Baby Skyrmions stabilized by vector mesons
Foster, David; Sutcliffe, Paul
2009-06-15
Recent results suggest that multi-Skyrmions stabilized by {omega} mesons have very similar properties to those stabilized by the Skyrme term. In this paper we present the results of a detailed numerical investigation of a (2+1)-dimensional analogue of this situation. Namely, we compute solitons in an O(3) {sigma} model coupled to a massive vector meson and compare the results to baby Skyrmions, which are solitons in an O(3) {sigma} model including a Skyrme term. We find that multisolitons in the vector meson model are surprisingly similar to those in the baby Skyrme model, and we explain this correspondence using a simple derivative expansion.
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.
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.
Existence of the critical endpoint in the vector meson extended linear sigma model
NASA Astrophysics Data System (ADS)
Kovács, P.; Szép, Zs.; Wolf, Gy.
2016-06-01
The chiral phase transition of the strongly interacting matter is investigated at nonzero temperature and baryon chemical potential (μB) within an extended (2 +1 ) flavor Polyakov constituent quark-meson model that incorporates the effect of the vector and axial vector mesons. The effect of the fermionic vacuum and thermal fluctuations computed from the grand potential of the model is taken into account in the curvature masses of the scalar and pseudoscalar mesons. The parameters of the model are determined by comparing masses and tree-level decay widths with experimental values in a χ2-minimization procedure that selects between various possible assignments of scalar nonet states to physical particles. We examine the restoration of the chiral symmetry by monitoring the temperature evolution of condensates and the chiral partners' masses and of the mixing angles for the pseudoscalar η -η' and the corresponding scalar complex. We calculate the pressure and various thermodynamical observables derived from it and compare them to the continuum extrapolated lattice results of the Wuppertal-Budapest collaboration. We study the T -μB phase diagram of the model and find that a critical endpoint exists for parameters of the model, which give acceptable values of χ2.
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.
Lepton flavor violating decays of vector mesons
Gutsche, Thomas; Lyubovitskij, Valery E.; Helo, Juan C.; Kovalenko, Sergey
2010-02-01
We estimate the rates of lepton flavor violating decays of the vector mesons {rho}, {omega}, and {phi}{yields}e{mu}. The theoretical tools are based on an effective Lagrangian approach without referring to any specific realization of the physics beyond the standard model responsible for lepton flavor violation (Le{sub f}). The effective lepton-vector meson couplings are extracted from the existing experimental bounds on the nuclear {mu}{sup -}-e{sup -} conversion. In particular, we derive an upper limit for the Le{sub f} branching ratio Br({phi}{yields}e{mu}){<=}1.3x10{sup -21} which is much more stringent than the recent experimental result Br({phi}{yields}e{mu})<2x10{sup -6} presented by the SND Collaboration. Very tiny limits on Le{sub f} decays of vector mesons derived in this paper make direct experimental observation of these processes unrealistic.
Vacuum phenomenology of the chiral partner of the nucleon in a linear sigma model with vector mesons
Gallas, Susanna; Giacosa, Francesco; Rischke, Dirk H.
2010-07-01
We investigate a linear sigma model with global chiral U(2){sub R}xU(2){sub L} symmetry. The mesonic degrees of freedom are the standard scalar and pseudoscalar mesons and the vector and axial-vector mesons. The baryonic degrees of freedom are the nucleon, N, and its chiral partner, N*, which is usually identified with N(1535). The chiral partner is incorporated in the so-called mirror assignment, where the nucleon mass is not solely generated by the chiral condensate but also by a chirally invariant mass term, m{sub 0}. The presence of (axial-) vector fields modifies the expressions for the axial-coupling constants of the nucleon, g{sub A}{sup N}, and its partner, g{sub A}{sup N*}. Using experimental data for the decays N*{yields}N{pi} and a{sub 1{yields}{pi}{gamma}}, as well as lattice results for g{sub A}{sup N}* we infer that in our model m{sub 0{approx}}500 MeV, i.e., an appreciable amount of the nucleon mass originates from sources other than the chiral condensate. We test our model by evaluating the decay N*{yields}N{eta} and the s-wave nucleon-pion scattering lengths a{sub 0}{sup ({+-})}.
Skyrmions and vector mesons: a symmetric approach
Caldi, D.G.
1984-01-01
We propose an extension of the effective, low-energy chiral Lagrangian known as the Skyrme model, to one formulated by a non-linear sigma model generalized to include vector mesons in a symmetric way. The model is based on chiral SU(6) x SU(6) symmetry spontaneously broken to static SU(6). The rho and other vector mesons are dormant Goldstone bosons since they are in the same SU(6) multiplet as the pion and other pseudoscalars. Hence the manifold of our generalized non-linear sigma model is the coset space (SU(6) x SU(6))/Su(6). Relativistic effects, via a spin-dependent mass term, break the static SU(6) and give the vectors a mass. The model can then be fully relativistic and covariant. The lowest-lying Skyrmion in this model is the whole baryonic 56-plet, which splits into the octet and decuplet in the presence of relativistic SU(6)-breaking. Due to the built-in SU(6) and the presence of vector mesons, the model is expected to have better phenomenological results, as well as providing a conceptually more unified picture of mesons and baryons. 29 references.
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
QCD description of backward vector meson hard electroproduction
NASA Astrophysics Data System (ADS)
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2015-05-01
We consider backward vector meson exclusive electroproduction off nucleons in the framework of collinear QCD factorization. Nucleon to vector meson transition distribution amplitudes (TDAs) arise as building blocks for the corresponding factorized amplitudes. In the near-backward kinematics, the suggested factorization mechanism results in the dominance of the transverse cross section of vector meson production (σT≫σL ) and in the characteristic 1 /Q8-scaling behavior of the cross section. We evaluate nucleon to vector meson TDAs in the cross-channel nucleon exchange model and present estimates of the differential cross section for backward ρ0, ω and ϕ meson production off protons. The resulting cross sections are shown to be measurable in the forthcoming JLab@12 GeV experiments.
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.
Quantum Electrodynamics for Vector Mesons
Djukanovic, Dalibor; Schindler, Matthias R.; Scherer, Stefan; Gegelia, Jambul
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}{sup +} 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{sub {rho}}{sub {sup 0}}-M{sub {rho}}{sub {sup {+-}}}{approx}1 MeV at tree order.
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.
NASA Astrophysics Data System (ADS)
Mishra, Amruta; Misra, S. P.; Greiner, W.
2015-07-01
We calculate the decay widths of the charmonium states, J/ψ, ψ(3686) and ψ(3770), to D\\bar {D} pairs, as well as the decay width of D* → Dπ, in isospin asymmetric strange hadronic matter, using a field theoretical model for composite hadrons with quark constituents. For this purpose, we use the quark-antiquark pair creation term of the free Dirac Hamiltonian written in terms of the constituent quark field operators, and use explicit charmonium, D, \\bar {D}, D* and π states to evaluate the matrix elements for the charmonium as well as D* decay amplitudes. The medium modifications of the partial decay widths of charmonium to D\\bar {D} pair, arising from the mass modifications of the D(\\bar {D}) and the charmonium states calculated in a chiral effective model, are also included. The results of the present investigations are then compared with the decay widths computed earlier, in a model using light quark pair creation in 3P0 state. As in 3P0 model, the decay amplitude in the present model is multiplied with a strength parameter for the light quark pair creation, which is fitted from the observed vacuum decay width. The effects of the isospin asymmetry, the strangeness fraction of the hadronic matter on the masses of the charmonium states and D(\\bar {D}) mesons and hence on the decay widths, have also been studied. The isospin asymmetry effect is observed to be dominant for high densities, leading to appreciable difference in the decay channels of the charmonium to D+ D- and D0 \\bar {D0} pairs. The decay width of D* → Dπ in the hadronic matter has also been calculated within the composite quark model in the present work, accounting for the medium modifications of the D and D* masses. The density modifications of the charmonium states and D(D*) mesons, which are observed to be appreciable at high densities, will be of relevance in the compressed baryonic matter (CBM) experiments at the future facility of FAIR, GSI, where charmed hadrons will be produced
Mssm Predictions on Lepton Flavor Violation Decays of Vector Mesons
NASA Astrophysics Data System (ADS)
Yang, Jing; Sun, Ke-Sheng
2012-12-01
In the minimal supersymmetric extension of the Standard Model (MSSM) the interactions between the SUSY particles and the Standard Model (SM) particles can contribute to the lepton flavor violation (LFV) decays of vector mesons at loop level. Taking the constraint on the lightest Higgs mass around 126 GeV, we study these decays by a scan over the parameter space which gives the predictions on μ-e conversion and τ→μγ satisfying the experimental bounds. The branching ratios of the vector mesons decays into eμ are strongly suppressed. However, the branching ratios of the heavy flavor mesons decays into τμ can reach the experimental sensitivity in near future. Therefore, the experimental signals of these decays may serve as a probe of the MSSM.
Nuclear photoproduction of vector mesons within a Monte Carlo approach
NASA Astrophysics Data System (ADS)
González, I.; Guzmán, F.; Deppman, A.
2014-05-01
We present recent improvements in the crisp code for nuclear reaction simulation. The photoproduction of vector mesons was included in the code, which can evaluate also final state interaction of these mesons with the nucleus. Effects such as shadowing, subthreshold production, and Pauli blocking can be observed. The model is described in detail and some important quantities, such as cross section and nuclear transparency, are calculated as examples of the potential of our code.
Exclusive vector meson production at HERMES
NASA Astrophysics Data System (ADS)
Movsisyan, Aram
2014-06-01
Exclusive electroproduction of vector mesons has been measured on hydrogen and deuterium targets at HERMES using the 27.6 GeV electron/positron beam of HERA. From this process, more information can be obtained about generalized parton distributions (GPDs), which provide a unified description of the structure of hadrons embedding longitudinal-momentum distributions (ordinary PDFs) and transverse-position information (form factors). The study of the azimuthal distribution of the decay products via spin-density matrix elements provide constraints on helicity-amplitudes used to describe exclusive vector-meson production. Recent results from the HERMES experiment on the production of rho, omega and phi mesons will be presented.
NASA Astrophysics Data System (ADS)
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2014-02-01
Although the meson decay amplitude described by a two-point function may be regarded as one of the simplest possible physical observables, it is interesting that this apparently simple amplitude bears abundant fundamental information on QCD vacuum dynamics and chiral symmetry. The light-front zero-mode issue of the vector meson decay constant fV is in this respect highly nontrivial and deserves careful analysis. We discuss the zero-mode issue in the light-front quark model (LFQM) prediction of fV from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable, manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible, realistic light-front quark model and present a self-consistent covariant description of fV, analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality.
Electromagnetic production of vector mesons at low energies
Oh, Y.; Titov, A. I.; Lee, T.-S. H.
2000-05-17
The authors have investigated exclusive photoproduction of light vector mesons ({omega}, {rho} and {phi}) on the nucleon at low energies. In order to explore the questions concerning the so-called missing nucleon resonances, they first establish the predictions from a model based on the Pomeron and meson exchange mechanisms. They have also explored the contributions due to the mechanisms involving s- and u-channel intermediate nucleon state. Some discrepancies found at the energies near threshold and large scattering angles suggest a possibility of using this reaction to identify the nucleon resonances.
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.
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
Production of polarized vector mesons off nuclei
Kopeliovich, B. Z.; Nemchik, J.; Schmidt, Ivan
2007-08-15
Using the light-cone QCD dipole formalism we investigate manifestations of color transparency (CT) and coherence length (CL) effects in electroproduction of longitudinally (L) and transversally (T) polarized vector mesons. Motivated by forthcoming data from the HERMES experiment we predict both the A and Q{sup 2} dependence of the L/T ratios for {rho}{sup 0} mesons produced coherently and incoherently off nuclei. For an incoherent reaction the CT and CL effects add up and result in a monotonic A dependence of the L/T ratio at different values of Q{sup 2}. In contrast, for a coherent process the contraction of the CL with Q{sup 2} causes an effect opposite to that of CT and we expect quite a nontrivial A dependence.
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.
Polarization analysis of vector-meson production in pion-nucleon interactions
NASA Astrophysics Data System (ADS)
Arash, Firooz; Habibi, Mohammad F.
1993-07-01
In view of the growing (though still incomplete) set of data on vector-meson production in pion-nucleon interactions, the polarization structure of this reaction is presented, together with polarization tests of one-particle-exchange processes in the s and t channels, as well as polarization tests for the Skyrmion model. The amplitude-observable relations are exhibited in the helicity, transversity, and planar-transverse frames. The desirable direction of future experimental programs is also outlined.
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.; Spiering, D.
2016-07-01
In this paper, we study leading neutron production in photon-hadron interactions that take place in p p and p A collisions at large impact parameters. Using a model that describes the recent leading neutron data at HERA, we consider exclusive vector meson production in association with a leading neutron in p p /p A collisions at RHIC and LHC energies. The total cross sections and rapidity distributions of ρ , ϕ , and J /Ψ produced together with a leading neutron are computed. Our results indicate that the study of these processes is feasible and that it can be used to improve the understanding of leading neutron processes and of exclusive vector meson production.
Electroproduction of the {phi}(1020) Vector Meson at 4 GeV
Konstantin Loukachine
2000-02-01
We studied the reaction ep {yields} e{prime}p{prime}{phi} with a 4.2 GeV incident electron beam in the region of the electroproduction variables Q{sup 2} from 0.7 to 2.2 GeV{sup 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{sup 2} and {Delta}{tau} in {phi} vector meson production. We find that the width of the forward {phi}-meson diffraction peak increases rapidly as the interaction time decreases below c{Delta}{tau} of 1 fm. Within a simple optical model framework, the data show that {phi} meson has a smaller size than the {rho}. The measured {phi} cross-section dependence on Q{sup 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 {phi} {yields} K{sup +} K{sup -}, assuming the s-channel helicity conservation, we extracted the longitudinal-to-transverse cross-section ratio, R, and Vector Meson Dominance scaling parameter, {xi}{sup 2}, which are consistent with the previous measurements and the model expectations.
Heavy vector and axial-vector mesons in hot and dense asymmetric strange hadronic matter
NASA Astrophysics Data System (ADS)
Kumar, Arvind; Chhabra, Rahul
2015-09-01
We calculate the effects of finite density and temperature of isospin asymmetric strange hadronic matter, for different strangeness fractions, on the in-medium properties of vector (D*,Ds*,B*,Bs*) and axial-vector (D1,D1 s,B1,B1 s) mesons, using the chiral hadronic SU(3) model and QCD sum rules. We focus on the evaluation of in-medium mass-shift and shift in decay constant of above vector and axial-vector mesons. In the quantum chromodynamics sum rule approach, the properties, e.g., the masses and decay constants of vector and axial-vector mesons are written in terms of quark and gluon condensates. These quark and gluon condensates are evaluated in the present work within the chiral SU(3) model, through the medium modification of scalar-isoscalar fields σ and ζ , the scalar-isovector field δ , and the scalar dilaton field χ , in the strange hadronic medium which includes both nucleons as well as hyperons. As we shall see in detail, the masses and decay constants of heavy vector and axial-vector mesons are affected significantly from isospin asymmetry and the strangeness fraction of the medium, and these modifications may influence the experimental observables produced in heavy-ion collision experiments. The results of present investigations of in-medium properties of vector and axial-vector mesons at finite density and temperature of strange hadronic medium may be helpful for understanding the experimental data from heavy-ion collision experiments in particular for the compressed baryonic matter (CBM) experiment of the FAIR facility at GSI, Germany.
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.
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.
Search for medium effects on light vector mesons
Djalali, C; Nasseripour, R; Weygand, D P; Wood, M H
2007-02-01
The photoproduction of vector mesons on various nuclei has been studied using the Cebaf Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. The rho, omega, and phi mesons are observed via their decay to e^{+}e^{₋}. The rho spectral function is extracted from the data on carbon, iron, and titanium. We observe no effects on the mass of the rho meson, some widening in titanium and iron is observed consistent with standard collisional broadening.
Strong coupling constants of decuplet baryons with vector mesons
Aliev, T. M.; Savci, M.; Azizi, K.
2010-11-01
We provide a comprehensive study of strong coupling constants of decuplet baryons with light nonet vector mesons in the framework of light cone QCD sum rules. Using the symmetry arguments, we argue that all coupling constants entering the calculations can be expressed in terms of only one invariant function even if the SU(3){sub f} symmetry breaking effects are taken into account. We estimate the order of SU(3){sub f} symmetry violations, which are automatically considered by the employed approach.
Medium Modification of the Light Vector Mesons in Nuclei
Nasseripour, Rakhsha; Djalali, Chaden; Wood, Michael; Weygand, Dennis
2008-11-01
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?. 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 nuc
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.
New Insights on Vector Mesons:. a Dialog Between fTV and fV
NASA Astrophysics Data System (ADS)
Catà, Oscar
We examine the high energy behavior of the two-point correlators
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.
Massive mesons in Weyl-Dirac theory
NASA Astrophysics Data System (ADS)
Mirabotalebi, S.; Ahmadi, F.; Salehi, H.
2008-01-01
In order to study the mass generation of the vector fields in the framework of a conformal invariant gravitational model, the Weyl-Dirac theory is considered. The mass of the Weyl’s meson fields plays a principal role in this theory, it connects basically the conformal and gauge symmetries. We estimate this mass by using the large-scale characteristics of the observed universe. To do this we firstly specify a preferred conformal frame as a cosmological frame, then in this frame, we introduce an exact possible solution of the theory. We also study the dynamical effect of the massive vector meson fields on the trajectories of an elementary particle. We show that a local change of the cosmological frame leads to a Hamilton-Jacobi equation describing a particle with an adjustable mass. The dynamical effect of the massive vector meson field presents itself in the form of a correction term for the mass of the particle.
