015-08-01
The direct collapse model for the formation of massive seed black holes in the early Universe attempts to explain the observed number density of supermassive black holes (SMBHs) at z ˜ 6 by assuming that they grow from seeds with masses M > 104 M⊙ that form by the direct collapse of metal-free gas in atomic cooling haloes in which H2 cooling is suppressed by a strong extragalactic radiation field. The viability of this model depends on the strength of the radiation field required to suppress H2 cooling, Jcrit: if this is too large, then too few seeds will form to explain the observed number density of SMBHs. In order to determine Jcrit reliably, we need to be able to accurately model the formation and destruction of H2 in gas illuminated by an extremely strong radiation field. In this paper, we use a reaction-based reduction technique to analyse the chemistry of H2 in these conditions, allowing us to identify the key chemical reactions that are responsible for determining the value of Jcrit. We construct a reduced network of 26 reactions that allows us to determine Jcrit accurately, and compare it with previous treatments in the literature. We show that previous studies have often omitted one or more important chemical reactions, and that these omissions introduce an uncertainty of up to a factor of 3 into previous determinations of Jcrit.
NASA Astrophysics Data System (ADS)
Randles, Amanda Elizabeth
Accurate and reliable modeling of cardiovascular hemodynamics has the potential to improve understanding of the localization and progression of heart diseases, which are currently the most common cause of death in Western countries. However, building a detailed, realistic model of human blood flow is a formidable mathematical and computational challenge. The simulation must combine the motion of the fluid, the intricate geometry of the blood vessels, continual changes in flow and pressure driven by the heartbeat, and the behavior of suspended bodies such as red blood cells. Such simulations can provide insight into factors like endothelial shear stress that act as triggers for the complex biomechanical events that can lead to atherosclerotic pathologies. Currently, it is not possible to measure endothelial shear stress in vivo, making these simulations a crucial component to understanding and potentially predicting the progression of cardiovascular disease. In this thesis, an approach for efficiently modeling the fluid movement coupled to the cell dynamics in real-patient geometries while accounting for the additional force from the expansion and contraction of the heart will be presented and examined. First, a novel method to couple a mesoscopic lattice Boltzmann fluid model to the microscopic molecular dynamics model of cell movement is elucidated. A treatment of red blood cells as extended structures, a method to handle highly irregular geometries through topology driven graph partitioning, and an efficient molecular dynamics load balancing scheme are introduced. These result in a large-scale simulation of the cardiovascular system, with a realistic description of the complex human arterial geometry, from centimeters down to the spatial resolution of red-blood cells. The computational methods developed to enable scaling of the application to 294,912 processors are discussed, thus empowering the simulation of a full heartbeat. Second, further extensions to enable
UV-extended E-MILES stellar population models: young components in massive early-type galaxies
NASA Astrophysics Data System (ADS)
Vazdekis, A.; Koleva, M.; Ricciardelli, E.; Röck, B.; Falcón-Barroso, J.
2016-12-01
We present UV-extended E-MILES stellar population synthesis models covering the spectral range λλ 1680-50 000 Å at moderately high resolution. We employ the NGSL space-based stellar library to compute spectra of single-age, single-metallicity stellar populations in the wavelength range from 1680 to 3540 Å. These models represent a significant improvement in resolution and age/metallicity coverage over previous studies based on earlier space-based libraries. These model spectra were joined with those we computed in the visible using MILES, and other empirical libraries for redder wavelengths. The models span the metallicity range -1.79≤ [M/H]≤ +0.26 and ages above 30 Myr, for a suite of initial mass function types with varying slopes. We focus on the behaviour of colours, spectra and line-strength indices in the UV range as a function of relevant stellar population parameters. Whereas some indices strengthen with increasing age and metallicity, as most metallicity indicators in the visible, other indices peak around 3 Gyr for metal-rich stellar populations, such as Mg at 2800 Å. Our models provide reasonably good fits to the integrated colours and most line strengths of the stellar clusters of the Milky Way and Large Magellanic Cloud. Our full spectrum fits in the UV range for a representative set of early-type galaxies (ETGs) of varying mass yield age and metallicity estimates in very good agreement with those obtained in the optical range. The comparison of UV colours and line strengths of massive ETGs with our models reveals the presence of young stellar components, with ages in the range 0.1-0.5 Gyr and mass fractions 0.1-0.5 per cent, on the top of an old stellar population.
Investigating Massive Dust Events Using a Coupled Weather-Chemistry Model
NASA Astrophysics Data System (ADS)
Raman, A.; Arellano, A. F.
2012-12-01
Prediction of local to regional scale dust events is challenging due to the complex nature of key processes driving emission, transport, and deposition of mineral dust. In particular, it is difficult to map precisely the sources of mineral dust across heterogeneous land surface properties and land-use changes. This is especially true for Arizona haboobs. These dust storm events are typically driven by thunderstorms and down-bursts over arid regions generating high atmospheric loading of dust in the order of hundreds to thousands of microgram per cubic meter. Modeling and prediction of these events are further complicated by the limitations in satellite-derived and in-situ measurements of dust and related geophysical variables. Here, we investigate the capability of a coupled weather-chemistry model in predicting Arizona haboobs. In particular, this research focuses on the simulation of July 5, 2011 Phoenix haboob using Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and Goddard Chemistry Aerosol Radiation and Transport Model (GOCART) dust scheme. We evaluate the ability of WRF-Chem in simulating the haboob using satellite retrievals of aerosol extinction properties and mass concentrations from Moderate Resolution Imaging Spectroradiometer (MODIS), Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO) and high resolution SEVIRI false color dust product, in conjunction with in-situ PM10 and PM2.5 measurements. The study uses a nested modeling domain covering Utah, California and Arizona at a horizontal resolution of 5.4 km (outer) and 1.8 km (inner). Boundary conditions for the model are obtained from NOAA Global Forecasting System six-hourly forecast. We present results illustrating the key features of the haboobs, such as the cold pools and surface wind speeds driving the horizontal and vertical structure of the dust, as well as the patterns of dust transport and deposition. Although the spatio-temporal patterns of the haboob
Ribay, Kathryn; Kim, Marlene T.; Wang, Wenyi; Pinolini, Daniel; Zhu, Hao
2016-01-01
Estrogen receptors (ERα) are a critical target for drug design as well as a potential source of toxicity when activated unintentionally. Thus, evaluating potential ERα binding agents is critical in both drug discovery and chemical toxicity areas. Using computational tools, e.g., Quantitative Structure-Activity Relationship (QSAR) models, can predict potential ERα binding agents before chemical synthesis. The purpose of this project was to develop enhanced predictive models of ERα binding agents by utilizing advanced cheminformatics tools that can integrate publicly available bioassay data. The initial ERα binding agent data set, consisting of 446 binders and 8307 non-binders, was obtained from the Tox21 Challenge project organized by the NIH Chemical Genomics Center (NCGC). After removing the duplicates and inorganic compounds, this data set was used to create a training set (259 binders and 259 non-binders). This training set was used to develop QSAR models using chemical descriptors. The resulting models were then used to predict the binding activity of 264 external compounds, which were available to us after the models were developed. The cross-validation results of training set [Correct Classification Rate (CCR) = 0.72] were much higher than the external predictivity of the unknown compounds (CCR = 0.59). To improve the conventional QSAR models, all compounds in the training set were used to search PubChem and generate a profile of their biological responses across thousands of bioassays. The most important bioassays were prioritized to generate a similarity index that was used to calculate the biosimilarity score between each two compounds. The nearest neighbors for each compound within the set were then identified and its ERα binding potential was predicted by its nearest neighbors in the training set. The hybrid model performance (CCR = 0.94 for cross validation; CCR = 0.68 for external prediction) showed significant improvement over the original QSAR
Bisetti, Fabrizio; Attili, Antonio; Pitsch, Heinz
2014-01-01
Combustion of fossil fuels is likely to continue for the near future due to the growing trends in energy consumption worldwide. The increase in efficiency and the reduction of pollutant emissions from combustion devices are pivotal to achieving meaningful levels of carbon abatement as part of the ongoing climate change efforts. Computational fluid dynamics featuring adequate combustion models will play an increasingly important role in the design of more efficient and cleaner industrial burners, internal combustion engines, and combustors for stationary power generation and aircraft propulsion. Today, turbulent combustion modelling is hindered severely by the lack of data that are accurate and sufficiently complete to assess and remedy model deficiencies effectively. In particular, the formation of pollutants is a complex, nonlinear and multi-scale process characterized by the interaction of molecular and turbulent mixing with a multitude of chemical reactions with disparate time scales. The use of direct numerical simulation (DNS) featuring a state of the art description of the underlying chemistry and physical processes has contributed greatly to combustion model development in recent years. In this paper, the analysis of the intricate evolution of soot formation in turbulent flames demonstrates how DNS databases are used to illuminate relevant physico-chemical mechanisms and to identify modelling needs. PMID:25024412
Bisetti, Fabrizio; Attili, Antonio; Pitsch, Heinz
2014-08-13
Combustion of fossil fuels is likely to continue for the near future due to the growing trends in energy consumption worldwide. The increase in efficiency and the reduction of pollutant emissions from combustion devices are pivotal to achieving meaningful levels of carbon abatement as part of the ongoing climate change efforts. Computational fluid dynamics featuring adequate combustion models will play an increasingly important role in the design of more efficient and cleaner industrial burners, internal combustion engines, and combustors for stationary power generation and aircraft propulsion. Today, turbulent combustion modelling is hindered severely by the lack of data that are accurate and sufficiently complete to assess and remedy model deficiencies effectively. In particular, the formation of pollutants is a complex, nonlinear and multi-scale process characterized by the interaction of molecular and turbulent mixing with a multitude of chemical reactions with disparate time scales. The use of direct numerical simulation (DNS) featuring a state of the art description of the underlying chemistry and physical processes has contributed greatly to combustion model development in recent years. In this paper, the analysis of the intricate evolution of soot formation in turbulent flames demonstrates how DNS databases are used to illuminate relevant physico-chemical mechanisms and to identify modelling needs.
Dilepton production with the SMASH model
NASA Astrophysics Data System (ADS)
Weil, Janus; Staudenmaier, Jan; Petersen, Hannah
2016-08-01
In this work the SMASH model is presented (“Simulating Many Accelerated Strongly-Interacting Hadrons”), a next-generation hadronic transport approach, which is designed to describe the non-equilibrium evolution of hadronic matter in heavy-ion collisions. We discuss first dilepton spectra obtained with SMASH in the few-GeV energy range of GSI/FAIR, where the dynamics of hadronic matter is dominated by the production and decay of various resonance states. In particular we show how electromagnetic transition form factors can emerge in a transport picture under the hypothesis of vector-meson dominance.
NASA Astrophysics Data System (ADS)
McKenzie, Judith A.; Aloisi, Giovanni; Anjos, Sylvia; Latgé, Ricardo; Matsuda, Nilo; Bontognali, Tomaso; Vasconcelos, Crisogono
2015-04-01
Sedimentologic and stratigraphic studies of the Lower Cretaceous sequence, deposited in the economically important Campos Basin, southeast Brazil, document the occurrence of ~20-m-thick dolomite intervals overlying the "massive salt" megasequences of the Lagoa Feia Formation. This stratigaphic succession marks the Aptian/Albian transition from extreme evaporitic conditions of the Lagoa Feia Formation to shallow marine conditions of the Macaé Formation, related to the early opening of the South Atlantic. The facies change from evaporites to dolomite is interpreted as a product of dolomitization resulting from the refuxing of hypersaline fluids from shallow embayments with intense evaporation (Latgé, 2001). Although the reflux model provides a mechanism to produce fluids with geochemical composition favorable for dolomite precipitation, it cannot account for all of the factors required to promote dolomite precipitation. In this study, we propose a different model to explain the post-evaporite deposition of massive dolomite based on the study of sequences deposited at the end Messinian Salinity Crisis, which were recovered from the deep basins of the Mediterranean Sea during DSDP/ODP drilling campaigns. At most of these deep-water sites, the cored interval contained unusual dolomite deposits overlying the uppermost evaporite sections. For example, the upper Messinian sedimentary sequence at DSDP Site 374 comprises non-fossiliferous dolomitic mudstone overlying dolomitic mudstone/gypsum cycles, which in turn overlie anhydrite and halite (Hsü, Montadert et al., 1978). We postulate that the end Messinian dolomite is a product of microbial activity under extreme hypersaline conditions. In the last 20 years, research into the factors controlling dolomite precipitation under Earth surface conditions has led to the development of new models involving the metabolism of microorganisms and associated biofilms to overcome the kinetic inhibitions associated with primary
Quenching versus quiescence: forming realistic massive ellipticals with a simple starvation model
NASA Astrophysics Data System (ADS)
Gutcke, Thales A.; Macciò, Andrea V.; Dutton, Aaron A.; Stinson, Greg S.
2017-04-01
The decrease in star formation (SF) and the morphological change necessary to produce the z = 0 elliptical galaxy population are commonly ascribed to a sudden quenching event, which is able to rid the central galaxy of its cold gas reservoir in a short time. Following this event, the galaxy is able to prevent further SF and stay quiescent via a maintenance mode. We test whether such a quenching event is truly necessary using a simple model of quiescence. In this model, hot gas (all gas above a temperature threshold) in an ˜1012 M⊙ halo mass galaxy at redshift z ˜ 3 is prevented from cooling. The cool gas continues to form stars at a decreasing rate and the galaxy stellar mass, morphology, velocity dispersion and position on the colour-magnitude diagram (CMD) proceed to evolve. By z = 0, the halo mass has grown to 1013 M⊙ and the galaxy has attained characteristics typical of an observed z = 0 elliptical galaxy. Our model is run in the framework of a cosmological, smooth particle hydrodynamic code that includes SF, early stellar feedback, supernova feedback, metal cooling and metal diffusion. Additionally, we post-process our simulations with a radiative transfer code to create a mock CMD. In contrast to previous assumptions that a pure 'fade away' model evolves too slowly to account for the sparsity of galaxies in the 'green valley', we demonstrate crossing times of ≲1 Gyr. We conclude that no sudden quenching event is necessary to produce such rapid colour transitions.
Quenching vs. Quiescence: forming realistic massive ellipticals with a simple starvation model
NASA Astrophysics Data System (ADS)
Gutcke, Thales A.; Macciò, Andrea V.; Dutton, Aaron A.; Stinson, Greg S.
2017-01-01
The decrease in star formation (SF) and the morphological change necessary to produce the z = 0 elliptical galaxy population are commonly ascribed to a sudden quenching event, which is able to rid the central galaxy of its cold gas reservoir in a short time. Following this event, the galaxy is able to prevent further SF and stay quiescent via a maintenance mode. We test whether such a quenching event is truly necessary using a simple model of quiescence. In this model, hot gas (all gas above a temperature threshold) in a ˜1012 M⊙ halo mass galaxy at redshift z ˜ 3 is prevented from cooling. The cool gas continues to form stars at a decreasing rate and the galaxy stellar mass, morphology, velocity dispersion and position on the color magnitude diagram (CMD) proceed to evolve. By z = 0, the halo mass has grown to 1013 M⊙ and the galaxy has attained characteristics typical of an observed z = 0 elliptical galaxy. Our model is run in the framework of a cosmological, smooth particle hydrodynamic code which includes SF, early stellar feedback, supernova feedback, metal cooling and metal diffusion. Additionally, we post-process our simulations with a radiative transfer code to create a mock CMD. In contrast to previous assumptions that a pure "fade away" model evolves too slowly to account for the sparsity of galaxies in the "green valley", we demonstrate crossing times of ≲ 1 Gyr. We conclude that no sudden quenching event is necessary to produce such rapid colour transitions.
A Structural Equation Modelling Approach for Massive Blended Synchronous Teacher Training
ERIC Educational Resources Information Center
Kannan, Kalpana; Narayanan, Krishnan
2015-01-01
This paper presents a structural equation modelling (SEM) approach for blended synchronous teacher training workshop. It examines the relationship among various factors that influence the Satisfaction (SAT) of participating teachers. Data were collected with the help of a questionnaire from about 500 engineering college teachers. These teachers…
A Structural Equation Modelling Approach for Massive Blended Synchronous Teacher Training
ERIC Educational Resources Information Center
Kannan, Kalpana; Narayanan, Krishnan
2015-01-01
This paper presents a structural equation modelling (SEM) approach for blended synchronous teacher training workshop. It examines the relationship among various factors that influence the Satisfaction (SAT) of participating teachers. Data were collected with the help of a questionnaire from about 500 engineering college teachers. These teachers…
Laborda, Mario A; Miller, Ralph R
2013-06-01
Fear conditioning and experimental extinction have been presented as models of anxiety disorders and exposure therapy, respectively. Moreover, the return of fear serves as a model of relapse after exposure therapy. Here we present two experiments, with rats as subjects in a lick suppression preparation, in which we assessed the additive effects of two different treatments to attenuate the return of fear. First, we evaluated whether two phenomena known to generate return of fear (i.e., spontaneous recovery and renewal) summate to produce a stronger reappearance of extinguished fear. At test, rats evaluated outside the extinction context following a long delay after extinction (i.e., a delayed context shift) exhibited greater return of extinguished fear than rats evaluated outside the extinction context alone, but return of extinguished fear following a delayed context shift did not significantly differ from the return of fear elicited in rats tested following a long delay after extinction alone. Additionally, extinction in multiple contexts and a massive extinction treatment each attenuated the strong return of fear produced by a delayed context shift. Moreover, the conjoint action of these treatments was significantly more successful in preventing the reappearance of extinguished fear, suggesting that extensive cue exposure administered in several different therapeutic settings has the potential to reduce relapse after therapy for anxiety disorders, more than either manipulation alone.
Laborda, Mario A.; Miller, Ralph R.
2013-01-01
Fear conditioning and experimental extinction have been presented as models of anxiety disorders and exposure therapy, respectively. Moreover, the return of fear serves as a model of relapse after exposure therapy. Here we present two experiments, with rats as subjects in a lick suppression preparation, in which we assessed the additive effects of two different treatments to attenuate the return of fear. First, we evaluated whether two phenomena known to generate return of fear (i.e., spontaneous recovery and renewal) summate to produce a stronger reappearance of extinguished fear. At test, rats evaluated outside the extinction context following a long delay after extinction (i.e., a delayed context shift) exhibited greater return of extinguished fear than rats evaluated outside the extinction context alone, but return of extinguished fear following a delayed context shift did not significantly differ from the return of fear elicited in rats tested following a long delay after extinction alone. Additionally, extinction in multiple contexts and a massive extinction treatment each attenuated the strong return of fear produced by a delayed context shift. Moreover, the conjoint action of these treatments was significantly more successful in preventing the reappearance of extinguished fear, suggesting that extensive cue exposure administered in several different therapeutic settings has the potential to reduce relapse after therapy for anxiety disorders, more than either manipulation alone. PMID:23611075
Ben Lulu, Shani; Coran, Arnold G; Shehadeh, Naim; Shamir, Raanan; Mogilner, Jorge G; Sukhotnik, Igor
2012-02-01
We have recently reported that oral insulin (OI) stimulates intestinal adaptation after bowel resection and that OI enhances enterocyte turnover in correlation with insulin receptor expression along the villus-crypt axis. The purpose of the present study was to evaluate the effect of OI on intestinal epithelial cell proliferation and apoptosis in a rat model of short bowel syndrome (SBS) and in a cell culture model. Caco-2 cells were incubated with increasing concentrations of insulin. Cell proliferation and apoptosis were determined by FACS cytometry. Cell viability was investigated using the Alamar Blue technique. Male rats were divided into three groups: Sham rats underwent bowel transection, SBS rats underwent a 75% bowel resection, and SBS-OI rats underwent bowel resection and were treated with OI given in drinking water (1 U/ml) from the third postoperative day. Parameters of intestinal adaptation, enterocyte proliferation and apoptosis were determined on day 15. Real time PCR was used to determine the level of bax and bcl-2 mRNA and western blotting was used to determine bax, bcl-2, p-ERK and AKT protein levels. Statistical analysis was performed using the one-way ANOVA test, with P < 0.05 considered statistically significant. Treatment of Caco-2 cells with insulin resulted in a significant increase in cell proliferation (twofold increase after 24 h and 37% increase after 48 h) and cell viability (in a dose-dependent manner), but did not change cell apoptosis. In a rat model of SBS, treatment with OI resulted in a significant increase in all parameters of intestinal adaptation. Elevated cell proliferation rate in insulin treated rats was accompanied by elevated AKT and p-ERK protein levels. Decreased cell apoptosis in SBS-INS rats corresponded with a decreased bax/bcl-2 ratio. Oral insulin stimulates intestinal epithelial cell turnover after massive small bowel resection in a rat model of SBS and a cell culture model.
Comparison of BT Settl Model Spectra in NIR to Brown Dwarfs and Massive Exoplanets
NASA Astrophysics Data System (ADS)
Popinchalk, Mark; Buzard, Cam; Alam, Munazza; Camnasio, Sara; Cruz, Kelle L.; Faherty, Jacqueline K.; Rice, Emily L.
2017-01-01
Brown dwarfs and giant exoplanets are difficult to observe, which hampers our understanding of their properties. Model spectra, such as the BT Settl model grid, can provide an opportunity to augment and validate our understanding of these faint objects by serving to contrast and complement our analysis of their observed spectra. We present work from an upcoming paper that leverages this opportunity. The near infrared (NIR) wavelength region is favorable for analysis of low mass brown dwarfs and high mass gaseous companions, in particular the K band (1.97 - 2.40 µm) due to its relatively high resolution and high signal-to-noise ratio wavelength range for spectra of planetary companions. We present a method to analyze two regions of the K band spectral structure (2.03 - 2.10 µm and 2.215 - 2.290 µm), and apply it to a sample of objects with field gravity, low gravity, and planetary mass as well as the BT Settl model grid for a similar range of effective temperatures and surface gravities. A correlation between spectral structure and effective temperature is found for the shorter wavelength region and there is evidence of gravity dependence for the longer wavelength range. This work suggests that the K band has the potential to be an indicator for brown dwarf and exoplanet surface gravity and effective temperature. We also present preliminary analysis from another upcoming paper. We examine equivalent widths of K I absorption lines at 1.1693 µm, 1.1773 µm, 1.2436 µm and 1.2525 µm in a selection of L dwarfs to explore their physical properties by comparing them to equivalent measurements in the BT Settl model grid.
Modeling Large Scale Circuits Using Massively Parallel Descrete-Event Simulation
2013-06-01
1,966,080 cores of the Sequoia Blue Gene/Q supercomputer system. For the PHOLD benchmark model, we demonstrate the ability to process 33 trillion...events in 65 seconds yielding a peak event-rate in excess of 504 billion events/second using 120 racks of Sequoia . 15. SUBJECT TERMS Circuit...13 Table 7 - SEQUOIA : Raw PHOLD Performance Data for 1, 2, 4, 8, and 48 Rack Runs ............ 18 Table 8 - SEQUOIA : Raw PHOLD Performance
gadgetbelt: A Tool for Modeling Planetary Sculpting of Massive Debris Disks
NASA Astrophysics Data System (ADS)
Dawson, Rebekah; Murray-Clay, Ruth
2013-07-01
In models of the sculpting of planetesimal disks by planets, the planetesimals are often treated as test particles, with their effect on the planet modeled analytically. However, this treatment is insufficient in certain regimes, including: when the self-gravity of the disk causes density waves, transporting the angular momentum imparted or removed by the planet (e.g. Hahn 2003); when the self-gravity of the disk causes the disk to precess, interfering with the resonant and secular effects of the planet on the disk; and/or when interaction of the planet with individual planetesimals causes stochasticity in the planet's orbital evolution (e.g.,Murray-Clay & Chiang 2006), not well captured by prescriptions of the planetesimal-induced orbital evolution. We are adapting gadget (Springel 2005), a cosmological simulation code, for use in collisionless debris disks, allowing us to model thousands to millions of planetesimals in a reasonable CPU time through gains in speed from gadget's parallel processing implementation and tree code for N-body interactions. We will use this code, gadgetbelt, to explore regimes in which the planetesimal disk's self-gravity and/or back-reaction on the planet cannot be neglected and to explore the effects of stochasticity, which may lead to constraints on the planetesimal size-distribution. Here we present results from our benchmarking of gadgetbelt to the full N-body integrator mercury (Chambers 1999) and plans for future work.
Confinement, solitons and the equivalence between the sine-Gordon and massive Thirring models
NASA Astrophysics Data System (ADS)
Blas Achic, H. S.; Ferreira, L. A.
2000-04-01
We consider a two-dimensional integrable and conformally invariant field theory possessing two Dirac spinors and three scalar fields. The interaction couples bilinear terms in the spinors to exponentials of the scalars. Its integrability properties are based on the sl(2) affine Kac-Moody algebra, and it is a simple example of the so-called conformal affine Toda theories coupled to matter fields. We show, using bosonization techniques, that the classical equivalence between a U(1) Noether current and the topological current holds true at the quantum level, and then leads to a bag model like mechanism for the confinement of the spinor fields inside the solitons. By bosonizing the spinors we show that the theory decouples into a sine-Gordon model and free scalars. We construct the two-soliton solutions and show that their interactions lead to the same time delays as those for the sine-Gordon solitons. The model provides a good laboratory to test duality ideas in the context of the equivalence between the sine-Gordon and Thirring theories.
Comparative assessment of SAS and DES turbulence modeling for massively separated flows
NASA Astrophysics Data System (ADS)
Zheng, Weilin; Yan, Chao; Liu, Hongkang; Luo, Dahai
2016-02-01
Numerical studies of the flow past a circular cylinder at Reynolds number 1.4× 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation (SAS) and detached eddy simulation (DES), in comparison with the existing experimental data. The new version of the model developed by Egorov and Menter is assessed, and advantages and disadvantages of the SAS simulation are analyzed in detail to provide guidance for industrial application in the future. Moreover, the mechanism of the scale-adaptive characteristics in separated regions is discussed, which is obscure in previous analyses. It is concluded that: the mean flow properties satisfactorily agree with the experimental results for the SAS simulation, although the prediction of the second order turbulent statistics in the near wake region is just reasonable. The SAS model can produce a larger magnitude of the turbulent kinetic energy in the recirculation bubble, and, consequently, a smaller recirculation region and a more rapid recovery of the mean velocity outside the recirculation region than the DES approach with the same grid resolution. The vortex shedding is slightly less irregular with the SAS model than with the DES approach, probably due to the higher dissipation of the SAS simulation under the condition of the coarse mesh.
NASA Astrophysics Data System (ADS)
Zernickel, A.