PQChPT with Staggered Sea and Valence Ginsparg-Wilson Quarks: Vector Meson Masses
Hovhannes R. Grigoryan; Anthony W. Thomas
2005-09-16
We consider partially quenched, mixed chiral perturbation theory with staggered sea and Ginsparg-Wilson valence quarks in order to extract a chiral-continuum extrapolation expression for the vector meson mass up to order O(a{sup 2}), at one-loop level. Based on general principles, we accomplish the task without explicitly constructing a sophisticated, heavy vector meson chiral Lagrangian.
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.
Self-consistent descriptions of vector mesons in hot matter reexamined
Riek, Felix; Knoll, Joern
2010-08-15
Technical concepts are presented that improve the self-consistent treatment of vector mesons in a hot and dense medium. First applications concern an interacting gas of pions and {rho} mesons. As an extension of earlier studies, we thereby include random-phase-approximation-type vertex corrections and further use dispersion relations to calculate the real part of the vector-meson self-energy. An improved projection method preserves the four transversality of the vector-meson polarization tensor throughout the self-consistent calculations, thereby keeping the scheme void of kinematical singularities.
The impact of vector mesons polarization on meson-nucleon interaction
NASA Astrophysics Data System (ADS)
Gevorkyan, Sergey
2016-02-01
Production of unstable particles off nuclei allows to determine the total cross section of the unstable particle interaction with nucleons. The interaction of vector mesons V(ρ, ω, ϕ) with nucleons are defined by a set of amplitudes corresponding to the transverse polarization of the vector meson (helicity λ = ±1) meson or longitudinal one (λ = 0). Whereas the total cross section for the interaction of the transversely polarized vector meson with nucleon σ T = σ(VTN) can be extract from the coherent photoproduction, measurements of vector meson interaction with nucleon σL= σ(VLN). As a good tool for such investigation we proposed the photoproduction of ω mesons on the set of nuclei in the incoherent region. Such experiment can be done using the feasibility of the new experiment GlueX at Jefferson Lab, designed to study the photoproduction of mesons in a large beam energy range up to 12 GeV.
Realizing vector meson dominance with transverse charge densities
NASA Astrophysics Data System (ADS)
Miller, G. A.; Strikman, M.; Weiss, C.
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 t≲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˜0.5-1.5fm in the isovector density are maximally sensitive to the ρ meson region, with only a ˜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 ω are comparatively more important. The dispersion approach suggests that the positive transverse charge density in the neutron at b˜1fm, found previously in a Fourier analysis of spacelike form factor data, could serve as a sensitive test of the the isoscalar strength in the ˜1GeV mass region. In terms of partonic structure, the transverse densities in the vector meson region b˜1fm support an approximate mean-field picture of the motion of valence quarks in the nucleon.
High-energy photoproduction of rho and phi vector mesons
Callahan, P.H.
1983-01-01
We have studied the photoproduction of rho and phi vector mesons from hydrogen in the Fermilab broad band neutral beam. Forward going two particle final states were detected in a multiparticle spectrometer consisting of two analyzing magnets, a multiwire-proportional-chamber tracking system and a particle identification system. Recoil protons and target fragments were observed in a recoil detector which surrounded the target. The total elastic cross-sections were measured to be independent of energy at the 10% level from 35 to 225 GeV at 10.6 ..mu..b for the rho and from 35 to 165 GeV at 0.64 ..mu..b for the phi. The elastic differential cross-sections were also measured. Approximately 20% of the diffractive rho and phi events were found to be inelastic from an analysis of the recoil detector. The t-dependence of the fraction of diffractive events which are inelastic for both the phi and the psi are consistent with a universal function determined from the rho data.
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.
NASA Astrophysics Data System (ADS)
Gonçalves, V. P.; Martins, L. A. S.; Sauter, W. K.
2016-02-01
The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken- x variable and low values of the hard scale Q^2. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon-hadron and hadron-hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrisations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalisation of the γ h cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small x and low Q^2.
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.
NASA Astrophysics Data System (ADS)
Islam, Chowdhury Aminul; Majumder, Sarbani; Mustafa, Munshi G.
2015-11-01
In this work we have reexplored our earlier study on the vector meson spectral function and its spectral property in the form of dilepton rate in a two-flavor Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model in the presence of a strong entanglement between the chiral and Polyakov loop dynamics. The entanglement considered here is generated through the four-quark scalar-type interaction in which the coupling strength depends on the Polyakov loop and runs with temperature and chemical potential. The entanglement effect is also considered for the four-quark vector-type interaction in the same manner. We observe that the entanglement effect relatively enhances the color degrees of freedom due to the running of both the scalar and vector couplings. This modifies the vector meson spectral function and, thus, the spectral property such as the dilepton production rate in the low invariant mass also gets modified.
Exclusive electroproduction of vector mesons in lepton nucleon scattering at the HERMES experiment
NASA Astrophysics Data System (ADS)
Augustyniak, W.
2013-12-01
Exclusive electroproduction of vector mesons has been measured on hydrogen and deuterium targets at HERMES using the 27.6 GeV electron/positron beam of HERA. From this process, information can be obtained about generalized parton distributions (GPDs), which provide a unified description of the structure of hadrons embedding longitudinal-momentum distributions (ordinary PDFs) and transverse-position information (form factors). The study of the azimuthal distribution of the decay products via spin-density matrix elements provide constraints on helicity-amplitudes used to describe exclusive vector-meson production. Recent results from the HERMES experiment on the production of ρ0, ω and ϕ vector mesons will be presented.
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.
NASA Astrophysics Data System (ADS)
Adamuscin, Cyril; Bartos, Erik; Dubnicka, Stanislav; Dubnickova, Anna Zuzana
2016-05-01
It is demonstrated how the use of all existing experimental information on electric and magnetic nucleon form factors, described by the unitary and analytic (U&A) nucleon electromagnetic structure model in spacelike and timelike regions simultaneously, can provide numerical values of fF,fD,andfS coupling constants in SU(3) invariant interaction Lagrangian of the vector-meson nonet with 1 /2+ octet baryons. The latter, together with universal vector-meson coupling constants fV, play an essential role in a prediction of 1 /2+ octet hyperon electromagnetic form factor behaviors.
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.
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.
The In-medium Mass and Widths of Light Vector Mesons
Djalali, C.; Paolone, M.; Weygand, D.; Wood, M. H.; Nasseripour, R.
2011-05-23
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 {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.
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.
Double vector meson production in photon-hadron interactions at hadronic colliders
NASA Astrophysics Data System (ADS)
Gonçalves, V. P.; Moreira, B. D.; Navarra, F. S.
2016-07-01
In this paper we analyze the double vector meson production in photon-hadron (γ h) interactions at pp / pA / AA collisions and present predictions for the ρ ρ , J/Ψ J/Ψ , and ρ J/Ψ production considering the double scattering mechanism. We estimate the total cross sections and rapidity distributions at LHC energies and compare our results with the predictions for the double vector meson production in γ γ interactions at hadronic colliders. We present predictions for the different rapidity ranges probed by the ALICE, ATLAS, CMS, and LHCb Collaborations. Our results demonstrate that the ρ ρ and J/Ψ J/Ψ production in PbPb collisions is dominated by the double-scattering mechanism, while the two-photon mechanism dominates in pp collisions. Moreover, our results indicate that the analysis of the ρ J/Ψ production at LHC can be useful to constrain the double-scattering mechanism.
NASA Astrophysics Data System (ADS)
Roy, P.
2016-05-01
Baryon spectroscopy is an indispensable tool for investigating the nature of strong interaction within baryons. The study of vector-meson photoproduction is expected to improve our understanding of the properties of known baryon resonances and also immensely aid in discovering new higher-mass resonances. Polarization observables, in addition to unpolarized cross sections, are required to identify the contributing resonances to these reactions with minimal ambiguities. Preliminary results from the FROST experiment on beam-polarization observables in γ →p →→p ω as well as γ →p →→p π+π- using a linearly-polarized beam and a transversely-polarized FROzen Spin butanol Target will be presented. The latter reaction will provide important information on N* to (broad) ρ vector-meson decay modes, which is difficult to extract directly from the data.
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.
Medium modifications of light vector mesons in photoproduction reactions at Jlab
Djalali, Chaden; Wood, Michael; Nasseripour, Rakhsha; Weygand, Dennis
2008-10-01
DOI: http://dx.doi.org/10.1088/0954-3899/35/10/104035
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. The light vector mesons (rho, omega, and phi) were photo-produced on H-2, C, Ti, Fe, and Pb targets at the Thomas Jefferson National Laboratory using the CEBAF Large Acceptance Spectrometer (CLAS). The data were taken with a beam of tagged photons with energies up to 4 GeV . The properties of the rho vector meson at normal nuclear densities and zero temperature,were investigated via their rare leptonic decay to e+e?. This decay channel is preferred over hadronic modes in order to eliminate final state interactions in the nuclear matter. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing techn
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. PMID:25768758
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.
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.
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. PMID:18999588
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.
NASA Astrophysics Data System (ADS)
Terschlüsen, Carla; Leupold, Stefan
2016-07-01
Starting from a relativistic Lagrangian for pseudoscalar Goldstone bosons and vector mesons in the antisymmetric tensor representation, a one-loop calculation is performed to pin down the divergent structures that appear for the effective low-energy action at chiral orders Q2 and Q4 . The corresponding renormalization-scale dependencies of all low-energy constants up to chiral order Q4 are determined. Calculations are carried out for both the pseudoscalar octet and the pseudoscalar nonet, the latter in the framework of chiral perturbation theory in the limit of a large number of colors.
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
NASA Astrophysics Data System (ADS)
Guzey, V.; Kryshen, E.; Zhalov, M.
2016-05-01
We make predictions for the cross sections of coherent photoproduction of ρ ,ϕ ,J /ψ ,ψ (2 S ) , and Υ (1 S ) mesons in Pb-Pb ultraperipheral collisions (UPCs) at √{sN N}=5.02 TeV in the kinematics of run 2 at the Large Hadron Collider extending the approaches successfully describing the available Pb-Pb UPC data at √{sN N}=2.76 TeV . Our results illustrate the important roles of hadronic fluctuations of the photon and inelastic nuclear shadowing in photoproduction of light vector mesons on nuclei and the large leading twist nuclear gluon shadowing in photoproduction of quarkonia on nuclei. We show that the ratio of ψ (2 S ) and J /ψ photoproduction cross sections in Pb-Pb UPCs is largely determined by the ratio of these cross sections on the proton. We also argue that UPCs with electromagnetic excitations of the colliding ions followed by the forward neutron emission allows one to significantly increase the range of photon energies accessed in vector meson photoproduction on nuclei.
Simulations for an experiment to probe the in-medium properties of photoproduced vector mesons
Clarisse Tur
2003-04-01
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{sup +}e{sup -} photoproduction in the incoherent region. The reaction of interest to g7 is {gamma}A {yields} VA{prime} {yields} e{sup +}e{sup -}A{prime} where V could be a {rho} an {omega} or a {phi} 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 {rho} {yields} e{sup +}e{sup -}, a very intense beam had to be sent on the target containing high-Z material. Thus, a huge background, formed of low energy e{sup +}e{sup -} 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
Solid modeling on a massively parallel processor
Strip, D. ); Karasick, M. )
1992-01-01
Solid modeling underlies many technologies that are key to modern manufacturing. These range from computer-aided design systems to robot simulators, from finite element analysis to integrated circuit process modeling. The accuracy, and hence the utility, of these models is often constrained by the amount of computer time required to perform the desired operations. This paper presents a family of algorithms for solid modeling operations using the Connection Machine, a massively parallel SIMD processor. The authors describe a data structure for representing solid models and algorithms that use the representation to implement efficiently a variety of solid modeling operations. The authors give a sketch of the algorithm for intersecting solids and present computational experience using these algorithms. The data structure and algorithms are contrasted with those of serial architectures, and execution times are compared.
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
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.
Goncalves, V. P.; Machado, M. V. T.
2011-07-15
In this Rapid Communication we update our predictions for the photoproduction of vector mesons in coherent pp and AA collisions at Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies using the color dipole approach and the Color Glass Condensate formalism. In particular, we present our predictions for the first run of the LHC at half energy and for the rapidity dependence of the ratio between the J/{Psi} and {rho} cross sections at RHIC energies.
NASA Astrophysics Data System (ADS)
Abelev, B. I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, B. D.; Arkhipkin, D.; Averichev, G. S.; Bai, Y.; Balewski, J.; Barannikova, O.; Barnby, L. S.; Baudot, J.; Baumgart, S.; Beavis, D. R.; Bellwied, R.; Benedosso, F.; Betts, R. R.; Bhardwaj, S.; Bhasin, A.; Bhati, A. K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Biritz, B.; Bland, L. C.; Bombara, M.; Bonner, B. E.; Botje, M.; Bouchet, J.; Braidot, E.; Brandin, A. V.; Bueltmann, S.; Burton, T. P.; Bystersky, M.; Cai, X. Z.; Caines, H.; Sánchez, M. Calderón De La Barca; Callner, J.; Catu, O.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chajecki, Z.; Chaloupka, P.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, J. Y.; Cheng, J.; Cherney, M.; Chikanian, A.; Choi, K. E.; Christie, W.; Chung, S. U.; Clarke, R. F.; Codrington, M. J. M.; Coffin, J. P.; Cormier, T. M.; Cosentino, M. R.; Cramer, J. G.; Crawford, H. J.; Das, D.; Dash, S.; Daugherity, M.; Moura, M. M. De; Dedovich, T. G.; Dephillips, M.; Derevschikov, A. A.; Souza, R. Derradi De; Didenko, L.; Dietel, T.; Djawotho, P.; Dogra, S. M.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, F.; Dunlop, J. C.; Mazumdar, M. R. Dutta; Edwards, W. R.; Efimov, L. G.; Elhalhuli, E.; Elnimr, M.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Eun, L.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Feng, A.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Gagliardi, C. A.; Gaillard, L.; Gangadharan, D. R.; Ganti, M. S.; Garcia-Solis, E.; Ghazikhanian, V.; Ghosh, P.; Gorbunov, Y. N.; Gordon, A.; Grebenyuk, O.; Grosnick, D.; Grube, B.; Guertin, S. M.; Guimaraes, K. S. F. F.; Gupta, A.; Gupta, N.; Guryn, W.; Haag, B.; Hallman, T. J.; Hamed, A.; Harris, J. W.; He, W.; Heinz, M.; Heppelmann, S.; Hippolyte, B.; Hirsch, A.; Hoffman, A. M.; Hoffmann, G. W.; Hofman, D. J.; Hollis, R. S.; Huang, H. Z.; Hughes, E. W.; Humanic, T. J.; Igo, G.; Iordanova, A.; Jacobs, P.; Jacobs, W. W.; Jakl, P.; Jin, F.; Jones, P. G.; Judd, E. G.; Kabana, S.; Kajimoto, K.; Kang, K.; Kapitan, J.; Kaplan, M.; Keane, D.; Kechechyan, A.; Kettler, D.; Khodyrev, V. Yu.; Kiryluk, J.; Kisiel, A.; Klein, S. R.; Knospe, A. G.; Kocoloski, A.; Koetke, D. D.; Kollegger, T.; Kopytine, M.; Kotchenda, L.; Kouchpil, V.; Kravtsov, P.; Kravtsov, V. I.; Krueger, K.; Kuhn, C.; Kumar, A.; Kumar, L.; Kurnadi, P.; Lamont, M. A. C.; Landgraf, J. M.; Lange, S.; Lapointe, S.; Laue, F.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, C.-H.; Levine, M. J.; Li, C.; Li, Y.; Lin, G.; Lin, X.; Lindenbaum, S. J.; Lisa, M. A.; Liu, F.; Liu, H.; Liu, J.; Liu, L.; Ljubicic, T.; Llope, W. J.; Longacre, R. S.; Love, W. A.; Lu, Y.; Ludlam, T.; Lynn, D.; Ma, G. L.; Ma, J. G.; Ma, Y. G.; Mahapatra, D. P.; Majka, R.; Mangotra, L. K.; Manweiler, R.; Margetis, S.; Markert, C.; Matis, H. S.; Matulenko, Yu. A.; McShane, T. S.; Meschanin, A.; Millane, J.; Miller, M. L.; Minaev, N. G.; Mioduszewski, S.; Mischke, A.; Mitchell, J.; Mohanty, B.; Morozov, D. A.; Munhoz, M. G.; Nandi, B. K.; Nattrass, C.; Nayak, T. K.; Nelson, J. M.; Nepali, C.; Netrakanti, P. K.; Ng, M. J.; Nogach, L. V.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Okada, H.; Okorokov, V.; Olson, D.; Pachr, M.; Pal, S. K.; Panebratsev, Y.; Pawlak, T.; Peitzmann, T.; Perevoztchikov, V.; Perkins, C.; Peryt, W.; Phatak, S. C.; Planinic, M.; Pluta, J.; Poljak, N.; Porile, N.; Poskanzer, A. M.; Potekhin, M.; Potukuchi, B. V. K. S.; Prindle, D.; Pruneau, C.; Pruthi, N. K.; Putschke, J.; Qattan, I. A.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Ridiger, A.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Rose, A.; Roy, C.; Ruan, L.; Russcher, M. J.; Rykov, V.; Sahoo, R.; Sakrejda, I.; Sakuma, T.; Salur, S.; Sandweiss, J.; Sarsour, M.; Schambach, J.; Scharenberg, R. P.; Schmitz, N.; Seger, J.; Selyuzhenkov, I.; Seyboth, P.; Shabetai, A.; Shahaliev, E.; Shao, M.; Sharma, M.; Shi, S. S.; Shi, X.-H.; Sichtermann, E. P.; Simon, F.; Singaraju, R. N.; Skoby, M. J.; Smirnov, N.; Snellings, R.; Sorensen, P.; Sowinski, J.; Spinka, H. M.; Srivastava, B.; Stadnik, A.; Stanislaus, T. D. S.; Staszak, D.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Suarez, M. C.; Subba, N. L.; Sumbera, M.; Sun, X. M.; Sun, Z.; Surrow, B.; Symons, T. J. M.; Toledo, A. Szanto De; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thein, D.; Thomas, J. H.; Tian, J.; Timmins, A. R.; Timoshenko, S.; Tokarev, M.; Trainor, T. A.; Tram, V. N.; Trattner, A. L.; Trentalange, S.; Tribble, R. E.; Tsai, O. D.; Ulery, J.; Ullrich, T.; Underwood, D. G.; Buren, G. Van; Kolk, N. Van Der; Leeuwen, M. Van; Molen, A. M. Vander; Varma, R.; Vasconcelos, G. M. S.; Vasilevski, I. M.; Vasiliev, A. N.; Videbaek, F.; Vigdor, S. E.; Viyogi, Y. P.; Vokal, S.; Voloshin, S. A.; Wada, M.; Waggoner, W. T.; Wang, F.; Wang, G.; Wang, J. S.; Wang, Q.; Wang, X.; Wang, X. L.; Wang, Y.; Webb, J. C.; Westfall, G. D.; Whitten, C., Jr.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, J.; Wu, Y.; Xu, N.; Xu, Q. H.; Xu, Z.; Yepes, P.; Yoo, I.-K.; Yue, Q.; Zawisza, M.; Zbroszczyk, H.; Zhan, W.; Zhang, H.; Zhang, S.; Zhang, W. M.; Zhang, Y.; Zhang, Z. P.; Zhao, Y.; Zhong, C.; Zhou, J.; Zoulkarneev, R.; Zoulkarneeva, Y.; Zuo, J. X.
2008-06-01
We present the first spin alignment measurements for the K*0(892) and ϕ(1020) vector mesons produced at midrapidity with transverse momenta up to 5 GeV/c at sNN=200 GeV at RHIC. The diagonal spin-density matrix elements with respect to the reaction plane in Au+Au collisions are ρ00=0.32±0.04 (stat) ± 0.09 (syst) for the K*0 (0.8
Population Models for Massive Globular Clusters
NASA Astrophysics Data System (ADS)
Lee, Young-Wook; Joo, Seok-Joo; Han, Sang-Il; Na, Chongsam; Lim, Dongwook; Roh, Dong-Goo
2015-03-01
Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y 2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).
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. PMID:26340182
Analysis of heavy spin-3/2 baryon-heavy spin-1/2 baryon-light vector meson vertices in QCD
Aliev, T. M.; Savci, M.; Azizi, K; Zamiralov, V. S.
2011-05-01
The heavy spin-3/2 baryon-heavy spin-1/2 baryon vertices with light vector mesons are studied within the light cone QCD sum rules method. These vertices are parametrized in terms of three coupling constants. These couplings are calculated for all possible transitions. It is shown that correlation functions for these transitions are described by only one invariant function for every Lorenz structure. The obtained relations between the correlation functions of the different transitions are structure independent while explicit expressions of invariant functions depend on the Lorenz structure.
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.
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 χc1 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.; et al
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.
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.
Massive Yang-Mills model and diffractive scattering
NASA Astrophysics Data System (ADS)
Forshaw, J. R.; Papavassiliou, J.; Parrinello, C.
1999-04-01
We argue that the massive Yang-Mills model of Kunimasa and Goto, Slavnov, and Cornwall, in which massive gauge vector bosons are introduced in a gauge-invariant way without resorting to the Higgs mechanism, may be useful for studying diffractive scattering of strongly interacting particles. With this motivation, we perform in this model explicit calculations of S-matrix elements between quark states, at the tree level, one loop, and two loops, and discuss issues of renormalizability and unitarity. In particular, it is shown that the S-matrix element for quark scattering is renormalizable at one-loop order, and is only logarithmically non-renormalizable at two loops. The discrepancies in the ultraviolet regime between the one-loop predictions of this model and those of massless QCD are discussed in detail. In addition, some of the similarities and differences between the massive Yang-Mills model and theories with a Higgs mechanism are analyzed at the level of the S matrix. Finally, we briefly discuss the high-energy behavior of the leading order amplitude for quark-quark elastic scattering in the diffractive region. The above analysis sets up the stage for carrying out a systematic computation of the higher order corrections to the two-gluon exchange model of the Pomeron using massive gluons inside quantum loops.
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.
Integration of massive states as contractions of nonlinear {sigma} models
Andrianopoli, L.; Ferrara, S.; Lledo, M.A.; Macia, O.
2005-07-01
We consider the contraction of some nonlinear {sigma} models which appear in effective supergravity theories. In particular we consider the contractions of maximally symmetric spaces corresponding to N=1 and N=2 theories, as they appear in certain low energy effective supergravity actions with mass deformations. The contraction procedure is shown to describe the integrating out of massive modes in the presence of interactions, as it happens in many supergravity models after spontaneous supersymmetry breaking.
Dynamical Models for High-Energy Emission from Massive Stars
NASA Astrophysics Data System (ADS)
Owocki, Stanley %FAA(University of Delaware)
Massive stars are prominent sources of X-rays and gamma-rays detected by both targeted and survey observations from orbiting telescopes like Chandra, XMM/Newton, RXTE, and Fermi. Such high-energy emissions represent key probes of the dynamics of massive-star mass loss, and their penetration through many magnitudes of visible interstellar extinction makes them effective beacons of massive stars in distant reaches of the Galaxy, and in young, active star-forming regions. The project proposed here will develop a comprehensive theoretical framework for interpreting both surveys and targeted observations of high-energy emission from massive stars. It will build on our team's extensive experience in both theoretical models and observational analyses for three key types of emission mechanisms in the stellar wind outflows of these stars, namely: 1) Embedded Wind Shocks (EWS) arising from internal instabilities in the wind driving; 2) shocks in Colliding Wind Binary (CWB) systems; and 3) High-Mass X-ray Binaries (HMXB) systems with interaction between massive-star wind with a compact companion (neutron star or black hole). Taking advantage of commonalities in the treatment of radiative driving, hydrodynamics, shock heating and cooling, and radiation transport, we will develop radiation hydrodynamical models for the key observational signatures like energy distribution, emission line spectrum, and variability, with an emphasis on how these can be used in affiliated analyses of both surveys like the recent Chandra mapping of the Carina association, and targeted observations of galactic X-ray and gamma-ray sources associated with each of the above specific model types. The promises of new clumping-insensitive diagnostics of mass loss rates, and the connection to mass transfer and binarity, all have broad relevance for understanding the origin, evolution, and fate of massive stars, in concert with elements of NASA's Strategic Subgoal 3D. Building on our team's expertise, the
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.
A Programming Model for Massive Data Parallelism with Data Dependencies
Cui, Xiaohui; Mueller, Frank; Potok, Thomas E; Zhang, Yongpeng
2009-01-01
Accelerating processors can often be more cost and energy effective for a wide range of data-parallel computing problems than general-purpose processors. For graphics processor units (GPUs), this is particularly the case when program development is aided by environments such as NVIDIA s Compute Unified Device Architecture (CUDA), which dramatically reduces the gap between domain-specific architectures and general purpose programming. Nonetheless, general-purpose GPU (GPGPU) programming remains subject to several restrictions. Most significantly, the separation of host (CPU) and accelerator (GPU) address spaces requires explicit management of GPU memory resources, especially for massive data parallelism that well exceeds the memory capacity of GPUs. One solution to this problem is to transfer data between the GPU and host memories frequently. In this work, we investigate another approach. We run massively data-parallel applications on GPU clusters. We further propose a programming model for massive data parallelism with data dependencies for this scenario. Experience from micro benchmarks and real-world applications shows that our model provides not only ease of programming but also significant performance gains.
Models for supernova progenitors in massive binary systems
NASA Astrophysics Data System (ADS)
Yoon, Sung Chul
2014-09-01
The diversity of core-collapse supernovae is closely related to binary interactions. For example, the majority of Type Ib/c and Type IIb supernovae may occur in massive binary systems as a result of mass transfer at various evolutionary stages. I will present some evolutionary models of massive binary stars including several important physical ingredients, like tidal interactions and mass and angular momentum exchange, and discuss their implications for supernova progenitors and their populations. I will particularly emphasize that Type Ib/c supernova progenitors at their pre-supernova stage should have very different properties compared to the observed Wolf-Rayet stars, which are widely believed to represent SN Ibc progenitors, and that many observed properties of SNe Ib/c and IIb can be explained well with the binary scenario.
A Massive Black Hole in NGC 3377: 3 Integral Models
NASA Astrophysics Data System (ADS)
Richstone, D.; Gebhardt, K.; Kormendy, J.; Bender, R.; Magorrian, J.; Tremaine, S.; Faber, S.; Lauer, T.
1996-12-01
We use a Hubble Space Telescope image combined with nuclear and flanking spectra of the galaxy NGC 3377 (E5, M_V = -19.7), together with somewhat lower resolution ground--based data from Hawaii, to determine the stellar kinematics of the central region of the galaxy. Because the galaxy is apparently very flat it must be highly inclined. We model the galaxy using an axisymmetric, fully general (3-integral) orbit-based maximum entropy program, which permits a complete exploration of all possible configurations in phase space consistent with a specified mass and light distribution. We considered intrinsic E5 models at 90 deg inclination and E6 models at 71 deg . All equilibrium models with satisfactory fits to the observations contain a massive central dark point mass in the range 0.5 - 2. x 10(8) M_sun. Models without a massive black hole cannot reproduce the rapid observed rotation seen at 0. arcsec 3 from the center in the HST data. Models matching the data have approximately isotropic distribution functions. The Nuker team was supported by HST data analysis funds through grant GO-02600.01-87A and by NSERC.
Stable and unstable cosmological models in bimetric massive gravity
NASA Astrophysics Data System (ADS)
Koennig, Frank; Akrami, Yashar; Amendola, Luca; Motta, Mariele; Solomon, Adam R.
2014-12-01
Nonlinear, ghost-free massive gravity has two tensor fields; when both are dynamical, the mass of the graviton can lead to cosmic acceleration that agrees with background data, even in the absence of a cosmological constant. Here the question of the stability of linear perturbations in this bimetric theory is examined. Instabilities are presented for several classes of models, and simple criteria for the cosmological stability of massive bigravity are derived. In this way, we identify a particular self-accelerating bigravity model, infinite-branch bigravity (IBB), which exhibits both viable background evolution and stable linear perturbations. We discuss the modified gravity parameters for IBB, which do not reduce to the standard Λ CDM result at early times, and compute the combined likelihood from measured growth data and type Ia supernovae. IBB predicts a present matter density Ωm 0=0.18 and an equation of state w (z )=-0.79 +0.21 z /(1 +z ) . The growth rate of structure is well approximated at late times by f (z )≈Ωm0.47[1 +0.21 z /(1 +z )] . The implications of the linear instability for other bigravity models are discussed: the instability does not necessarily rule these models out, but rather presents interesting questions about how to extract observables from them when linear perturbation theory does not hold.
Hamiltonian approach to the lattice massive Schwinger model
Sidorov, A.V.; Zastavenko, L.G.
1996-08-01
The authors consider the limit e{sup 2}/m{sup 2} {much_lt} 1 of the lattice massive Schwinger model, i.e., the lattice massive QED in two space-time dimensions, up to lowest order in the effective coupling constant e{sup 2}/m{sup 2}. Here, m is the fermion mass parameter and e is the electron charge. They compare their lattice QED model with the analogous continuous space and lattice space models, (CSM and LSM), which do not take account of the zero momentum mode, z.m.m., of the vector potential. The difference is that (due to extra z.m.m. degree of freedom) to every eigenstate of the CSM and LSM there corresponds a family of eigenstates of the authors lattice QED with the parameter {lambda}. They restrict their consideration to small values of the parameter {lambda}. Then, the energies of the particle states of their lattice QED and LSM do coincide (in their approximation). In the infinite periodicity length limit the Hamiltonian of the authors lattice QED (as well as the Hamiltonian of the LSM) possesses two different Hilbert spaces of eigenfunctions. Thus, in this limit the authors lattice QED model (as well as LSM) describes something like two connected, but different, worlds.
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.
Massive fermion model in 3d and higher spin currents
NASA Astrophysics Data System (ADS)
Bonora, L.; Cvitan, M.; Prester, P. Dominis; de Souza, B. Lima; Smolić, I.
2016-05-01
We analyze the 3d free massive fermion theory coupled to external sources. The presence of a mass explicitly breaks parity invariance. We calculate two- and three-point functions of a gauge current and the energy momentum tensor and, for instance, obtain the well-known result that in the IR limit (but also in the UV one) we reconstruct the relevant CS action. We then couple the model to higher spin currents and explicitly work out the spin 3 case. In the UV limit we obtain an effective action which was proposed many years ago as a possible generalization of spin 3 CS action. In the IR limit we derive a different higher spin action. This analysis can evidently be generalized to higher spins. We also discuss the conservation and properties of the correlators we obtain in the intermediate steps of our derivation.
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
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.
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.
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.
NASA Astrophysics Data System (ADS)
Brandt, Bastian B.; Francis, Anthony; Jäger, Benjamin; Meyer, Harvey B.
2016-03-01
We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures T /Tc=0.156 , 0.8, 1.0, 1.25 and 1.67 with Tc≃203 MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of ≃270 MeV . Exploiting exact sum rules and applying a phenomenologically motivated Ansatz allows us to determine the spectral function ρ (ω ,T ) via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the ρ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic theory predictions and previously published phenomenological spectral functions to our lattice study.
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.
Inclusive production of strange and vector mesons in e/sup +/e/sup -/ annihilation at 29 GeV
Schellman, H.M.
1984-11-01
The Mark II detector is used to measure the inclusive production rates for K/sup 0/, K/sup + -/, rho/sup 0/, K*/sup 0/ and K*/sup + -/ in a sample of 59,489 hadronic events produced in e/sup +/e/sup -/ annihilation at 29 GeV. The inclusive rates for rho/sup 0/ and K*/sup 0/ + anti K*/sup 0/ production for momenta greater than 1 GeV/c are found to be 0.44 +- 0.04 +- 0.06 per event and 0.42 +- 0.05 +- 0.08 per event respectively. The rate for K*/sup + -/ production for momenta greater than 2 GeV/c is found to be 0.26 +- 0.05 +- 0.06 per event. The rate for K/sup 0/ + anti K/sup 0/ production over the full momentum range is found to be 1.27 + 0.03 +- 0.15 per event. The differential production rates for K/sup 0/, rho/sup 0/ and K*/sup + -/ are, in addition, determined as a function of the particle energy. The inclusive rate for K/sup + -/ is also measured for K/sup + -/ momenta less than 900 MeV/c and is found to be 1.31 +- 0.09 +- 0.19 times the K/sup 0/ + anti K/sup 0/ rate in the same momentum region. These production rates are used to determine the particle content of hadronic events at 29 GeV and are compared to the rates predicted by theoretical models of parton fragmentation. 31 references.
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.
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.
Time efficient 3-D electromagnetic modeling on massively parallel computers
Alumbaugh, D.L.; Newman, G.A.
1995-08-01
A numerical modeling algorithm has been developed to simulate the electromagnetic response of a three dimensional earth to a dipole source for frequencies ranging from 100 to 100MHz. The numerical problem is formulated in terms of a frequency domain--modified vector Helmholtz equation for the scattered electric fields. The resulting differential equation is approximated using a staggered finite difference grid which results in a linear system of equations for which the matrix is sparse and complex symmetric. The system of equations is solved using a preconditioned quasi-minimum-residual method. Dirichlet boundary conditions are employed at the edges of the mesh by setting the tangential electric fields equal to zero. At frequencies less than 1MHz, normal grid stretching is employed to mitigate unwanted reflections off the grid boundaries. For frequencies greater than this, absorbing boundary conditions must be employed by making the stretching parameters of the modified vector Helmholtz equation complex which introduces loss at the boundaries. To allow for faster calculation of realistic models, the original serial version of the code has been modified to run on a massively parallel architecture. This modification involves three distinct tasks; (1) mapping the finite difference stencil to a processor stencil which allows for the necessary information to be exchanged between processors that contain adjacent nodes in the model, (2) determining the most efficient method to input the model which is accomplished by dividing the input into ``global`` and ``local`` data and then reading the two sets in differently, and (3) deciding how to output the data which is an inherently nonparallel process.
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.
Massive quiver matrix models for massive charged particles in AdS
NASA Astrophysics Data System (ADS)
Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric
2016-01-01
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.
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.
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.
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.
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.
A model of massive neutrinos with a conserved lepton number
NASA Astrophysics Data System (ADS)
Ecker, G.; Grimus, W.; Gronau, M.