2015-05-01
Context. How massive stars (M>8 Ms) form and how they accrete gas is still an open research field, but it is known that their influence on the interstellar medium (ISM) is immense. Star formation involves the gravitational collapse of gas from scales of giant molecular clouds (GMCs) down to dense hot molecular cores (HMCs). Thus, it is important to understand the mass flows and kinematics in the ISM. Aims. This dissertation focuses on the detailed study of the region NGC 6334, located in the Galaxy at a distance of 1.7 kpc. It is aimed to trace the gas velocities in the filamentary, massive star-forming region NGC 6334 at several scales and to explain its dynamics. For that purpose, different scales are examined from 0.01-10 pc to collect information about the density, molecular abundance, temperature and velocity, and consequently to gain insights about the physio-chemical conditions of molecular clouds. The two embedded massive protostellar clusters NGC 6334I and I(N), which are at different stages of development, were selected to determine their infall velocities and mass accretion rates. Methods. This astronomical source was surveyed by a combination of different observatories, namely with the Submillimeter Array (SMA), the single-dish telescope Atacama Pathfinder Experiment (APEX), and the Herschel Space Observatory (HSO). It was mapped with APEX in carbon monoxide (13CO and C18O, J=2-1) at 220.4 GHz to study the filamentary structure and turbulent kinematics on the largest scales of 10 pc. The spectral line profiles are decomposed by Gaussian fitting and a dendrogram algorithm is applied to distinguish velocity-coherent structures and to derive statistical properties. The velocity gradient method is used to derive mass flow rates. The main filament was mapped with APEX in hydrogen cyanide (HCN) and oxomethylium (HCO+, J=3-2) at 267.6 GHz to trace the dense gas. To reproduce the position- velocity diagram (PVD), a cylindrical model with the radiative transfer
Digital relief 3D model of the Khibiny massive (Kola peninsula)
NASA Astrophysics Data System (ADS)
Chesalova, Elena; Asavin, Alex
2015-04-01
On the basis of maps of 1: 50,000 and 1: 200,000 3D model Khibiny massif developed. We used software ARC / INFO v10.2 ESRI. This project will be organised to build background for gas pollution monitoring network. We planned to use the model to estimate local heterogeneities in the composition of the atmosphere at the emanation of greenhouse gases in the area, the construction of models of vertical distribution of the content of trace gases in the rock mass. In addition to the project GIS digital elevation model contains layers of geological and tectonic map that allows us to estimate the area of the output of certain petrographic rock groups characterized by different ratios of emitted hydrocarbons (CH4/ H2). The model allows to construct a classification of fault in the array. At first glance, there are two groups of faults - the ancient associated with the formation of the intrusive phases sequence, and the young - due to recent tectonic shifts. Ancient faults form a common semicircular structure of the pluton cause overall asymmetry Khibin heights with the transition to the border area between the Khibiny and Lovoozero. Modern tectonics mainly represented by radial and chord faults which are formed narrow mountain valleys and troughs. It remains an open question as to which system fault (old or young) is more productive to gas emanations? On the one hand the system characterized by a large old depth, on the other hand a young more active faults. Address these issues require further detailed observations. The essential question is to assess the possibility of maintaining a constant concentration gradient of these impurities in the atmosphere due to gas emanations of fracture zones and areas enriched occluded gases. In the simulation of these processes can be used initially set parameters: 1 the flow rate of the gas impurities 2 the value of wind flows in closed and open valley 3 Assessment of thermal diffusion coefficients determined by the temperature gradient
Mathematical model of massive dynamics in the neighborhood of disturbance focus
Alexeeva, Lyudmila A.; Sarsenov, Bakytbek T.
2015-09-18
We consider a model problem for the research of Earth’s surface state caused by discharge of tectonic stress on the deep cracks in the earth’s crust. Using the numerical method of bicharacteristics, algorithm is developed and solution of the problem of non-stationary dynamics of a homogeneous isotropic elastic half-space is built under plane strain when one resets the vertical stress on crack. Diffraction of waves on the surface is studied, pictures of wave fields and stress-strain state of the medium and the surface for different moments of time are built.
NASA Astrophysics Data System (ADS)
Caranicolas, Nicolaos D.; Zotos, Euaggelos E.
2013-02-01
We investigate the transition from regular to chaotic motion in a composite galaxy model with a disk-halo, a massive dense nucleus and a dark halo component. We obtain relationships connecting the critical value of the mass of the nucleus or the critical value of the angular momentum Lzc, with the mass Mh of the dark halo, where the transition from regular motion to chaos occurs. We also present 3D diagrams connecting the mass of nucleus the energy and the percentage of stars that can show chaotic motion. The fraction of the chaotic orbits observed in the (r,pr) phase plane, as a function of the mass of the dark halo is also computed. We use a semi-numerical method, that is a combination of theoretical and numerical procedure. The theoretical results obtained using the version 8.0 of the Mathematica package, while all the numerical calculations were made using a Bulirsch-Stöer FORTRAN routine in double precision. The results can be obtained in semi-numerical or numerical form and give good description for the connection of the physical quantities entering the model and the transition between regular and chaotic motion. We observe that the mass of the dark halo, the mass of the dense nucleus and the Lz component of the angular momentum, are important physical quantities, as they are linked to the regular or chaotic character of orbits in disk galaxies described by the model. Our numerical experiments suggest, that the amount of the dark matter plays an important role in disk galaxies represented by the model, as the mass of the halo affects, not only the regular or chaotic nature of motion but it is also connected with the existence of the different families of regular orbits. Comparison of the present results with earlier work is also presented.
Massive gravity in three dimensions.
Bergshoeff, Eric A; Hohm, Olaf; Townsend, Paul K
2009-05-22
A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes "topologically-massive" gravity as a special case, propagates the two spin-2 helicity states with different masses. We discuss the extension to massive N-extended supergravity, and we present a "cosmological" extension that admits an anti-de Sitter vacuum.
Weakly-interacting massive particles in non-supersymmetric SO(10) grand unified models
NASA Astrophysics Data System (ADS)
Nagata, Natsumi; Olive, Keith A.; Zheng, Jiaming
2015-10-01
Non-supersymmetric SO(10) grand unified theories provide a framework in which the stability of dark matter is explained while gauge coupling unification is realized. In this work, we systematically study this possibility by classifying weakly interacting dark matter candidates in terms of their quantum numbers of SU(2) L ⊗ U(1) Y , B - L, and SU(2) R . We consider both scalar and fermion candidates. We show that the requirement of a sufficiently high unification scale to ensure a proton lifetime compatible with experimental constraints plays a strong role in selecting viable candidates. Among the scalar candidates originating from either a 16 or 144 of SO(10), only SU(2) L singlets with zero hypercharge or doublets with Y = 1 /2 satisfy all constraints for SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(3) C ⊗ SU(2) L ⊗ SU(2) R ⊗ U(1) B- L intermediate scale gauge groups. Among fermion triplets with zero hypercharge, only a triplet in the 45 with intermediate group SU(4) C ⊗ SU(2) L ⊗ SU(2) R leads to solutions with M GUT > M int and a long proton lifetime. We find three models with weak doublets and Y = 1 /2 as dark matter candidates for the SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(4) C ⊗ SU(2) L ⊗ U(1) R intermediate scale gauge groups assuming a minimal Higgs content. We also discuss how these models may be tested at accelerators and in dark matter detection experiments.
NASA Astrophysics Data System (ADS)
Marrero, J. M.; García, A.; Llinares, A.; Rodríguez-Losada, J. A.; Ortiz, R.
2010-04-01
Volcanic eruptions are among the most awesome and powerful displays of nature's force, constituting a major natural hazard for society (a single eruption can claim thousands of lives in an instant). Consequently, assessment and management of volcanic risk have become critically important goals of modern volcanology. Over recent years, numerous tools have been developed to evaluate volcanic risk and support volcanic crisis management: probabilistic analysis of future eruptions, hazard and risk maps, event trees, etc. However, there has been little improvement in the tools that may help Civil Defense officials to prepare Emergency Plans. Here we present a new tool for simulating massive evacuation processes during volcanic crisis: the Variable Scale Evacuation Model (VSEM). The main objective of the VSEM software is to optimize the evacuation process of Emergency Plans during volcanic crisis. For this, the VSEM allows the simulation of an evacuation considering different strategies depending on diverse impact scenarios. VSEM is able to calculate the required time for the complete evacuation taking into account diverse evacuation scenarios (number and type of population, infrastructure, road network, etc.) and to detect high-risk or "blackspots" of the road network. The program is versatile and can work at different scales, thus being capable of simulating the evacuation of small villages as well as huge cities.
NASA Astrophysics Data System (ADS)
Orgogozo, L.; Renon, N.; Soulaine, C.; Hénon, F.; Tomer, S. K.; Labat, D.; Pokrovsky, O. S.; Sekhar, M.; Ababou, R.; Quintard, M.
2014-12-01
In this paper we present a massively parallel open source solver for Richards equation, named the RichardsFOAM solver. This solver has been developed in the framework of the open source generalist computational fluid dynamics tool box OpenFOAM® and is capable to deal with large scale problems in both space and time. The source code for RichardsFOAM may be downloaded from the CPC program library website. It exhibits good parallel performances (up to ˜90% parallel efficiency with 1024 processors both in strong and weak scaling), and the conditions required for obtaining such performances are analysed and discussed. These performances enable the mechanistic modelling of water fluxes at the scale of experimental watersheds (up to few square kilometres of surface area), and on time scales of decades to a century. Such a solver can be useful in various applications, such as environmental engineering for long term transport of pollutants in soils, water engineering for assessing the impact of land settlement on water resources, or in the study of weathering processes on the watersheds.
Renormalizable Electrodynamics of Scalar and Vector Mesons. Part II
DOE R&D Accomplishments Database
Salam, Abdus; Delbourgo, Robert
1964-01-01
The "gauge" technique" for solving theories introduced in an earlier paper is applied to scalar and vector electrodynamics. It is shown that for scalar electrodynamics, there is no {lambda}φ*2φ2 infinity in the theory, while with conventional subtractions vector electrodynamics is completely finite. The essential ideas of the gauge technique are explained in section 3, and a preliminary set of rules for finite computation in vector electrodynamics is set out in Eqs. (7.28) - (7.34).
Search for ηc' decays into vector meson pairs
NASA Astrophysics Data System (ADS)
Ablikim, M.; Achasov, M. N.; Alberto, D.; An, F. F.; An, Q.; An, Z. H.; Bai, J. Z.; Baldini, R.; Ban, Y.; Becker, J.; Berger, N.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, X.; Calcaterra, A. C.; Cao, G. F.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, Y.; Chen, Y. B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denysenko, I.; Destefanis, M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y. P.; Han, Y. L.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Heng, Y. K.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, B.; Huang, G. M.; Huang, J. S.; Huang, X. T.; Huang, Y. P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jia, L. K.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Kuehn, W.; Lai, W.; Lange, J. S.; Leung, J. K. C.; Li, C. H.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, Lei; Li, N. B.; Li, Q. J.; Li, S. L.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, X. T.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, C. Y.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H.; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K.; Liu, K. Y.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. H.; Liu, Y. B.; Liu, Y. W.; Liu, Yong; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J. G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Ma, C. L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X.; Ma, X. Y.; Maggiora, M.; Malik, Q. A.; Mao, H.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Muchnoi, N. Yu.; Nefedov, Y.; Nikolaev, I. B.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Park, J. W.; Pelizaeus, M.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Pun, C. S. J.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, X. S.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schulze, J.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, X. D.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tian, H. L.; Toth, D.; Varner, G. S.; Wang, B.; Wang, B. Q.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q.; Wang, Q. J.; Wang, S. G.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. Y.; Wei, D. H.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, G. M.; Xu, H.; Xu, Q. J.; Xu, X. P.; Xu, Y.; Xu, Z. R.; Xu, Z. Z.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, T.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, S. P.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, S. H.; Zhang, T. R.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. S.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, Jiawei; Zhao, Jingwei; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhao, Z. L.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.; Zheng, Z. P.; Zhong, B.; Zhong, J.; Zhong, L.; Zhou, L.; Zhou, X. K.; Zhou, X. R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S. H.; Zhu, X. L.; Zhu, X. W.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Zuo, J. X.
2011-11-01
The processes ηc'→ρ0ρ0, K*0K¯*0, and ϕϕ are searched for using a sample of 1.06×108 ψ' events collected with the BESIII detector at the BEPCII collider. No signals are observed in any of the three final states. The upper limits on the decay branching fractions are determined to be B(ηc'→ρ0ρ0)<3.1×10-3, B(ηc'→K*0K¯*0)<5.4×10-3, and B(ηc'→ϕϕ)<2.0×10-3 at the 90% confidence level. The upper limits are lower than the existing theoretical predictions.
Boson Stars with Vector Meson Exchange Repulsive Interaction
NASA Astrophysics Data System (ADS)
Fitrah, M.; Rangga Sakti, Alfian; Sulaksono, Anto
2016-08-01
Spherically symmetric static boson stars are solutions of the system of equations of Klein-Gordon equation which is coupled to the Einstein and Proca equation with complex scalar field with U(1) gauge symmetry. In this work, we do not solve these equations directly but first we solve simultaneous equations Klein-Gordon and Proca in flat space-time numerically to obtain interacting boson equation of state (EOS), then we ”boost” the corresponding EOS to curved space-time so that, we can solve Einstein equations. If we assume that the distribution of boson in boson stars is inhomogeneous, the boosted EOS is anisotropic in the sense that the pressure to the tangential direction is not the same as the one in the radial direction. We find numerically solutions to see the EOS which are formed in boson stars as the consequence of inhomogeneous assumption. We have found that there is no physically stable solution for inhomogeneous EOS. However, if we assume that the distribution of bosons in matter is homogeneous, we can get a stable solution for static boson stars.
NASA Astrophysics Data System (ADS)
Elmegreen, Bruce G.
2017-02-01
The self-enrichment of massive star clusters by p-processed elements is shown to increase significantly with increasing gas density as a result of enhanced star formation rates and stellar scatterings compared to the lifetime of a massive star. Considering the type of cloud core where a globular cluster (GC) might have formed, we follow the evolution and enrichment of the gas and the time dependence of stellar mass. A key assumption is that interactions between massive stars are important at high density, including interactions between massive stars and massive-star binaries that can shred stellar envelopes. Massive-star interactions should also scatter low-mass stars out of the cluster. Reasonable agreement with the observations is obtained for a cloud-core mass of ∼4 × 106 M ⊙ and a density of ∼2 × 106 cm‑3. The results depend primarily on a few dimensionless parameters, including, most importantly, the ratio of the gas consumption time to the lifetime of a massive star, which has to be low, ∼10%, and the efficiency of scattering low-mass stars per unit dynamical time, which has to be relatively large, such as a few percent. Also for these conditions, the velocity dispersions of embedded GCs should be comparable to the high gas dispersions of galaxies at that time, so that stellar ejection by multistar interactions could cause low-mass stars to leave a dwarf galaxy host altogether. This could solve the problem of missing first-generation stars in the halos of Fornax and WLM.
NASA Astrophysics Data System (ADS)
Dubovsky, Sergei L.
2004-10-01
We systematically study the most general Lorentz-violating graviton mass invariant under three-dimensional Eucledian group. We find that at general values of mass parameters the massive graviton has six propagating degrees of freedom, and some of them are ghosts or lead to rapid classical instabilities. However, there is a number of different regions in the mass parameter space where massive gravity is described by a consistent low-energy effective theory with cutoff ~ (mMPl)1/2. This theory is free of rapid instabilities and vDVZ discontinuity. Each of these regions is characterized by certain fine-tuning relations between mass parameters, generalizing the Fierz Pauli condition. In some cases the required fine-tunings are consequences of the existence of the subgroups of the diffeomorphism group that are left unbroken by the graviton mass. We found two new cases, when the resulting theories have a property of UV insensitivity, i.e. remain well behaved after inclusion of arbitrary higher dimension operators without assuming any fine-tunings among the coefficients of these operators, besides those enforced by the symmetries. These theories can be thought of as generalizations of the ghost condensate model with a smaller residual symmetry group. We briefly discuss what kind of cosmology can one expect in massive gravity and argue that the allowed values of the graviton mass may be quite large, affecting growth of primordial perturbations, structure formation and, perhaps, enhancing the backreaction of inhomogeneities on the expansion rate of the Universe.
Campbell, Sean T; Ecklund, Kier J; Chu, Eileen H; McGarry, Michelle H; Gupta, Ranjan; Lee, Thay Q
2014-08-01
Superior migration of the humeral head after massive rotator cuff tear (mRCT) is thought to lead to cuff tear arthropathy. Previous biomechanical studies have demonstrated the ability of the pectoralis major and latissimus dorsi (PM/LD) muscles to resist this migration. This study examined the role of PM/LD muscles on glenohumeral joint forces and acromiohumeral contact pressures in a mRCT model. Six cadaveric shoulders were tested using a custom shoulder-testing system. Muscle insertions of the rotator cuff, deltoid, and PM/LD were preserved and used for muscle loading. Specimens were tested in 3 different humeral rotation positions at 0° abduction and 2 rotation positions at 60° abduction. Testing was performed for intact specimens, after supraspinatus removal, and after supraspinatus/infraspinatus/teres minor removal. PM/LD were loaded or unloaded to determine their effect. Humeral head kinematics, glenohumeral joint forces, and acromiohumeral contact area and pressure were measured. For the mRCT condition at 0° abduction, unloading the PM/LD resulted in superior shift of the humeral head. Acromiohumeral contact pressures were undetectable when the PM/LD were loaded but increased significantly after PM/LD unloading. After mRCT, superior joint forces were increased and compressive forces were decreased compared with intact; loading the PM/LD resolved these abnormal forces in some testing conditions. In mRCT, the PM and LD muscles are effective in improving glenohumeral kinematics and reducing acromiohumeral pressures. Strengthening or neuromuscular training of this musculature, or both, may delay the progression to cuff tear arthropathy. Published by Mosby, Inc.
The Destructive Birth of Massive Stars and Massive Star Clusters
NASA Astrophysics Data System (ADS)
Rosen, Anna; Krumholz, Mark; McKee, Christopher F.; Klein, Richard I.; Ramirez-Ruiz, Enrico
2017-01-01
Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Previous theoretical and observational studies have concluded that the feedback associated with massive stars' radiation fields is the dominant mechanism regulating massive star and massive star cluster (MSC) formation. Therefore detailed simulation of the formation of massive stars and MSCs, which host hundreds to thousands of massive stars, requires an accurate treatment of radiation. For this purpose, we have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. We use our new tool to perform a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, we simulate the collapse of massive pre-stellar cores with laminar and turbulent initial conditions and properly resolve regions where we expect instabilities to grow. We find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor (RT) instabilities. For laminar initial conditions, proper treatment of the direct radiation field produces later onset of RT instability, but does not suppress it entirely provided the edges of the radiation-dominated bubbles are adequately resolved. RT instabilities arise immediately for turbulent pre-stellar cores because the initial turbulence seeds the instabilities. To model MSC formation, we simulate the collapse of a dense, turbulent, magnetized Mcl = 106 M⊙ molecular cloud. We find that the influence of the magnetic pressure and radiative feedback slows down star formation. Furthermore, we find that star formation is suppressed along dense filaments where the magnetic field is
Massive transfusion and massive transfusion protocol
Patil, Vijaya; Shetmahajan, Madhavi
2014-01-01
Haemorrhage remains a major cause of potentially preventable deaths. Rapid transfusion of large volumes of blood products is required in patients with haemorrhagic shock which may lead to a unique set of complications. Recently, protocol based management of these patients using massive transfusion protocol have shown improved outcomes. This section discusses in detail both management and complications of massive blood transfusion. PMID:25535421
Shendure, Jay; Fields, Stanley
2016-06-01
Human genetics has historically depended on the identification of individuals whose natural genetic variation underlies an observable trait or disease risk. Here we argue that new technologies now augment this historical approach by allowing the use of massively parallel assays in model systems to measure the functional effects of genetic variation in many human genes. These studies will help establish the disease risk of both observed and potential genetic variants and to overcome the problem of "variants of uncertain significance." Copyright © 2016 by the Genetics Society of America.
Parameterization of form factors of a K-p interaction model based on one hadron exchange
NASA Astrophysics Data System (ADS)
Alam, A. L. A.; Salam, A.; Fachruddin, I.
2017-07-01
K-p interaction is modeled as one hadron exchange potential with the exchanged hadrons being scalar-meson- σ; vector-meson-ω, ρ; and hyperon-Λ, Σ. The cutoff parameters of the form factors at each vertex are determined by means of fitting processes to experimental data of K-p differential cross section for scattering laboratory energies of about 50 MeV to 225 MeV. The differential cross sections are calculated using a three-dimensional technique without partial-wave expansion. We obtain a K-p interaction model with χ2/N value being 3.9.
Cockrell, Robert Chase; Christley, Scott; Chang, Eugene; An, Gary
2015-01-01
Perhaps the greatest challenge currently facing the biomedical research community is the ability to integrate highly detailed cellular and molecular mechanisms to represent clinical disease states as a pathway to engineer effective therapeutics. This is particularly evident in the representation of organ-level pathophysiology in terms of abnormal tissue structure, which, through histology, remains a mainstay in disease diagnosis and staging. As such, being able to generate anatomic scale simulations is a highly desirable goal. While computational limitations have previously constrained the size and scope of multi-scale computational models, advances in the capacity and availability of high-performance computing (HPC) resources have greatly expanded the ability of computational models of biological systems to achieve anatomic, clinically relevant scale. Diseases of the intestinal tract are exemplary examples of pathophysiological processes that manifest at multiple scales of spatial resolution, with structural abnormalities present at the microscopic, macroscopic and organ-levels. In this paper, we describe a novel, massively parallel computational model of the gut, the Spatially Explicitly General-purpose Model of Enteric Tissue_HPC (SEGMEnT_HPC), which extends an existing model of the gut epithelium, SEGMEnT, in order to create cell-for-cell anatomic scale simulations. We present an example implementation of SEGMEnT_HPC that simulates the pathogenesis of ileal pouchitis, and important clinical entity that affects patients following remedial surgery for ulcerative colitis. PMID:25806784
Cockrell, Robert Chase; Christley, Scott; Chang, Eugene; An, Gary
2015-01-01
Perhaps the greatest challenge currently facing the biomedical research community is the ability to integrate highly detailed cellular and molecular mechanisms to represent clinical disease states as a pathway to engineer effective therapeutics. This is particularly evident in the representation of organ-level pathophysiology in terms of abnormal tissue structure, which, through histology, remains a mainstay in disease diagnosis and staging. As such, being able to generate anatomic scale simulations is a highly desirable goal. While computational limitations have previously constrained the size and scope of multi-scale computational models, advances in the capacity and availability of high-performance computing (HPC) resources have greatly expanded the ability of computational models of biological systems to achieve anatomic, clinically relevant scale. Diseases of the intestinal tract are exemplary examples of pathophysiological processes that manifest at multiple scales of spatial resolution, with structural abnormalities present at the microscopic, macroscopic and organ-levels. In this paper, we describe a novel, massively parallel computational model of the gut, the Spatially Explicitly General-purpose Model of Enteric Tissue_HPC (SEGMEnT_HPC), which extends an existing model of the gut epithelium, SEGMEnT, in order to create cell-for-cell anatomic scale simulations. We present an example implementation of SEGMEnT_HPC that simulates the pathogenesis of ileal pouchitis, and important clinical entity that affects patients following remedial surgery for ulcerative colitis.
NASA Astrophysics Data System (ADS)
Liu, Lu; Sletten, Ronald S.; Hagedorn, Birgit; Hallet, Bernard; McKay, Christopher P.; Stone, John O.
2015-08-01
A massive ice body buried under several decimeters of dry regolith in Beacon Valley, Antarctica, is believed to be more than 1 Ma old and perhaps over 8.1 Ma; however, vapor diffusion models suggest that subsurface ice in this region is not stable under current climate conditions. To better understand the controls on sublimation rates and stability of this massive ice, we have modeled vapor diffusion using 12 years of climate and soil temperature data from 1999 to 2011, including field measurements of episodic snow cover and snowmelt events that have not been represented in previous models of ground ice sublimation. The model is then extended to reconstruct the sublimation history over the last 200 ka using paleotemperatures estimated from ice core data from nearby Taylor Dome and a relationship between atmospheric temperature and humidity derived from our meteorological records. The model quantifies the impact of episodic snow events; they account for a nearly 30% reduction in the massive ice loss. The sublimation rate of ground ice averages 0.11 mm a-1 between 1999 and 2011 in Beacon Valley. Parameterized with past environmental conditions and assuming the same regolith thickness, the modeled sublimation rate of ground ice in Beacon Valley averages 0.09 mm a-1 for the last 200 ka, comparable to the long-term average rate estimated independently from various studies based on cosmogenic isotopes. This study provides a realistic estimate of the long-term sublimation history and supports the inference that the buried ice in Beacon Valley is older than 1 Ma.
NASA Astrophysics Data System (ADS)
Porritt, L. A.; Cas, R. A. F.; Crawford, B. B.
2008-06-01
The origins of massive, poorly sorted fragmental kimberlite and kimberlite breccias in the diatremes of kimberlite volcanic pipes is currently poorly understood. Studies of the textural features of the major infill of the Fox kimberlite, Ekati Diamond Mine, NWT, Canada, show that it may have formed as a result of the collapse of the explosive eruption column above the vent into the deep open pipe during the climactic stage of the eruption. As the eruption intensity increased the column became critically overloaded with dense particles and rapidly collapsed onto itself. Unlike deposits typically preserved from column collapse events, such as ignimbrites, some portion of the collapsing mass was trapped in the deep pipe, forming a distinct type of pyroclastic deposit, "in-vent/vent-fill column collapse lapilli-tuff". This deposit has previously been tentatively identified as tuffisitic kimberlite (TK) or massive volcaniclastic kimberlite (MVK), based on broadly similar textural characteristics with these lithologies. Though every individual deposit will have formed under slightly different circumstances, mass emplacement from column collapse is proposed as a viable model for massive volcaniclastic kimberlite emplacement, based on extrapolation of modern volcanological processes.
Hamiltonian Lattice Studies of Pionic Collective Excitations in the Non-linear Sigma Model
NASA Astrophysics Data System (ADS)
Chin, Siu A.
2001-04-01
The latticization of the non-linear sigma model reduces a chiral meson field theory to an O(4) spin system with quantum fluctuations. By solving the resulting lattice Hamiltonian by Monte Carlo methods, the dynamics and thermodynamics of pions can be determined non-perturbatively. In particular, the mas gap of pionic collective excitations with quantum number of vector mesons can be determined as the chiral phase transition is approached. Results based on a newly discovered 4th order method of solving for the ground state of a quantum many-body Hamitonian will be presented.
Hadronic matter at finite temperature and density within an effective relativistic mean-field model
NASA Astrophysics Data System (ADS)
Lavagno, A.
2012-10-01
We study hot and dense hadronic matter by means of an effective relativistic mean-field model with the inclusion of the full octet of baryons, the Δ-isobar degrees of freedom and the lightest pseudoscalar and vector mesons. These last particles are considered by taking into account an effective chemical potential and an effective mass depending on the self-consistent interaction between baryons. The analysis is performed by requiring the Gibbs conditions on the global conservation of baryon number, electric charge fraction and zero net strangeness.