1987-01-01
We consider a left-right symmetric model with three generations and with the standard assignments of fermion and scalar fields. The left-right symmetry gives rise to a unique conserved lepton number which is of the Zel'dovich-Konopinski-Mahmoud type. The neutrino mass matrix yields one Dirac and one Majorana neutrino, both in the light and in the heavy sector. Up to small mixings with right-handed neutrinos, the left-handed ν e and ν τ combine to the light Dirac neutrino whereas ν μ is the light Majoranan neutrino. With a right-handed scale in the TeV range all light neutrino lepton masses. Phenomenological consequences of the model are discussed. charged lepton masses. Phenomenological consequences of the model are discussed.
Benchmarking ocean circulation models on massively parallel computers
Poling, D.A.
1997-08-01
General circulation models are becoming the premier theoretical tools for studying the complex structure of the global climate. GEONET was envisioned as exercising the resources developed for the nuclear weapons program to address environmental problems. The similarity of circulation models to weapons codes made them an attractive field for them to develop expertise. The author hoped to become an active player in mainline climate research through computer simulation. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The intention of this research was to establish the Laboratory in mainstream climate research in conjunction with the GEONET project.
Massively parallel determination and modeling of endonuclease substrate specificity
Thyme, Summer B.; Song, Yifan; Brunette, T. J.; Szeto, Mindy D.; Kusak, Lara; Bradley, Philip; Baker, David
2014-01-01
We describe the identification and characterization of novel homing endonucleases using genome database mining to identify putative target sites, followed by high throughput activity screening in a bacterial selection system. We characterized the substrate specificity and kinetics of these endonucleases by monitoring DNA cleavage events with deep sequencing. The endonuclease specificities revealed by these experiments can be partially recapitulated using 3D structure-based computational models. Analysis of these models together with genome sequence data provide insights into how alternative endonuclease specificities were generated during natural evolution. PMID:25389263
Coupled cluster expansions for the massive Schwinger model in the lattice Hamiltonian formalism
Fang, Xi-Yan; Schutte, D.; Wethkamp, V.; Wichmann, A.
2001-07-01
The coupled cluster method is used to study the lattice massive Schwinger model with staggered fermions. The vacuum energy and mass gaps are calculated. Good agreement is found between these calculations, the exact results in the continuum limit, and the results obtained by other approximation methods.
Lithium formation in massive AGB stars: new models
NASA Astrophysics Data System (ADS)
Mazzitelli, I.; D'Antona, F.; Ventura, P.
We present new AGB models including full coupling of nuclear evolution and turbulent transport in a diffusive scheme (Ventura et al. 1998). The novelty of these computations resides in the use of a Full Spectrum of Turbulence (FST) convective model, which allows to compute not only the appropriate convective flux distribution of billions of eddy scales (opposed to the one-eddy Mixing Length approximation), but also the self consistent average turbulent velocity and convective scale length which enter in the computation of the diffusion coefficient. Thus this new model contains a smaller number of free parameters with respect to previous MLT based computations. The coupled diffusion scheme treats independently 14 elements from ^1H to 18O, and in particular treats the production and destruction of ^7Li in the Hot Bottom Burning phase, which the FST convective models naturally achieve for masses approximately greater than 4.5M_odot (D'Antona and Mazzitelli 1996). The dependence of Lithium production on the evolving stellar mass, on the mass loss rate and on the chemical composition is presented. Predictions are given on the role of this lithium production for the galactic chemical evolution (e.g. D'Antona and Matteucci 1991), and the complete project for the computations is outlined.
Scientific development of a massively parallel ocean climate model
Semtner, A.J. Jr. ); Chervin, R.M. )
1992-01-01
A thorough examination was made of existing results from the global ocean model with high resolution. Additional experiments were chosen to help investigate the sensitivity of global ocean circulation and its associated transports of heat and salt to proposed changes in high-latitude buoyancy forcing and wind forcing.
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
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.
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)
Hadronic Scattering in AdS/QCD Models
Bayona, C. A. Ballon; Boschi-Filho, Henrique; Braga, Nelson R. F.; Torres, Marcus A. C.
2010-11-12
We review some recent works concerning the description of hadronic scattering processes using AdS/QCD models. First we consider the calculation of deep inelastic scattering structure functions for hadrons. Then we discuss the calculation of elastic form factors for vector mesons.
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.
A semi-analytical model for exploring Galilean satellites formation from a massive disk
NASA Astrophysics Data System (ADS)
Miguel, Yamila; Ida, Shigeru
2016-03-01
A better knowledge of jovian satellites' origins will bring light on the environment that surrounded Jupiter during its formation and can help us to understand the characteristics of this unique satellite system. We developed a semi-analytical model to investigate Jupiter's regular satellite formation and present the results of our population synthesis calculations. We performed simulations adopting a massive, static, low-viscosity circumplanetary disk model, in agreement with a current study of magnetorotational instability in a circum-planetary disk. We find that the high gas density leads to very rapid migration of satellitesimals due to gas drag and type II migration of satellites in a faster disk-dominated mode. A large concentration of solids, large building blocks and longer type II migration time-scales favor formation and survival of large satellites. However, bodies as massive as Ganymede and those located far away from Jupiter, such as Callisto, are difficult to form with this scenario.
NASA Astrophysics Data System (ADS)
Šoln, Josip
2009-08-01
For the electroweak interactions, the massive neutrino perturbative kinematical procedure is developed in the massive neutrino Fock space. The perturbation expansion parameter is the ratio of neutrino mass to its energy. This procedure, within the Pontecorvo-Maki-Nakagawa-Sakata (PMNS)-modified electroweak Lagrangian, calculates the cross-sections with the new neutrino energy projection operators in the massive neutrino Fock space, resulting in the dominant Lorentz invariant standard model massless flavor neutrino cross-sections. As a consequence of the kinematical relations between the massive and massless neutrinos, some of the neutrino oscillation cross-sections are Lorentz invariance violating. But all these oscillating cross-sections, some of which violate the flavor conservation, being proportional to the squares of neutrino masses are practically unobservable in the laboratory. However, these neutrino oscillating cross-sections are consistent with the original Pontecorvo neutrino oscillating transition probability expression at short time (baseline), as presented by Dvornikov. From these comparisons, by mimicking the time dependence of the original Pontecorvo neutrino oscillating transition probability, one can formulate the dimensionless neutrino intensity-probability I, by phenomenologically extrapolating the time t, or, equivalently the baseline distance L away from the collision point for the oscillating differential cross-section. For the incoming neutrino of 10 MeV in energy and neutrino masses from Fritzsch analysis with the neutrino mixing matrix of Harrison, Perkins and Scott, the baseline distances at the first two maxima of the neutrino intensity are Lsime281 and 9279 km. The intensity I at the first maximum conserves the flavor, while at the second maximum, the intensities violate the flavor, respectively, in the final and initial state. At the end some details are given as to how one should be able to verify experimentally these neutrino
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.
Light-front description for the theta dependence of meson masses in the massive Schwinger model
Burkardt, M.; Harada, K.
1998-05-01
We present a continuum formulation for {theta} vacua in the massive Schwinger model on the light front, where {theta} enters as a background electric field. The effective coupling of the external field is partially screened due to vacuum polarization processes. For small fermion masses and small {theta}, we calculate the mass of the meson and find agreement with results from bosonization. {copyright} {ital 1998} {ital The American Physical Society}
NASA Astrophysics Data System (ADS)
Amaro, J. E.; Barbaro, M. B.; Caballero, J. A.; Donnelly, T. W.; Williamson, C. F.
2011-01-01
We evaluate the quasielastic double differential neutrino cross sections obtained in a phenomenological model based on the superscaling behavior of electron scattering data. We compare our results with the recent experimental data for neutrinos of MiniBooNE and estimate the contribution of the vector meson-exchange currents in the 2p-2h sector.
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.
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.
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.
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.
The decay τ → K0K‑ντ in the extended Nambu-Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Volkov, M. K.; Pivovarov, A. A.
2016-07-01
The full and differential widths of the decay τ → K0K‑ν τ are calculated in the framework of the extended Nambu-Jona-Lasinio model.The contributions of the subprocesses with the intermediate vector mesons ρ(770) and ρ(1450) are taken into account. The obtained results are in satisfactory agreement with the experimental data.
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
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.
Leading logarithms in the massive O(N) nonlinear sigma model
NASA Astrophysics Data System (ADS)
Bijnens, Johan; Carloni, Lisa
2010-03-01
We review Büchler and Colangelo's result that leading divergences at any loop order can be calculated using only one-loop calculations and we provide an alternative proof. We then use this method to calculate the leading divergences of and thus the leading logarithmic corrections to the meson mass in the massive O(N) nonlinear sigma model to five-loop order. We also calculate the all-loop result to leading order in the large N expansion by showing that only cactus diagrams contribute and by summing these via a generalized gap equation.
Modeling X-ray emission line profiles from massive star winds - A review
NASA Astrophysics Data System (ADS)
Ignace, Richard
2016-09-01
The Chandra and XMM-Newton X-ray telescopes have led to numerous advances in the study and understanding of astrophysical X-ray sources. Particularly important has been the much increased spectral resolution of modern X-ray instrumentation. Wind-broadened emission lines have been spectroscopically resolved for many massive stars. This contribution reviews approaches to the modeling of X-ray emission line profile shapes from single stars, including smooth winds, winds with clumping, optically thin versus thick lines, and the effect of a radius-dependent photoabsorption coefficient.
Shanks, W.C. Pat, III; Koski, Randolph A.; Mosier, Dan L.; Schulz, Klaus J.; Morgan, Lisa A.; Slack, John F.; Ridley, W. Ian; Dusel-Bacon, Cynthia; Seal, Robert R., II; Piatak, Nadine M.
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.
Radiation transfer of models of massive star formation. III. The evolutionary sequence
Zhang, Yichen; Tan, Jonathan C.; Hosokawa, Takashi E-mail: jt@astro.ufl.edu
2014-06-20
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 M{sub c} , the mass surface density of the ambient clump Σ{sub cl}, and the ratio of the core's initial rotational to gravitational energy β {sub c}. Evolutionary sequences with various M{sub c} , Σ{sub cl}, and β {sub c} are constructed. We find that in a fiducial model with M{sub c} = 60 M {sub ☉}, Σ{sub cl} = 1 g cm{sup –2}, and β {sub c} = 0.02, the final mass of the protostar reaches at least ∼26 M {sub ☉}, 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 Σ{sub cl}, with higher temperatures in a higher Σ{sub cl} core, but only weakly on M{sub c} . 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 Σ{sub cl} and β {sub c} (which determines disk size) are discussed. We find that, despite scatter caused by different M{sub c} , Σ{sub cl}, β {sub c}, and inclinations, sources at a given evolutionary stage appear in similar regions of
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.
Massively parallel implementation of the Penn State/NCAR Mesoscale Model
Foster, I.; Michalakes, J.
1992-01-01
Parallel computing promises significant improvements in both the raw speed and cost performance of mesoscale atmospheric models. On distributed-memory massively parallel computers available today, the performance of a mesoscale model will exceed that of conventional supercomputers; on the teraflops machines expected within the next five years, performance will increase by several orders of magnitude. As a result, scientists will be able to consider larger problems, more complex model processes, and finer resolutions. In this paper. we report on a project at Argonne National Laboratory that will allow scientists to take advantage of parallel computing technology. This Massively Parallel Mesoscale Model (MPMM) will be functionally equivalent to the Penn State/NCAR Mesoscale Model (MM). In a prototype study, we produced a parallel version of MM4 using a static (compile-time) coarse-grained patch'' decomposition. This code achieves one-third the performance of a one-processor CRAY Y-MP on twelve Intel 1860 microprocessors. The current version of MPMM is based on all MM5 and uses a more fine-grained approach, decomposing the grid as finely as the mesh itself allows so that each horizontal grid cell is a parallel process. This will allow the code to utilize many hundreds of processors. A high-level language for expressing parallel programs is used to implement communication strearns between the processes in a way that permits dynamic remapping to the physical processors of a particular parallel computer. This facilitates load balancing, grid nesting, and coupling with graphical systems and other models.
Massively parallel implementation of the Penn State/NCAR Mesoscale Model
Foster, I.; Michalakes, J.
1992-12-01
Parallel computing promises significant improvements in both the raw speed and cost performance of mesoscale atmospheric models. On distributed-memory massively parallel computers available today, the performance of a mesoscale model will exceed that of conventional supercomputers; on the teraflops machines expected within the next five years, performance will increase by several orders of magnitude. As a result, scientists will be able to consider larger problems, more complex model processes, and finer resolutions. In this paper. we report on a project at Argonne National Laboratory that will allow scientists to take advantage of parallel computing technology. This Massively Parallel Mesoscale Model (MPMM) will be functionally equivalent to the Penn State/NCAR Mesoscale Model (MM). In a prototype study, we produced a parallel version of MM4 using a static (compile-time) coarse-grained ``patch`` decomposition. This code achieves one-third the performance of a one-processor CRAY Y-MP on twelve Intel 1860 microprocessors. The current version of MPMM is based on all MM5 and uses a more fine-grained approach, decomposing the grid as finely as the mesh itself allows so that each horizontal grid cell is a parallel process. This will allow the code to utilize many hundreds of processors. A high-level language for expressing parallel programs is used to implement communication strearns between the processes in a way that permits dynamic remapping to the physical processors of a particular parallel computer. This facilitates load balancing, grid nesting, and coupling with graphical systems and other models.
NASA Astrophysics Data System (ADS)
Carter-McAuslan, Angela; Lelievre, Peter; Farquharson, Colin
2013-04-01
Gravity methods have long been used in mineral exploration. However, gravity methods have difficulty resolving small details. Seismic methods provide high resolving potential for use in mineral exploration. However, complicated hard-rock geology can make seismic data processing and interpretation difficult. By jointly inverting seismic tomography data with gravity data these difficulty may be overcome. We investigated the viability of deterministic minimum-structure style joint inversion of seismic traveltime and gravity data for the delineation of magmatic massive sulphide type geological targets. These tests also assessed the potential of employing borehole gravity. A number of synthetic Earth models were created. These models were built on triangular unstructured meshes, allowing for efficient generation of complicated, realistic geological structures. 2D models were based on conceptualized models of the magmatic massive sulphide body similar to the Eastern Deeps of the Voisey's Bay, Labrador, Canada. Single property and joint inversions were performed with seismic traveltimes and both ground-based and borehole gravity. There is a known relationship between seismic velocity and density for both silicate rocks and sulphide minerals for the models constructed; this lithological relationship was used to design an appropriate coupling strategy in the joint inversions. Joint inversions were able to successfully locate a buried high contrast target with a variety of survey designs. 2D inversions results provided guidance to 3D inversion. Experimentation with noise levels, mesh design, and various inversion parameters has led to a better understanding of how to practically apply joint inversion of traveltimes and gravity data to this and similar exploration problems.
Vector meson masses in nuclear medium
NASA Astrophysics Data System (ADS)
Morones-Ibarra, Jose Ruben
1998-11-01
In this work I carry out theoretical calculations of the Rho meson mass in nuclear medium when it couples to two pions which strongly couple to in medium N/wedge/*N/wedge([-]1) states. The calculations are done from the modified Rho meson propagator in a non-relativistic approximation. Defining the Rho meson mass as the position of the peak of the spectral function, we find that there is an increase of the Rho meson mass as the density of the nuclear medium augments. The width of the spectral function becomes larger and the peak height is reduced with increasing nuclear densities.
A New Occurrence Model for National Assessment of Undiscovered Volcanogenic Massive Sulfide Deposits
Shanks, W.C. Pat, III; 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.
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.
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
Dark matter and MOND dynamical models of the massive spiral galaxy NGC 2841
NASA Astrophysics Data System (ADS)
Samurović, S.; Vudragović, A.; Jovanović, M.
2015-08-01
We study dynamical models of the massive spiral galaxy NGC 2841 using both the Newtonian models with Navarro-Frenk-White (NFW) and isothermal dark haloes, as well as various MOND (MOdified Newtonian Dynamics) models. We use the observations coming from several publicly available data bases: we use radio data, near-infrared photometry as well as spectroscopic observations. In our models, we find that both tested Newtonian dark matter approaches can successfully fit the observed rotational curve of NGC 2841. The three tested MOND models (standard, simple and, for the first time applied to another spiral galaxy than the Milky Way, Bekenstein's toy model) provide fits of the observed rotational curve with various degrees of success: the best result was obtained with the standard MOND model. For both approaches, Newtonian and MOND, the values of the mass-to-light ratios of the bulge are consistent with the predictions from the stellar population synthesis (SPS) based on the Salpeter initial mass function (IMF). Also, for Newtonian and simple and standard MOND models, the estimated stellar mass-to-light ratios of the disc agree with the predictions from the SPS models based on the Kroupa IMF, whereas the toy MOND model provides too low a value of the stellar mass-to-light ratio, incompatible with the predictions of the tested SPS models. In all our MOND models, we vary the distance to NGC 2841, and our best-fitting standard and toy models use the values higher than the Cepheid-based distance to the galaxy NGC 2841, and the best-fitting simple MOND model is based on the lower value of the distance. The best-fitting NFW model is inconsistent with the predictions of the Λ cold dark matter cosmology, because the inferred concentration index is too high for the established virial mass.