Massive star forming environments
NASA Astrophysics Data System (ADS)
Devine, Kathryn Elizabeth
2010-12-01
We present a study of the earliest stages of massive star formation, in which we focus on Infrared Dark Clouds (IRDCs) and young massive clusters. We present Very Large Array spectral line observations of ammonia (NH 3) and CCS toward four IRDCs. The NH3 lines provide diagnostics of the temperature and density structure within IRDCs. Based upon the NH 3 column density, IRDCs have masses of ˜ 103 to 10 4 M⊙ . We detect twenty NH3 clumps within four IRDCs, with radii < 0.3 pc and masses ˜ 102 to 103 M⊙ . A majority of the clumps are associated with signatures of star formation: 24 mum emission, H2O masers, 8 GHz continuum emission, and/or outflows. The physical properties of the clumps are consistent with massive cluster progenitors. From the NH3 emission we also find distinct velocity components, or "subclouds", within each IRDC. Although they appear ubiquitous in IRDCs, subclouds have not previously been reported. Subclouds may represent an intermediate stage of molecular cloud fragmentation, between filamentary structure and clump formation. The spatial distribution of the CCS and NH3 emission is generally anti-correlated, with the NH 3 predominantly in the high-density clumps, and CCS in lower-density gas. This spatial distribution may be explained by chemical evolution models for star forming gas, where in chemically young clouds with recently disrupted gas CCS forms quickly. In early clump formation CCS is abundant and in the centers of more evolved star forming clumps CCS is depleted. Near infrared observations of three embedded massive star forming regions are presented from the Near Infrared Imager (NIRIM) camera on the 3.5 m WIYN telescope. We report J, H, and K' band photometry in the clusters AFGL437, AFGL5180, and AFGL5142 and use these results to probe the stellar populations, extinction, and ages of the clusters. We find that all three clusters suffer significant extinction (AK ˜1), have ages ≤ 5 Myr, and are actively forming stars. We
NASA Technical Reports Server (NTRS)
Keppenne, Christian L.; Rienecker, Michele; Borovikov, Anna Y.; Suarez, Max
1999-01-01
A massively parallel ensemble Kalman filter (EnKF)is used to assimilate temperature data from the TOGA/TAO array and altimetry from TOPEX/POSEIDON into a Pacific basin version of the NASA Seasonal to Interannual Prediction Project (NSIPP)ls quasi-isopycnal ocean general circulation model. The EnKF is an approximate Kalman filter in which the error-covariance propagation step is modeled by the integration of multiple instances of a numerical model. An estimate of the true error covariances is then inferred from the distribution of the ensemble of model state vectors. This inplementation of the filter takes advantage of the inherent parallelism in the EnKF algorithm by running all the model instances concurrently. The Kalman filter update step also occurs in parallel by having each processor process the observations that occur in the region of physical space for which it is responsible. The massively parallel data assimilation system is validated by withholding some of the data and then quantifying the extent to which the withheld information can be inferred from the assimilation of the remaining data. The distributions of the forecast and analysis error covariances predicted by the ENKF are also examined.
NASA Technical Reports Server (NTRS)
Keppenne, Christian L.; Rienecker, Michele; Borovikov, Anna Y.; Suarez, Max
1999-01-01
A massively parallel ensemble Kalman filter (EnKF)is used to assimilate temperature data from the TOGA/TAO array and altimetry from TOPEX/POSEIDON into a Pacific basin version of the NASA Seasonal to Interannual Prediction Project (NSIPP)ls quasi-isopycnal ocean general circulation model. The EnKF is an approximate Kalman filter in which the error-covariance propagation step is modeled by the integration of multiple instances of a numerical model. An estimate of the true error covariances is then inferred from the distribution of the ensemble of model state vectors. This inplementation of the filter takes advantage of the inherent parallelism in the EnKF algorithm by running all the model instances concurrently. The Kalman filter update step also occurs in parallel by having each processor process the observations that occur in the region of physical space for which it is responsible. The massively parallel data assimilation system is validated by withholding some of the data and then quantifying the extent to which the withheld information can be inferred from the assimilation of the remaining data. The distributions of the forecast and analysis error covariances predicted by the ENKF are also examined.
Gauged linear sigma model and pion-pion scattering
Fariborz, Amir H.; Schechter, Joseph; Shahid, M. Naeem
2009-12-01
A simple gauged linear sigma model with several parameters to take the symmetry breaking and the mass differences between the vector meson and the axial vector meson into account is considered here as a possibly useful 'template' for the role of a light scalar in QCD as well as for (at a different scale) an effective Higgs sector for some recently proposed walking technicolor models. An analytic procedure is first developed for relating the Lagrangian parameters to four well established (in the QCD application) experimental inputs. One simple equation distinguishes three different cases: i. QCD with axial vector particle heavier than vector particle, ii. possible technicolor model with vector particle heavier than the axial vector one, iii. the unphysical QCD case where both the Kawarabayashi-Suzuki-Riazuddin-Fayazuddin and Weinberg relations hold. The model is applied to the s-wave pion-pion scattering in QCD. Both the near threshold region and (with an assumed unitarization) the 'global' region up to about 800 MeV are considered. It is noted that there is a little tension between the choice of 'bare' sigma mass parameter for describing these two regions. If a reasonable 'global' fit is made, there is some loss of precision in the near threshold region.
NASA Astrophysics Data System (ADS)
Weber, J. A.; Pauldrach, A. W. A.; Knogl, J. S.; Hoffmann, T. L.
2013-07-01
Context. The first generation of stars, which formed directly from the primordial gas, is believed to have played a crucial role in the early phase of the epoch of reionization of the universe. Theoretical studies indicate that the initial mass function (IMF) of this first stellar population differs significantly from the present IMF, being top-heavy and thus allowing for the presence of supermassive stars with masses up to several thousand solar masses. The first generation of population III stars was therefore not only very luminous, but due to its lack of metals its emission of UV radiation considerably exceeded that of present stars. Because of the short lifetimes of these stars the metals produced in their cores were quickly returned to the environment, from which early population II stars with a different IMF and different spectral energy distributions (SEDs) were formed, already much earlier than the time at which the universe became completely reionized (at a redshift of z ≳ 6). Aims: Using a state-of-the-art model atmosphere code we calculate realistic SEDs of very massive stars (VMSs) of different metallicities to serve as input for the 3-dimensional radiative transfer code we have developed to simulate the temporal evolution of the ionization of the inhomogeneous interstellar and intergalactic medium, using multiple stellar clusters as sources of ionizing radiation. The ultimate objective of these simulations is not only to quantify the processes which are believed to have lead to the reionized state of the universe, but also to determine possible observational diagnostics to constrain the nature of the ionizing sources. Methods: The multifrequency treatment in our combination of 3d radiative transfer - based on ray-tracing - and time-dependent simulation of the ionization structure of hydrogen and helium allows, in principle, to deduce information about the spectral characteristics of the first generations of stars and their interaction with the
NASA Astrophysics Data System (ADS)
Wofford, A.; Charlot, S.; Bruzual, G.; Eldridge, J. J.; Calzetti, D.; Adamo, A.; Cignoni, M.; de Mink, S. E.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Lee, J. C.; Östlin, G.; Smith, L. J.; Ubeda, L.; Zackrisson, E.
2016-04-01
We test the predictions of spectral synthesis models based on seven different massive-star prescriptions against Legacy ExtraGalactic UV Survey (LEGUS) observations of eight young massive clusters in two local galaxies, NGC 1566 and NGC 5253, chosen because predictions of all seven models are available at the published galactic metallicities. The high angular resolution, extensive cluster inventory, and full near-ultraviolet to near-infrared photometric coverage make the LEGUS data set excellent for this study. We account for both stellar and nebular emission in the models and try two different prescriptions for attenuation by dust. From Bayesian fits of model libraries to the observations, we find remarkably low dispersion in the median E(B - V) (˜0.03 mag), stellar masses (˜104 M⊙), and ages (˜1 Myr) derived for individual clusters using different models, although maximum discrepancies in these quantities can reach 0.09 mag and factors of 2.8 and 2.5, respectively. This is for ranges in median properties of 0.05-0.54 mag, 1.8-10 × 104 M⊙, and 1.6-40 Myr spanned by the clusters in our sample. In terms of best fit, the observations are slightly better reproduced by models with interacting binaries and least well reproduced by models with single rotating stars. Our study provides a first quantitative estimate of the accuracies and uncertainties of the most recent spectral synthesis models of young stellar populations, demonstrates the good progress of models in fitting high-quality observations, and highlights the needs for a larger cluster sample and more extensive tests of the model parameter space.
Semtner, A.J. Jr.; Chervin, R.M.
1993-05-01
During the second year of CHAMMP funding to the principal investigators, progress has been made in the proposed areas of research, as follows: investigation of the physics of the thermohaline circulation; examination of resolution effects on ocean general circulation; and development of a massively parallel ocean climate model.
NASA Technical Reports Server (NTRS)
Cowie, L. L.
1977-01-01
The Bondi-Hoyle-Lyttleton (1944) accretion model is considered which involves accretion onto a massive body moving at a high Mach number with respect to the ambient medium and the production of a high-density accretion column along the axis where particle orbits intersect. The stability of steady-state solutions with respect to short-wavelength perturbations is analyzed using the WKB approximation, and the accretion column is shown to be unstable toward such perturbations. It is noted that this instability is not affected by the position of the stagnation point in the steady-state solution.
NASA Astrophysics Data System (ADS)
Keszthelyi, Z.; Puls, J.; Wade, G. A.
2017-02-01
Context. Stellar evolution models of massive stars are very sensitive to the adopted mass-loss scheme. The magnitude and evolution of mass-loss rates significantly affect the main sequence evolution, and the properties of post-main sequence objects, including their rotational velocities. Aims: Driven by potential discrepancies between theoretically predicted and observationally derived mass-loss rates in the OB star range, we aim in particular to investigate the response to mass-loss rates that are lower than currently adopted, in parallel with the mass-loss behavior at the "first" bi-stability jump. Methods: We performed 1D hydrodynamical model calculations of single 20-60 M⊙ Galactic (Z = 0.014) stars where the effects of stellar winds are already significant in the main sequence phase. We have developed an experimental wind routine to examine the behavior and response of the models under the influence of different mass-loss rates. This observationally guided, simple and flexible wind routine is not a new mass-loss description but a useful tool based on the wind-momentum luminosity relation and other scaling relations, and provides a meaningful base for various tests and comparisons. Results: The main result of this study indicates a dichotomy between solutions of currently debated problems regarding mass-loss rates of hot massive stars. In a fully diffusive approach, and for commonly adopted initial rotational velocities, lower mass-loss rates than theoretically predicted require to invoke an additional source of angular momentum loss (either due to bi-stability braking, or yet unidentified) to brake down surface rotational velocities. On the other hand, a large jump in the mass-loss rates due to the bi-stability mechanism (a factor of 5-7 predicted by Vink et al. (2000, A&A, 362, 295), but a factor of 10-20 in modern models of massive stars) is challenged by observational results, and might be avoided if the early mass-loss rates agreed with the theoretically
Two-current nucleon observables in Skyrme model
NASA Astrophysics Data System (ADS)
Chemtob, Marc
1987-11-01
Three independent two-current nucléon observables are studied within the two-flavor Skyrme model for the παω system. The effective lagrangian is that of the gauged chiral symmetry approach, consistent with the vector meson dominance, in the linear realization (for the vector mesons) of the global chiral symmetry. The first application deals with the nucleon electric polarizability and magnetic susceptibilty. Both seagull and dispersive contributions appear and we evaluate the latter in terms of the sums over intermediate states. The results are compared with existing quark model results as well as with empirical determinations. The second application concerns the zero-point quantum correction to the skyrmion mass. We apply a chiral perturbation theory approach to evaluate the pion loop contribution to the nucleon mass. The comparison with the conventional Skyrme model result reveals an important sensitivity to the stabilization mechanism. The third application is to lepton-nucleon deep inelastic scattering in the Bjorken scaling limit. The structure tensor is calculated in terms of the representation as a commutator product of two currents. Numerical results are presented for the scaling function F2( x). An essential use is made of the large Nc. (number of colors) approximation in all these applications. In the numerical computations we ignore the distortion effects, relative to the free plane wave limit, on the pionic fluctuations.
NASA Technical Reports Server (NTRS)
Lamb, Susan A.
1993-01-01
The Final Technical Report covering the period from 15 Aug. 1989 to 14 Aug. 1991 is presented. Areas of research included Infrared Astronomy Satellite (IRAS) high resolution studies and modeling of closely interacting galaxies; galaxy collisions: infrared observations and analysis of numerical models; and UV spectroscopy of massive young stellar populations in interacting galaxies. Both observational studies and theoretical modelling of interacting galaxies are covered. As a consequence the report is divided into two parts, one on each aspect of the overall project.
Higher dimensional massive bigravity
NASA Astrophysics Data System (ADS)
Do, Tuan Q.
2016-08-01
We study higher-dimensional scenarios of massive bigravity, which is a very interesting extension of nonlinear massive gravity since its reference metric is assumed to be fully dynamical. In particular, the Einstein field equations along with the following constraint equations for both physical and reference metrics of a five-dimensional massive bigravity will be addressed. Then, we study some well-known cosmological spacetimes such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini metrics for the five-dimensional massive bigravity. As a result, we find that massive graviton terms will serve as effective cosmological constants in both physical and reference sectors if a special scenario, in which reference metrics are chosen to be proportional to physical ones, is considered for all mentioned metrics. Thanks to the constancy property of massive graviton terms, consistent cosmological solutions will be figured out accordingly.
NASA Astrophysics Data System (ADS)
Zhang, Tianxi
2014-01-01
Slightly modifying the standard big bang theory, the author has recently developed a new cosmological model called black hole universe, which is consistent with Mach’s principle, governed by Einstein’s general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, cosmic microwave background radiation, and acceleration of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates the emissions of dynamic black holes according to the black hole universe model and provides a self-consistent explanation for the observations of gamma ray bursts (GRBs), X-ray flares, and quasars as emissions of dynamic star-like, massive, and supermassive black holes. It is shown that a black hole, when it accretes its ambient matter or merges with other black holes, becomes dynamic. Since the event horizon of a dynamic black hole is broken, the inside hot (or high-frequency) blackbody radiation leaks out. The leakage of the inside hot blackbody radiation leads to a GRB if it is a star-like black hole, an X-ray flare if it is a massive black hole like the one at the center of the Milky Way, or a quasar if it is a supermassive black hole like an active galactic nucleus (AGN). The energy spectra and amount of emissions produced by the dynamic star-like, massive, and supermassive black holes can be consistent with the measurements of GRBs, X-ray flares, and quasars.
NASA Astrophysics Data System (ADS)
Nieto, Carlos M.; Rodríguez, Yeinzon
2016-06-01
Gauge-flation model at zeroth-order in cosmological perturbation theory offers an interesting scenario for realizing inflation within a particle physics context, allowing us to investigate interesting possible connections between inflation and the subsequent evolution of the Universe. Difficulties, however, arise at the perturbative level, thus motivating a modification of the original model. In order to agree with the latest Planck observations, we modify the model such that the new dynamics can produce a relation between the spectral index ns and the tensor-to-scalar ratio r allowed by the data. By including an identical mass term for each of the fields of the system, we find interesting dynamics leading to slow-roll inflation of the right length. The presence of the mass term has the potential to modify the ns versus r relation so as to agree with the data. As a first step, we study the model at zeroth-order in cosmological perturbation theory, finding the conditions required for slow-roll inflation and the number of e-foldings of inflation. Numerical solutions are used to explore the impact of the mass term. We conclude that the massive version of gauge-flation offers a viable inflationary model.
Quark fragmentation functions in NJL-jet model
NASA Astrophysics Data System (ADS)
Bentz, Wolfgang; Matevosyan, Hrayr; Thomas, Anthony
2014-09-01
We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. We report on our studies of quark fragmentation functions in the Nambu-Jona-Lasinio (NJL) - jet model. The results of Monte-Carlo simulations for the fragmentation functions to mesons and nucleons, as well as to pion and kaon pairs (dihadron fragmentation functions) are presented. The important role of intermediate vector meson resonances for those semi-inclusive deep inelastic production processes is emphasized. Our studies are very relevant for the extraction of transverse momentum dependent quark distribution functions from measured scattering cross sections. Supported by Grant in Aid for Scientific Research, Japanese Ministry of Education, Culture, Sports, Science and Technology, Project No. 20168769.
Logistics of massive transfusions.
DeLoughery, Thomas G
2010-01-01
Care of the patient with massive bleeding involves more than aggressive surgery and infusion of large amounts of blood products. The proper management of massive transfusions-whether they are in trauma patients or other bleeding patients-requires coordination of the personnel in the surgical suite or the emergency department, the blood bank, and laboratory.
[Massive traumatic hemoptysis].
Bourdereau, J M; Mathé, D; Voultoury, J C
1985-01-01
A case is reported of a patient who suffered a rupture of one lung as result of thoracic trauma. This gave rise to respiratory distress with massive haemoptysis which was initially treated with a double-lumen endotracheal tube, with separate lung ventilation, a chest drain and massive transfusion. A haemostatic pneumonectomy had to be performed because of the persisting and profuse bleeding.
Chiral bag model for the nucleon
NASA Astrophysics Data System (ADS)
Hosaka, Atsushi; Toki, Hiroshi
1996-12-01
We review the chiral bag model for the nucleon at low energy. The model is a hybrid model of quark and meson degrees of freedom, interpolating the two limits of the Skyrme model at R → 0 and the MIT bag model at R → ∞, where R is the bag radius. Baryon number one ( B = 1) solutions are obtained in the semiclassical method, where the nucleon is regarded as a slowly rotating hedgehog. We investigate static properties of the nucleon such as masses and magnetic moments as functions of R, first in the original chiral bag model and second in the models with vector mesons. We find a reasonably good description for the nucleon in both cases at an intermediate bag radius R ~ 0.6 fm. Results of the model calculations are then re-derived using a group theoretical method in the large- Nc limit.
NASA Astrophysics Data System (ADS)
Yadav, Abhay Pratap; Glatzel, Wolfgang
2017-02-01
The stability with respect to radial perturbations of massive zero-age main-sequence stars having solar chemical composition and masses between 50 and 150 M⊙ is reinvestigated. As a first step, a linear non-adiabatic stability analysis is performed, confirming the existence of dynamical strange mode instabilities for models with masses above 58 M⊙. For selected models, the evolution of the strange mode instabilities into the non-linear regime is followed by numerical simulation. The final results of strange mode instabilities are thus found to be finite amplitude pulsations with periods between 3 and 24 h. Mean acoustic luminosities capable to drive winds with mass-loss rates of the order of 0.5 × 10-7 M⊙ yr-1, which can at most marginally affect stellar evolution in the vicinity of the zero-age main sequence, are associated with these finite amplitude pulsations.
Transverse Instability of Line Solitary Waves in Massive Dirac Equations
NASA Astrophysics Data System (ADS)
Pelinovsky, Dmitry; Shimabukuro, Yusuke
2016-04-01
Working in the context of localized modes in periodic potentials, we consider two systems of the massive Dirac equations in two spatial dimensions. The first system, a generalized massive Thirring model, is derived for the periodic stripe potentials. The second one, a generalized massive Gross-Neveu equation, is derived for the hexagonal potentials. In both cases, we prove analytically that the line solitary waves are spectrally unstable with respect to periodic transverse perturbations of large periods. The spectral instability is induced by the spatial translation for the generalized massive Thirring model and by the gauge rotation for the generalized massive Gross-Neveu model. We also observe numerically that the spectral instability holds for the transverse perturbations of any period in the generalized massive Thirring model and exhibits a finite threshold on the period of the transverse perturbations in the generalized massive Gross-Neveu model.
NASA Astrophysics Data System (ADS)
Nardon, E.; Fil, A.; Hoelzl, M.; Huijsmans, G.; contributors, JET
2017-01-01
3D non-linear MHD simulations of a D 2 massive gas injection (MGI) triggered disruption in JET with the JOREK code provide results which are qualitatively consistent with experimental observations and shed light on the physics at play. In particular, it is observed that the gas destabilizes a large m/n = 2/1 tearing mode, with the island O-point coinciding with the gas deposition region, by enhancing the plasma resistivity via cooling. When the 2/1 island gets so large that its inner side reaches the q = 3/2 surface, a 3/2 tearing mode grows. Simulations suggest that this is due to a steepening of the current profile right inside q = 3/2. Magnetic field stochastization over a large fraction of the minor radius as well as the growth of higher n modes ensue rapidly, leading to the thermal quench (TQ). The role of the 1/1 internal kink mode is discussed. An I p spike at the TQ is obtained in the simulations but with a smaller amplitude than in the experiment. Possible reasons are discussed.
Lichtner, Peter C.; Hammond, Glenn E.; Lu, Chuan; Karra, Satish; Bisht, Gautam; Andre, Benjamin; Mills, Richard; Kumar, Jitendra
2015-01-20
PFLOTRAN solves a system of generally nonlinear partial differential equations describing multi-phase, multicomponent and multiscale reactive flow and transport in porous materials. The code is designed to run on massively parallel computing architectures as well as workstations and laptops (e.g. Hammond et al., 2011). Parallelization is achieved through domain decomposition using the PETSc (Portable Extensible Toolkit for Scientific Computation) libraries for the parallelization framework (Balay et al., 1997). PFLOTRAN has been developed from the ground up for parallel scalability and has been run on up to 218 processor cores with problem sizes up to 2 billion degrees of freedom. Written in object oriented Fortran 90, the code requires the latest compilers compatible with Fortran 2003. At the time of this writing this requires gcc 4.7.x, Intel 12.1.x and PGC compilers. As a requirement of running problems with a large number of degrees of freedom, PFLOTRAN allows reading input data that is too large to fit into memory allotted to a single processor core. The current limitation to the problem size PFLOTRAN can handle is the limitation of the HDF5 file format used for parallel IO to 32 bit integers. Noting that 2^{32} = 4; 294; 967; 296, this gives an estimate of the maximum problem size that can be currently run with PFLOTRAN. Hopefully this limitation will be remedied in the near future.
Some interesting features of new massive gravity
NASA Astrophysics Data System (ADS)
Accioly, Antonio; Helayël-Neto, José; Scatena, Eslley; Morais, Jefferson; Turcati, Rodrigo; Pereira-Dias, Bruno
2011-11-01
A sketch of a proof that new massive gravity—the massive 3D gravity model proposed by Bergshoeff, Hohm and Townsend (BHT)—is the only unitary system at the tree level that can be constructed by augmenting 3D general relativity through (curvature)2-terms is presented. Two interesting gravitational properties of the BHT model, namely, time dilation and time delay, which have no counterpart in the usual Einstein 3D gravity, are analyzed as well.
ERIC Educational Resources Information Center
Janicke, Eugene M.
1981-01-01
An intensive reading clinic used the Massive Oral Decoding (MOD) technique to help 10 reading disabled students (grades 7 and 8) increase independent reading skills. MOD stresses large amounts of reading practice at the student's independent level. (CL)
NASA Astrophysics Data System (ADS)
Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Mário Castelo-Branco, José; Granado, Isabel; Carvalho, João; João Baptista, Maria; Represas, Patrícia; Pereira, Zélia; Oliveira, Tomás; Araujo, Vitor
2013-04-01
The Iberian Pyrite Belt (IPB) hosts one of the largest concentrations of massive sulfides in the Earth's crust. This highly productive VMS belt contains more than 85 massive sulfide deposits, totalling an estimate of 1600 Mt of massive ore and about 250 Mt of stockwork ore (Leistel et al., 1998; Oliveira et al., 2005; Tornos, 2006). Included in the South Portuguese Zone the IPB is represented by the Phyllite-Quartzite Group (PQG) composed of shales and quartzites of late Devonian age followed by the Volcanic-Sedimentary Complex (VSC) a submarine succession of sediments and felsic and basic volcanic rocks (late Famennian-late Viséan age). Above the IPB a turbidite sedimentary unit occurs being represented by the Baixo Alentejo Flysch Group (BAFG). The ore deposits are hosted by felsic volcanic rocks and sediments that are dominant in the lower part of the VSC succession. The Neves Corvo (ProMine, EU FP7) project area is focused on the Neves Corvo deposit, an active copper mine. The project area is located between the Messejana Fault and the Portuguese/Spanish border which has been selected for the 3D geological and geophysical modelling study, based on high exploration potential of the Neves Corvo area (Oliveira et al. 2006, Relvas et al. 2006, Pereira et al. 2008, Rosa et al. 2008, Matos et al. 2011, Oliveira et al. 2013). In this study existing LNEG and AGC geological, geophysical and geochemistry databases were considered. New surveys were done: i) - A physical volcanology and palynostratigraphic age data study and log of the Cotovio drill-hole core (1,888 m, drilled by AGC). ii) - Interpretation of 280 km of Squid TEM performed by AGC. Based on the TEM data, significant conductors have been identified related with: shallow conductive cover, graphitic shale, black shale and sulphide mineralizations. The most important TEM conductors are related with the Neves Corvo massive sulphides lenses (1-10 Ωm). iii) - Ground and residual gravimetry studies including
NASA Astrophysics Data System (ADS)
Sui, Yi; Shao, Fengjing; Wang, Changying; Sun, Rencheng; Ji, Jun
2016-12-01
Feature bands selection and targets classification is of great importance in spectral remotely sensed imagery interpretation. In this work, complex network is adopted for modeling spectral remotely sensed imagery. Subnet is constructed for each band based on spatial neighboring characteristic. Feature bands could be obtained by analyzing and comparing topological characteristics between subnets. After finding feature bands, subnets of feature bands are compounded. Targets classification could be measured by degree distribution of the composited network. This approach is evaluated with empirical experiments based on detecting massive green algae blooms with MODIS data. Feature bands found are coincided with spectral mechanism of green algae. By comparing with FAI, RVI, NDVI, EVI and OSABI methods, our approach improves correct classification rates.
Cosmological perturbations in massive bigravity
Lagos, Macarena; Ferreira, Pedro G. E-mail: p.ferreira1@physics.ox.ac.uk
2014-12-01
We present a comprehensive analysis of classical scalar, vector and tensor cosmological perturbations in ghost-free massive bigravity. In particular, we find the full evolution equations and analytical solutions in a wide range of regimes. We show that there are viable cosmological backgrounds but, as has been found in the literature, these models generally have exponential instabilities in linear perturbation theory. However, it is possible to find stable scalar cosmological perturbations for a very particular choice of parameters. For this stable subclass of models we find that vector and tensor perturbations have growing solutions. We argue that special initial conditions are needed for tensor modes in order to have a viable model.
Voids in massive neutrino cosmologies
Massara, Elena; Villaescusa-Navarro, Francisco; Viel, Matteo; Sutter, P.M. E-mail: villaescusa@oats.inaf.it E-mail: sutter@oats.inaf.it
2015-11-01
Cosmic voids are a promising environment to characterize neutrino-induced effects on the large-scale distribution of matter in the universe. We perform a comprehensive numerical study of the statistical properties of voids, identified both in the matter and galaxy distributions, in massive and massless neutrino cosmologies. The matter density field is obtained by running several independent N-body simulations with cold dark matter and neutrino particles, while the galaxy catalogs are modeled by populating the dark matter halos in simulations via a halo occupation distribution (HOD) model to reproduce the clustering properties observed by the Sloan Digital Sky Survey (SDSS) II Data Release 7. We focus on the impact of massive neutrinos on the following void statistical properties: number density, ellipticities, two-point statistics, density and velocity profiles. Considering the matter density field, we find that voids in massive neutrino cosmologies are less evolved than those in the corresponding massless neutrinos case: there is a larger number of small voids and a smaller number of large ones, their profiles are less evacuated, and they present a lower wall at the edge. Moreover, the degeneracy between σ{sub 8} and Ω{sub ν} is broken when looking at void properties. In terms of the galaxy density field, we find that differences among cosmologies are difficult to detect because of the small number of galaxy voids in the simulations. Differences are instead present when looking at the matter density and velocity profiles around these voids.
KOSKI,JORMAN A.; SUO-ANTITLA,AHTI; KRAMER,M. ALEX; GREINER,MILES
2000-05-11
Recent observations show that the thermal boundary conditions within large-scale fires are significantly affected by the presence of thermally massive objects. These objects cool the soot and gas near their surfaces, and these effects reduce the incoming radiant heat-flux to values lower than the levels expected from simple {sigma}T{sub fire}{sup 4} models. They also affect the flow and temperature fields in the fire far from their surfaces. The Cask Analysis Fire Environment (CAFE) code has been developed at Sandia National Laboratories to provide an enhanced fire boundary condition for the design of radioactive material packages. CAFE is a set of computer subroutines that use computational fluid mechanics methods to predict convective heat transfer and mixing. It also includes models for fuel and oxygen transport, chemical reaction, and participating-media radiation heat transfer. This code uses two-dimensional computational models so that it has reasonably short turnaround times on standard workstations and is well suited for design and risk studies. In this paper, CAFE is coupled with a commercial finite-element program to model a large cylindrical calorimeter fully engulfed in a pool fire. The time-dependent heat-flux to the calorimeter and the calorimeter surface temperature are determined for several locations around the calorimeter circumference. The variation of heat-flux with location is determined for calorimeters with different diameters and wall thickness, and the observed effects discussed.
Chacko, Z.; Graesser, M.L.; Grojean, C.; Pilo, L.
2003-12-11
At present no theory of a massive graviton is known that is consistent with experiments at both long and short distances. The problem is that consistency with long distance experiments requires the graviton mass to be very small. Such a small graviton mass however implies an ultraviolet cutoff for the theory at length scales far larger than the millimeter scale at which gravity has already been measured. In this paper we attempt to construct a model which avoids this problem. We consider a brane world setup in warped AdS spacetime and we investigate the consequences of writing a mass term for the graviton on a the infrared brane where the local cutoff is of order a large (galactic) distance scale. The advantage of this setup is that the low cutoff for physics on the infrared brane does not significantly affect the predictivity of the theory for observers localized on the ultraviolet brane. For such observers the predictions of this theory agree with general relativity at distances smaller than the infrared scale but go over to those of a theory of massive gravity at longer distances. A careful analysis of the graviton two-point function, however, reveals the presence of a ghost in the low energy spectrum. A mode decomposition of the higher dimensional theory reveals that the ghost corresponds to the radion field. We also investigate the theory with a brane localized mass for the graviton on the ultraviolet brane, and show that the physics of this case is similar to that of a conventional four dimensional theory with a massive graviton, but with one important difference: when the infrared brane decouples and the would-be massive graviton gets heavier than the regular Kaluza-Klein modes, it becomes unstable and it has a finite width to decay off the brane into the continuum of Kaluza-Klein states.
Su, Xiaoquan; Hu, Jianqiang; Huang, Shi; Ning, Kang
2014-01-01
The research in microbial communities would potentially impact a vast number of applications in “bio”-related disciplines. Large-scale analyses became a clear trend in microbial community studies, thus it is increasingly important to perform efficient and in-depth data mining for insightful biological principles from large number of samples. However, as microbial communities are from different sources and of different structures, comparison and data-mining from large number of samples become quite difficult. In this work, we have proposed a data model to represent large-scale comparison of microbial community samples, namely the “Multi-Dimensional View” data model (the MDV model) that should at least include 3 aspects: samples profile (S), taxa profile (T) and meta-data profile (V). We have also proposed a method for rapid data analysis based on the MDV model and applied it on the case studies with samples from various environmental conditions. Results have shown that though sampling environments usually define key variables, the analysis could detect bio-makers and even subtle variables based on large number of samples, which might be used to discover novel principles that drive the development of communities. The efficiency and effectiveness of data analysis method based on the MDV model have been validated by the results. PMID:25227622
NASA Astrophysics Data System (ADS)
Su, Xiaoquan; Hu, Jianqiang; Huang, Shi; Ning, Kang
2014-09-01
The research in microbial communities would potentially impact a vast number of applications in ``bio''-related disciplines. Large-scale analyses became a clear trend in microbial community studies, thus it is increasingly important to perform efficient and in-depth data mining for insightful biological principles from large number of samples. However, as microbial communities are from different sources and of different structures, comparison and data-mining from large number of samples become quite difficult. In this work, we have proposed a data model to represent large-scale comparison of microbial community samples, namely the ``Multi-Dimensional View'' data model (the MDV model) that should at least include 3 aspects: samples profile (S), taxa profile (T) and meta-data profile (V). We have also proposed a method for rapid data analysis based on the MDV model and applied it on the case studies with samples from various environmental conditions. Results have shown that though sampling environments usually define key variables, the analysis could detect bio-makers and even subtle variables based on large number of samples, which might be used to discover novel principles that drive the development of communities. The efficiency and effectiveness of data analysis method based on the MDV model have been validated by the results.
Su, Xiaoquan; Hu, Jianqiang; Huang, Shi; Ning, Kang
2014-09-17
The research in microbial communities would potentially impact a vast number of applications in "bio"-related disciplines. Large-scale analyses became a clear trend in microbial community studies, thus it is increasingly important to perform efficient and in-depth data mining for insightful biological principles from large number of samples. However, as microbial communities are from different sources and of different structures, comparison and data-mining from large number of samples become quite difficult. In this work, we have proposed a data model to represent large-scale comparison of microbial community samples, namely the "Multi-Dimensional View" data model (the MDV model) that should at least include 3 aspects: samples profile (S), taxa profile (T) and meta-data profile (V). We have also proposed a method for rapid data analysis based on the MDV model and applied it on the case studies with samples from various environmental conditions. Results have shown that though sampling environments usually define key variables, the analysis could detect bio-makers and even subtle variables based on large number of samples, which might be used to discover novel principles that drive the development of communities. The efficiency and effectiveness of data analysis method based on the MDV model have been validated by the results.
A cosmological study in massive gravity theory
Pan, Supriya Chakraborty, Subenoy
2015-09-15
A detailed study of the various cosmological aspects in massive gravity theory has been presented in the present work. For the homogeneous and isotropic FLRW model, the deceleration parameter has been evaluated, and, it has been examined whether there is any transition from deceleration to acceleration in recent past, or not. With the proper choice of the free parameters, it has been shown that the massive gravity theory is equivalent to Einstein gravity with a modified Newtonian gravitational constant together with a negative cosmological constant. Also, in this context, it has been examined whether the emergent scenario is possible, or not, in massive gravity theory. Finally, we have done a cosmographic analysis in massive gravity theory.
NASA Astrophysics Data System (ADS)
Chashkina, A.; Popov, S. B.
2012-08-01
Some modern models of neutron star evolution predict that initially large magnetic fields rapidly decay down to some saturation value ˜ few ×1013 G and weaker magnetic fields do not decay significantly (Pons et al., 2009). It is difficult to check the predictions of this model for initially highly magnetized objects on the time scale of a few million years. We propose to use Be/X-ray binaries for this purpose. We apply several methods to estimate magnetic fields of neutron stars in these accreting systems using the data obtained by the RXTE satellite (Galache et al., 2008). Only using the most modern approach for estimating the magnetic field strengths of long period NSs as proposed by Shakura et al. (2012) we are able to obtain a field distribution compatible with predictions of the theoretical model of field decay of Pons et al. (2009).
Killian, Megan L; Cavinatto, Leonardo; Shah, Shivam A; Sato, Eugene J; Ward, Samuel R; Havlioglu, Necat; Galatz, Leesa M; Thomopoulos, Stavros
2014-03-01
The objective of this study was to understand the effect of pre-repair rotator cuff chronicity on post-repair healing outcomes using a chronic and acute multi-tendon rat rotator cuff injury model. Full-thickness dual tendon injuries (supra- and infraspinatus) were created unilaterally in adult male Sprague Dawley rats, and left chronically detached for 8 or 16 weeks. After chronic detachment, tears were repaired and acute dual tendon injuries were created and immediately repaired on contralateral shoulders. Tissue level outcomes for bone, tendon, and muscle were assessed 4 or 8 weeks after repair using histology, microcomputed tomography, biomechanical testing, and biochemical assays. Substantial gap formation was seen in 35% of acute repairs and 44% of chronic repairs. Gap formation negatively correlated with mechanical and structural outcomes for both healing time points regardless of injury duration. Bone and histomorphometry, as well as biomechanics, were similar between acute and chronic injury and repair regardless of chronicity and duration of healing. This study was the first to implement a multi-tendon rotator cuff injury with surgical repair following both chronic and acute injuries. Massive tear in a rodent model resulted in gap formation regardless of injury duration which had detrimental effects on repair outcomes. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.
Killian, Megan L.; Cavinatto, Leonardo; Shah, Shivam A.; Sato, Eugene J.; Ward, Samuel R.; Havlioglu, Necat; Galatz, Leesa M.; Thomopoulos, Stavros
2014-01-01
The objective of this study was to understand the effect of pre-repair rotator cuff chronicity on post-repair healing outcomes using a chronic and acute multi-tendon rat rotator cuff injury model. Full-thickness dual tendon injuries (supra- and infraspinatus) were created unilaterally in adult male Sprague Dawley rats, and left chronically detached for 8 or 16 weeks. After chronic detachment, tears were repaired and acute dual tendon injuries were created and immediately repaired on contralateral shoulders. Tissue level outcomes for bone, tendon, and muscle were assessed 4 or 8 weeks after repair using histology, microcomputed tomography, biomechanical testing, and biochemical assays. Substantial gap formation was seen in 35% of acute repairs and 44% of chronic repairs. Gap formation negatively correlated with mechanical and structural outcomes for both healing time points regardless of injury duration. Bone and histomorphometry, as well as biomechanics, were similar between acute and chronic injury and repair regardless of chronicity and duration of healing. This study was the first to implement a multi-tendon rotator cuff injury with surgical repair following both chronic and acute injuries. Massive tear in a rodent model resulted in gap formation regardless of injury duration which had detrimental effects on repair outcomes. PMID:24243733
NASA Astrophysics Data System (ADS)
Kumar, J.; Mills, R. T.; Lichtner, P. C.; Hammond, G. E.
2010-12-01
Fracture dominated flows occur in numerous subsurface geochemical processes and at many different scales in rock pore structures, micro-fractures, fracture networks and faults. Fractured porous media can be modeled as multiple interacting continua which are connected to each other through transfer terms that capture the flow of mass and energy in response to pressure, temperature and concentration gradients. However, the analysis of large-scale transient problems using the multiple interacting continuum approach presents an algorithmic and computational challenge for problems with very large numbers of degrees of freedom. A generalized dual porosity model based on the Dual Continuum Disconnected Matrix approach has been implemented within a massively parallel multiphysics-multicomponent-multiphase subsurface reactive flow and transport code PFLOTRAN. Developed as part of the Department of Energy's SciDAC-2 program, PFLOTRAN provides subsurface simulation capabilities that can scale from laptops to ultrascale supercomputers, and utilizes the PETSc framework to solve the large, sparse algebraic systems that arises in complex subsurface reactive flow and transport problems. It has been successfully applied to the solution of problems composed of more than two billions degrees of freedom, utilizing up to 131,072 processor cores on Jaguar, the Cray XT5 system at Oak Ridge National Laboratory that is the world’s fastest supercomputer. Building upon the capabilities and computational efficiency of PFLOTRAN, we will present an implementation of the multiple interacting continua formulation for fractured porous media along with an application case study.
NASA Astrophysics Data System (ADS)
Aalto, R. E.; Lauer, J. W.; Darby, S. E.; Best, J.; Dietrich, W. E.
2015-12-01
During glacial-marine transgressions vast volumes of sediment are deposited due to the infilling of lowland fluvial systems and shallow shelves, material that is removed during ensuing regressions. Modelling these processes would illuminate system morphodynamics, fluxes, and 'complexity' in response to base level change, yet such problems are computationally formidable. Environmental systems are characterized by strong interconnectivity, yet traditional supercomputers have slow inter-node communication -- whereas rapidly advancing Graphics Processing Unit (GPU) technology offers vastly higher (>100x) bandwidths. GULLEM (GpU-accelerated Lowland Landscape Evolution Model) employs massively parallel code to simulate coupled fluvial-landscape evolution for complex lowland river systems over large temporal and spatial scales. GULLEM models the accommodation space carved/infilled by representing a range of geomorphic processes, including: river & tributary incision within a multi-directional flow regime, non-linear diffusion, glacial-isostatic flexure, hydraulic geometry, tectonic deformation, sediment production, transport & deposition, and full 3D tracking of all resulting stratigraphy. Model results concur with the Holocene dynamics of the Fly River, PNG -- as documented with dated cores, sonar imaging of floodbasin stratigraphy, and the observations of topographic remnants from LGM conditions. Other supporting research was conducted along the Mekong River, the largest fluvial system of the Sunda Shelf. These and other field data provide tantalizing empirical glimpses into the lowland landscapes of large rivers during glacial-interglacial transitions, observations that can be explored with this powerful numerical model. GULLEM affords estimates for the timing and flux budgets within the Fly and Sunda Systems, illustrating complex internal system responses to the external forcing of sea level and climate. Furthermore, GULLEM can be applied to most ANY fluvial system to
Tavares, J; Silva, L; Oliveira, L
2017-07-11
Ephestia kuehniella (Lepidoptera, Pyralidae) and Sitotroga cerealella (Lepidoptera, Gelechiidae) are important factitious hosts used for production of biological control agents. Their differences in terms of biology and behavior require adjustments in their mass production, particularly when using corn or barley as food in grain or in bran. We modeled adult emergence, oviposition period and egg production along time after emergence, as a function of the food source. Significant differences between hosts or food type were found for these variables and for adult weight but not for sex ratio. Our results confirm the possibility of mass production of these hosts using corn or barley as food source. Integrating adult emergence patterns and age specific fecundity patterns into a single model, it is clear that rearing E. kuehniella on barley would result in the highest egg output in much shorter time than E. kuehniella on corn or S. cerealella on barley.
Wienke, B R; O'Leary, T R
2008-05-01
Linking model and data, we detail the LANL diving reduced gradient bubble model (RGBM), dynamical principles, and correlation with data in the LANL Data Bank. Table, profile, and meter risks are obtained from likelihood analysis and quoted for air, nitrox, helitrox no-decompression time limits, repetitive dive tables, and selected mixed gas and repetitive profiles. Application analyses include the EXPLORER decompression meter algorithm, NAUI tables, University of Wisconsin Seafood Diver tables, comparative NAUI, PADI, Oceanic NDLs and repetitive dives, comparative nitrogen and helium mixed gas risks, USS Perry deep rebreather (RB) exploration dive,world record open circuit (OC) dive, and Woodville Karst Plain Project (WKPP) extreme cave exploration profiles. The algorithm has seen extensive and utilitarian application in mixed gas diving, both in recreational and technical sectors, and forms the bases forreleased tables and decompression meters used by scientific, commercial, and research divers. The LANL Data Bank is described, and the methods used to deduce risk are detailed. Risk functions for dissolved gas and bubbles are summarized. Parameters that can be used to estimate profile risk are tallied. To fit data, a modified Levenberg-Marquardt routine is employed with L2 error norm. Appendices sketch the numerical methods, and list reports from field testing for (real) mixed gas diving. A Monte Carlo-like sampling scheme for fast numerical analysis of the data is also detailed, as a coupled variance reduction technique and additional check on the canonical approach to estimating diving risk. The method suggests alternatives to the canonical approach. This work represents a first time correlation effort linking a dynamical bubble model with deep stop data. Supercomputing resources are requisite to connect model and data in application.
Massive Warm/Hot Galaxy Coronae as Probed by UV/X-Ray Oxygen Absorption and Emission. I. Basic Model
NASA Astrophysics Data System (ADS)
Faerman, Yakov; Sternberg, Amiel; McKee, Christopher F.
2017-01-01
We construct an analytic phenomenological model for extended warm/hot gaseous coronae of L* galaxies. We consider UV O vi Cosmic Origins Spectrograph (COS)-Halos absorption line data in combination with Milky Way (MW) X-ray O vii and O viii absorption and emission. We fit these data with a single model representing the COS-Halos galaxies and a Galactic corona. Our model is multi-phased, with hot and warm gas components, each with a (turbulent) log-normal distribution of temperatures and densities. The hot gas, traced by the X-ray absorption and emission, is in hydrostatic equilibrium in an MW gravitational potential. The median temperature of the hot gas is 1.5× {10}6 K and the mean hydrogen density is ∼ 5× {10}-5 {{cm}}-3. The warm component as traced by the O vi, is gas that has cooled out of the high density tail of the hot component. The total warm/hot gas mass is high and is 1.2× {10}11 {M}ȯ . The gas metallicity we require to reproduce the oxygen ion column densities is 0.5 solar. The warm O vi component has a short cooling time (∼ 2× {10}8 years), as hinted by observations. The hot component, however, is ∼ 80 % of the total gas mass and is relatively long-lived, with {t}{cool}∼ 7× {10}9 years. Our model supports suggestions that hot galactic coronae can contain significant amounts of gas. These reservoirs may enable galaxies to continue forming stars steadily for long periods of time and account for “missing baryons” in galaxies in the local universe.
NASA Astrophysics Data System (ADS)
Garcia, E. V.; Stassun, Keivan G.; Pavlovski, K.; Hensberge, H.; Gómez Maqueo Chew, Y.; Claret, A.
2014-09-01
We determine the absolute dimensions of the eclipsing binary V578 Mon, a detached system of two early B-type stars (B0V + B1V, P = 2.40848 days) in the star-forming region NGC 2244 of the Rosette Nebula. From the light curve analysis of 40 yr of photometry and the analysis of HERMES spectra, we find radii of 5.41 ± 0.04 R⊙ and 4.29 ± 0.05 R⊙, and temperatures of 30,000 ± 500 K and 25,750 ± 435 K, respectively. We find that our disentangled component spectra for V578 Mon agree well with previous spectral disentangling from the literature. We also reconfirm the previous spectroscopic orbit of V578 Mon finding that masses of 14.54 ± 0.08 M⊙ and 10.29 ± 0.06 M⊙ are fully compatible with the new analysis. We compare the absolute dimensions to the rotating models of the Geneva and Utrecht groups and the models of the Granada group. We find that all three sets of models marginally reproduce the absolute dimensions of both stars with a common age within the uncertainty for gravity-effective temperature isochrones. However, there are some apparent age discrepancies for the corresponding mass-radius isochrones. Models with larger convective overshoot, >0.35, worked best. Combined with our previously determined apsidal motion of 0.07089^{+0.00021}_{-0.00013} deg cycle-1, we compute the internal structure constants (tidal Love number) for the Newtonian and general relativistic contribution to the apsidal motion as log k 2 = -1.975 ± 0.017 and log k 2 = -3.412 ± 0.018, respectively. We find the relativistic contribution to the apsidal motion to be small, <4%. We find that the prediction of log k 2, theo = -2.005 ± 0.025 of the Granada models fully agrees with our observed log k 2.
Garcia, E. V.; Stassun, Keivan G.; Pavlovski, K.; Hensberge, H.; Chew, Y. Gómez Maqueo; Claret, A.
2014-09-01
We determine the absolute dimensions of the eclipsing binary V578 Mon, a detached system of two early B-type stars (B0V + B1V, P = 2.40848 days) in the star-forming region NGC 2244 of the Rosette Nebula. From the light curve analysis of 40 yr of photometry and the analysis of HERMES spectra, we find radii of 5.41 ± 0.04 R{sub ☉} and 4.29 ± 0.05 R{sub ☉}, and temperatures of 30,000 ± 500 K and 25,750 ± 435 K, respectively. We find that our disentangled component spectra for V578 Mon agree well with previous spectral disentangling from the literature. We also reconfirm the previous spectroscopic orbit of V578 Mon finding that masses of 14.54 ± 0.08 M{sub ☉} and 10.29 ± 0.06 M{sub ☉} are fully compatible with the new analysis. We compare the absolute dimensions to the rotating models of the Geneva and Utrecht groups and the models of the Granada group. We find that all three sets of models marginally reproduce the absolute dimensions of both stars with a common age within the uncertainty for gravity-effective temperature isochrones. However, there are some apparent age discrepancies for the corresponding mass-radius isochrones. Models with larger convective overshoot, >0.35, worked best. Combined with our previously determined apsidal motion of 0.07089{sub −0.00013}{sup +0.00021} deg cycle{sup –1}, we compute the internal structure constants (tidal Love number) for the Newtonian and general relativistic contribution to the apsidal motion as log k {sub 2} = –1.975 ± 0.017 and log k {sub 2} = –3.412 ± 0.018, respectively. We find the relativistic contribution to the apsidal motion to be small, <4%. We find that the prediction of log k {sub 2,theo} = –2.005 ± 0.025 of the Granada models fully agrees with our observed log k {sub 2}.
Supertwistors and massive particles
Mezincescu, Luca; Routh, Alasdair J.; Townsend, Paul K.
2014-07-15
In the (super)twistor formulation of massless (super)particle mechanics, the mass-shell constraint is replaced by a “spin-shell” constraint from which the spin content can be read off. We extend this formalism to massive (super)particles (with N-extended space–time supersymmetry) in three and four space–time dimensions, explaining how the spin-shell constraints are related to spin, and we use it to prove equivalence of the massive N=1 and BPS-saturated N=2 superparticle actions. We also find the supertwistor form of the action for “spinning particles” with N-extended worldline supersymmetry, massless in four dimensions and massive in three dimensions, and we show how this simplifies special features of the N=2 case. -- Highlights: •Spin-shell constraints are related to Poincaré Casimirs. •Twistor form of 4D spinning particle for spin N/2. •Twistor proof of scalar/antisymmetric tensor equivalence for 4D spin 0. •Twistor form of 3D particle with arbitrary spin. •Proof of equivalence of N=1 and N=2 BPS massive 4D superparticles.
Massively Redundant Electromechanical Actuators
2014-08-30
date of determination). DoD Controlling Office is (insert controlling DoD office). "Massively Redundant Electromechanical Actuators" August... electromechanical systems) processes are used to manufacture reliable and reproducible stators and sliders for the actuators. These processes include
Massive binary stars as a probe of massive star formation
NASA Astrophysics Data System (ADS)
Kiminki, Daniel C.
2010-10-01
Massive stars are among the largest and most influential objects we know of on a sub-galactic scale. Binary systems, composed of at least one of these stars, may be responsible for several types of phenomena, including type Ib/c supernovae, short and long gamma ray bursts, high-velocity runaway O and B-type stars, and the density of the parent star clusters. Our understanding of these stars has met with limited success, especially in the area of their formation. Current formation theories rely on the accumulated statistics of massive binary systems that are limited because of their sample size or the inhomogeneous environments from which the statistics are collected. The purpose of this work is to provide a higher-level analysis of close massive binary characteristics using the radial velocity information of 113 massive stars (B3 and earlier) and binary orbital properties for the 19 known close massive binaries in the Cygnus OB2 Association. This work provides an analysis using the largest amount of massive star and binary information ever compiled for an O-star rich cluster like Cygnus OB2, and compliments other O-star binary studies such as NGC 6231, NGC 2244, and NGC 6611. I first report the discovery of 73 new O or B-type stars and 13 new massive binaries by this survey. This work involved the use of 75 successful nights of spectroscopic observation at the Wyoming Infrared Observatory in addition to observations obtained using the Hydra multi-object spectrograph at WIYN, the HIRES echelle spectrograph at KECK, and the Hamilton spectrograph at LICK. I use these data to estimate the spectrophotometric distance to the cluster and to measure the mean systemic velocity and the one-sided velocity dispersion of the cluster. Finally, I compare these data to a series of Monte Carlo models, the results of which indicate that the binary fraction of the cluster is 57 +/- 5% and that the indices for the power law distributions, describing the log of the periods, mass
NASA Astrophysics Data System (ADS)
Petrov, Blagovest; Vink, Jorick S.; Gräfener, Götz
2016-05-01
Luminous blue variables (LBVs) have been suggested to be the direct progenitors of supernova Types IIb and IIn, with enhanced mass loss prior to explosion. However, the mechanism of this mass loss is not yet known. Here, we investigate the qualitative behaviour of theoretical stellar wind mass loss as a function of Teff across two bi-stability jumps in blue supergiant regime and also in proximity to the Eddington limit, relevant for LBVs. To investigate the physical ingredients that play a role in the radiative acceleration we calculate blue supergiant wind models with the CMFGEN non-local thermodynamic equilibrium model atmosphere code over an effective temperature range between 30 000 and 8800 K. Although our aim is not to provide new mass-loss rates for BA supergiants, we study and confirm the existence of two bi-stability jumps in mass-loss rates predicted by Vink et al. However, they are found to occur at somewhat lower Teff (20 000 and 9000 K, respectively) than found previously, which would imply that stars may evolve towards lower Teff before strong mass loss is induced by the bi-stability jumps. When the combined effects of the second bi-stability jump and the proximity to Eddington limit are accounted for, we find a dramatic increase in the mass-loss rate by up to a factor of 30. Further investigation of both bi-stability jumps is expected to lead to a better understanding of discrepancies between empirical modelling and theoretical mass-loss rates reported in the literature, and to provide key inputs for the evolution of both normal AB supergiants and LBVs, as well as their subsequent supernova Type II explosions.
Robert Podgorney; Hai Huang; Derek Gaston
2010-02-01
Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing) to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid system and our ability to reliably predict how reservoirs behave under stimulation and production. In order to increase our understanding of how reservoirs behave under these conditions, we have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a continuum multiphase flow and heat transport model. In DEM simulations, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external load is applied. DEM models have been applied to a very wide range of fracturing processes from the molecular scale (where thermal fluctuations play an important role) to scales on the order of 1 km or greater. In this approach, the continuum flow and heat transport equations are solved on an underlying fixed finite element grid with evolving porosity and permeability for each grid cell that depends on the local structure of the discrete element network (such as DEM particle density). The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms and
NASA Technical Reports Server (NTRS)
Combi, Michael R.