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
Matter power spectra in viable f (R) gravity models with massive neutrinos
NASA Astrophysics Data System (ADS)
Geng, Chao-Qiang; Lee, Chung-Chi; Shen, Jia-Liang
2015-01-01
We investigate the matter power spectra in the power law and exponential types of viable f (R) theories along with massive neutrinos. The enhancement of the matter power spectrum is found to be a generic feature in these models. In particular, we show that in the former type, such as the Starobinsky model, the spectrum is magnified much larger than the latter one, such as the exponential model. A greater scale of the total neutrino mass, ∑mν, is allowed in the viable f (R) models than that in the ΛCDM one. We obtain the constraints on the neutrino masses by using the CosmoMC package with the modified MGCAMB. Explicitly, we get ∑mν < 0.451 (0.214) eV at 95% C.L. in the Starobinsky (exponential) model, while the corresponding one for the ΛCDM model is ∑mν < 0.200 eV. Furthermore, by treating the effective number of neutrino species Neff as a free parameter along with ∑mν, we find that Neff =3.78-0.84+0.64 (3.47-0.60+0.74) and ∑mν =0.533-0.411+0.254 (< 0.386) eV at 95% C.L. in the Starobinsky (exponential) model.
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
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
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.
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.
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
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.
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.
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)
Meyer, D. M.-A.; Mackey, J.; Langer, N.; Gvaramadze, V. V.; Mignone, A.; Izzard, R. G.; Kaper, L.
2014-11-01
At least 5 per cent of the massive stars are moving supersonically through the interstellar medium (ISM) and are expected to produce a stellar wind bow shock. We explore how the mass-loss and space velocity of massive runaway stars affect the morphology of their bow shocks. We run two-dimensional axisymmetric hydrodynamical simulations following the evolution of the circumstellar medium of these stars in the Galactic plane from the main sequence to the red supergiant phase. We find that thermal conduction is an important process governing the shape, size and structure of the bow shocks around hot stars, and that they have an optical luminosity mainly produced by forbidden lines, e.g. [O III]. The Hα emission of the bow shocks around hot stars originates from near their contact discontinuity. The Hα emission of bow shocks around cool stars originates from their forward shock, and is too faint to be observed for the bow shocks that we simulate. The emission of optically thin radiation mainly comes from the shocked ISM material. All bow shock models are brighter in the infrared, i.e. the infrared is the most appropriate waveband to search for bow shocks. Our study suggests that the infrared emission comes from near the contact discontinuity for bow shocks of hot stars and from the inner region of shocked wind for bow shocks around cool stars. We predict that, in the Galactic plane, the brightest, i.e. the most easily detectable bow shocks are produced by high-mass stars moving with small space velocities.
Wind modelling of very massive stars up to 300 solar masses
NASA Astrophysics Data System (ADS)
Vink, Jorick S.; Muijres, L. E.; Anthonisse, B.; de Koter, A.; Gräfener, G.; Langer, N.
2011-07-01
The stellar upper-mass limit is highly uncertain. Some studies have claimed there is a universal upper limit of 150 M⊙. A factor that is often overlooked is that there might be a significant difference between the present-day and the initial masses of the most massive stars - as a result of mass loss. The upper-mass limit may easily supersede 200 M⊙. For these reasons, we present new mass-loss predictions from Monte Carlo radiative transfer models for very massive stars (VMS) in the mass range 40-300 M⊙, and with very high luminosities 6.0 ≤ log (L ⋆ /L⊙) ≤ 7.03, corresponding to large Eddington factors Γ. Using our new dynamical approach, we find an upturn or "kink" in the mass-loss versus Γ dependence, at the point where the model winds become optically thick. This coincides with the location where our wind efficiency numbers surpass the single-scattering limit of η = 1, reaching values up to η ≃ 2.5. In all, our modelling suggests a transition from common O-type winds to Wolf-Rayet characteristics at the point where the winds become optically thick. This transitional behaviour is also revealed with respect to the wind acceleration parameter, β, which starts at values below 1 for the optically thin O-stars, and naturally reaches values as high as 1.5-2 for the optically thick Wolf-Rayet models. An additional finding concerns the transition in spectral morphology of the Of and WN characteristic He ii line at 4686 Å. When we express our mass-loss predictions as a function of the electron scattering Eddington factor Γe L ⋆ /M ⋆ alone, we obtain an Ṁ vs. Γe dependence that is consistent with a previously reported power law Ṁ∝ Γ_e{5} (Vink 2006) that was based on our previous semi-empirical modelling approach. When we express Ṁ in terms of both Γe and stellar mass, we find optically thin winds and Ṁ ∝ Mstar0.68 Γ_e^{2.2} for the Γe range 0.4 ≲ Γe ≲ 0.7, and mass-loss rates that agree with the standard Vink et al. recipe
HOT X-RAY CORONAE AROUND MASSIVE SPIRAL GALAXIES: A UNIQUE PROBE OF STRUCTURE FORMATION MODELS
Bogdan, Akos; Forman, William R.; Vogelsberger, Mark; Sijacki, Debora; Mazzotta, Pasquale; Kraft, Ralph P.; Jones, Christine; David, Laurence P.; Bourdin, Herve; Gilfanov, Marat; Churazov, Eugene
2013-08-01
Luminous X-ray gas coronae in the dark matter halos of massive spiral galaxies are a fundamental prediction of structure formation models, yet only a few such coronae have been detected so far. In this paper, we study the hot X-ray coronae beyond the optical disks of two 'normal' massive spirals, NGC 1961 and NGC 6753. Based on XMM-Newton X-ray observations, hot gaseous emission is detected to {approx}60 kpc-well beyond their optical radii. The hot gas has a best-fit temperature of kT {approx} 0.6 keV and an abundance of {approx}0.1 Solar, and exhibits a fairly uniform distribution, suggesting that the quasi-static gas resides in hydrostatic equilibrium in the potential well of the galaxies. The bolometric luminosity of the gas in the (0.05-0.15)r{sub 200} region (r{sub 200} is the virial radius) is {approx}6 Multiplication-Sign 10{sup 40} erg s{sup -1} for both galaxies. The baryon mass fractions of NGC 1961 and NGC 6753 are f{sub b,NGC1961} {approx} 0.11 and f{sub b,NGC6753} {approx} 0.09, which values fall short of the cosmic baryon fraction. The hot coronae around NGC 1961 and NGC 6753 offer an excellent basis to probe structure formation simulations. To this end, the observations are confronted with the moving mesh code AREPO and the smoothed particle hydrodynamics code GADGET. Although neither model gives a perfect description, the observed luminosities, gas masses, and abundances favor the AREPO code. Moreover, the shape and the normalization of the observed density profiles are better reproduced by AREPO within {approx}0.5r{sub 200}. However, neither model incorporates efficient feedback from supermassive black holes or supernovae, which could alter the simulated properties of the X-ray coronae. With the further advance of numerical models, the present observations will be essential in constraining the feedback effects in structure formation simulations.
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
Modelling massive sulphate aerosol pollution, following the large 1783 Laki basaltic eruption
NASA Astrophysics Data System (ADS)
Chenet, Anne-Lise; Fluteau, Frédéric; Courtillot, Vincent
2005-08-01
The climatic impact of volcanic eruptions depends mainly on the amount of sulphur-rich gases released into the stratosphere. These are rapidly converted to sulphate aerosols, which result in cooling of the lower troposphere and warming of the lower stratosphere. These gases are retained in the stratosphere and then concentrated by atmospheric processes, forming acid fog near the Earth's surface, with potentially dramatic environmental consequences on plants, animals and humans. We have modelled such emissions in the case of the unusually large 1783-1784 basaltic fissure eruption of Laki (Iceland), using an Atmospheric General Circulation Model. Results show good agreement with historical observations, such as typical time taken by individual pulses to reach continental Europe or geographical extent of the deadly haze that covered much of the northern hemisphere. The model could be adjusted to predict the climatic consequences of very large eruptions, up to the scale of massive flood basalts, and test the proposal that these are the main agent in most mass extinctions of life on Earth.
A two-phase thermal model for subsurface transport on massively parallel computers
Martinez, M.J.; Hopkins, P.L.
1997-12-01
Many research activities in subsurface transport require the numerical simulation of multiphase flow in porous media. This capability is critical to research in environmental remediation (e.g. contaminations with dense, non-aqueous-phase liquids), nuclear waste management, reservoir engineering, and to the assessment of the future availability of groundwater in many parts of the world. This paper presents an unstructured grid numerical algorithm for subsurface transport in heterogeneous porous media implemented for use on massively parallel (MP) computers. The mathematical model considers nonisothermal two-phase (liquid/gas) flow, including capillary pressure effects, binary diffusion in the gas phase, conductive, latent, and sensible heat transport. The Galerkin finite element method is used for spatial discretization, and temporal integration is accomplished via a predictor/corrector scheme. Message-passing and domain decomposition techniques are used for implementing a scalable algorithm for distributed memory parallel computers. Illustrative applications are shown to demonstrate capabilities and performance, one of which is modeling hydrothermal transport at the Yucca Mountain site for a radioactive waste facility.
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.
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.
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.
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.
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)
Vacaru, Sergiu I.
2015-04-01
We reinvestigate how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates can be constructed in massive and -modified gravity using the anholonomic frame deformation method. New classes of locally anisotropic and (in-) homogeneous cosmological metrics are constructed with open and closed spatial geometries. By resorting to such solutions, we show that they describe the late time acceleration due to effective cosmological terms induced by nonlinear off-diagonal interactions, possible modifications of the gravitational action and graviton mass. The cosmological metrics and related Stückelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann-Lamaître-Robertson-Walker (FLRW) coordinates. The solutions include matter, graviton mass, and other effective sources modeling nonlinear gravitational and matter field interactions with polarization of physical constants and deformations of metrics, which may explain dark energy and dark matter effects. However, we argue that it is not always necessary to modify gravity if we consider the effective generalized Einstein equations with nontrivial vacuum and/or non-minimal coupling with matter. Indeed, we state certain conditions when such configurations mimic interesting solutions in general relativity and modifications, for instance, when we can extract the general Painlevé-Gullstrand and FLRW metrics. In a more general context, we elaborate on a reconstruction procedure for off-diagonal cosmological solutions which describe cyclic and ekpyrotic universes. Finally, open issues and further perspectives are discussed.
Smith, Robin P; Taher, Leila; Patwardhan, Rupali P; Kim, Mee J; Inoue, Fumitaka; Shendure, Jay; Ovcharenko, Ivan; Ahituv, Nadav
2013-09-01
Despite continual progress in the cataloging of vertebrate regulatory elements, little is known about their organization and regulatory architecture. Here we describe a massively parallel experiment to systematically test the impact of copy number, spacing, combination and order of transcription factor binding sites on gene expression. A complex library of ∼5,000 synthetic regulatory elements containing patterns from 12 liver-specific transcription factor binding sites was assayed in mice and in HepG2 cells. We find that certain transcription factors act as direct drivers of gene expression in homotypic clusters of binding sites, independent of spacing between sites, whereas others function only synergistically. Heterotypic enhancers are stronger than their homotypic analogs and favor specific transcription factor binding site combinations, mimicking putative native enhancers. Exhaustive testing of binding site permutations suggests that there is flexibility in binding site order. Our findings provide quantitative support for a flexible model of regulatory element activity and suggest a framework for the design of synthetic tissue-specific enhancers. PMID:23892608
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.
3D Modeling of the Massive Binary Wind Interaction Region in Eta Carinae
NASA Astrophysics Data System (ADS)
Madura, Thomas; Gull, T.; Owocki, S.; Okazaki, A.; Russell, C.
2009-01-01
We present recent work on the theoretical modeling of low excitation ([Fe II]) and high excitation ([Fe III]) wind lines observed in Eta Carinae using the HST/STIS. The spatially resolved structures seen in these lines are interpreted as the time-averaged, outer extensions of the wind from the primary star and the wind-wind interaction region of the massive binary system. For most of the orbit, the wind-wind interface can be approximated as a cone with a half-opening angle of 65° whose axis of rotation is aligned with the major axis of the binary orbit and appears to lie in the plane of the Homunculus disk. However, because the orbit is highly elliptical, this approximation breaks down at periastron and so full 3D Smoothed Particle Hydrodynamics (SPH) simulations become necessary. By analyzing the results of these 3D SPH simulations of the binary interactions and comparing them to the spectra obtained with the HST/STIS we place further constraints on the orientation of the binary orbit, and hope to eventually determine how/where UV light is escaping in the system, to search for any direct signatures of the companion star, and to ultimately establish a mass ratio for the system.
Fermion condensate and the spectrum of massive Schwinger model in Bogoliubov transformed vacuum
Tomachi, T.; Fujita, T. )
1993-05-01
The authors calculate the spectrum of the charge zero sector in two-dimensional quantum electrodynamics (massive Schwinger model). The calculations are first done in the rest frame with the perturbative vacuum within given subspaces. This leads to the infrared instability at small fermion mass. Then, the Bogoliubov transformation of the vacuum is made. There, it is found that the quasi-particle states achieve a remarkably good description of the boson mass spectrum. At small fermion mass (m[sub 0][le]0.1(g/[pi][sup 1/2])), the Bogoliubov transformed state predicts the boson mass which agrees with the analytic estimation and thus is better than that calculated by the discretized light cone quantization methods at the same level of matrix dimensions. The fermion condensate of the vacuum is also estimated as the function of the fermion mass. At the massless limit, the right condensate value is reproduced as obtained analytically in the continuum limit. 16 refs., 6 figs.
Jensen, Andrew; Dar, Ayelet; Eliasberg, Claire; Kelley, Benjamin; Devana, Sai; McAllister, David R.; Petrigliano, Frank A.
2016-01-01
Picro Sirius staining demonstrated that supraspinatus tissue reliably underwent significant fibroadipogenic changes that increased over time and were more pronounced 6 weeks following TT+DN. At 6 weeks following massive rotator cuff tears, PDGFRα+ GFP+ cells, GFP+ fibrotic tissue, and GFP+ adipocytes were detected in interstitial scar tissue (Fig. 1), indicating a contribution of PDGFRα+ PDGFRβ+ cells to fibroadipogenesis. Flow cytometry analyses revealed that the frequency of adipogenic PDGFRα+ sub-population was significantly increased 5 days postop and subsequently decreased to basal levels within 2 weeks. PDGFRα+ GFP+ cell populations were significantly more fibrogenic than other cell populations and increased fibrogenic potential was detected in PDGFRα cells from TT+DN mice in vitro (Table 1). Conclusion: PDGFRα+ fibroadipogenic progenitor cells directly contribute to post-injury rotator cuff fibroadipogenesis in a mouse model of massive rotator cuff tears. This cell population likely contributes to muscle atrophy and fatty degeneration of the rotator cuff in human pathology as well. With further development of clinical protocols, perioperative inhibition of this cell population or depletion of PDGFRα+ cells prior to cell transplantation in a regenerative treatment strategy may diminish fatty degeneration and improve clinical outcomes associated with rotator cuff tears.
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.
NASA Astrophysics Data System (ADS)
Hopkins, Philip F.; Quataert, Eliot
2011-08-01
We present analytic calculations of angular momentum transport and gas inflow in galaxies, from scales of ˜ kpc to deep inside the potential of a central massive black hole (BH). We compare these analytic calculations to numerical simulations and use them to develop a sub-grid model of BH growth that can be incorporated into semi-analytic calculations or cosmological simulations. Motivated by both analytic calculations and simulations of gas inflow in galactic nuclei, we argue that the strongest torque on gas arises when non-axisymmetric perturbations to the stellar gravitational potential produce orbit crossings and shocks in the gas. This is true both at large radii ˜0.01-1 kpc, where bar-like stellar modes dominate the non-axisymmetric potential, and at smaller radii ≲10 pc, where a lopsided/eccentric stellar disc dominates. The traditional orbit-crossing criterion is not always adequate to predict the locations of, and inflow due to, shocks in gas+stellar discs with finite sound speeds. We derive a modified criterion that predicts the presence of shocks in stellar-dominated systems even absent formal orbit crossing. We then derive analytic expressions for the loss of angular momentum and the resulting gas inflow rates in the presence of such shocks. We test our analytic predictions using hydrodynamic simulations at a range of galactic scales, and show that they successfully predict the mass inflow rates and quasi-steady gas surface densities with a small scatter ≃0.3 dex. We use our analytic results to construct a new estimate of the BH accretion rate given galaxy properties at larger radii, for use in galaxy and cosmological simulations and semi-analytic models. While highly simplified, this accretion rate predictor captures the key scalings in the numerical simulations. By contrast, alternate estimates such as the local viscous accretion rate or the spherical Bondi rate fail systematically to reproduce the simulations and have significantly larger
Modeling the drift of massive icebergs to the subtropical North Atlantic
NASA Astrophysics Data System (ADS)
Condron, A.; Hill, J. C.
2013-12-01
New evidence from high-resolution seafloor bathymetry data indicates that massive (>300m thick) icebergs from the Laurentide Ice Sheet (LIS) drifted south to the tip of Florida during the last deglaciation. This finding is particularly exciting as it contradicts evidence from marine sediments that icebergs were mainly confined to the subpolar North Atlantic (50 - 70N) at this time. Indeed, the freshwater released from icebergs melting in the subpolar gyre is repeatedly cited as a main trigger for a slow-down of the Atlantic MOC in the past, and the possible cause of any climate cooling related to the melting of the Greenland Ice Sheet in the future. Using a sophisticated iceberg model (MITberg), coupled to a high (18-km; 1/6 deg.) resolution ocean model (MITgcm), we investigate the ocean circulation dynamics required to allow icebergs to drift to the southern tip of Florida. We find that icebergs only reach this location if they turn right at the Grand Banks of Newfoundland, and stay inshore of the Gulf Stream all the way to Florida. Modern-day circulation dynamics do not readily allow this to happen as cold, southward flowing, Labrador Current Water (important for iceberg survival) has little penetration south of Cape Hatteras. However, when a liquid meltwater flood is released from Hudson Bay at the same time, icebergs are rapidly transported (inshore of the Gulf Stream) in a narrow, buoyant, coastal current all the way to southern Florida. The meltwater and icebergs result in a significant freshening of the subtropical North Atlantic and weaken the strength of the Gulf Stream, suggesting such an event would have a large cooling effect on climate. We are only able to simulate the flow of meltwater and icebergs to the subtropics by modeling ocean circulation at a resolution that is 5 - 10 times higher than the majority of existing paleoclimate models; at lower resolutions the narrow, coastal boundary currents important for iceberg transport to the subtropics are
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).
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
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. PMID:26919675
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
Nonresonant Background in Isobaric Models of Photoproduction of η-Mesons on Nucleons
NASA Astrophysics Data System (ADS)
Tryasuchev, V. A.; Alekseev, B. A.; Yakovleva, V. S.; Kondratyeva, A. G.
2016-07-01
Within the framework of isobaric models of pseudoscalar meson photoproduction, the nonresonant background of photoproduction of η-mesons on nucleons is investigated as a function of energy. A bound on the magnitude of the pseudoscalar coupling constant of the η-meson with a nucleon is obtained: g {ηNN/ 2}/4π ≤ 0.01, and a bound on vector meson exchange models is also obtained.
Dimension Six Correction to the Vector Sector of AdS/QCD Model
Hovhannes Grigoryan
2007-09-06
We study the effect of dimension six term F^3 on the predictions of the holographic model for the vector meson form factor. It is shown that the dimensionless parameter with which this term enters the action determines the corrections to the electric radius, magnetic and quadrupole moments of the rho meson. The results suggest that the addition of higher order terms may improve the holographic model.
Nonresonant Background in Isobaric Models of Photoproduction of η-Mesons on Nucleons
NASA Astrophysics Data System (ADS)
Tryasuchev, V. A.; Alekseev, B. A.; Yakovleva, V. S.; Kondratyeva, A. G.
2016-07-01
Within the framework of isobaric models of pseudoscalar meson photoproduction, the nonresonant background of photoproduction of η-mesons on nucleons is investigated as a function of energy. A bound on the magnitude of the pseudoscalar coupling constant of the η-meson with a nucleon is obtained: g η NN 2 /4π ≤ 0.01, and a bound on vector meson exchange models is also obtained.
Supersymmetrizing massive gravity
NASA Astrophysics Data System (ADS)
Malaeb, O.
2013-07-01
When four scalar fields with global Lorentz symmetry are coupled to gravity and take a vacuum expectation value, breaking diffeomorphism invariance spontaneously, the graviton becomes massive. This model is supersymmetrized by considering four N=1 chiral superfields with global Lorentz symmetry. The global supersymmetry is promoted to a local one using the rules of tensor calculus of coupling the N=1 supergravity Lagrangian to the four chiral multiplets. When the scalar components of the chiral multiplets zA acquire a vacuum expectation value, both diffeomorphism invariance and local supersymmetry are broken spontaneously. The global Lorentz index A becomes identified with the space-time Lorentz index, making the scalar fields zA vectors and the chiral spinors ψA spin-3/2 Rarita-Schwinger fields. We show that the spectrum of the model in the broken phase consists of a massive spin-2 field, two massive spin-3/2 fields with different mass and a massive vector.
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.
Low-energy processes of meson production in the extended Nambu-Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Volkov, M. K.; Arbuzov, A. B.
2016-07-01
The processes of meson production in electron-positron collisions at low energies are characterized within the extended Nambu-Jona-Lasinio model. It is demonstrated that intermediate vector mesons (both in the ground state and in the first radially excited one) play a critical part in these processes. The obtained results are in reasonable agreement with the available experimental data. A number of theoretical predictions are made, which can be tested experimentally in the near future.
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)
Schaerer, D.
1996-05-01
We present a simple analytical method to describe the structure of a spherically expanding envelope with strong mass outflow. The structure is consistently connected to the hydrostatic stellar interior and provides an adequate description of the outer boundary conditions for stellar models with large mass loss rates. We apply our treatment to evolutionary models of Wolf-Rayet (WR) stars in order to study the possible influence of the stellar winds on the interior, and to determine more reliable radii of WR stars. Independently of the wind parameters (wind density, opacity, velocity law) the interior structure and evolution of WR stars is found to be unaffected by the outer layers. On the other hand, the stellar parameters (radii, effective temperatures) may well depend on the wind structure. For hydrogen rich WR stars (WNL) we find the existence of a temperature domain in the HR-diagram, where a transient concentration of stars on their blueward track is predicted in case of a strong backwarming from the wind. For WNE and WC/WO stars with strong mass loss rates we also derive subphotospheric radii corresponding to Rosseland optical depths of τ~10-20. The dependence of the subphotospheric radii on the adopted envelope structure is discussed. With respect to wind-free stellar models the subphotospheric radii are increased by up to a factor of ~4 for the most luminous WNE or WC stars. These radii and the corresponding effective temperatures should roughly be comparable with the stellar parameters (``core'' radii and temperatures) of non-LTE atmosphere models of WR stars. Comparisons using the newly derived subphotospheric radii yields a better agreement with observations. The stellar parameters obtained with the new treatment allow a better assignment of theoretical spectra to evolutionary tracks of evolved WR stars (WNE, WC). This also provides the base for future studies of the spectral evolution of post main-sequence massive stars and their descendants. We also
NASA Astrophysics Data System (ADS)
LeFloch, Philippe G.; Ma, Yue
2016-01-01
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.
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.
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
Polarization in massive X-ray binaries. I - A low-inclination model for Cygnus X-1
NASA Technical Reports Server (NTRS)
Friend, D. B.; Cassinelli, J. P.
1986-01-01
The possibility that variable linear polarization in massive X-ray binaries is produced by electron scattering in an asymmetric stellar wind is investigated. The stellar wind is asymmetric because of the gravitational field of the secondary (X-ray source). The degree of asymmetry and the magnitude of the linear polarization are controlled by the degree to which the primary star fills its Roche lobe. For the well-observed X-ray binary Cyg X-1, the present model can produce the correct magnitude for the polarization. Provided that the inclination of the system is less than about 20 deg, the present model should also predict the correct phase dependence of the polarization. Modifications to the model are described which would enable it to apply to systems with higher inclination.
NASA Astrophysics Data System (ADS)
Wang, S.; De Hoop, M. V.; Xia, J.; Li, X.
2011-12-01
We consider the modeling of elastic seismic wave propagation on a rectangular domain via the discretization and solution of the inhomogeneous coupled Helmholtz equation in 3D, by exploiting a parallel multifrontal sparse direct solver equipped with Hierarchically Semi-Separable (HSS) structure to reduce the computational complexity and storage. In particular, we are concerned with solving this equation on a large domain, for a large number of different forcing terms in the context of seismic problems in general, and modeling in particular. We resort to a parsimonious mixed grid finite differences scheme for discretizing the Helmholtz operator and Perfect Matched Layer boundaries, resulting in a non-Hermitian matrix. We make use of a nested dissection based domain decomposition, and introduce an approximate direct solver by developing a parallel HSS matrix compression, factorization, and solution approach. We cast our massive parallelization in the framework of the multifrontal method. The assembly tree is partitioned into local trees and a global tree. The local trees are eliminated independently in each processor, while the global tree is eliminated through massive communication. The solver for the inhomogeneous equation is a parallel hybrid between multifrontal and HSS structure. The computational complexity associated with the factorization is almost linear with the size of the Helmholtz matrix. Our numerical approach can be compared with the spectral element method in 3D seismic applications.
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. PMID:26207457
Weekes, Leroy R.
1977-01-01
This ten-year study of the massive fibroid at the Queen of Angels Hospital will reveal an average of 66 cases per year which could be classified as large and massive. Only about ten cases per year qualify as massive (four gestational months or larger). There were none considered giant size (25 lbs or more). The literature is replete with these, one of which (weighing 100.2 lbs) will be reported in detail. The mortality rate continues to be considerable in these (14.8 to 16.7 percent). In the smaller tumors, mortality is rare and morbidity is minimal. Bleeding, pain, and pressure symptoms, due to impingement on neighboring organs, are the principal symptoms. Sarcomatous change, fortunately, still remains quite rare. Treatment usually involves a pre-operative dilatation and curettage when bleeding is a problem, followed by total abdominal hysterectomy and bilateral salpingo-oophorectomy where indicated. Appendectomy is usually incidental. Anesthesia is usually spinal, if not otherwise contraindicated. Ultrasound is a new and refined diagnostic tool. PMID:833892
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.
Introduction to Massive Gravity
NASA Astrophysics Data System (ADS)
de Rham, Claudia
We review recent progress on massive gravity. We first show how extra dimensions prove to be a useful tool in building theories of modified gravity, including Galileon theories and their DBI extensions. DGP arises from an infinite size extra dimension, and we show how massive gravity arises from `deconstructing' the extra dimension in the vielbein formalism. We then explain how the ghost issue is resolved in that special theory of massive gravity. The viability of such models relies on the Vainshtein mechanism which is best described in terms of Galileons. While its implementation is successful in most of these models it also comes hand in hand with superluminalities and strong coupling which are reviewed and their real consequences are discussed.
NASA Astrophysics Data System (ADS)
Cristiano Amorisco, Nicola; Martinez-Delgado, David
2015-08-01
Low surface brightness tidal features around massive galaxies are the smoking gun of hierarchical galaxy formation. These debris are informative of: (i) the evolutionary struggles of the progenitor dwarf galaxies, transformed and partially destroyed by the tides; (ii) the formation history of the massive host, its halo populations and the structure of its dark matter halo. However, extracting reliable measurements of the progenitor’s initial mass, infall time, host halo mass and density profile has so far been difficult, as the parameter space is too wide to explore with N-body simulations.We use new deep imaging data of the extended, X shaped stream in NGC1097 [1,2] and a new dynamical technique to quantitatively reconstruct: (i) the density profile of the massive spiral host (inferred virial mass M200=1012.25±0.1 M⊙) ; and (ii) the dramatic evolution of the progenitor galaxy; by modeling its stream within a fully statistical framework. I will show that the current location of the remnant coincides with a nucleated dwarf Spheroidal, with a luminosity of ~3.3x106LV,⊙ [3], and a predicted total mass of M(<0.45±0.2 kpc)=107.8±0.6 M⊙. This is the result of a strong transformation: at its first interaction with the host, 4.4±0.4 Gyr and three pericentric passages ago, the progenitor was over two orders of magnitude more massive, with Mtot(3.2±0.7 kpc)=1010.4±0.2 M⊙. Its orbit has a pericenter of a few kpc, but reaches out to 150±12 kpc. In this range the stream’s morphology allows us to see the total density slope of the host bending and steepening towards large radii. For the first time in a single galaxy (rather than on stacked data), both central and outer slope are constrained by observations and can be compared to LCDM expectations [4]. Finally, I will discuss prospects of applying this technique to more known streams, to map the structure of a wider sample of galaxy haloes and unveil the evolutionary histories of more individual dwarf galaxies
NASA Astrophysics Data System (ADS)
Domínguez-Tenreiro, R.; Oñorbe, J.; Martínez-Serrano, F.; Serna, A.
2011-06-01
implications for diffuse or shocked mass elements), as well as on their possible observational implications, these patterns have been confronted with some generic properties of singular flows as described by the adhesion model (i.e. potential character of the velocity field, singular versus regular points, dressing, locality when a spectrum of perturbations is implemented). We have found that the common patterns the simulations show can be interpreted as a natural consequence of flow properties that, moreover, could explain different generic observational results from massive galaxies or their samples. We briefly discuss some of them.
Massive Bleeding and Massive Transfusion
Meißner, Andreas; Schlenke, Peter
2012-01-01
Massive bleeding in trauma patients is a serious challenge for all clinicians, and an interdisciplinary diagnostic and therapeutic approach is warranted within a limited time frame. Massive transfusion usually is defined as the transfusion of more than 10 units of packed red blood cells (RBCs) within 24 h or a corresponding blood loss of more than 1- to 1.5-fold of the body's entire blood volume. Especially male trauma patients experience this life-threatening condition within their productive years of life. An important parameter for clinical outcome is to succeed in stopping the bleeding preferentially within the first 12 h of hospital admission. Additional coagulopathy in the initial phase is induced by trauma itself and aggravated by consumption and dilution of clotting factors. Although different aspects have to be taken into consideration when viewing at bleedings induced by trauma compared to those caused by major surgery, the basic strategy is similar. Here, we will focus on trauma-induced massive hemorrhage. Currently there are no definite, worldwide accepted algorithms for blood transfusion and strategies for optimal coagulation management. There is increasing evidence that a higher ratio of plasma and RBCs (e.g. 1:1) endorsed by platelet transfusion might result in a superior survival of patients at risk for trauma-induced coagulopathy. Several strategies have been evolved in the military environment, although not all strategies should be transferred unproven to civilian practice, e.g. the transfusion of whole blood. Several agents have been proposed to support the restoration of coagulation. Some have been used for years without any doubt on their benefit-to-risk profile, whereas great enthusiasm of other products has been discouraged by inefficacy in terms of blood transfusion requirements and mortality or significant severe side effects. This review surveys current literature on fluid resuscitation, blood transfusion, and hemostatic agents currently
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
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…
New massive supergravity multiplets
NASA Astrophysics Data System (ADS)
Gates, S. James, Jr.; Kuzenko, Sergei M.; Tartaglino-Mazzucchelli, Gabriele
2007-02-01
We present new off-shell formulations for the massive superspin-3/2 multiplet. In the massless limit, they reduce respectively to the old minimal (n = -1/3) and non-minimal (n≠-1/3,0) linearized formulations for 4D Script N = 1 supergravity. Duality transformations, which relate the models constructed, are derived.
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.
NASA Astrophysics Data System (ADS)
Madhusudhan, Nikku; Burrows, Adam; Currie, Thayne
2011-08-01
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 μm modal particle size and (2) clouds made of 1 μm 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 MJ , 6-13 MJ , and 3-11 MJ , respectively, and imply coeval ages between ~10 and ~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.
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
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. PMID:25024412
Massive Stars: Stellar Populations
NASA Astrophysics Data System (ADS)
Bianchi, Luciana
2007-07-01
Massive stars dominate the chemical and dynamical evolution of the ISM, and ultimately of their parent galaxy and the universe, because of their fast evolution and intense supersonic winds. Four decades ago, the first rocket UV spectra of massive stars revealed the importance of mass loss and began to change our understanding of their evolution. Recently, advances in stellar modeling, and the observation of crucial ions in the far-UV spectral range, led to the resolution of long-standing issues in our understanding of massive star atmospheres. A revised (downwards) calibration of Teff for early spectral types is emerging as a result. Meanwhile, HST imaging, and large ground-based telescopes with multislit spectroscopic capabilities, had opened the possibility of resolved studies of stellar populations in Local Group galaxies, which sample a variety of metallicity and environment conditions. More recently, GALEX is providing a global, deep view of the young stellar populations for hundreds of nearby galaxies, revealing their recent star-formation history and modalities. The wide-field coverage and sensitivity of the GALEX UV imaging, easily detecting extremely low levels of star formation, is again changing some of our views on massive star formation in galaxies.
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.
2016-09-01
We present UV-extended E-MILES stellar population synthesis models covering the spectral range λλ 1680 - 50000 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 IMF 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 LMC. Our full-spectrum fits in the UV range for a representative set of 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%, on the top of an old stellar population.
Scientific development of a massively parallel ocean climate model. Progress report, 1991--1992
Semtner, A.J. Jr.; Chervin, R.M.
1992-09-01
A thorough examination was made of existing results from the global ocean model with high resolution. Additional experiments were chosen to help investigate the sensitivity of global ocean circulation and its associated transports of heat and salt to proposed changes in high-latitude buoyancy forcing and wind forcing.
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…
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
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
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. PMID:23611075
Instability of the Ackerman-Carroll-Wise model, and problems with massive vectors during inflation
Himmetoglu, Burak; Peloso, Marco; Contaldi, Carlo R.
2009-03-15
We prove that the anisotropic inflationary background of the Ackerman-Carroll-Wise model, characterized by a fixed-norm vector field, is unstable. We found the instability by explicitly solving the linearized equations for the most general set of perturbations around this background, and by noticing that the solutions diverge close to horizon crossing. This happens because one perturbation becomes a ghost at that moment. A simplified computation, with only the perturbations of the vector field included, shows the same instability, clarifying the origin of the problem. We then discuss several other models, with a particular emphasis on the case of a nonminimal coupling to the curvature, in which vector fields are used either to support an anisotropic expansion, or to generate cosmological perturbations on an isotropic background. In many cases, the mass squared of the vector needs to be negative; we show that, as a consequence, the longitudinal vector mode is a ghost (a field with negative kinetic term, and negative energy, and not simply a tachyon). We comment on problems that arise at the quantum level. In particular, the presence of a ghost can be a serious difficulty for the UV completion that such models require in the subhorizon regime.
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.
Battye, Richard A.; Sutcliffe, Paul M.