2004-01-01
In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic (MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important. At the University of Michigan we have an established base of experience and expertise in numerical simulations based on particle codes which address these physical regimes. The Principal Investigator, Dr. Michael Combi, has over 20 years of experience in the development of particle-kinetic and hybrid kinetichydrodynamics models and their direct use in data analysis. He has also worked in ground-based and space-based remote observational work and on spacecraft instrument teams. His research has involved studies of cometary atmospheres and ionospheres and their interaction with the solar wind, the neutral gas clouds escaping from Jupiter s moon Io, the interaction of the atmospheres/ionospheres of Io and Europa with Jupiter s corotating magnetosphere, as well as Earth s ionosphere. This report describes our progress during the year. The contained in section 2 of this report will serve as the basis of a paper describing the method and its application to the cometary coma that will be continued under a research and analysis grant that supports various applications of theoretical comet models to understanding the
Kim, Ji-hoon; Abel, Tom; Wise, John H.; Alvarez, Marcelo A.
2011-09-01
There is mounting evidence for the coevolution of galaxies and their embedded massive black holes (MBHs) in a hierarchical structure formation paradigm. To tackle the nonlinear processes of galaxy-MBH interaction, we describe a self-consistent numerical framework which incorporates both galaxies and MBHs. The high-resolution adaptive mesh refinement (AMR) code Enzo is modified to model the formation and feedback of molecular clouds at their characteristic scale of 15.2 pc and the accretion of gas onto an MBH. Two major channels of MBH feedback, radiative feedback (X-ray photons followed through full three-dimensional adaptive ray tracing) and mechanical feedback (bipolar jets resolved in high-resolution AMR), are employed. We investigate the coevolution of a 9.2 x 10{sup 11} M{sub sun} galactic halo and its 10{sup 5} M{sub sun} embedded MBH at redshift 3 in a cosmological {Lambda}CDM simulation. The MBH feedback heats the surrounding interstellar medium (ISM) up to 10{sup 6} K through photoionization and Compton heating and locally suppresses star formation in the galactic inner core. The feedback considerably changes the stellar distribution there. This new channel of feedback from a slowly growing MBH is particularly interesting because it is only locally dominant and does not require the heating of gas globally on the disk. The MBH also self-regulates its growth by keeping the surrounding ISM hot for an extended period of time.
Kim, Ji-hoon; Wise, John H.; Alvarez, Marcelo A.; Abel, Tom; /KIPAC, Menlo Park /Stanford U., Phys. Dept.
2011-11-04
There is mounting evidence for the coevolution of galaxies and their embedded massive black holes (MBHs) in a hierarchical structure formation paradigm. To tackle the nonlinear processes of galaxy-MBH interaction, we describe a self-consistent numerical framework which incorporates both galaxies and MBHs. The high-resolution adaptive mesh refinement (AMR) code Enzo is modified to model the formation and feedback of molecular clouds at their characteristic scale of 15.2 pc and the accretion of gas onto an MBH. Two major channels of MBH feedback, radiative feedback (X-ray photons followed through full three-dimensional adaptive ray tracing) and mechanical feedback (bipolar jets resolved in high-resolution AMR), are employed. We investigate the coevolution of a 9.2 x 10{sup 11} M {circle_dot} galactic halo and its 10{sup 5} {circle_dot} M embedded MBH at redshift 3 in a cosmological CDM simulation. The MBH feedback heats the surrounding interstellar medium (ISM) up to 10{sup 6} K through photoionization and Compton heating and locally suppresses star formation in the galactic inner core. The feedback considerably changes the stellar distribution there. This new channel of feedback from a slowly growing MBH is particularly interesting because it is only locally dominant and does not require the heating of gas globally on the disk. The MBH also self-regulates its growth by keeping the surrounding ISM hot for an extended period of time.
NASA Astrophysics Data System (ADS)
Oliva-Altamirano, P.; Brough, S.; Lidman, C.; Couch, W. J.; Hopkins, A. M.; Colless, M.; Taylor, E.; Robotham, A. S. G.; Gunawardhana, M. L. P.; Ponman, T.; Baldry, I.; Bauer, A. E.; Bland-Hawthorn, J.; Cluver, M.; Cameron, E.; Conselice, C. J.; Driver, S.; Edge, A. C.; Graham, A. W.; van Kampen, E.; Lara-López, M. A.; Liske, J.; López-Sánchez, A. R.; Loveday, J.; Mahajan, S.; Peacock, J.; Phillipps, S.; Pimbblet, K. A.; Sharp, R. G.
2014-05-01
We have analysed the growth of Brightest Group Galaxies and Brightest Cluster Galaxies (BGGs/BCGs) over the last 3 billion years using a large sample of 883 galaxies from the Galaxy And Mass Assembly survey. By comparing the stellar mass of BGGs and BCGs in groups and clusters of similar dynamical masses, we find no significant growth between redshift z = 0.27 and 0.09. We also examine the number of BGGs/BCGs that have line emission, finding that approximately 65 per cent of BGGs/BCGs show Hα in emission. From the galaxies where the necessary spectroscopic lines were accurately recovered (54 per cent of the sample), we find that half of this (i.e. 27 per cent of the sample) harbour ongoing star formation with rates up to 10 M⊙ yr-1, and the other half (i.e. 27 per cent of the sample) have an active nucleus (AGN) at the centre. BGGs are more likely to have ongoing star formation, while BCGs show a higher fraction of AGN activity. By examining the position of the BGGs/BCGs with respect to their host dark matter halo, we find that around 13 per cent of them do not lie at the centre of the dark matter halo. This could be an indicator of recent cluster-cluster mergers. We conclude that BGGs and BCGs acquired their stellar mass rapidly at higher redshifts as predicted by semi-analytic models, mildly slowing down at low redshifts.
NASA Astrophysics Data System (ADS)
McKee, Christopher F.; Chakrabarti, Sukanya
Massive protostars are generally enshrouded in dust, so that most of their radiation emerges in the far infrared. For protostars embedded in opaque, spherical cores, the spectral energy distribution (SED) is determined by two distance-independent parameters, the luminosity-to-mass ratio, L/M_c, and the surface density of the core, Σ=M_c/(π R_c^2), where R_c is the radius of the core. Chakrabarti & McKee (2005a) have derived an approximate analytic expression for the SED that agrees well with numerical results. It is generally not possible to infer the power-law of the density from the SED of a massive protostar. Masses and accretion rates are inferred for several well-studied sources.
NASA Astrophysics Data System (ADS)
Siess, L.
2007-12-01
Context: Massive AGB (hereafter super-AGB or SAGB) stars ignite carbon off-center and have initial masses ranging between Mup, the minimum initial mass for carbon ignition, and M_mas the minimum mass for the formation of an iron core collapse supernova. In this mass interval, stars more massive than Mn will undergo an electron capture supernova (EC-SN). Aims: We study the fate and selected evolutionary properties of SAGB stars up to the end of the carbon burning phase as a function of metallicity and core overshooting. Methods: The method is based on the analysis of a large set of stellar models covering the mass range 5-13 M⊙ and calculated for 7 different metallicities between Z=10-5 and twice solar. Core overshooting was considered in two subsets for Z=10-4 and 0.02. The models are available online at http://www-astro.ulb.ac.be/ siess/database.html. The fate of SAGB stars is investigated through a parametric model which allows us to assess the role of mass loss and of the third dredge-up. Results: Our main results can be summarized as follows: a) prior to C-burning, the evolution of SAGB stars is very similar to that of intermediate-mass stars, being more luminous, b) SAGB stars suffer a large He enrichment at the end of the second dredge-up, c) the limiting masses Mup, Mn and M_mas present a nonlinear behavior with Z, characterized by a minimum around Z=10-4, d) the values of Mup, Mn and M_mas are decreased by 2 M⊙ when core overshooting is considered, e) our models predict a minimum oxygen-neon white dwarf mass of 1.05 M⊙, f) the determination of Mn is highly dependent on the mass loss and core growth rates, g) the evolutionary channel for EC-SN is limited to a very narrow mass range of ⪉1-1.5 M⊙ width and this mass window can be further decreased if some metallicity scaling factor is applied to the mass loss rate, h) the final fate of SAGB stars is connected to the second dredge-up and this property allowed us to refine the initial mass range for
Proper Motions of Massive Stars in 30 Doradus
NASA Astrophysics Data System (ADS)
Lennon, Daniel
2013-10-01
We propose an ambitious proper motion survey of massive stars in the 30 Doradus region of the Large Magellanic Cloud using the unique capabilities of HST. We will derive the directions of motion of massive runaway stars, searching in particular for massive stars which have been ejected from the central very massive cluster R136. These data will be combined with radial velocities from the VLT-FLAMES Survey of the Tarantula Nebula and with atmospheric analyses and stellar evolution models to constrain their origins. We will also search for very young isolated massive stars to test models of single-star formation. This work is highly relevant to star formation, cluster dynamics, the origin of field WR stars and GRBs, the creation of very massive stars by runaway mergers, and the possible formation of intermediate-mass black holes.
NASA Astrophysics Data System (ADS)
Dereli, T.; Yetişmişoğlu, C.
2016-06-01
We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first-order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space AdS 3) and constant torsion provide exact solutions.
Ozeki, Nobutake; Muneta, Takeshi; Koga, Hideyuki; Katagiri, Hiroki; Otabe, Koji; Okuno, Makiko; Tsuji, Kunikazu; Kobayashi, Eiji; Matsumoto, Kenji; Saito, Hirohisa; Saito, Tomoyuki; Sekiya, Ichiro
2013-01-01
Objective This study was undertaken to examine whether bone morphogenetic protein 7 (BMP-7) induces ectopic cartilage formation in the rat tendon, and whether transplantation of tendon treated with BMP-7 promotes meniscal regeneration. Additionally, we analyzed the relative contributions of host and donor cells on the healing process after tendon transplantation in a rat model. Methods BMP-7 was injected in situ into the Achilles tendon of rats, and the histologic findings and gene profile were evaluated. Achilles tendon injected with 1 μg of BMP-7 was transplanted into a meniscal defect in rats. The regenerated meniscus and articular cartilage were evaluated at 4, 8, and 12 weeks. Achilles tendon from LacZ-transgenic rats was transplanted into the meniscal defect in wild-type rats, and vice versa. Results Injection of BMP-7 into the rat Achilles tendon induced the fibrochondrocyte differentiation of tendon cells and changed the collagen gene profile of tendon tissue to more closely approximate meniscal tissue. Transplantation of the rat Achilles tendon into a meniscal defect increased meniscal size. The rats that received the tendon treated with BMP-7 had a meniscus matrix that exhibited increased Safranin O and type II collagen staining, and showed a delay in articular cartilage degradation. Using LacZ-transgenic rats, we determined that the regeneration of the meniscus resulted from contribution from both donor and host cells. Conclusion Our findings indicate that BMP-7 induces ectopic cartilage formation in rat tendons. Transplantation of Achilles tendon treated with BMP-7 promotes meniscus regeneration and prevents cartilage degeneration in a rat model of massive meniscal defect. Native cells in the rat Achilles tendon contribute to meniscal regeneration. PMID:23897174
NASA Astrophysics Data System (ADS)
Mazzali, P. A.; Sauer, D. N.; Pian, E.; Deng, J.; Prentice, S.; Ben Ami, S.; Taubenberger, S.; Nomoto, K.
2017-08-01
An analysis of the Type Ic supernova (SN) 2004aw is performed by means of models of the photospheric and nebular spectra and of the bolometric light curve. SN 2004aw is shown not to be 'broad-lined', contrary to previous claims, but rather a 'fast-lined' SN Ic. The spectral resemblance to the narrow-lined Type Ic SN 1994I, combined with the strong nebular [O i] emission and the broad light curve, points to a moderately energetic explosion of a massive C+O star. The ejected 56Ni mass is ≈0.20 M⊙. The ejecta mass as constrained by the models is ∼3-5 M⊙, while the kinetic energy is estimated as EK ∼3-6 × 1051 erg. The ratio EK/M⊙, the specific energy that influences the shape of the spectrum, is therefore ≈1. The corresponding zero-age main-sequence mass of the progenitor star may have been ∼23-28 M⊙. Tests show that a flatter outer density structure may have caused a broad-lined spectrum at epochs before those observed without affecting the later epochs when data are available, implying that our estimate of EK is a lower limit. SN 2004aw may have been powered by either a collapsar or a magnetar, both of which have been proposed for gamma-ray burst SNe. Evidence for this is seen in the innermost layers, which appear to be highly aspherical as suggested by the nebular line profiles. However, any engine was not extremely powerful, as the outer ejecta are more consistent with a spherical explosion and no gamma-ray burst was detected in coincidence with SN 2004aw.
Massive stars in the galaxies of the Local Group
NASA Astrophysics Data System (ADS)
Massey, Philip
2013-07-01
The star-forming galaxies of the Local Group act as our laboratories for testing massive star evolutionary models. In this review, I briefly summarize what we believe we know about massive star evolution, and the connection between OB stars, Luminous Blue Variables, yellow supergiants, red supergiants, and Wolf-Rayet stars. The difficulties and recent successes in identifying these various types of massive stars in the neighboring galaxies of the Local Group will be discussed.
Fundamental Parameters of Four Massive Eclipsing Binaries in Westerlund 1
NASA Astrophysics Data System (ADS)
Koumpia, E.; Bonanos, A. Z.
2012-04-01
We present fundamental parameters of four massive eclipsing binaries in the young massive cluster Westerlund 1. The goal is to measure accurate masses and radii of their component stars, which provide much needed constraints for evolutionary models of massive stars. Accurate parameters can further be used to determine a dynamical lower limit for the magnetar progenitor and to obtain an independent distance to the cluster. Our results confirm and extend the evidence for a high mass for the progenitor of the magnetar.
Fundamental Parameters of Four Massive Eclipsing Binaries in Westerlund 1
NASA Astrophysics Data System (ADS)
Bonanos, A.; Koumpia, E.
2012-01-01
We present fundamental parameters of four massive eclipsing binaries in the young massive cluster Westerlund 1. The goal is to measure accurate masses and radii of their component stars, which provide much needed constraints for evolutionary models of massive stars. Accurate parameters can further be used to determine a dynamical lower limit for the magnetar progenitor and to obtain an independent distance to the cluster. Our results confirm and extend the evidence for a high mass for the progenitor of the magnetar.
Neutron Electric Dipole Moment from Gauge-String Duality
NASA Astrophysics Data System (ADS)
Bartolini, Lorenzo; Bigazzi, Francesco; Bolognesi, Stefano; Cotrone, Aldo L.; Manenti, Andrea
2017-03-01
We compute the electric dipole moment of nucleons in the large Nc QCD model by Witten, Sakai, and Sugimoto with Nf=2 degenerate massive flavors. Baryons in the model are instantonic solitons of an effective five-dimensional action describing the whole tower of mesonic fields. We find that the dipole electromagnetic form factor of the nucleons, induced by a finite topological θ angle, exhibits complete vector meson dominance. We are able to evaluate the contribution of each vector meson to the final result—a small number of modes are relevant to obtain an accurate estimate. Extrapolating the model parameters to real QCD data, the neutron electric dipole moment is evaluated to be dn=1.8 ×10-16θ e cm . The electric dipole moment of the proton is exactly the opposite.
NASA Astrophysics Data System (ADS)
Anosova, Joanna P.
2017-06-01
On 14 Sept, 2015 The LIGO reported the first direct detection of gravitational waves and the first direct observation of a binary black hole. These observations demonstrate the existence of binary black holes in stellar systems predicted by Einstein in his general theory of relativity a century earlier.A lot of violent and complicated phenomena take place on different scales in the Universe. Many of them may be caused by multiple centers of gravitational attraction: planetary rings, accretion discs of various scales, peculiar structures of single galaxies and interacting galaxies. In this work, we show that various features of celestial objects can be understood by assuming the existence of two dominant centers of gravity in stellar systems.We study numerically the dynamical evolution of models with the central super-massive binary black holes and extended shells with numerous low-mass particles inside and around the orbits of binaries. These particles could be star clusters or gas and dust complexes. We consider several tens of thousands of initial conditions for the general three-body problem and compile them. We studied the dynamical evolution of all spherical shells together and separately. Our method permits us to study the individual trajectories of particles, their close double and triple approaches, and inspect the time-depending structures in the models. Multiple runs of the models allow us to classify the numerous strong triple interactions of the binary components with low-mass particles; frequently, the "gravitational slingshot" effect occurs in the center of systems. Such strong interactions of bodies are results in various structures with "dumb-bell" bars, close and open spirals, different types of flows, jets etc. These structures are often very similar the observed structures of galaxies.We found some combinations of the initial conditions and model parameters that produce at some time similar structures as that found in the galaxies Arp 5, 87, 214
NASA Astrophysics Data System (ADS)
Haemmerlé, Lionel; Peters, Thomas
2016-05-01
Massive star formation requires the accretion of gas at high rate while the star is already bright. Its actual luminosity depends sensitively on the stellar structure. We compute pre-main-sequence tracks for massive and intermediate-mass stars with variable accretion rates and study the evolution of stellar radius, effective temperature and ionizing luminosity, starting at 2 M⊙ with convective or radiative structures. The radiative case shows a much stronger swelling of the protostar for high accretion rates than the convective case. For radiative structures, the star is very sensitive to the accretion rate and reacts quickly to accretion bursts, leading to considerable changes in photospheric properties on time-scales as short as 100-1000 yr. The evolution for convective structures is much less influenced by the instantaneous accretion rate, and produces a monotonically increasing ionizing flux that can be many orders of magnitude smaller than in the radiative case. For massive stars, it results in a delay of the H II region expansion by up to 10 000 yr. In the radiative case, the H II region can potentially be engulfed by the star during the swelling, which never happens in the convective case. We conclude that the early stellar structure has a large impact on the radiative feedback during the pre-main-sequence evolution of massive protostars and introduces an important uncertainty that should be taken into account. Because of their lower effective temperatures, our convective models may hint at a solution to an observed discrepancy between the luminosity distribution functions of massive young stellar objects and compact H II regions.
Solid holography and massive gravity
NASA Astrophysics Data System (ADS)
Alberte, Lasma; Baggioli, Matteo; Khmelnitsky, Andrei; Pujolàs, Oriol
2016-02-01
Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric response. We show that the types of response that can be consistently described within this framework is much wider than what is captured by the narrow class of models mostly considered so far.
The Fate of Massive Closed Strings
Chen Bin; Li Miao; She Jianhuang
2005-12-02
We calculate the semi-inclusive decay rate of an average string state with toroidal compactification in the the superstring theory. We also apply this calculation to a brane-inflation model in a warped geometry and find that the decay rate is greatly suppressed if the final strings are both massive and enhanced for massless radiation.
Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G
2007-04-11
The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.
Van de Sande, Jesse; Franx, Marijn; Kriek, Mariska; Bezanson, Rachel; Van Dokkum, Pieter G.
2015-02-01
We explore the relation between the dynamical mass-to-light ratio (M/L) and rest-frame color of massive quiescent galaxies out to z ∼ 2. We use a galaxy sample with measured stellar velocity dispersions in combination with Hubble Space Telescope and ground-based multi-band photometry. Our sample spans a large range in log M {sub dyn}/L {sub g} (of 1.6 dex) and log M {sub dyn}/L {sub K} (of 1.3 dex). There is a strong, approximately linear correlation between the M/L for different wavebands and rest-frame color. The root-mean-square scatter in log M {sub dyn}/L residuals implies that it is possible to estimate the M/L with an accuracy of ∼0.25 dex from a single rest-frame optical color. Stellar population synthesis (SPS) models with a Salpeter stellar initial mass function (IMF) cannot simultaneously match M {sub dyn}/L {sub g} versus (g – z){sub rest-frame} and M {sub dyn}/L {sub K} versus (g – K){sub rest-frame}. By changing the slope of the IMF we are still unable to explain the M/L of the bluest and reddest galaxies. We find that an IMF with a slope between α = 2.35 and α = 1.35 provides the best match. We also explore a broken IMF with a Salpeter slope at M < 1 M {sub ☉} and M > 4 M {sub ☉} and a slope α in the intermediate region. The data favor a slope of α = 1.35 over α = 2.35. Nonetheless, our results show that variations between different SPS models are comparable to the IMF variations. In our analysis we assume that the variation in M/L and color is driven by differences in age, and that other contributions (e.g., metallicity evolution, dark matter) are small. These assumptions may be an important source of uncertainty as galaxies evolve in more complex ways.
NASA Astrophysics Data System (ADS)
Alishahiha, Mohsen; Qaemmaqami, Mohammad M.; Naseh, Ali; Shirzad, Ahmad
2014-12-01
We study linearized equations of motion of the newly proposed three dimensional gravity, known as minimal massive gravity, using its metric formulation. By making use of a redefinition of the parameters of the model, we observe that the resulting linearized equations are exactly the same as that of TMG. In particular the model admits logarithmic modes at critical points. We also study several vacuum solutions of the model, specially at a certain limit where the contribution of Chern-Simons term vanishes.
Evolutionary tracks of massive stars during formation
NASA Astrophysics Data System (ADS)
Smith, Michael D.
2014-02-01
A model for massive stars is constructed by piecing together evolutionary algorithms for the protostellar structure, the environment, the inflow and the radiation feedback. We investigate specified accretion histories of constant, decelerating and accelerating forms and consider both hot and cold accretion, identified with spherical free-fall and disc accretion, respectively. Diagnostic tools for the interpretation of the phases of massive star formation and testing the evolutionary models are then developed. Evolutionary tracks able to fit Herschel Space Telescope data require the generated stars to be three to four times less massive than in previous interpretations, thus being consistent with clump star formation efficiencies of 10-15 per cent. However, for these cold Herschel clumps, the bolometric temperature is not a good diagnostic to differentiate between accretion models. We also find that neither spherical nor disc accretion can explain the high radio luminosities of many protostars. Nevertheless, we discover a solution in which the extreme ultraviolet flux needed to explain the radio emission is produced if the accretion flow is via free-fall on to hotspots covering less than 10 per cent of the surface area. Moreover, the protostar must be compact, and so has formed through cold accretion. We show that these conclusions are independent of the imposed accretion history. This suggests that massive stars form via gas accretion through discs which, in the phase before the star bloats, download their mass via magnetic flux tubes on to the protostar.
Embeddings of the "New Massive Gravity"
NASA Astrophysics Data System (ADS)
Dalmazi, D.; Mendonça, E. L.
2016-07-01
Here we apply different types of embeddings of the equations of motion of the linearized "New Massive Gravity" in order to generate alternative and even higher-order (in derivatives) massive gravity theories in D=2+1. In the first part of the work we use the Weyl symmetry as a guiding principle for the embeddings. First we show that a Noether gauge embedding of the Weyl symmetry leads to a sixth-order model in derivatives with either a massive or a massless ghost, according to the chosen overall sign of the theory. On the other hand, if the Weyl symmetry is implemented by means of a Stueckelberg field we obtain a new scalar-tensor model for massive gravitons. It is ghost-free and Weyl invariant at the linearized level around Minkowski space. The model can be nonlinearly completed into a scalar field coupled to the NMG theory. The elimination of the scalar field leads to a nonlocal modification of the NMG. In the second part of the work we prove to all orders in derivatives that there is no local, ghost-free embedding of the linearized NMG equations of motion around Minkowski space when written in terms of one symmetric tensor. Regarding that point, NMG differs from the Fierz-Pauli theory, since in the latter case we can replace the Einstein-Hilbert action by specific f(R,Box R) generalizations and still keep the theory ghost-free at the linearized level.
Massively parallel MRI detector arrays.
Keil, Boris; Wald, Lawrence L
2013-04-01
Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas via reception, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called "ultimate" SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. Copyright © 2013 Elsevier Inc. All rights reserved.
Stable massive particles at colliders
Fairbairn, M.; Kraan, A.C.; Milstead, D.A.; Sjostrand, T.; Skands, P.; Sloan, T.; /Lancaster U.
2006-11-01
We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.
Massively Parallel MRI Detector Arrays
Keil, Boris; Wald, Lawrence L
2013-01-01
Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758
Derivative couplings in massive bigravity
Gao, Xian; Heisenberg, Lavinia E-mail: lavinia.heisenberg@eth-its.ethz.ch
2016-03-01
In this work we study the cosmological perturbations in massive bigravity in the presence of non-minimal derivative couplings. For this purpose we consider a specific subclass of Horndeski scalar-tensor interactions that live on the unique composite effective metric. For the viability of the model both metrics have to be dynamical. Nevertheless, the number of allowed kinetic terms is crucial. We adapt to the restriction of having one single kinetic term. After deriving the full set of equations of motion for flat Friedmann-Lemaitre-Robertson-Walker background, we study linear perturbations on top of it. We show explicitly that only four tensor, two vector and two scalar degrees of freedom propagate, one of which being the Horndeski scalar, while the Boulware-Deser ghost can be integrated out.
NASA Astrophysics Data System (ADS)
Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.
2014-07-01
We present an alternative to topologically massive gravity (TMG) with the same ‘minimal’ bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new ‘minimal massive gravity’ has both a positive energy graviton and positive central charges for the asymptotic AdS-boundary conformal algebra.
The 2nd Symposium on the Frontiers of Massively Parallel Computations
NASA Technical Reports Server (NTRS)
Mills, Ronnie (Editor)
1988-01-01
Programming languages, computer graphics, neural networks, massively parallel computers, SIMD architecture, algorithms, digital terrain models, sort computation, simulation of charged particle transport on the massively parallel processor and image processing are among the topics discussed.
Massively parallel mathematical sieves
Montry, G.R.
1989-01-01
The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.
Massive acute arsenic poisonings.
Lech, Teresa; Trela, Franciszek
2005-07-16
Arsenic poisonings are still important in the field of toxicology, though they are not as frequent as about 20-30 years ago. In this paper, the arsenic concentrations in ante- and post-mortem materials, and also forensic and anatomo-pathological aspects in three cases of massive acute poisoning with arsenic(III) oxide (two of them with unexplained criminalistic background, in which arsenic was taken for amphetamine and one suicide), are presented. Ante-mortem blood and urine arsenic concentrations ranged from 2.3 to 6.7 microg/ml, respectively. Post-mortem tissue total arsenic concentrations were also detected in large concentrations. In case 3, the contents of the duodenum contained as much as 30.1% arsenic(III) oxide. The high concentrations of arsenic detected in blood and tissues in all presented cases are particularly noteworthy in that they are very rarely detected at these concentrations in fatal arsenic poisonings.
Magnetospheres of massive stars
NASA Astrophysics Data System (ADS)
Küker, M.
We study the interaction of line-driven winds from massive stars with the magnetic field rooted in these stars by carrying out numerical simulations using the Nirvana MHD code in 2D in spherical polar coordinates. The code's adaptive mesh refinement feature allows high spatial resolution across the whole simulation box. We study both O and Wolf-Rayet stars for a range of magnetic field strengths from weak to strong as measured by the confinement parameter. For weak fields our simulations show that the initially dipolar field opens up far away from the star and a thin disk-like structure forms in the equatorial plane of the magnetic field. For stronger fields the disk is disrupted close to the stellar surface and closed field lines persist at low latitudes. For very strong fields a pronounced magnetosphere forms where the gas is forced to move along the field lines and eventually falls back to the stellar surface.