2006-05-15
In the Skyrme model with massless pions, the minimal energy multi-Skyrmions are shell-like, with the baryon density localized on the edges of a polyhedron that is approximately spherical and generically of the fullerene-type. In this paper we show that in the Skyrme model with massive pions these configurations are unstable for sufficiently large baryon number. Using numerical simulations of the full nonlinear field theory, we show that these structures collapse to form qualitatively different stable Skyrmion solutions. These new Skyrmions have a flat structure and display a clustering phenomenon into lower charge components, particularly components of baryon numbers three and four. These new qualitative features of Skyrmions with massive pions are encouraging in comparison with the expectations based on real nuclei.
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
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
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.
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)
Portegies Zwart, Simon F.; McMillan, Stephen L. W.; Gieles, Mark
2010-09-01
Young massive clusters (YMCs) are dense aggregates of young stars that form the fundamental building blocks of galaxies. Several examples exist in the Milky Way Galaxy and the Local Group, but they are particularly abundant in starburst and interacting galaxies. The few YMCs that are close enough to resolve are of prime interest for studying the stellar mass function and the ecological interplay between stellar evolution and stellar dynamics. The distant unresolved clusters may be effectively used to study the star-cluster mass function, and they provide excellent constraints on the formation mechanisms of young cluster populations. YMCs are expected to be the nurseries for many unusual objects, including a wide range of exotic stars and binaries. So far only a few such objects have been found in YMCs, although their older cousins, the globular clusters, are unusually rich in stellar exotica. In this review, we focus on star clusters younger than ˜100 Myr, more than a few current crossing times old, and more massive than ˜104M⊙; the size of the cluster and its environment are considered less relevant as distinguishing parameters. We describe the global properties of the currently known young massive star clusters in the Local Group and beyond, and discuss the state of the art in observations and dynamical modeling of these systems. In order to make this review readable by observers, theorists, and computational astrophysicists, we also review the cross-disciplinary terminology.
Baryon octet electromagnetic form factors in a confining NJL model
NASA Astrophysics Data System (ADS)
Carrillo-Serrano, Manuel E.; Bentz, Wolfgang; Cloët, Ian C.; Thomas, Anthony W.
2016-08-01
Electromagnetic form factors of the baryon octet are studied using a Nambu-Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp < rEΣ+ and | rEn | < | rEΞ0 |, whereas the magnetic radii have a pattern largely consistent with a naive expectation based on the dressed quark masses.
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).
HOW MASSIVE ARE MASSIVE COMPACT GALAXIES?
Muzzin, Adam; Van Dokkum, Pieter; Marchesini, Danilo; Franx, Marijn; Kriek, Mariska; Labbe, Ivo
2009-11-20
Using a sample of nine massive compact galaxies at zapprox 2.3 with rest-frame optical spectroscopy and comprehensive U -> 8 mum photometry, we investigate how assumptions in spectral energy distribution (SED) modeling change the stellar mass estimates of these galaxies, and how this affects our interpretation of their size evolution. The SEDs are fitted to tau-models with a range of metallicities, dust laws, and different stellar population synthesis codes. These models indicate masses equal to, or slightly smaller than, our default masses. The maximum difference is 0.16 dex for each parameter considered, and only 0.18 dex for the most extreme combination of parameters. Two-component populations with a maximally old stellar population superposed with a young component provide reasonable fits to these SEDs using the models of Bruzual and Charlot; however, when using models with updated treatment of TP-AGB stars, the fits are poorer. The two-component models predict masses that are 0.08-0.22 dex larger than the tau-models. We also test the effect of a bottom-light initial mass function (IMF) and find that it would reduce the masses of these galaxies by 0.3 dex. Considering the range of allowable masses from the tau-models, two-component fits, and IMF, we conclude that on average these galaxies lie below the mass-size relation of galaxies in the local universe by a factor of 3-9, depending on the SED models used.
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
NASA Astrophysics Data System (ADS)
Bergshoeff, Eric A.; Fernández-Melgarejo, J. J.; Rosseel, Jan; Townsend, Paul K.
2012-04-01
We construct a four-dimensional (4D) gauge theory that propagates, unitarily, the five polarization modes of a massive spin-2 particle. These modes are described by a "dual" graviton gauge potential and the Lagrangian is 4th-order in derivatives. As the construction mimics that of 3D "new massive gravity", we call this 4D model (linearized) "new massive dual gravity". We analyse its massless limit, and discuss similarities to the Eddington-Schrödinger model.
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
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 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 Astrophysics Data System (ADS)
Deser, S.; Izumi, K.; Ong, Y. C.; Waldron, A.
2015-01-01
The method of characteristics is a key tool for studying consistency of equations of motion; it allows issues such as predictability, maximal propagation speed, superluminality, unitarity and acausality to be addressed without requiring explicit solutions. We review this method and its application to massive gravity (mGR) theories to show the limitations of these models' physical viability: Among their problems are loss of unique evolution, superluminal signals, matter coupling inconsistencies and micro-acausality (propagation of signals around local closed time-like curves (CTCs)/closed causal curves (CCCs)). We extend previous no-go results to the entire three-parameter range of mGR theories. It is also argued that bimetric models suffer a similar fate.
Feedback During Massive Star Formation
NASA Astrophysics Data System (ADS)
Tanaka, Kei; Tan, Jonathan C.; Zhang, Yichen
2016-01-01
We present models of photoionization of massive protostellar cores, and show the impact of this ionization feedback on the efficiency of star formation and its observational features. Based on the Core Accretion scenario, we construct the collapse model of rotating massive-protostellar cloud cores together with a protostellar evolutional calculation, including feedback effects from a MHD disk wind, photoionization and radiation pressure. First, the MHD wind creates a bipolar outflow whose opening angle increases over the timescale of mass accretion. The ionizing luminosity dramatically increases after the protostar reaches ~ 5 Msun due to Kelvin-Helmholz contraction, and the MHD wind is photoionized when the protostellar mass reaches ~ 10 - 20 Msun. As the ionizing and bolometric luminosities increase, the outflow opening angle becomes wider due to radiation pressure feedback. By this combination of feedback processes, the envelope is eroded and the mass infall rate is significantly reduced to that arriving only from the disk-shielded equatorial region. At a protostellar mass of ~ 50 - 100 Msun, depending on the initial core properties, the mass accretion is halted by disk photoevaporation. In this way, feedback significantly reduces the star formation efficiency when forming massive stars from massive cloud cores, which could produce a cutoff at the high-mass end of the initial mass function. Along this evolutionary calculation, we also compute the detailed structure of the photoionized regions using a ray-tracing radiative transfer code and evaluate their emission signatures. Their free-free continuum and recombination line emissions are consistent with the variety of observed radio sources associated with massive protostars, i.e., jets and ultra/hyper-compact HII regions. The comparison between our models and such observations enables us to better define the evolutionary sequence of massive star formation.
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.
Paterson, Neil A
2009-05-01
We present the case of a 5-year-old girl who was brought to hospital having suffered an intracranial bleed. She was found to have a large cerebral arteriovenous malformation which was unsuitable for coiling. Uncontrollable raised intracranial pressure refractory to all therapies necessitated surgery as a last resort. Massive hemorrhage eventuated during the procedure with the estimated loss of between five and six blood volumes, the majority occurring within the space of an hour and a half. We describe management using a locally developed protocol and correlate this with laboratory findings. PMID:19453586
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.
Sedeonic Equations of Massive Fields
NASA Astrophysics Data System (ADS)
Mironov, Sergey V.; Mironov, Victor L.
2015-01-01
Prior work on space-time sedeon algebra models relativistic quantum mechanical equation of motion with corresponding field equations, mediated by massive or massless spin-1 or spin-1/2 particles. In the massless spin-1 case, such exchange particles mediate fields in analogy to Maxwell's equations in Lorentz gauge. This paper demonstrates fundamental aspects of massive field's theory, such as gauge invariance, charge conservation, Poynting's theorem, potential of a stationary scalar point source, plane wave solution, and interaction between point sources. We briefly discuss some aspects of sedeonic algebra and their potential physical applications.
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.
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.
Off-shell suppressions and two body radiative processes in a vector dominance model
Lahiri, A.; Bagchi, B.; Gautam, V.P.; Nandy, A.
1980-08-01
The radiative decays of rho,K*, omega and phi are studied in a one-parameter vector dominance model by introducing corrections for the off-shell vector meson-photon coupling constants. It is found that off-shell values rho and omega are suppressed by 1/1.5 while off-shell phi is suppressed by 1/1.9 compared with their on-shell values. In addition, we have also considered P ..-->.. ..gamma.. ..gamma.. decays and sigma/sub tot/ (VP), and found generally good agreement with the available data.
Microscopic model of the timelike electromagnetic form factor of the nucleon
Doenges, H.C.; Schaefer, M.; Mosel, U. )
1995-02-01
A microscopic model of the electromagnetic form factor of the nucleon is developed in a hadronic framework, including pions, nucleons and the [Delta]-resonance explicitly. The spacelike on-shell form factors are reproduced and predictions for the half off-shell dependence are made. The impact of this off-shell dependence in the time like sector ([ital q][sup 2][lt]1 GeV[sup 2], thus including the region of vector meson dominance) is of main interest in this investigation.
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)
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.
Octonic Massive Field Equations
NASA Astrophysics Data System (ADS)
Demir, Süleyman; Kekeç, Seray
2016-03-01
In the present paper we propose the octonic form of massive field equations based on the analogy with electromagnetism and linear gravity. Using the advantages of octon algebra the Maxwell-Dirac-Proca equations have been reformulated in compact and elegant way. The energy-momentum relations for massive field are discussed.
Octonic Massive Field Equations
NASA Astrophysics Data System (ADS)
Demir, Süleyman; Kekeç, Seray
2016-07-01
In the present paper we propose the octonic form of massive field equations based on the analogy with electromagnetism and linear gravity. Using the advantages of octon algebra the Maxwell-Dirac-Proca equations have been reformulated in compact and elegant way. The energy-momentum relations for massive field are discussed.
NASA Astrophysics Data System (ADS)
Hachisu, I.; Kato, M.
We have analyzed the optical light curve of the symbiotic star V407 Cyg that underwent a classical nova outburst in 2010 March. Being guided by a supersoft X-ray phase observed during days 20--40 after the nova outburst, we are able to reproduce the light curve during a very early phase of the nova outburst. Our model consists of an outbursting white dwarf and an extended equatorial disk. An extremely massive white dwarf of 1.35--1.37 M⊙ is suggested. The optical light curve is also consistent with a sharp drop 47 days after the outburst, which is the end of hydrogen shell-burning on the white dwarf. Although the extremely massive white dwarf is favourable to the interpretation that V407 Cyg is a recurrent nova, enrichment of heavy elements in the ejecta suggests that the white dwarf is eroded and, as a result, its mass is not increasing. Therefore, V407 Cyg may not explode as a Type Ia supernova even if it is a carbon-oxygen white dwarf.
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.
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)
Quantum massive conformal gravity
NASA Astrophysics Data System (ADS)
Faria, F. F.
2016-04-01
We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.
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.
Evolved Massive Stars in the Local Group
NASA Astrophysics Data System (ADS)
Drout, M. R.; Massey, P.
2015-05-01
In this manuscript we describe a number of recent advances in the study of evolved massive stars in the Local Group, with an emphasis on how representative populations of these stars can be used to test models of massive star evolution. In honor of the 50th anniversary of the Cerro Tololo Inter-American Observatory (CTIO) we attempt to put these finding in some historical context by discussing how our understanding of the various stages in the lives of massive stars has evolved since Cerro Tololo was first selected as the site for the observatory which would become CTIO.
Massive photon and dark energy
NASA Astrophysics Data System (ADS)
Kouwn, Seyen; Oh, Phillial; Park, Chan-Gyung
2016-04-01
We investigate the cosmology of massive electrodynamics and explore the possibility whether the massive photon could provide an explanation of dark energy. The action is given by the scalar-vector-tensor theory of gravity, which is obtained by nonminimal coupling of the massive Stueckelberg QED with gravity; its cosmological consequences are studied by paying particular attention to the role of photon mass. We find that the theory allows for cosmological evolution where the radiation- and matter-dominated epochs are followed by a long period of virtually constant dark energy that closely mimics a Λ CDM model. We also find that the main source of the current acceleration is provided by the nonvanishing photon mass governed by the relation Λ ˜m2 . A detailed numerical analysis shows that the nonvanishing photon mass on the order of ˜1 0-34 eV is consistent with current observations. This magnitude is far less than the most stringent limit on the photon mass available so far, which is on the order of m ≤1 0-27 eV .
NASA Astrophysics Data System (ADS)
Velimsky, J.
2011-12-01
Inversion of observatory and low-orbit satellite geomagnetic data in terms of the three-dimensional distribution of electrical conductivity in the Earth's mantle can provide an independent constraint on the physical, chemical, and mineralogical composition of the Earth's mantle. This problem has been recently approached by different numerical methods. There are several key challenges from the numerical and algorithmic point of view, in particular the accuracy and speed of the forward solver, the effective evaluation of sensitivities of data to changes of model parameters, and the dependence of results on the a-priori knowledge of the spatio-temporal structure of the primary ionospheric and magnetospheric electric currents. Here I present recent advancements of the time-domain, spherical harmonic-finite element approach. The forward solver has been adapted to distributed-memory parallel architecture using band-matrix routines from the ScaLapack library. The evaluation of gradient of data misfit in the model space using adjoint approach has been also paralellized. Finally, the inverse problem has been reformulated in a way which allows for simultaneous reconstruction of conductivity model and external field model directly from the data.
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.
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
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. PMID:18371945
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.
Massive star birth: A crossroads of Astrophysics
NASA Astrophysics Data System (ADS)
Cesaroni, R.; Felli, M.; Churchwell, E.; Walmsley, M.
Massive stars, those with between 10 and 100 times the mass of the Sun, are among the rarest stars of all. They live fast and die young, but during their short lives produce the most dramatic effects on the surrounding interstellar medium in terms of dynamics, ionization, and chemical enrichment. Until a few decades ago massive star birth was literally shrouded in mystery, since these stars are born deep inside dense clouds of swirling dust and gas that obscures our view. At IAU S227, more than 200 of the world's leading astronomers presented a cornucopia of new results concerning the birth and infancy of massive stars. These proceedings show the achievements reached in this field, due to observations in the radio at mm and sub-mm wavelengths and in the infrared, and to theoretical models that simulate what happens in the cradle of a massive star.
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}.
NASA Astrophysics Data System (ADS)
van der Tak, F. F. S.; van Dishoeck, E. F.; Caselli, P.
2000-09-01
The chemistry of CH3OH and H2CO in thirteen regions of massive star formation is studied through single-dish and interferometer line observations at submillimeter wavelengths. Single-dish spectra at 241 and 338 GHz indicate that Trot = 30-200 K for CH3OH, but only 60-90 K for H2CO. The tight correlation between Trot(CH3OH) and Tex(C2H2) from infrared absorption suggests a common origin of these species, presumably outgassing of icy grain mantles. The CH3OH line widths are 3-5 km s-1, consistent with those found earlier for C17O and C34S, except in GL 7009S and IRAS 20126, whose line shapes reveal CH3OH in the outflows. This difference suggests that for low-luminosity objects, desorption of CH3OH-rich ice mantles is dominated by shocks, while radiation is more important around massive stars. The wealth of CH3OH and H2CO lines covering a large range of excitation conditions allows us to calculate radial abundance profiles , using the physical structures of the sources derived earlier from submillimeter continuum and CS line data. The data indicate three types of abundance profiles: flat profiles at CH3OH/H2 ~ 10-9 for the coldest sources, profiles with a jump in its abundance from ~ 10-9 to ~ 10-7 for the warmer sources, and flat profiles at CH3OH/H2 ~ few 10-8 for the hot cores. The models are consistent with the ~ 3'' size of the CH3OH 107 GHz emission measured interferometrically. The location of the jump at T~ 100 K suggests that it is due to evaporation of grain mantles, followed by destruction in gas-phase reactions in the hot core stage. In contrast, the H2CO data can be well fit with a constant abundance of a few x 10-9 throughout the envelope, providing limits on its grain surface formation. These results indicate that Trot (CH3OH) can be used as evolutionary indicator during the embedded phase of massive star formation, independent of source optical depth or orientation. Model calculations of gas-grain chemistry show that CO is primarily reduced (into CH3OH
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 Astrophysics Data System (ADS)
Rust, A.; Annen, C.; Blundy, J. D.; Caricchi, L.
2010-12-01
The Lago Della Vacca granitoid is an intrusive body emplaced at about 4-6 km in up to 1 My. The core of the body is characterised by the presence of dyke-like structures, enclave-swarms and randomly distributed enclaves, which appear undeformed. Enclaves become oblate with the short axis perpendicular to the foliation, which, in turn follows the margin of the plutonic body (John and Blundy, 1993). Geothermometry and experimental data have been used to constrain the temperature of injection of the mafic component (1273-1323 K), the temperature of the host granitic magma (1173-1223), and to characterise the evolution of crystallinity with temperature for both magmas (Blundy and Sparks, 1992). Based on these data thermal and rheological modelling have been combined to interpret the growth and deformation history of the Lago della Vacca intrusive body. The pluton was modeled as a series of incrementally emplaced nested cylinders with 1D-cylindrical conductive heat transfer. The evolution of temperature and melt fraction distribution in the pluton and country rock were determined and used as input parameters for the rheological modelling. The rheology of each magma depends on the viscosity of the melt and, more importantly, on crystallinity. Field observations suggest that the mafic magma was injected as dykes. Their partial or total disaggregation produced mafic enclaves. The presence of randomly distributed enclaves in the core of Lago Della Vacca body indicates that convection was active in this portion of the intrusion. The undeformed nature of the enclaves in this region also implies that the contrast in temperature between host magma and mafic material produced a sudden (hours) rheological inversion with the mafic magma becoming more viscous than the felsic end-member. In these conditions, the enclaves would be transported passively by the felsic-host without suffering any substantial deformation. Thermal modelling indicates that to maintain the core of the pluton
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
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.