Massive higher spins from BRST and tractors
NASA Astrophysics Data System (ADS)
Grigoriev, Maxim; Waldron, Andrew
2011-12-01
We obtain the higher spin tractor equations of motion conjectured by Gover et al. from a BRST approach and use those methods to prove that they describe massive, partially massless and massless higher spins in conformally flat backgrounds. The tractor description makes invariance under local choices of unit systems manifest. In this approach, physical models are described by conformal, rather than (pseudo-)Riemannian geometry. In particular masses become geometric quantities, namely the weights of tractor fields. Massive models can therefore be handled in a unified and simple manner mimicking the gauge principle usually employed for massless models. From a holographic viewpoint, these models describe both the bulk and boundary theories in terms of conformal geometry. This is an important advance, because tying the boundary conformal structure to that of the bulk theory gives greater control over a bulk-boundary correspondence.
BPS black hole horizons from massive IIA
NASA Astrophysics Data System (ADS)
Guarino, Adolfo
2017-08-01
The maximal four-dimensional supergravity with a dyonic ISO(7) gauging that arises from the reduction of massive IIA on a six-sphere has recently been shown to accommodate static BPS black holes with hyperbolic horizons. When restricted to the N=2 subsector that retains one vector multiplet and the universal hypermultiplet, the attractor mechanism was shown to fix both the vector charges and the scalar fields at the horizon to a unique configuration in terms of the gauging parameters. In order to assess the (non-)uniqueness of BPS black hole horizons from massive IIA, we extend the study of the attractor mechanism to other N=2 subsectors including additional matter multiplets. We note that, while extending the hypermultiplet sector does not modify the set of solutions to the attractor equations, the inclusion of additional vector multiplets results in new hyperbolic/spherical horizon configurations containing free parameters. The model with three vector multiplets and the universal hypermultiplet, which is the massive IIA analogue of the STU-model from M-theory, may play a relevant role in massive IIA holography.
Nonlinear dynamics of 3D massive gravity
NASA Astrophysics Data System (ADS)
de Rham, Claudia; Gabadadze, Gregory; Pirtskhalava, David; Tolley, Andrew J.; Yavin, Itay
2011-06-01
We explore the nonlinear classical dynamics of the three-dimensional theory of "New Massive Gravity" proposed by Bergshoeff, Hohm and Townsend. We find that the theory passes remarkably highly nontrivial consistency checks at the nonlinear level. In particular, we show that: (1) In the decoupling limit of the theory, the interactions of the helicity-0 mode are described by a single cubic term — the so-called cubic Galileon — previously found in the context of the DGP model and in certain 4D massive gravities. (2) The conformal mode of the metric coincides with the helicity-0 mode in the decoupling limit. Away from this limit the nonlinear dynamics of the former is described by a certain generalization of Galileon interactions, which like the Galileons themselves have a well-posed Cauchy problem. (3) We give a non-perturbative argument based on the presence of additional symmetries that the full theory does not lead to any extra degrees of freedom, suggesting that a 3D analog of the 4D Boulware-Deser ghost is not present in this theory. Last but not least, we generalize "New Massive Gravity" and construct a class of 3D cubic order massive models that retain the above properties.
The Dynamics of Massive Starless Cores
NASA Astrophysics Data System (ADS)
Tan, Jonathan; Caselli, P.; Fontani, F.; Kong, S.; Butler, M. J.
2012-05-01
Progress towards resolving a decade-long debate about how massive stars form can be made by determining if massive starless cores exist in a state of near virial equilibrium. These are the initial conditions invoked by the Core Accretion model of McKee & Tan (2003). Alternatively, the Competitive Accretion model of Bonnell et al. (2001) requires sub-virial conditions. We have identified 4 prime examples of massive ( 50 Msun) cores from mid-infrared (MIR) extinction mapping (Butler & Tan 2009, 2012) of Infrared Dark Clouds. We have found spectacularly high deuterated fractions of N_2H+ of 0.5 in these objects with the IRAM 30m telescope (Fontani et al. 2011). Thus N_2D+ is expected to be an excellent tracer of the kinematics of these cold, dark cores, where most other molecular tracers are thought to be depleted from the gas phase. We report on ALMA Cycle 0 Compact Configuration Band 6 observations of these 4 cores that probe the N_2D+(3-2) line on scales from 9" down to 2.3", well-matched to the structures we see in MIR extinction and discuss their implications for massive star formation theories.
The Rb problem in massive AGB stars.
NASA Astrophysics Data System (ADS)
Pérez-Mesa, V.; García-Hernández, D. A.; Zamora, O.; Plez, B.; Manchado, A.; Karakas, A. I.; Lugaro, M.
2017-03-01
The asymptotic giant branch (AGB) is formed by low- and intermediate-mass stars (0.8 M_{⊙} < M < 8 M_{⊙}) in their last nuclear-burning phase, when they develop thermal pulses (TP) and suffer extreme mass loss. AGB stars are the main contributor to the enrichment of the interstellar medium (ISM) and thus to the chemical evolution of galaxies. In particular, the more massive AGB stars (M > 4 M_{⊙}) are expected to produce light (e.g., Li, N) and heavy neutron-rich s-process elements (such as Rb, Zr, Ba, Y, etc.), which are not formed in lower mass AGB stars and Supernova explosions. Classical chemical analyses using hydrostatic atmospheres revealed strong Rb overabundances and high [Rb/Zr] ratios in massive AGB stars of our Galaxy and the Magellanic Clouds (MC), confirming for the first time that the ^{22}Ne neutron source dominates the production of s-process elements in these stars. The extremely high Rb abundances and [Rb/Zr] ratios observed in the most massive stars (specially in the low-metallicity MC stars) uncovered a Rb problem; such extreme Rb and [Rb/Zr] values are not predicted by the s-process AGB models, suggesting fundamental problems in our present understanding of their atmospheres. We present more realistic dynamical model atmospheres that consider a gaseous circumstellar envelope with a radial wind and we re-derive the Rb (and Zr) abundances in massive Galactic AGB stars. The new Rb abundances and [Rb/Zr] ratios derived with these dynamical models significantly resolve the problem of the mismatch between the observations and the theoretical predictions of the more massive AGB stars.
Mesonic quasinormal modes of the Sakai-Sugimoto model at high temperature
Evans, Nick; Threlfall, Ed
2008-06-15
We examine the mesonic thermal spectrum of the Sakai-Sugimoto model of holographic QCD by finding the quasinormal frequencies of the supergravity dual. If flavor is added using D8-D8 branes there exist embeddings where the D-brane world volume contains a black hole. For these embeddings (the high-temperature phase of the Sakai-Sugimoto model) we determine the quasinormal spectra of scalar and vector mesons arising from the world volume Dirac-Born-Infeld (DBI) action of the D-brane. We stress the importance of a coordinate change that makes the infalling quasinormal modes regular at the horizon allowing a simple numerical shooting technique. Finally we examine the effect of finite spatial momentum on quasinormal spectra.
Isospin Mixing of Quark Cluster Diybaryon Resonances in the Bag Model*
NASA Astrophysics Data System (ADS)
Ward, Thomas
2000-10-01
Calculations of isospin mixing of dibaryon resonaces composed of color magentic six quark states using the quark cluster bag model are shown to result in a low lying J=2 dibaryon at 1913 MeV. The 1913 MeV resonance can only transition into NN states and a low energy (29-35 MeV) isoscaler meson multiplet, the sigma mesons (J=0,1,2). The J=1 axial-vector meson may already have been discovered at the Rutherford ISIS Facility, detected as a neutrino time anomaly known as the KARMEN particle. The predicted J=0 meson has the long sought after properties of the sigma meson or Higgs particle required for the Chiral Symmetry Breaking partner of the pion and light mass hadron generation. The influence of this predicted isoscaler multiplet in QCD and QFD is interpreted using the effective low energy model of Chiral Perturbation Theory.
Interactions in Massive Colliding Wind Binaries
NASA Technical Reports Server (NTRS)
Corcoran, M.
2012-01-01
The most massive stars (M> 60 Solar Mass) play crucial roles in altering the chemical and thermodynamic properties of their host galaxies. Stellar mass is the fundamental stellar parameter that determines their ancillary properties and which ultimately determines the fate of these stars and their influence on their galactic environs. Unfortunately, stellar mass becomes observationally and theoretically less well constrained as it increases. Theory becomes uncertain mostly because very massive stars are prone to strong, variable mass loss which is difficult to model. Observational constraints are uncertain too. Massive stars are rare, and massive binary stars (needed for dynamical determination of mass) are rarer still: and of these systems only a fraction have suitably high orbital inclinations for direct photometric and spectroscopic radial-velocity analysis. Even in the small number of cases in which a high-inclination binary near the upper mass limit can be identified, rotational broadening and contamination of spectral line features from thick circumstellar material (either natal clouds or produced by strong stellar wind driven mass loss from one or both of he stellar components) biases the analysis. In the wilds of the upper HR diagram, we're often left with indirect and circumstantial means of determining mass, a rather unsatisfactory state of affairs.
Spatial Disrtribution and Evolution of Massive Stars
NASA Astrophysics Data System (ADS)
Aghakhanlootakanloo, Mojgan; Murphy, Jeremiah W.
2017-01-01
Observations show that luminous blue variables (LBVs) are far more dispersed than other massive stars, and Smith & Tombleson (2015) suggested that these large separations are inconsistent with the standard single-star evolution model of LBVs. Instead, they suggest that the large distances are most consistent with some sort of binary evolution. To test these suggestions, we modeled young stellar clusters and their passive dissolution, and we find that, indeed, the single-star evolution model is inconsistent with observations. Most importantly, we find two binary scenario models that are consistent. Our crude models suggest that LBVs are either the result of mergers and are rejuvenated stars, or they are mass gainers and received a kick when the primary star exploded. In the merger scenario, LBVs have more time to disperse because they are the merger of two lesser mass, in which the primary has a mass of about 19 solar masses. In the mass gainer and kick scenario, we find that LBV isolation is consistent with an average kick of 200 km/s. In either scenario, binarity plays a major role in the isolation of LBVs. In addition to constraining the evolution of LBVs, we suggest that careful scrutiny of the spatial distribution of massive stars in general will lead to a greater understanding for the evolution of massive stars.
NASA Astrophysics Data System (ADS)
Chiu, Hong-Yee
1990-05-01
The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.
NASA Technical Reports Server (NTRS)
Chiu, Hong-Yee
1990-01-01
The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.
Massively parallel processor computer
NASA Technical Reports Server (NTRS)
Fung, L. W. (Inventor)
1983-01-01
An apparatus for processing multidimensional data with strong spatial characteristics, such as raw image data, characterized by a large number of parallel data streams in an ordered array is described. It comprises a large number (e.g., 16,384 in a 128 x 128 array) of parallel processing elements operating simultaneously and independently on single bit slices of a corresponding array of incoming data streams under control of a single set of instructions. Each of the processing elements comprises a bidirectional data bus in communication with a register for storing single bit slices together with a random access memory unit and associated circuitry, including a binary counter/shift register device, for performing logical and arithmetical computations on the bit slices, and an I/O unit for interfacing the bidirectional data bus with the data stream source. The massively parallel processor architecture enables very high speed processing of large amounts of ordered parallel data, including spatial translation by shifting or sliding of bits vertically or horizontally to neighboring processing elements.
Benchmarking massively parallel architectures
Lubeck, O.; Moore, J.; Simmons, M.; Wasserman, H.
1993-01-01
The purpose of this paper is to summarize some initial experiences related to measuring the performance of massively parallel processors (MPPs) at Los Alamos National Laboratory (LANL). Actually, the range of MPP architectures the authors have used is rather limited, being confined mostly to the Thinking Machines Corporation (TMC) Connection Machine CM-2 and CM-5. Some very preliminary work has been carried out on the Kendall Square KSR-1, and efforts related to other machines, such as the Intel Paragon and the soon-to-be-released CRAY T3D are planned. This paper will concentrate more on methodology rather than discuss specific architectural strengths and weaknesses; the latter is expected to be the subject of future reports. MPP benchmarking is a field in critical need of structure and definition. As the authors have stated previously, such machines have enormous potential, and there is certainly a dire need for orders of magnitude computational power over current supercomputers. However, performance reports for MPPs must emphasize actual sustainable performance from real applications in a careful, responsible manner. Such has not always been the case. A recent paper has described in some detail, the problem of potentially misleading performance reporting in the parallel scientific computing field. Thus, in this paper, the authors briefly offer a few general ideas on MPP performance analysis.
NASA Technical Reports Server (NTRS)
Chiu, Hong-Yee
1990-01-01
The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.
Two-dimensional thermofield bosonization II: Massive fermions
Amaral, R.L.P.G.
2008-11-15
We consider the perturbative computation of the N-point function of chiral densities of massive free fermions at finite temperature within the thermofield dynamics approach. The infinite series in the mass parameter for the N-point functions are computed in the fermionic formulation and compared with the corresponding perturbative series in the interaction parameter in the bosonized thermofield formulation. Thereby we establish in thermofield dynamics the formal equivalence of the massive free fermion theory with the sine-Gordon thermofield model for a particular value of the sine-Gordon parameter. We extend the thermofield bosonization to include the massive Thirring model.
Limiting Accretion onto Massive Stars by Fragmentation-Induced Starvation
Peters, Thomas; Klessen, Ralf S.; Mac Low, Mordecai-Mark; Banerjee, Robi; /ZAH, Heidelberg
2010-08-25
Massive stars influence their surroundings through radiation, winds, and supernova explosions far out of proportion to their small numbers. However, the physical processes that initiate and govern the birth of massive stars remain poorly understood. Two widely discussed models are monolithic collapse of molecular cloud cores and competitive accretion. To learn more about massive star formation, we perform simulations of the collapse of rotating, massive, cloud cores including radiative heating by both non-ionizing and ionizing radiation using the FLASH adaptive mesh refinement code. These simulations show fragmentation from gravitational instability in the enormously dense accretion flows required to build up massive stars. Secondary stars form rapidly in these flows and accrete mass that would have otherwise been consumed by the massive star in the center, in a process that we term fragmentation-induced starvation. This explains why massive stars are usually found as members of high-order stellar systems that themselves belong to large clusters containing stars of all masses. The radiative heating does not prevent fragmentation, but does lead to a higher Jeans mass, resulting in fewer and more massive stars than would form without the heating. This mechanism reproduces the observed relation between the total stellar mass in the cluster and the mass of the largest star. It predicts strong clumping and filamentary structure in the center of collapsing cores, as has recently been observed. We speculate that a similar mechanism will act during primordial star formation.
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION
Peters, Thomas; Klessen, Ralf S.; Banerjee, Robi; Low, Mordecai-Mark Mac
2010-12-10
Massive stars influence their surroundings through radiation, winds, and supernova explosions far out of proportion to their small numbers. However, the physical processes that initiate and govern the birth of massive stars remain poorly understood. Two widely discussed models are monolithic collapse of molecular cloud cores and competitive accretion. To learn more about massive star formation, we perform and analyze simulations of the collapse of rotating, massive, cloud cores including radiative heating by both non-ionizing and ionizing radiation using the FLASH adaptive-mesh refinement code. These simulations show fragmentation from gravitational instability in the enormously dense accretion flows required to build up massive stars. Secondary stars form rapidly in these flows and accrete mass that would have otherwise been consumed by the massive star in the center, in a process that we term fragmentation-induced starvation. This explains why massive stars are usually found as members of high-order stellar systems that themselves belong to large clusters containing stars of all masses. The radiative heating does not prevent fragmentation, but does lead to a higher Jeans mass, resulting in fewer and more massive stars than would form without the heating. This mechanism reproduces the observed relation between the total stellar mass in the cluster and the mass of the largest star. It predicts strong clumping and filamentary structure in the center of collapsing cores, as has recently been observed. We speculate that a similar mechanism will act during primordial star formation.
Fragmentation in massive star formation.
Beuther, Henrik; Schilke, Peter
2004-02-20
Studies of evolved massive stars indicate that they form in a clustered mode. During the earliest evolutionary stages, these regions are embedded within their natal cores. Here we present high-spatial-resolution interferometric dust continuum observations disentangling the cluster-like structure of a young massive star-forming region. The derived protocluster mass distribution is consistent with the stellar initial mass function. Thus, fragmentation of the initial massive cores may determine the initial mass function and the masses of the final stars. This implies that stars of all masses can form via accretion processes, and coalescence of intermediate-mass protostars appears not to be necessary.
Electromagnetic properties of massive neutrinos
Dobrynina, A. A. Mikheev, N. V.; Narynskaya, E. N.
2013-10-15
The vertex function for a virtual massive neutrino is calculated in the limit of soft real photons. A method based on employing the neutrino self-energy operator in a weak external electromagnetic field in the approximation linear in the field is developed in order to render this calculation of the vertex function convenient. It is shown that the electric charge and the electric dipole moment of the real neutrino are zero; only the magnetic moment is nonzero for massive neutrinos. A fourth-generation heavy neutrino of mass not less than half of the Z-boson mass is considered as a massive neutrino.
Cyg X-1 - A massive neutron star
NASA Technical Reports Server (NTRS)
Goldman, I.
1981-01-01
The expected X-ray emission from Cyg X-1, considered a massive neutron star (8-15 solar masses) according to some gravity theories, is studied within the framework of Rosen's bimetric gravity theory (1973, 1974). It is shown that in such massive neutron stars, the innermost stable orbit lies far outside the star surface, and therefore the X-ray spectrum consists of two components: a soft one emitted from a cold accretion disk and a hard one emitted by the matter striking the neutron star surface after spiraling down freely from the disk. The proposed model is shown to be in good agreement with the observed luminosities. The model predicts a surface gravitational redshift of 3.16 which could be tested by the future X- and gamma-ray detectors.
Magnetic Field Distribution for Massive Stars
NASA Astrophysics Data System (ADS)
Medvedev, A.; Kholtygin, A.
2017-06-01
A model of the evolution of an ensemble of magnetic massive stars on the main sequence is developed. We use our own population synthesis code, which allows us to obtain distributions of stars by radii, ages, masses, temperatures, effective magnetic fields, and magnetic fluxes from the pre-main sequence up to the TAMS stages. We assume that magnetic fields in massive stars decrease with time. The rate of magnetic field dissipation may depend on the mass of a star on ZAMS. The distribution of magnetic fluxes of the ZAMS stars is assumed to be log-normal. We show that such kind of distribution may be a result of the dynamo action occurring at the pre-MS evolutionary stage of magnetic stars. Our model also includes capabilities for statistical simulations and parameter estimation necessary for the analysis of real data. Comparison of model magnetic field distributions with those obtained from recent measurements of stellar magnetic fields allows us to conclude that the evolution of magnetic fields of massive stars is very slow if not absent. The shape of the real magnetic field distribution has no indications of the “magnetic desert,” previously suggested by Lignieres et al. (2014). Based on those findings we argue that the observed fraction of magnetic stars is determined only by physical conditions at early stages of stellar evolution.
Simulating A Massive, Mobile Structure
NASA Technical Reports Server (NTRS)
Fantasia, Peter M.; Kahn, Jon B.; Sprague, Benny B.
1990-01-01
Simulator replicates, kinematically and dynamically, mating of large, massive mobile structure with similarly large and massive fixed structure. Developed for testing berthing-and-latching mechanism. Fixed section holds active berthing-and-latching mechanism and its motor control system with optical encoder to maintain synchronization among four latches in mechanism. Tripodal load-cell network gathers data on load history of berthing operation, and infrared tracking system including light-emitting diodes produces data for position history.
Reconstructing the massive black hole cosmic history through gravitational waves
Sesana, Alberto; Gair, Jonathan; Berti, Emanuele; Volonteri, Marta
2011-02-15
The massive black holes we observe in galaxies today are the natural end-product of a complex evolutionary path, in which black holes seeded in proto-galaxies at high redshift grow through cosmic history via a sequence of mergers and accretion episodes. Electromagnetic observations probe a small subset of the population of massive black holes (namely, those that are active or those that are very close to us), but planned space-based gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA) can measure the parameters of 'electromagnetically invisible' massive black holes out to high redshift. In this paper we introduce a Bayesian framework to analyze the information that can be gathered from a set of such measurements. Our goal is to connect a set of massive black hole binary merger observations to the underlying model of massive black hole formation. In other words, given a set of observed massive black hole coalescences, we assess what information can be extracted about the underlying massive black hole population model. For concreteness we consider ten specific models of massive black hole formation, chosen to probe four important (and largely unconstrained) aspects of the input physics used in structure formation simulations: seed formation, metallicity ''feedback'', accretion efficiency and accretion geometry. For the first time we allow for the possibility of 'model mixing', by drawing the observed population from some combination of the 'pure' models that have been simulated. A Bayesian analysis allows us to recover a posterior probability distribution for the ''mixing parameters'' that characterize the fractions of each model represented in the observed distribution. Our work shows that LISA has enormous potential to probe the underlying physics of structure formation.
Reconstructing the massive black hole cosmic history through gravitational waves
NASA Astrophysics Data System (ADS)
Sesana, Alberto; Gair, Jonathan; Berti, Emanuele; Volonteri, Marta
2011-02-01
The massive black holes we observe in galaxies today are the natural end-product of a complex evolutionary path, in which black holes seeded in proto-galaxies at high redshift grow through cosmic history via a sequence of mergers and accretion episodes. Electromagnetic observations probe a small subset of the population of massive black holes (namely, those that are active or those that are very close to us), but planned space-based gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA) can measure the parameters of “electromagnetically invisible” massive black holes out to high redshift. In this paper we introduce a Bayesian framework to analyze the information that can be gathered from a set of such measurements. Our goal is to connect a set of massive black hole binary merger observations to the underlying model of massive black hole formation. In other words, given a set of observed massive black hole coalescences, we assess what information can be extracted about the underlying massive black hole population model. For concreteness we consider ten specific models of massive black hole formation, chosen to probe four important (and largely unconstrained) aspects of the input physics used in structure formation simulations: seed formation, metallicity “feedback”, accretion efficiency and accretion geometry. For the first time we allow for the possibility of “model mixing”, by drawing the observed population from some combination of the “pure” models that have been simulated. A Bayesian analysis allows us to recover a posterior probability distribution for the “mixing parameters” that characterize the fractions of each model represented in the observed distribution. Our work shows that LISA has enormous potential to probe the underlying physics of structure formation.
Massive Star Burps, Then Explodes
NASA Astrophysics Data System (ADS)
2007-04-01
evolved stars that have shed their outer envelopes. Swift XRT Image Swift XRT Image (Credit: NASA / GSFC / CXC /S.Immler) Most astronomers did not expect that a massive star would explode so soon after a major outburst, or that a Wolf-Rayet star would produce such a luminous eruption, so SN 2006jc represents a puzzle for theorists. "It challenges some aspects of our current model of stellar evolution," says Foley. "We really don't know what caused this star to have such a large eruption so soon before it went supernova." "SN 2006jc provides us with an important clue that LBV-style eruptions may be related to the deaths of massive stars, perhaps more closely than we used to think," adds coauthor and UC Berkeley astronomer Nathan Smith. "The fact that we have no well-established theory for what actually causes these outbursts is the elephant in the living room that nobody is talking about." SN 2006jc occurred in galaxy UGC 4904, located 77 million light years from Earth in the constellation Lynx. The supernova explosion, a peculiar variant of a Type Ib, was first sighted by Itagaki, American amateur astronomer Tim Puckett and Italian amateur astronomer Roberto Gorelli. See also NASA Goddard press release at: http://www.nasa.gov/centers/goddard/news/topstory/ 2007/supernova_imposter.html
Massive gravity with mass term in three dimensions
Nakasone, Masashi; Oda, Ichiro
2009-05-15
We analyze the effect of the Pauli-Fierz mass term on a recently established, new massive gravity theory in three space-time dimensions. We show that the Pauli-Fierz mass term makes the new massive gravity theory nonunitary. Moreover, although we add the gravitational Chern-Simons term to this model, the situation remains unchanged and the theory stays nonunitary despite that the structure of the graviton propagator is greatly changed. Thus, the Pauli-Fierz mass term is not allowed to coexist with mass-generating higher-derivative terms in the new massive gravity.
Large N phase transitions in massive N = 2 gauge theories
Russo, J. G.
2014-07-23
Using exact results obtained from localization on S{sup 4}, we explore the large N limit of N = 2 super Yang-Mills theories with massive matter multiplets. In this talk we discuss two cases: N = 2* theory, describing a massive hypermultiplet in the adjoint representation, and super QCD with massive quarks. When the radius of the four-sphere is sent to infinity these theories are described by solvable matrix models, which exhibit a number of interesting phenomena including quantum phase transitions at finite 't Hooft coupling.
Fundamental Parameters of 4 Massive Eclipsing Binaries in Westerlund 1
NASA Astrophysics Data System (ADS)
Bonanos, Alceste Z.; Koumpia, E.
2011-05-01
We present fundamental parameters of 4 massive eclipsing binaries in the young massive cluster Westerlund 1. The goal is to measure accurate masses and radii of their component stars, which provide much needed constraints for evolutionary models of massive stars. Accurate parameters can further be used to determine a dynamical lower limit for the magnetar progenitor and to obtain an independent distance to the cluster. Our results confirm and extend the evidence for a high mass for the progenitor of the magnetar. The authors acknowledge research and travel support from the European Commission Framework Program Seven under the Marie Curie International Reintegration Grant PIRG04-GA-2008-239335.
AIMS: Asteroseismic Inference on a Massive Scale
NASA Astrophysics Data System (ADS)
Reese, Daniel R.
2016-11-01
AIMS (Asteroseismic Inference on a Massive Scale) estimates stellar parameters and credible intervals/error bars in a Bayesian manner from a set of seismic frequency data and so-called classic constraints. To achieve reliable parameter estimates and computational efficiency it searches through a grid of pre-computed models using an MCMC algorithm; interpolation within the grid of models is performed by first tessellating the grid using a Delaunay triangulation and then doing a linear barycentric interpolation on matching simplexes. Inputs for the modeling consists of individual frequencies from peak-bagging, which can be complemented with classic spectroscopic constraints.
A massive early atmosphere on Triton
NASA Technical Reports Server (NTRS)
Lunine, Jonathan I.; Nolan, Michael C.
1992-01-01
The idea of an early greenhouse atmosphere for Triton is presented and the conditions under which it may have been sustained are quantified. The volatile content of primordial Triton is modeled, and tidal heating rates are assessed to set bounds on the available energy. The atmospheric model formalism is presented, and it is shown how a massive atmosphere could have been raised by modest tidal heating fluxes. The implications of the model atmospheres for the atmospheric escape rates, the chemical evolution, and the cratering record are addressed.
Axionlike particle assisted strongly interacting massive particle
NASA Astrophysics Data System (ADS)
Kamada, Ayuki; Kim, Hyungjin; Sekiguchi, Toyokazu
2017-07-01
We propose a new realization of strongly interacting massive particles (SIMPs) as self-interacting dark matter, where SIMPs couple to the standard model (SM) sector through an axionlike particle. Our model overcomes major obstacles accompanying the original SIMP model, such as a missing mechanism of kinetically equilibrating SIMPs with the SM plasma as well as marginal perturbativity of the chiral Lagrangian density. Remarkably, the parameter region realizing σself/mDM≃0.1 - 1 cm2/g is within the reach of future beam dump experiments such as the Search for Hidden Particles experiment.
Parallel rendering techniques for massively parallel visualization
Hansen, C.; Krogh, M.; Painter, J.
1995-07-01
As the resolution of simulation models increases, scientific visualization algorithms which take advantage of the large memory. and parallelism of Massively Parallel Processors (MPPs) are becoming increasingly important. For large applications rendering on the MPP tends to be preferable to rendering on a graphics workstation due to the MPP`s abundant resources: memory, disk, and numerous processors. The challenge becomes developing algorithms that can exploit these resources while minimizing overhead, typically communication costs. This paper will describe recent efforts in parallel rendering for polygonal primitives as well as parallel volumetric techniques. This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume render use a MIMD approach. Implementations for these algorithms are presented for the Thinking Ma.chines Corporation CM-5 MPP.
Solitonic solutions of the SU(2) Nambu-Jona-Lasinio model with σ, π, ρ, A1 and ω mesons
NASA Astrophysics Data System (ADS)
Döring, F.; Schüren, C.; Arriola, E. Ruiz; Goeke, K.
1993-01-01
We present the first solitonic solutions of the SU(2) Nambu-Jona-Lasinio model including σ, π, ρ, A1 and ω mesons for hedgehog configurations on the chiral circle. The lagrangian incorporates Sakurai's universality and vector meson dominance by means of current-field identities. In order to fix the parameters of the lagrangian we make use of the full momentum dependent mesonic two point functions in the one quark loop approximation. For reasonable values of the consistuent quark mass we find that solitons exist provided that mω>870 MeV. In addition, whether the baryon number is carried by valence quarks or by the Dirac sea, depends strongly on the particular values of the constituent quark mass and the ω meson mass.
Branching fractions of semileptonic D and D_s decays from the covariant light-front quark model
NASA Astrophysics Data System (ADS)
Cheng, Hai-Yang; Kang, Xian-Wei
2017-09-01
Based on the predictions of the relevant form factors from the covariant light-front quark model, we show the branching fractions for the D (D_s) → (P, S, V, A) ℓ ν _ℓ (ℓ =e or μ ) decays, where P denotes the pseudoscalar meson, S the scalar meson with a mass above 1 GeV, V the vector meson and A the axial-vector one. Comparison with the available experimental results are made, and we find an excellent agreement. The predictions for other decay modes can be tested in a charm factory, e.g., the BESIII detector. The future measurements will definitely further enrich our knowledge of the hadronic transition form factors as well as the inner structure of the even-parity mesons ( S and A).
Holographically viable extensions of topologically massive and minimal massive gravity?
NASA Astrophysics Data System (ADS)
Altas, Emel; Tekin, Bayram
2016-01-01
Recently [E. Bergshoeff et al., Classical Quantum Gravity 31, 145008 (2014)], an extension of the topologically massive gravity (TMG) in 2 +1 dimensions, dubbed as minimal massive gravity (MMG), which is free of the bulk-boundary unitarity clash that inflicts the former theory and all the other known three-dimensional theories, was found. Field equations of MMG differ from those of TMG at quadratic terms in the curvature that do not come from the variation of an action depending on the metric alone. Here we show that MMG is a unique theory and there does not exist a deformation of TMG or MMG at the cubic and quartic order (and beyond) in the curvature that is consistent at the level of the field equations. The only extension of TMG with the desired bulk and boundary properties having a single massive degree of freedom is MMG.
Massive transfusion: blood component ratios.
Lal, Devika S; Shaz, Beth H
2013-11-01
This review will address recent developments in the transfusion management of massively transfused trauma patients, focusing on the use of fixed blood component ratios in massive transfusion protocols. The majority of trauma centers have migrated from laboratory-based transfusion protocols to massive transfusion protocols with fixed blood component ratios. These protocols with red blood cell : plasma : platelet ratio of 1 : 1 : 1 are associated with improved survival in severely injured patients. However, alternate ratios have also demonstrated improved survival. Thus, the optimal ratio has not been determined. In addition, the use of medications, such as antifibrinolytics, and point of care testing, such as thromboelastography, are increasingly being used as part of massive transfusion protocols to adjust transfusion therapy and decrease bleeding. However, their optimal integration has yet to be determined. Massive transfusion protocols with fixed ratios of red blood cells to plasma and platelets have improved survival in both civilian and military trauma patients. Continued studies of ratios as well as integration of other therapies and testing are ongoing in order to continue to improve patient outcome.
Observational constraints on massive-star evolution
NASA Astrophysics Data System (ADS)
Schulte-Ladbeck, Regina
1997-07-01
Massive stars are important constitutents of galaxies and are increasingly used as probes of galaxy evolution out to high redshifts. Yet, a very basic problem remains in understanding the distribution of massive stars across the Hertzsprung- Russell Diagram. This is known as the problem of the blue-to- red supergiant ratios in galaxies of different metallicities, a very sensitive indicator of the evolutionary paths that massive stars in different chemical environments appear to follow. Observations suggest a trend that the numbers of red supergiants increase with decreasing metallicity, but stellar- evolution models predict the opposite. We discuss various limitations of ground-based observations which have so far restricted accurate star counts to a few, nearby galaxies. We then argue that the HST archive contains a perfect set of photometric data to determine number counts of red supergiants in galaxies out to 5 Mpc. We propose to analyze WFPC2 observations in F555W {V} and F814W {I} filters to derive color-magnitude diagrams and complete luminosity functions of the red supergiant populations in 6 galaxies spanning a factor of 60 in metallicity. This systematic approach will put the functional form of the blue-to-red supergiant ratio with metallicity on firm observational footing.
MASSIVE STAR FORMATION IN NGC 2074
Fleener, Christine E.; Chu, Y.-H.; Gruendl, Robert A.; Payne, James T.; Chen, C.-H. Rosie
2010-01-15
Spitzer observations of the Large Magellanic Cloud (LMC) have revealed a large population of young stellar objects (YSOs), but complementary high-resolution images in the optical or near-IR wavelengths are still needed to resolve the multiplicity and immediate environments of the YSOs. The Hubble Space Telescope imaged the star-forming region NGC 2074 in the LMC during its 100,000th orbit, providing an opportunity to more closely examine the YSOs and their environments in this region. We have studied the 10 YSO candidates identified from Spitzer observations, confirming their nature and determining their physical parameters by modeling their spectral energy distributions. The majority of the YSOs and central stars of ultracompact H II regions in NGC 2074 have masses consistent with spectral types of early B to late O. The co-existence of massive early-type O stars and the less massive YSOs indicates that their formation may have started at a similar time, a few 10{sup 5} yr ago. NGC 2074 provides an opportunity to study the evolution of massive stars at their infancy.
The feeding and feedback of massive protostars
NASA Astrophysics Data System (ADS)
Smith, Michael
2013-07-01
A model for massive stars is constructed by piecing together evolutionary algorithms for the protostellar structure, the environment, the inflow and the radiation feedback. The framework requires the accretion rate from the clump to be specified. We investigate constant, decelerating and accelerating accretion rate scenarios and consider both hot and cold accretion, identified with spherical free-fall and disk accretion, respectively. We find that accelerated accretion is not favoured on the basis of the often-used diagnostic diagram which correlates the bolometric luminosity and clump mass. Instead, source counts as a function of the bolometric temperature can distinguish the accretion mode. Specifically, accelerated accretion yields a relatively high number of lowtemperatureob jects. On this basis, we demonstrate that evolutionary tracks to fit Herschel Space Telescope data require the generated stars to be three to four times less massive than in previous interpretations. Neither spherical nor disk accretion can explain the high radio luminosities of many protostars. Nevertheless, we discover a solution in which the extreme ultraviolet flux needed to explain the radio emission is produced if the accretion flow is via free-fall on to hot spots covering less than 20% of the surface area. Moreover, the protostar must be compact, and so has formed through cold accretion. This suggest that massive stars form via gas accretion through disks which, in the phase before the star bloats, download their mass via magnetic flux tubes on to the protostar.
Massive-Star Nucleosynthesis: Lessons from INTEGRAL
NASA Astrophysics Data System (ADS)
Diehl, Roland; Lang, Michael; Kretschmer, Karsten; Martin, Pierrick; Ohlendorf, Henrike; Voss, Rasmus
2010-08-01
Gamma-ray line observations with INTEGRAL measure decay of unstable isotopes which are ejected from sites of nucleosynthesis. Massive stars are believed to be producers of gamma-ray emitting isotopes 44Ti, 26Al, 60Fe. Measurements with the Ge spectrometer have shown that (1) inner core-collapse supernova ejecta from the Cas A supernova remnant appear to still travel at velocities beyond a few hundred km/sec (2) 26Al synthesis occurs throughout the Galaxy corresponds to a supernova rate from core collapses of about one every 50 years; (3) 60Fe synthesis expected from massive stars is above the constraints from gamma-ray observations; 26Al synthesis in the Cygnus region appears on the high side of predictions from models; 26Al emission from the nearby Sco-Cen group of stars has been identified demonstrates massive-star activity close to the Sun. 26Al gamma-rays have been used to determine a longitude-velocity distribution of the presumably hot tenuous ISM which carries 26Al, which can be compared to molecular-gas star motions to help understand the Galaxy's bar spiral-arm structure. Implications of the above nucleosynthesis constraints suggest that INTEGRAL's observed positron annihilation gamma-rays need a contribution from another source located in the central regions of our Galaxy, and/or positrons may propagate kpc-distances away from their sources before annihilating.
Cosmology in general massive gravity theories
Comelli, D.; Nesti, F.; Pilo, L. E-mail: fabrizio.nesti@aquila.infn.it
2014-05-01
We study the cosmological FRW flat solutions generated in general massive gravity theories. Such a model are obtained adding to the Einstein General Relativity action a peculiar non derivative potentials, function of the metric components, that induce the propagation of five gravitational degrees of freedom. This large class of theories includes both the case with a residual Lorentz invariance as well as the case with rotational invariance only. It turns out that the Lorentz-breaking case is selected as the only possibility. Moreover it turns out that that perturbations around strict Minkowski or dS space are strongly coupled. The upshot is that even though dark energy can be simply accounted by massive gravity modifications, its equation of state w{sub eff} has to deviate from -1. Indeed, there is an explicit relation between the strong coupling scale of perturbations and the deviation of w{sub eff} from -1. Taking into account current limits on w{sub eff} and submillimiter tests of the Newton's law as a limit on the possible strong coupling scale, we find that it is still possible to have a weakly coupled theory in a quasi dS background. Future experimental improvements on short distance tests of the Newton's law may be used to tighten the deviation of w{sub eff} form -1 in a weakly coupled massive gravity theory.
Diffractive vector meson production at COMPASS and plans for GPDs measurements
Sandacz, Andrzej
2006-07-11
Preliminary results on the spin dependence of exclusive {rho}0 muoproduction at COMPASS are discussed. The Q2 dependence of several spin density matrix elements and of R = {sigma}L/{sigma}T is presented. The data are consistent with a substantial increase of R with Q2 and a weak violation of SCHC. Next, the longitudinal double-spin asymmetry A{sub 1}{sup {rho}} for {rho}0 production on polarized deuterons is shown as a function of Q2 and xBj. The asymmetry is compatible with zero in the whole kinematical range. Finally, we discuss the prospects for measuring DVCS and exclusive meson production at COMPASS in order to investigate GPDs.
Vector meson backgrounds at high-energy e anti e machines
Hinchliffe, I.
1982-08-01
This note presents cross sections for e anti e ..-->.. W/sup -/W/sup +/, ZZ, Z..gamma.. at high energies. The first of these is available in the LEP reports and elsewhere, but the remaining two seem to be unavailable. These cross-sections represent a background to potentially interesting physics on mass scales of order 1 TeV. They are large due to t channel lepton exchange diagrams.
Santini, E.; Steinheimer, J.; Bleicher, M.; Schramm, S.
2011-07-15
We analyze dilepton emission from hot and dense matter using a hybrid approach based on the ultrarelativistic quantum molecular dynamics (UrQMD) transport model with an intermediate hydrodynamic stage for the description of heavy-ion collisions at relativistic energies. During the hydrodynamic stage, the production of lepton pairs is described by radiation rates for a strongly interacting medium in thermal equilibrium. In the low-mass region, hadronic thermal emission is evaluated by assuming vector meson dominance including in-medium modifications of the {rho} meson spectral function through scattering from nucleons and pions in the heat bath. In the intermediate-mass region, the hadronic rate is essentially determined by multipion annihilation processes. Emission from quark-antiquark annihilation in the quark gluon plasma (QGP) is taken into account as well. When the system is sufficiently dilute, the hydrodynamic description breaks down and a transition to a final cascade stage is performed. In this stage dimuon emission is evaluated as commonly done in transport models. By focusing on the enhancement with respect to the contribution from long-lived hadron decays after freezeout observed at the SPS in the low-mass region of the dilepton spectra, the relative importance of the different thermal contributions and of the two dynamical stages is investigated. We find that three separated regions can be identified in the invariant mass spectra. Whereas the very low and the intermediate-mass regions mostly receive contribution from the thermal dilepton emission, the region around the vector meson peak is dominated by the cascade emission. Above the {rho}-peak region the spectrum is driven by QGP radiation. Analysis of the dimuon transverse mass spectra reveals that the thermal hadronic emission shows an evident mass ordering not present in the emission from the QGP. A comparison of our calculation to recent acceptance-corrected NA60 data on invariant as well as
Positive signs in massive gravity
Cheung, Clifford; Remmen, Grant N.
2016-04-01
Here, we derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. Furthermore, the high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small islandmore » in the parameter space of ghost-free massive gravity. And while the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.« less
Positive signs in massive gravity
Cheung, Clifford; Remmen, Grant N.
2016-04-01
Here, we derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. Furthermore, the high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small island in the parameter space of ghost-free massive gravity. And while the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.
Massive ascites of unknown origin
Yuan, Shi-Min
2014-01-01
Massive ascites of unknown origin is an uncommon condition, which represent a diagnostic challenge. Patients with delayed diagnosis and treatment may have a poor prognosis. A 22-year-old female was referred to this hospital due to a 4-year progressive abdominal distension with massive ascites of unknown origin. By thorough investigations, she was eventually diagnosed as chronic calcified constrictive pericarditis. She received pericardiectomy and had an uneventful postoperative course. With a few day paracentesis, ascites did not progress any more. She was doing well at 5-month follow-up and has returned to work. Extracardiac manifestations, such as massive ascites and liver cirrhosis, were rare in patients with constrictive pericarditis. Pericardiectomy can be a radical solution for the treatment of chronic constrictive pericarditis. In order to avoid delayed diagnosis and treatment, physicians have to bear in mind this rare manifestation of chronic calcified constrictive pericarditis. PMID:24600502
Positive signs in massive gravity
NASA Astrophysics Data System (ADS)
Cheung, Clifford; Remmen, Grant N.
2016-04-01
We derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. The high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small island in the parameter space of ghost-free massive gravity. While the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.
Holographic complexity and action growth in massive gravities
NASA Astrophysics Data System (ADS)
Pan, Wen-Jian; Huang, Yong-Chang
2017-06-01
In this paper, we investigate the growth rates of action for the anti-de Sitter black holes in massive-Einstein gravity models and obtain the universal behaviors of the growth rates of action (the rates of holographic complexity) within the "Wheeler-DeWitt" (WDW) patch at the late limit. Furthermore, we find that, for the static neutral cases, when the same mass of black holes is given, the computational speed of the neutral massive black hole is the same as its Einstein gravity counterpart, which is independent with the effect of the graviton mass terms; nevertheless, for the static charged cases, when the same mass and charge parameters of black holes are given, the growth rates of action for the massive charged black holes are always superior to the growth rates of action without graviton mass terms, which directly shows that the massive charged black holes as computers on the computational speeds are faster than their Einstein gravity counterparts.
TWO MASSIVE, LOW-LUMINOSITY CORES TOWARD INFRARED DARK CLOUDS
Swift, Jonathan J.
2009-11-10
This article presents high-resolution interferometric mosaics in the 850 mum wave band of two massive, quiescent infrared dark clouds. The two clouds were chosen based on their likelihood to represent environments preceding the formation of massive stars. The brightest compact sources detected in each cloud have masses approx110 M{sub sun} and approx60 M{sub sun} with radii <0.1 pc, implying mean densities of (n) approx 10{sup 6} cm{sup -3} and (N) approx 1 g cm{sup -2}. Supplementary data show these cores to be cold and inactive. Low upper limits to their bolometric luminosities and temperatures place them at a very early stage of evolution, while current models of massive star formation suggest they have the potential to form massive stars.
Generalized massive gravity in arbitrary dimensions and its Hamiltonian formulation
Huang, Qing-Guo; Zhang, Ke-Chao; Zhou, Shuang-Yong E-mail: zkc@itp.ac.cn
2013-08-01
We extend the four-dimensional de Rham-Gabadadze-Tolley (dRGT) massive gravity model to a general scalar massive-tensor theory in arbitrary dimensions, coupling a dRGT massive graviton to multiple scalars and allowing for generic kinetic and mass matrix mixing between the massive graviton and the scalars, and derive its Hamiltonian formulation and associated constraint system. When passing to the Hamiltonian formulation, two different sectors arise: a general sector and a special sector. Although obtained via different ways, there are two second class constraints in either of the two sectors, eliminating the BD ghost. However, for the special sector, there are still ghost instabilities except for the case of two dimensions. In particular, for the special sector with one scalar, there is a ''second BD ghost''.
Topologically massive gravity and Ricci-Cotton flow
NASA Astrophysics Data System (ADS)
Lashkari, Nima; Maloney, Alexander
2011-05-01
We consider topologically massive gravity (TMG), which is three-dimensional general relativity with a cosmological constant and a gravitational Chern-Simons term. When the cosmological constant is negative the theory has two potential vacuum solutions: anti-de Sitter space and warped anti-de Sitter space. The theory also contains a massive graviton state which renders these solutions unstable for certain values of the parameters and boundary conditions. We study the decay of these solutions due to the condensation of the massive graviton mode using Ricci-Cotton flow, which is the appropriate generalization of Ricci flow to TMG. When the Chern-Simons coupling is small the AdS solution flows to warped AdS by the condensation of the massive graviton mode. When the coupling is large the situation is reversed, and warped AdS flows to AdS. Minisuperspace models are constructed where these flows are studied explicitly.
Broadbeam for Massive MIMO Systems
NASA Astrophysics Data System (ADS)
Qiao, Deli; Qian, Haifeng; Li, Geoffrey Ye
2016-05-01
Massive MIMO has been identified as one of the promising disruptive air interface techniques to address the huge capacity requirement demanded by 5G wireless communications. For practical deployment of such systems, the control message need to be broadcast to all users reliably in the cell using broadbeam. A broadbeam is expected to have the same radiated power in all directions to cover users in any place in a cell. In this paper, we will show that there is no perfect broadbeam. Therefore, we develop a method for generating broadbeam that can allow tiny fluctuations in radiated power. Overall, this can serve as an ingredient for practical deployment of the massive MIMO systems.
Processing massive datasets in genomics
NASA Astrophysics Data System (ADS)
Artiguenave, F.
2011-02-01
Life science researches have been profoundly impacted by technological advances allowing faster and cheaper DNA sequencing. Opening a wide range of applications in medical and biology, the last generation sequencing platforms raised new challenges, in particular in processing, analysing and interpreting massive data. In this talk, the growing role of bioinformatics will be illustrated by providing some figures about genome sequencing and others applications aimed at unravelling biological mechanisms. Methods to gather insights from massive amount of data will be illustrated by the genome annotation process, by which genes are identified in the genome sequence.
Massive photons and Lorentz violation
NASA Astrophysics Data System (ADS)
Cambiaso, Mauro; Lehnert, Ralf; Potting, Robertus
2012-04-01
All quadratic translation- and gauge-invariant photon operators for Lorentz breakdown are included into the Stueckelberg Lagrangian for massive photons in a generalized Rξ gauge. The corresponding dispersion relation and tree-level propagator are determined exactly, and some leading-order results are derived. The question of how to include such Lorentz-violating effects into a perturbative quantum-field expansion is addressed. Applications of these results within Lorentz-breaking quantum-field theories include the regularization of infrared divergences as well as the free propagation of massive vector bosons.
Hydrodynamical simulations of realistic massive cluster populations
NASA Astrophysics Data System (ADS)
Barnes, David J.; Henson, Monique A.; Kay, Scott T.; McCarthy, Ian G.; Bahe, Yannick M.; Eagle Collaboration
2015-09-01
Galaxy clusters are seeded by density fluctuations in the early Universe and grow via hierarchical collapse to become the most massive virialised objects we observed today. They are powerful probes that study both cosmology and astrophysical processes. Their internal structure at the current epoch is the result of a non-trivial interplay between gravitational collapse and the energy fed into the intra-cluster medium (ICM) by star formation and active galactic nuclei (AGN). These processes shape the ICM during its formation at high redshift, but current observations of galaxy clusters are limited to z<0.5. The resolution and sensitivity of textit{Athena+} will allow it to study galaxy clusters in unprecedented detail. It will constrain cluster properties, such as its entropy, temperature and gas fraction, out to z˜2, enabling it to investigate the progenitors of today's massive clusters and observing the evolution of the properties of the ICM for the first time. Athena+ will produce a significant change in our understanding of the formation of galaxy clusters. Recently the theoretical modelling of clusters has advanced significantly and issues, such as the 'cooling catastophea', have been overcome by including feedback from star formation and AGN. We present the MAssive ClusterS and Intercluster Structures (MACSIS) project. The MACSIS project is a representative sample of 390 of galaxy clusters, with M_{FOF} > 10(15} M_{⊙) , re-simulated using the cosmo-OWLS model (Le Brun et al. 2014, McCarthy et al. in prep.) to extend it to the most massive and rarest objects. We demonstrate that this sample reproduces the scaling relations, with intrinsic scatter, observed with current instruments at low redshift. Under the hierarchical paradigm, the progenitors of these systems will be the first objects to collapse at high redshift and we examine to z=2 how the scaling relations of these massive objects evolve with redshift. Finally, we investigate methods of defining a
QCD coupling constants and VDM
Erkol, G.; Ozpineci, A.; Zamiralov, V. S.
2012-10-23
QCD sum rules for coupling constants of vector mesons with baryons are constructed. The corresponding QCD sum rules for electric charges and magnetic moments are also derived and with the use of vector-meson-dominance model related to the coupling constants. The VDM role as the criterium of reciprocal validity of the sum rules is considered.
Fast, Massively Parallel Data Processors
NASA Technical Reports Server (NTRS)
Heaton, Robert A.; Blevins, Donald W.; Davis, ED
1994-01-01
Proposed fast, massively parallel data processor contains 8x16 array of processing elements with efficient interconnection scheme and options for flexible local control. Processing elements communicate with each other on "X" interconnection grid with external memory via high-capacity input/output bus. This approach to conditional operation nearly doubles speed of various arithmetic operations.
NASA Astrophysics Data System (ADS)
Martins, F.
2015-12-01
In this contribution we review the properties of the winds of massive stars. We focus on OB stars, red supergiants, Luminous Blue Variables (LBVs) and Wolf-Rayet stars. For each type of star, we summarize the main wind properties and we give a brief description of the physical mechanism(s) responsible for mass loss.
Planckian Interacting Massive Particles as Dark Matter
NASA Astrophysics Data System (ADS)
Garny, Mathias; Sandora, McCullen; Sloth, Martin S.
2016-03-01
The standard model could be self-consistent up to the Planck scale according to the present measurements of the Higgs boson mass and top quark Yukawa coupling. It is therefore possible that new physics is only coupled to the standard model through Planck suppressed higher dimensional operators. In this case the weakly interacting massive particle miracle is a mirage, and instead minimality as dictated by Occam's razor would indicate that dark matter is related to the Planck scale, where quantum gravity is anyway expected to manifest itself. Assuming within this framework that dark matter is a Planckian interacting massive particle, we show that the most natural mass larger than 0.01 Mp is already ruled out by the absence of tensor modes in the cosmic microwave background (CMB). This also indicates that we expect tensor modes in the CMB to be observed soon for this type of minimal dark matter model. Finally, we touch upon the Kaluza-Klein graviton mode as a possible realization of this scenario within UV complete models, as well as further potential signatures and peculiar properties of this type of dark matter candidate. This paradigm therefore leads to a subtle connection between quantum gravity, the physics of primordial inflation, and the nature of dark matter.
Dipolar dark matter with massive bigravity
Blanchet, Luc; Heisenberg, Lavinia E-mail: laviniah@kth.se
2015-12-01
Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.
Planckian Interacting Massive Particles as Dark Matter.
Garny, Mathias; Sandora, McCullen; Sloth, Martin S
2016-03-11
The standard model could be self-consistent up to the Planck scale according to the present measurements of the Higgs boson mass and top quark Yukawa coupling. It is therefore possible that new physics is only coupled to the standard model through Planck suppressed higher dimensional operators. In this case the weakly interacting massive particle miracle is a mirage, and instead minimality as dictated by Occam's razor would indicate that dark matter is related to the Planck scale, where quantum gravity is anyway expected to manifest itself. Assuming within this framework that dark matter is a Planckian interacting massive particle, we show that the most natural mass larger than 0.01M_{p} is already ruled out by the absence of tensor modes in the cosmic microwave background (CMB). This also indicates that we expect tensor modes in the CMB to be observed soon for this type of minimal dark matter model. Finally, we touch upon the Kaluza-Klein graviton mode as a possible realization of this scenario within UV complete models, as well as further potential signatures and peculiar properties of this type of dark matter candidate. This paradigm therefore leads to a subtle connection between quantum gravity, the physics of primordial inflation, and the nature of dark matter.
Dipolar dark matter with massive bigravity
Blanchet, Luc; Heisenberg, Lavinia
2015-12-14
Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.
Eta Carinae in the Context of the Most Massive Stars
NASA Technical Reports Server (NTRS)
Gull, Theodore R.; Damineli, Augusto
2009-01-01
Eta Car, with its historical outbursts, visible ejecta and massive, variable winds, continues to challenge both observers and modelers. In just the past five years over 100 papers have been published on this fascinating object. We now know it to be a massive binary system with a 5.54-year period. In January 2009, Car underwent one of its periodic low-states, associated with periastron passage of the two massive stars. This event was monitored by an intensive multi-wavelength campaign ranging from -rays to radio. A large amount of data was collected to test a number of evolving models including 3-D models of the massive interacting winds. August 2009 was an excellent time for observers and theorists to come together and review the accumulated studies, as have occurred in four meetings since 1998 devoted to Eta Car. Indeed, Car behaved both predictably and unpredictably during this most recent periastron, spurring timely discussions. Coincidently, WR140 also passed through periastron in early 2009. It, too, is a intensively studied massive interacting binary. Comparison of its properties, as well as the properties of other massive stars, with those of Eta Car is very instructive. These well-known examples of evolved massive binary systems provide many clues as to the fate of the most massive stars. What are the effects of the interacting winds, of individual stellar rotation, and of the circumstellar material on what we see as hypernovae/supernovae? We hope to learn. Topics discussed in this 1.5 day Joint Discussion were: Car: the 2009.0 event: Monitoring campaigns in X-rays, optical, radio, interferometry WR140 and HD5980: similarities and differences to Car LBVs and Eta Carinae: What is the relationship? Massive binary systems, wind interactions and 3-D modeling Shapes of the Homunculus & Little Homunculus: what do we learn about mass ejection? Massive stars: the connection to supernovae, hypernovae and gamma ray bursters Where do we go from here? (future
A MASSIVE PROTOSTAR FORMING BY ORDERED COLLAPSE OF A DENSE, MASSIVE CORE
Zhang, Yichen; Tan, Jonathan C.; Telesco, Charles; De Buizer, James M.; Sandell, Goeran; Shuping, Ralph; Beltran, Maria T.; Churchwell, Ed; Whitney, Barbara; McKee, Christopher F.; Staff, Jan E.
2013-04-10
We present 30 and 40 {mu}m imaging of the massive protostar G35.20-0.74 with SOFIA-FORCAST. The high surface density of the natal core around the protostar leads to high extinction, even at these relatively long wavelengths, causing the observed flux to be dominated by that emerging from the near-facing outflow cavity. However, emission from the far-facing cavity is still clearly detected. We combine these results with fluxes from the near-infrared to mm to construct a spectral energy distribution (SED). For isotropic emission the bolometric luminosity would be 3.3 Multiplication-Sign 10{sup 4} L{sub Sun }. We perform radiative transfer modeling of a protostar forming by ordered, symmetric collapse from a massive core bounded by a clump with high-mass surface density, {Sigma}{sub cl}. To fit the SED requires protostellar masses {approx}20-34 M{sub Sun} depending on the outflow cavity opening angle (35 Degree-Sign -50 Degree-Sign ), and {Sigma}{sub cl} {approx} 0.4-1 g cm{sup -2}. After accounting for the foreground extinction and the flashlight effect, the true bolometric luminosity is {approx}(0.7-2.2) Multiplication-Sign 10{sup 5} L{sub Sun }. One of these models also has excellent agreement with the observed intensity profiles along the outflow axis at 10, 18, 31, and 37 {mu}m. Overall our results support a model of massive star formation involving the relatively ordered, symmetric collapse of a massive, dense core and the launching bipolar outflows that clear low-density cavities. Thus a unified model may apply for the formation of both low- and high-mass stars.
Construction of a massive ABJM theory without Higgs superfields
NASA Astrophysics Data System (ADS)
Upadhyay, Sudhaker
2017-01-01
A massive Aharony-Bergman-Jafferis-Maldacena (ABJM) model in N =1 superspace is analysed by considering a Proca-type mass term into the most general Faddeev-Popov action in a covariant gauge. The presence of a mass term breaks the original BRST and anti-BRST invariance of the model. Further, the symmetry of the massive ABJM model is restored by extending the BRST and anti-BRST transformations. We show that the supergauge dependence of the generating functional for connected diagrams occurs in the presence of mass and ghost–anti-ghost condensates in the theory.
NASA Technical Reports Server (NTRS)
Keppenne, C. L.; Rienecker, M.; Borovikov, A. Y.
1999-01-01
Two massively parallel data assimilation systems in which the model forecast-error covariances are estimated from the distribution of an ensemble of model integrations are applied to the assimilation of 97-98 TOPEX/POSEIDON altimetry and TOGA/TAO temperature data into a Pacific basin version the NASA Seasonal to Interannual Prediction Project (NSIPP)ls quasi-isopycnal ocean general circulation model. in the first system, ensemble of model runs forced by an ensemble of atmospheric model simulations is used to calculate asymptotic error statistics. The data assimilation then occurs in the reduced phase space spanned by the corresponding leading empirical orthogonal functions. The second system is an ensemble Kalman filter in which new error statistics are computed during each assimilation cycle from the time-dependent ensemble distribution. The data assimilation experiments are conducted on NSIPP's 512-processor CRAY T3E. The two data assimilation systems are validated by withholding part of the data and quantifying the extent to which the withheld information can be inferred from the assimilation of the remaining data. The pros and cons of each system are discussed.
NASA Astrophysics Data System (ADS)
Gasper, F.; Goergen, K.; Kollet, S.; Shrestha, P.; Sulis, M.; Rihani, J.; Geimer, M.
2014-06-01
Continental-scale hyper-resolution simulations constitute a grand challenge in characterizing non-linear feedbacks of states and fluxes of the coupled water, energy, and biogeochemical cycles of terrestrial systems. Tackling this challenge requires advanced coupling and supercomputing technologies for earth system models that are discussed in this study, utilizing the example of the implementation of the newly developed Terrestrial Systems Modeling Platform (TerrSysMP) on JUQUEEN (IBM Blue Gene/Q) of the Jülich Supercomputing Centre, Germany. The applied coupling strategies rely on the Multiple Program Multiple Data (MPMD) paradigm and require memory and load balancing considerations in the exchange of the coupling fields between different component models and allocation of computational resources, respectively. These considerations can be reached with advanced profiling and tracing tools leading to the efficient use of massively parallel computing environments, which is then mainly determined by the parallel performance of individual component models. However, the problem of model I/O and initialization in the peta-scale range requires major attention, because this constitutes a true big data challenge in the perspective of future exa-scale capabilities, which is unsolved.
Holographic renormalization of new massive gravity
Alishahiha, Mohsen; Naseh, Ali
2010-11-15
We study holographic renormalization for three-dimensional new massive gravity. By studying the general falloff conditions for the metric allowed by the model at infinity, we show that at the critical point where the central charges of the dual conformal field theory (CFT) are zero, it contains a leading logarithmic behavior. In the context of AdS/CFT correspondence it can be identified as a source for an irrelevant operator in the dual CFT. The presence of the logarithmic falloff may be interpreted as the fact that the dual CFT would be a logarithmic conformal field theory.
Massively-Parallel Dislocation Dynamics Simulations
Cai, W; Bulatov, V V; Pierce, T G; Hiratani, M; Rhee, M; Bartelt, M; Tang, M
2003-06-18
Prediction of the plastic strength of single crystals based on the collective dynamics of dislocations has been a challenge for computational materials science for a number of years. The difficulty lies in the inability of the existing dislocation dynamics (DD) codes to handle a sufficiently large number of dislocation lines, in order to be statistically representative and to reproduce experimentally observed microstructures. A new massively-parallel DD code is developed that is capable of modeling million-dislocation systems by employing thousands of processors. We discuss the general aspects of this code that make such large scale simulations possible, as well as a few initial simulation results.
Non-Pauli-Fierz Massive Gravitons
Dvali, Gia; Pujolas, Oriol; Redi, Michele
2008-10-24
We study general Lorentz invariant theories of massive gravitons. We show that, contrary to the standard lore, there exist consistent theories where the graviton mass term violates Pauli-Fierz structure. For theories where the graviton is a resonance, this does not imply the existence of a scalar ghost if the deviation from a Pauli-Fierz structure becomes sufficiently small at high energies. These types of mass terms are required by any consistent realization of the Dvali-Gabadadze-Porrati model in higher dimension.
Dynamics of Massive Atmospheres
NASA Astrophysics Data System (ADS)
Chemke, Rei; Kaspi, Yohai
2017-08-01
The many recently discovered terrestrial exoplanets are expected to hold a wide range of atmospheric masses. Here the dynamic-thermodynamic effects of atmospheric mass on atmospheric circulation are studied using an idealized global circulation model by systematically varying the atmospheric surface pressure. On an Earth analog planet, an increase in atmospheric mass weakens the Hadley circulation and decreases its latitudinal extent. These changes are found to be related to the reduction of the convective fluxes and net radiative cooling (due to the higher atmospheric heat capacity), which, respectively, cool the upper troposphere at mid-low latitudes and warm the troposphere at high latitudes. These together decrease the meridional temperature gradient, tropopause height and static stability. The reduction of these parameters, which play a key role in affecting the flow properties of the tropical circulation, weakens and contracts the Hadley circulation. The reduction of the meridional temperature gradient also decreases the extraction of mean potential energy to the eddy fields and the mean kinetic energy, which weakens the extratropical circulation. The decrease of the eddy kinetic energy decreases the Rhines wavelength, which is found to follow the meridional jet scale. The contraction of the jet scale in the extratropics results in multiple jets and meridional circulation cells as the atmospheric mass increases.
Propagation peculiarities of mean field massive gravity
Deser, S.; Waldron, A.; Zahariade, G.
2015-07-28
Massive gravity (mGR) describes a dynamical “metric” on a fiducial, background one. We investigate fluctuations of the dynamics about mGR solutions, that is about its “mean field theory”. Analyzing mean field massive gravity (m¯GR) propagation characteristics is not only equivalent to studying those of the full non-linear theory, but also in direct correspondence with earlier analyses of charged higher spin systems, the oldest example being the charged, massive spin 3/2 Rarita–Schwinger (RS) theory. The fiducial and mGR mean field background metrics in the m¯GR model correspond to the RS Minkowski metric and external EM field. The common implications in bothmore » systems are that hyperbolicity holds only in a weak background-mean-field limit, immediately ruling both theories out as fundamental theories; a situation in stark contrast with general relativity (GR) which is at least a consistent classical theory. Moreover, even though both m¯GR and RS theories can still in principle be considered as predictive effective models in the weak regime, their lower helicities then exhibit superluminal behavior: lower helicity gravitons are superluminal as compared to photons propagating on either the fiducial or background metric. Thus our approach has uncovered a novel, dispersive, “crystal-like” phenomenon of differing helicities having differing propagation speeds. As a result, this applies both to m¯GR and mGR, and is a peculiar feature that is also problematic for consistent coupling to matter.« less
Reappraising the concept of massive transfusion in trauma
2010-01-01
Introduction The massive-transfusion concept was introduced to recognize the dilutional complications resulting from large volumes of packed red blood cells (PRBCs). Definitions of massive transfusion vary and lack supporting clinical evidence. Damage-control resuscitation regimens of modern trauma care are targeted to the early correction of acute traumatic coagulopathy. The aim of this study was to identify a clinically relevant definition of trauma massive transfusion based on clinical outcomes. We also examined whether the concept was useful in that early prediction of massive transfusion requirements could allow early activation of blood bank protocols. Methods Datasets on trauma admissions over a 1 or 2-year period were obtained from the trauma registries of five large trauma research networks. A fractional polynomial was used to model the transfusion-associated probability of death. A logistic regression model for the prediction of massive transfusion, defined as 10 or more units of red cell transfusions, was developed. Results In total, 5,693 patient records were available for analysis. Mortality increased as transfusion requirements increased, but the model indicated no threshold effect. Mortality was 9% in patients who received none to five PRBC units, 22% in patients receiving six to nine PRBC units, and 42% in patients receiving 10 or more units. A logistic model for prediction of massive transfusion was developed and validated at multiple sites but achieved only moderate performance. The area under the receiver operating characteristic curve was 0.81, with specificity of only 50% at a sensitivity of 90% for the prediction of 10 or more PRBC units. Performance varied widely at different trauma centers, with specificity varying from 48% to 91%. Conclusions No threshold for definition exists at which a massive transfusion specifically results in worse outcomes. Even with a large sample size across multiple trauma datasets, it was not possible to develop a
Massive stars. A chemical signature of first-generation very massive stars.
Aoki, W; Tominaga, N; Beers, T C; Honda, S; Lee, Y S
2014-08-22
Numerical simulations of structure formation in the early universe predict the formation of some fraction of stars with several hundred solar masses. No clear evidence of supernovae from such very massive stars has, however, yet been found in the chemical compositions of Milky Way stars. We report on an analysis of a very metal-poor star SDSS J001820.5-093939.2, which possesses elemental-abundance ratios that differ significantly from any previously known star. This star exhibits low [α-element Fe] ratios and large contrasts between the abundances of odd and even element pairs, such as scandium/titanium and cobalt/nickel. Such features have been predicted by nucleosynthesis models for supernovae of stars more than 140 times as massive as the Sun, suggesting that the mass distribution of first-generation stars might extend to 100 solar masses or larger.
Topologically massive higher spin gravity
NASA Astrophysics Data System (ADS)
Bagchi, Arjun; Lal, Shailesh; Saha, Arunabha; Sahoo, Bindusar
2011-10-01
We look at the generalisation of topologically massive gravity (TMG) to higher spins, specifically spin-3. We find a special "chiral" point for the spin-three, analogous to the spin-two example, which actually coincides with the usual spin-two chiral point. But in contrast to usual TMG, there is the presence of a non-trivial trace and its logarithmic partner at the chiral point. The trace modes carry energy opposite in sign to the traceless modes. The logarithmic partner of the traceless mode carries negative energy indicating an instability at the chiral point. We make several comments on the asymptotic symmetry and its possible deformations at this chiral point and speculate on the higher spin generalisation of LCFT2 dual to the spin-3 massive gravity at the chiral point.
Spin-3 topologically massive gravity
NASA Astrophysics Data System (ADS)
Chen, Bin; Long, Jiang; Wu, Jun-bao
2011-11-01
In this Letter, we study the spin-3 topologically massive gravity (TMG), paying special attention to its properties at the chiral point. We propose an action describing the higher spin fields coupled to TMG. We discuss the traceless spin-3 fluctuations around the AdS3 vacuum and find that there is an extra local massive mode, besides the left-moving and right-moving boundary massless modes. At the chiral point, such extra mode becomes massless and degenerates with the left-moving mode. We show that at the chiral point the only degrees of freedom in the theory are the boundary right-moving graviton and spin-3 field. We conjecture that spin-3 chiral gravity with generalized Brown-Henneaux boundary condition is holographically dual to 2D chiral CFT with classical W3 algebra and central charge cR = 3 l / G.
New branches of massive gravity
NASA Astrophysics Data System (ADS)
Comelli, D.; Crisostomi, M.; Koyama, K.; Pilo, L.; Tasinato, G.
2015-06-01
The basic building block for Lorentz-invariant and ghost-free massive gravity is the square root of the combination g-1η , where g-1 is the inverse of the physical metric and η is a reference metric. Since the square root of a matrix is not uniquely defined, it is possible to have physically inequivalent potentials corresponding to different branches. We show that around the Minkowski background, the only perturbatively well-defined branch is the potential proposed by de Rham, Gabadadze and Tolley. On the other hand, if Lorentz symmetry is broken spontaneously, other potentials exist with a standard perturbative expansion. We show this explicitly building new Lorentz-invariant, ghost-free massive gravity potentials for theories that in the background preserve rotational invariance but break Lorentz boosts.
Black holes in massive gravity
NASA Astrophysics Data System (ADS)
Babichev, Eugeny; Brito, Richard
2015-08-01
We review the black hole (BH) solutions of the ghost-free massive gravity theory and its bimetric extension, and outline the main results on the stability of these solutions against small perturbations. Massive (bi)-gravity accommodates exact BH solutions, analogous to those of general relativity (GR). In addition to these solutions, hairy BHs—solutions with no correspondent in GR—have been found numerically, whose existence is a natural consequence of the absence of Birkhoff’s theorem in these theories. The existence of extra propagating degrees of freedom, makes the stability properties of these BHs richer and more complex than those of GR. In particular, the bi-Schwarzschild BH exhibits an unstable spherically symmetric mode, while the bi-Kerr geometry is also generically unstable, both against the spherical mode and against superradiant instabilities. If astrophysical BHs are described by these solutions, the superradiant instability of the Kerr solution imposes stringent bounds on the graviton mass.
Formation of Massive Stars: Theoretical Considerations
NASA Technical Reports Server (NTRS)
Yorke, Harold W.
2008-01-01
This slide presentation reviews theoretical considerations of the formation of massive stars. It addresses the questions that assuming a gravitationally unstable massive clump, how does enough material become concentrated into a sufficiently small volume within a sufficiently short time? and how does the forming massive star influence its immediate surroundings to limit its mass?
Theoretical Considerations of Massive Star Formation
NASA Technical Reports Server (NTRS)
Yorke, Harold W.
2006-01-01
This viewgraph presentation reviews the formation of massive stars. The formation of massive stars is different in many ways from the formation of other stars. The presentation shows the math, and the mechanisms that must be possible for a massive star to form.
Formation of Massive Stars: Theoretical Considerations
NASA Technical Reports Server (NTRS)
Yorke, Harold W.
2008-01-01
This slide presentation reviews theoretical considerations of the formation of massive stars. It addresses the questions that assuming a gravitationally unstable massive clump, how does enough material become concentrated into a sufficiently small volume within a sufficiently short time? and how does the forming massive star influence its immediate surroundings to limit its mass?
Theoretical Considerations of Massive Star Formation
NASA Technical Reports Server (NTRS)
Yorke, Harold W.
2006-01-01
This viewgraph presentation reviews the formation of massive stars. The formation of massive stars is different in many ways from the formation of other stars. The presentation shows the math, and the mechanisms that must be possible for a massive star to form.
Massive star clusters in galaxies.
Harris, William E
2010-02-28
The ensemble of all star clusters in a galaxy constitutes its star cluster system. In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GC research, and highlight some of the outstanding questions that are emerging from recent work.
Massive pulmonary embolus without hypoxemia.
Baird, J Scott; Greene, Anne; Schleien, Charles L
2005-09-01
To describe a patient who had been taking ibuprofen for 3 days before the diagnosis of a massive pulmonary embolus without hypoxemia. Institutional review board-approved case report. Pediatric intensive care unit. A 16-yr-old male with a history of supraventricular tachycardia. The patient underwent an electrophysiology study and developed mild shortness of breath and then chest pain 2 and 4 days later, respectively. He took ibuprofen for 3 days. Evaluation 1 wk following the procedure revealed dyspnea and tachycardia. Arterial blood gas in room air was significant for hypocarbia without hypoxemia (Pao2, 108 mm Hg; Paco2, 28 mm Hg). Ventilation perfusion scan and computed axial tomography with intravenous contrast were consistent with a massive pulmonary embolus and left external iliac vein thrombus. He received anticoagulation, thrombolysis, a stent in the left iliac vein, and a filter in the inferior vena cava. Perfusion gradually improved and he was discharged home on oral anticoagulation. The absence of hypoxemia (including a normal alveolar-arterial oxygen difference) in our patient with a massive pulmonary embolus may have been related to cyclooxygenase inhibition due to ibuprofen, with improvement in ventilation-perfusion mismatch.
Extinction in young massive clusters
NASA Astrophysics Data System (ADS)
De Marchi, Guido; Panagia, Nino
2016-01-01
Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, causing considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars (luminosities, effective temperatures, masses, ages, etc.) we must understand and measure the local extinction law. We have developed a powerful method to unambiguously determine the extinction law everywhere across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC) and are applying it to young massive clusters in the Local Group. In the Large Magellanic Cloud, with about 20 RC stars per arcmin2, for each field we can easily derive an accurate extinction curve over the entire wavelength range of the photometry. As an example, we present the extinction law of the Tarantula nebula (30 Dor) based on thousands of stars observed as part of the Hubble Tarantula Treasury Project. We discuss how the incautious adoption of the Milky Way extinction law in the analysis of massive star forming regions may lead to serious underestimates of the fluxes and of the star formation rates by factors of 2 or more.
Massive Science with VO and Grids
NASA Astrophysics Data System (ADS)
Nichol, R.; Smith, G.; Miller, C.; Freeman, P.; Genovese, C.; Wasserman, L.; Bryan, B.; Gray, A.; Schneider, J.; Moore, A.
2006-07-01
There is a growing need for massive computational resources for the analysis of new astronomical datasets. To tackle this problem, we present here our first steps towards marrying two new and emerging technologies; the Virtual Observatory (e.g, AstroGrid) and the computational grid (e.g. TeraGrid, COSMOS etc.). We discuss the construction of VOTechBroker, which is a modular software tool designed to abstract the tasks of submission and management of a large number of computational jobs to a distributed computer system. The broker will also interact with the AstroGrid workflow and MySpace environments. We discuss our planned usages of the VOTechBroker in computing a huge number of n--point correlation functions from the SDSS data and massive model-fitting of millions of CMBfast models to WMAP data. We also discuss other applications including the determination of the XMM Cluster Survey selection function and the construction of new WMAP maps.
The Dynamics and Chemistry of Massive Starless Cores
NASA Astrophysics Data System (ADS)
Tan, J. C.; Kong, S.; Butler, M. J.; Caselli, P.; Fontani, F.
2013-10-01
How do massive stars form? They may be born from massive pre-stellar gas cores that are much more massive than the Jeans mass. The Turbulent Core Accretion model invokes such cores as being in approximate virial and pressure equilibrium with their surrounding clump medium. Their internal pressure is provided by a combination of turbulence and magnetic fields. On the other hand, the Competitive Accretion model requires strongly sub-virial initial conditions that then lead to extensive fragmentation to the thermal Jeans scale, with high-mass stars later forming by competitive Bondi-Hoyle accretion. To test these models, we have identified four prime examples of massive (˜ 100 M⊙) clumps from mid-infrared (MIR) extinction mapping of Infrared Dark Clouds (IRDCs). At ˜16″ resolution, we found high deuteration fractions of N2H+ in these objects, consistent with them being starless. We then observed these 4 clumps with ALMA in Cycle 0 to probe the N2D+(3-2) line at ˜2″ resolution, finding 6 N2D+ cores. Their observed velocity dispersions and sizes are broadly consistent with the predictions of the Turbulent Core model of virialized, magnetized (with Alfvén Mach number mA ˜ 1), self-gravitating cores that are bounded by the high pressures of their surrounding clumps. However, the most massive core with ˜ 60 M⊙, appears to require moderately enhanced magnetic fields to be in virial equilibrium, implying mA ≃ 0.3. If confirmed, this suggests magnetic fields play a greater role than turbulence in setting the initial conditions of massive star formation. In this case the timescale for the core to be assembled may be significantly longer than a local dynamical or free-fall time. This is consistent with astrochemical modeling of the deuteration ages of the cores, which indicates a core age similar to the ambipolar diffusion time.
NASA Technical Reports Server (NTRS)
Karpoukhin, Mikhii G.; Kogan, Boris Y.; Karplus, Walter J.
1995-01-01
The simulation of heart arrhythmia and fibrillation are very important and challenging tasks. The solution of these problems using sophisticated mathematical models is beyond the capabilities of modern super computers. To overcome these difficulties it is proposed to break the whole simulation problem into two tightly coupled stages: generation of the action potential using sophisticated models. and propagation of the action potential using simplified models. The well known simplified models are compared and modified to bring the rate of depolarization and action potential duration restitution closer to reality. The modified method of lines is used to parallelize the computational process. The conditions for the appearance of 2D spiral waves after the application of a premature beat and the subsequent traveling of the spiral wave inside the simulated tissue are studied.
NASA Technical Reports Server (NTRS)
Karpoukhin, Mikhii G.; Kogan, Boris Y.; Karplus, Walter J.
1995-01-01
The simulation of heart arrhythmia and fibrillation are very important and challenging tasks. The solution of these problems using sophisticated mathematical models is beyond the capabilities of modern super computers. To overcome these difficulties it is proposed to break the whole simulation problem into two tightly coupled stages: generation of the action potential using sophisticated models. and propagation of the action potential using simplified models. The well known simplified models are compared and modified to bring the rate of depolarization and action potential duration restitution closer to reality. The modified method of lines is used to parallelize the computational process. The conditions for the appearance of 2D spiral waves after the application of a premature beat and the subsequent traveling of the spiral wave inside the simulated tissue are studied.
A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game
2013-03-05
A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game Peter M. Landwehr March 5, 2013 CMU-ISR-13...massively multiplayer online games (MMOG) - social and cultural model embedding technologies. Additional support was provided by CASOS — the center for...SUBTITLE A Collection of Economic and Social Data from Glitch, a Massively Multiplayer Online Game 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM
Massive Stars in Colliding Wind Systems: the GLAST Perspective
Reimer, Anita; Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park
2011-11-29
Colliding winds of massive stars in binary systems are considered as candidate sites of high-energy non-thermal photon emission. They are already among the suggested counterparts for a few individual unidentified EGRET sources, but may constitute a detectable source population for the GLAST observatory. The present work investigates such population study of massive colliding wind systems at high-energy gamma-rays. Based on the recent detailed model (Reimer et al. 2006) for non-thermal photon production in prime candidate systems, we unveil the expected characteristics of this source class in the observables accessible at LAT energies. Combining the broadband emission model with the presently cataloged distribution of such systems and their individual parameters allows us to conclude on the expected maximum number of LAT-detections among massive stars in colliding wind binary systems.
Massive fields as systematics for single field inflation
NASA Astrophysics Data System (ADS)
Jiang, Hongliang; Wang, Yi
2017-06-01
During inflation, massive fields can contribute to the power spectrum of curvature perturbation via a dimension-5 operator. This contribution can be considered as a bias for the program of using ns and r to select inflation models. Even the dimension-5 operator is suppressed by Λ = Mp, there is still a significant shift on the ns-r diagram if the massive fields have m ~ H. On the other hand, if the heavy degree of freedom appears only at the same energy scale as the suppression scale of the dimension-5 operator, then significant shift on the ns-r diagram takes place at m=Λ ~ 70H, which is around the inflationary time-translation symmetry breaking scale. Hence, the systematics from massive fields pose a greater challenge for future high precision experiments for inflationary model selection. This result can be thought of as the impact of UV sensitivity to inflationary observables.
Massive Stars in Interactive Binaries
NASA Astrophysics Data System (ADS)
St.-Louis, Nicole; Moffat, Anthony F. J.
Massive stars start their lives above a mass of ~8 time solar, finally exploding after a few million years as core-collapse or pair-production supernovae. Above ~15 solar masses, they also spend most of their lives driving especially strong, hot winds due to their extreme luminosities. All of these aspects dominate the ecology of the Universe, from element enrichment to stirring up and ionizing the interstellar medium. But when they occur in close pairs or groups separated by less than a parsec, the interaction of massive stars can lead to various exotic phenomena which would not be seen if there were no binaries. These depend on the actual separation, and going from wie to close including colliding winds (with non-thermal radio emission and Wolf-Rayet dust spirals), cluster dynamics, X-ray binaries, Roche-lobe overflow (with inverse mass-ratios and rapid spin up), collisions, merging, rejuventation and massive blue stragglers, black-hole formation, runaways and gamma-ray bursts. Also, one wonders whether the fact that a massive star is in a binary affects its parameters compared to its isolated equivalent. These proceedings deal with all of these phenomena, plus binary statistics and determination of general physical properties of massive stars, that would not be possible with their single cousins. The 77 articles published in these proceedings, all based on oral talks, vary from broad revies to the lates developments in the field. About a third of the time was spent in open discussion of all participants, both for ~5 minutes after each talk and 8 half-hour long general dialogues, all audio-recorded, transcribed and only moderately edited to yield a real flavour of the meeting. The candid information in these discussions is sometimes more revealing than the article(s) that preceded them and also provide entertaining reading. The book is suitable for researchers and graduate students interested in stellar astrophysics and in various physical processes involved when