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.
Jayachandran, Guha; Vishal, V; Pande, Vijay S
2006-04-28
We report on the use of large-scale distributed computing simulation and novel analysis techniques for examining the dynamics of a small protein. Matters addressed include folding rate, very long time scale kinetics, ensemble properties, and interaction with water. The target system for the study, the villin headpiece, has been of great interest to experimentalists and theorists both. Sampling totaled nearly 500 mus-the most extensive published to date for a system of villin's size in explicit solvent with all atom detail-and was in the form of tens of thousands of independent molecular dynamics trajectories, each several tens of nanoseconds in length. We report on kinetics sensitivity analyses that, using a set of short simulations, probed the role of water in villin's folding and sensitivity to the simulation's electrostatics treatment. By constructing Markovian state models (MSMs) from the collected data, we were able to propagate dynamics to times far beyond those directly simulated and to rapidly compute mean first passage times, long time kinetics (tens of microseconds), and evolution of ensemble property distributions over long times, otherwise currently impossible. We also tested our MSM by using it to predict the structure of villin de novo. PMID:16674165
McKeown, Andrew DJ; Beattie, Rebekah F; Murrell, George AC
2015-01-01
Background Massive irreparable rotator cuff tears are a difficult problem. Modalities such as irrigation and debridement, partial repair, tendon transfer and grafts have been utilized with high failure rates and mixed results. Synthetic interpositional patch repairs are a novel and increasingly used approach. The present study aimed to examine the biomechanical properties of common synthetic materials for interpositional repairs in contrast to native tendon. Methods Six ovine tendons, six polytetrafluoroethylene (PTFE) felt sections and six expanded PTFE (ePTFE) patch sections were pulled-to-failure to analyze their biomechanical and material properties. Six direct tendon-to-bone surgical method repairs, six interpositional PTFE felt patch repairs and six interpositional ePTFE patch repairs were also constructed in ovine shoulders and pulled-to-failure to examine the biomechanical properties of each repair construct. Results Ovine tendon had higher load-to-failure (591 N) and had greater stiffness (108 N/mm) than either PTFE felt (296 N, 28 N/mm) or ePTFE patch sections (323 N, 34 N/mm). Both PTFE felt and ePTFE repair techniques required greater load-to-failure (225 N and 177 N, respectively) than direct tendon-to-bone surgical repairs (147 N) in ovine models. Conclusions Synthetic materials lacked several biomechanical properties, including strength and stiffness, compared to ovine tendon. Interpositional surgical repair models with these materials were significantly stronger than direct tendon-to-bone model repairs. PMID:27582997
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)
Toth, L. Viktor; Marton, Gabor; Zahorecz, Sarolta
2015-08-01
The all-sky Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015) allows an almost unbiased study of the early phases of star-formation in our Galaxy. Several thousand of the clumps have also distance estimates allowing a mass, and density determination. The nature of Planck clumps varies from IRDCs to tiny nearby cold clouds with masses ranging from one to several tens of thousands solar masses. Some of the clumps are embedded in GMCs, others are isolated. Some are close or even very close to OB associations, while others lay far from any UV luminous objects.The small scale clustering of these objects was studied with the improved Minimum Spanning Tree method of Cartwright & Whitworth identifying groups in 3D space. As a result also massive cold cloud clusters were identified. We analyse the MST structures, and discuss their relation to ongoing and future massive star formation.
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.
Massive Binaries: Dynamical and Evolutionary Transformations
NASA Astrophysics Data System (ADS)
Gies, D. R.
2012-12-01
Observations of massive binaries offer us key insight about the formation, evolution, and destinies of massive stars. Here I review some advances in observational and theoretical studies of massive binaries. Surveys for binaries using radial velocity, photometric, and high angular resolution methods show that the binary frequency is high for O stars in clusters. Evolutionary models for interacting binaries demonstrate the importance of angular momentum transfer during Roche lobe overflow. The mass gainer may reach critical rotation and stem further accretion, and there are many observed cases that show the consequences of such mass loss and transfer. New hydrodynamical models describe colliding wind physics in eccentric binaries such as η Carinae and WR 140. All these research topics are championed by Tony Moffat, and the current richness of this field is due in large measure to his energetic pursuits.
Clarifying Massive Protostellar Evolution and Circumstellar Processing
NASA Astrophysics Data System (ADS)
Indebetouw, Remy; Brogan, Crystal; Hoare, Melvin; Lumsden, Stuart; Robitaille, Thomas; Sewilo, Marta; Urquhart, James; Viti, Serena; Whitney, Barbara
2008-03-01
Massive stars dominate the evolution of galaxies and even as protostars, their feedback can affect their own formation and that of their host clusters. We propose a systematic study of massive protostars through the stages of their early evolution, to derive a clearer evolutionary sequence and a better link between the state of the central source and physical conditions in circumstellar material. This experiment will improve over existing work by careful source selection to systematically span evolutionary parameter space, resulting in a more uniform and comprehensive sample. Sophisticated radiative transfer, ionization, and chemical modeling will be used to extract the full riches of each IRS spectrum and find trends in how massive stars form and process their natal material: We will be able to determine the temperature, density, and chemical state (heating history) of circumstellar dust and ice in the accretion disk and envelope, and at later evolutionary stages the ionizing and soft (PAH-exciting) ultraviolet radiation emitted by the protostars and how that radiation is quenched and shadowed by circumstellar material. This investigation is the key to realizing the full potential of previous infrared imaging surveys like MSX and Spitzer's GLIMPSE and MIPSGAL to study massive star formation. These surveys have provided a basis for us to select a large relatively unbiased sample spanning evolutionary state. In return, revealing the spectroscopic signature of massive YSOs will greatly clarify the modeling and interpretation of the thousands of other protostars in these imaging survey data.
Analyzing Unfavored Fragmentation Functions Using NJL-Jet Model
Matevosyan, Hrayr H.; Thomas, Anthony W.; Bentz, Wolfgang
2011-10-24
The Nambu-Jona-Lasinio (NJL)-jet model provides a sound framework for calculating the fragmentation functions in an effective chiral quark theory, where the momentum and isospin sum rules are satisfied without the introduction of ad hoc parameters. The most recent version of the model includes the fragmentation of the light and strange quarks to pions, kaons, nucleons, and antinucleons; where the effects of the production of secondary pions and kaons from the vector mesons {rho}, K* and {phi} are also calculated. The results for the model fragmentation function exhibit a qualitative agreement with the empirical parameterizations. The results also allow to test, within the model assumptions, several assumption in parametrizations of the unfavored fragmentation functions used in empirical fits to the experimental data.
Kamionkowski, Marc; Profumo, Stefano
2008-12-31
Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle annihilation occurs in the first collapsed dark-matter halos. We show that severe constraints to the annihilation cross section derive from measurements of the diffuse extragalactic radiation and from ionization and heating of the intergalactic medium. PMID:19437633
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.
The simultaneous formation of massive stars and stellar clusters
NASA Astrophysics Data System (ADS)
Smith, Rowan J.; Longmore, Steven; Bonnell, Ian
2009-12-01
We show that massive stars and stellar clusters are formed simultaneously, the global evolution of the forming cluster is what allows the central stars to become massive. We predict that massive star-forming clumps, such as those observed in Motte et al., contract and grow in mass leading to the formation of massive stars. This occurs as mass is continually channelled from large radii on to the central protostars, which can become massive through accretion. Using smoothed particle hydrodynamic simulations of massive star-forming clumps in a giant molecular cloud, we show that clumps are initially diffuse and filamentary, and become more concentrated as they collapse. Simulated interferometry observations of our data provide an explanation as to why young massive star-forming regions show more substructure than older ones. The most massive stars in our model are found within the most bound cluster. Most of the mass accreted by the massive stars was originally distributed throughout the clump at low densities and was later funnelled to the star due to global infall. Even with radiative feedback no massive pre-stellar cores are formed. The original cores are of intermediate mass and gain their additional mass in the protostellar stage. We also find that cores which form low-mass stars exist within the volume from which the high-mass stars accrete, but are largely unaffected by this process.
Massive supersymmetric quantum gauge theory
NASA Astrophysics Data System (ADS)
Grigore, D. R.; Gut, M.; Scharf, G.
2005-08-01
We continue the study of the supersymmetric vector multiplet in a purely quantum framework. We obtain some new results which make the connection with the standard literature. First we construct the one-particle physical Hilbert space taking into account the (quantum) gauge structure of the model. Then we impose the condition of positivity for the scalar product only on the physical Hilbert space. Finally we obtain a full supersymmetric coupling which is gauge invariant in the supersymmetric sense in the first order of perturbation theory. By integrating out the Grassmann variables we get an interacting Lagrangian for a massive Yang-Mills theory related to ordinary gauge theory; however the number of ghost fields is doubled so we do not obtain the same ghost couplings as in the standard model Lagrangian.
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.
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Kim, Hyun-Chul; Goeke, Klaus
2008-10-01
We investigate the vector transition form factors of the nucleon and vector meson K to the pentaquark baryon Θ within the framework of the SU(3) chiral quark-soliton model. We take into account the rotational 1/N and linear m corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU(3) symmetry-breaking terms yield sizeable effects on the vector transition form factors. In particular, the main contribution to the electric-like transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo-Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the K vector and tensor coupling constants for the Θ: g=0.74-0.87 and f=0.53-1.16. We argue that the outcome of the present work is consistent with the null results of the CLAS experiments in the reactions γn→KΘ and γp→KΘ. The results of the present work are also consistent with the recent experiments at KEK. In addition, we present the results of the Σ→NK transition form factors and its KNΣ coupling constants.
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.
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.
Derivative couplings in massive bigravity
NASA Astrophysics Data System (ADS)
Gao, Xian; Heisenberg, Lavinia
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.
Massively parallel MRI detector arrays
NASA Astrophysics Data System (ADS)
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.
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
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. PMID:23453758
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.
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.
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.
Higher dimensional nonlinear massive gravity
NASA Astrophysics Data System (ADS)
Do, Tuan Q.
2016-05-01
Inspired by a recent ghost-free nonlinear massive gravity in four-dimensional spacetime, we study its higher dimensional scenarios. As a result, we are able to show the constantlike behavior of massive graviton terms for some well-known metrics such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini (anti-) de Sitter metrics in a specific five-dimensional nonlinear massive gravity under an assumption that its fiducial metrics are compatible with physical ones. In addition, some simple cosmological solutions of the five-dimensional massive gravity are figured out consistently.
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. PMID:15939162
Aspergilloma and massive haemoptysis
Ding, Wern Yew; Chan, Tze; Yadavilli, Rajesh Kumar; McWilliams, Richard
2014-01-01
A 40-year-old homeless woman who was a known intravenous drug user and heroin smoker, presented with massive haemoptysis. Initial CT-pulmonary angiogram (CT-PA) did not show active haemorrhage but found an opacity in a right upper lobe cavity likely to represent a mycetoma. She was started on antifungal therapy but haemoptysis persisted and bronchial angiography was performed. Again no active haemorrhage was identified but abnormal vasculature was seen supplying the right upper lobe. This was empirically embolised with particles which did not improve her symptoms. A subsequent CT-PA identified a pulmonary artery pseudoaneurysm in the cavity wall which was successfully embolised. There was no further haemoptysis and a repeat CT-PA 3 weeks later showed continuing occlusion of the pulmonary artery aneurysm. Investigations for tuberculosis were negative and she was discharged clinically well and on long-term antifungal therapy. PMID:24739651
Impact-parameter dependent color glass condensate dipole model and new combined HERA data
NASA Astrophysics Data System (ADS)
Rezaeian, Amir H.; Schmidt, Ivan
2013-10-01
The impact-parameter dependent color glass condensate (b-CGC) dipole model is based on the Balitsky-Kovchegov nonlinear evolution equation and improves the Iancu-Itakura-Munier dipole model by incorporating the impact-parameter dependence of the saturation scale. Here we confront the model to the recently released high precision combined Hadron Electron Ring Accelerator (HERA) data and obtain its parameters. The b-CGC results are then compared to data at small x for the structure function, the longitudinal structure function, the charm structure function, exclusive vector meson (J/ψ, ϕ, and ρ) production and deeply virtual Compton scattering. We also compare our results with the impact-parameter dependent saturation (IP-Sat) model. We show that most features of inclusive deep inelastic scattering and exclusive diffractive data, including the Q2, W, |t|, and x dependence, are correctly reproduced in both models. Nevertheless, the b-CGC and the impact-parameter dependent saturation (IP-Sat) models give different predictions beyond the current HERA kinematics, namely for the structure functions at very low x and high virtualities Q2, and for the exclusive diffractive vector meson and deeply virtual Compton scattering production at high t. This can be traced back to the different power-law behavior of the saturation scale in x and to a different impact-parameter b dependence of the saturation scale in these models. Nevertheless, both models give approximately similar saturation scales QS<1GeV for the proton in HERA kinematics, and also both models lead to the same conclusion that the typical impact parameter probed in the total γ*p cross section is about b≈2-3GeV-1. Our results provide a benchmark for further investigation of QCD at small x in heavy ion collisions at RHIC and the LHC and also at future experiments such as an electron-ion collider and the LHeC.
NASA Astrophysics Data System (ADS)
González Delgado, Rosa María
2007-07-01
Starbursts are the preferred place where massive stars form; the main source of thermal and mechanical heating in the interstellar medium, and the factory where the heavy elements form. Thus, starbursts play an important role in the origin and evolution of galaxies. Starbursts are bright at ultraviolet (UV) wavelengths, and after the pioneering IUE program, high spatial and spectral resolution UV observations of local starburst galaxies, mainly taken with HST and FUSE, have made relevant contributions to the following issues: a) The determination of the initial mass function (IMF) in violent star forming systems in low and high metallicity environments, and in dense (e.g. in stellar clusters) and diffuse environments: A Salpeter IMF with high-mass stars constrains well the UV properties. b) Stellar clusters are an important mode of star formation in starbursts. c) The role of starbursts in AGN: Nuclear starbursts can dominate the UV light in Seyfert 2 galaxies, having bolometric luminosities similar to the estimated bolometric luminosities of the obscured AGN. d) The interaction between massive stars and the interstellar medium: Outflows in cold, warm and coronal phases leave their imprints on the UV interstellar lines. Outflows of a few hundred km s%u22121 are ubiquitous phenomena in starbursts. Despite the very significant progress obtained over the past two decades of UV observations of starbursts, there are important problems that still need to be solved. High-spatial resolution UV observations of nearby starbursts are crucial to further progress in understanding the violent star formation processes in galaxies, the interaction between the stellar clusters and the interstellar medium, and the variation of the IMF. High-spatial resolution spectra are also needed to isolate the light from the center to the disk in UV luminous galaxies found by GALEX. Thus, a new UV mission furnished with an intermediate spectral resolution spectrograph with high spatial
On the generalized minimal massive gravity
NASA Astrophysics Data System (ADS)
Setare, M. R.
2015-09-01
In this paper we study the Generalized Minimal Massive Gravity (GMMG) in asymptotically AdS3 background. The generalized minimal massive gravity theory is realized by adding the CS deformation term, the higher derivative deformation term, and an extra term to pure Einstein gravity with a negative cosmological constant. We study the linearized excitations around the AdS3 background and find that at special point (tricritical) in parameter space the two massive graviton solutions become massless and they are replaced by two solutions with logarithmic and logarithmic-squared boundary behavior. So it is natural to propose that GMMG model could also provide a holographic description for a 3-rank Logarithmic Conformal Field Theory (LCFT). We calculate the energy of the linearized gravitons in AdS3 background, and show that the theory is free of negative-energy bulk modes. Then we obtain the central charges of the CFT dual explicitly and show GMMG also avoids the aforementioned "bulk-boundary unitarity clash". After that we show that General Zwei-Dreibein Gravity (GZDG) model can reduce to GMMG model. Finally by a Hamiltonian analysis we show that the GMMG model has no Boulware-Deser ghosts and this model propagates only two physical modes.
How I treat patients with massive hemorrhage.
Johansson, Pär I; Stensballe, Jakob; Oliveri, Roberto; Wade, Charles E; Ostrowski, Sisse R; Holcomb, John B
2014-11-13
Massive hemorrhage is associated with coagulopathy and high mortality. The transfusion guidelines up to 2006 recommended that resuscitation of massive hemorrhage should occur in successive steps using crystalloids, colloids, and red blood cells (RBCs) in the early phase and plasma and platelets in the late phase. With the introduction of the cell-based model of hemostasis in the mid-1990s, our understanding of the hemostatic process and of coagulopathy has improved. This has contributed to a change in resuscitation strategy and transfusion therapy of massive hemorrhage along with an acceptance of the adequacy of whole blood hemostatic tests to monitor these patients. Thus, in 2005, a strategy aiming at avoiding coagulopathy by proactive resuscitation with blood products in a balanced ratio of RBC:plasma:platelets was introduced, and this has been reported to be associated with reduced mortality in observational studies. Concurrently, whole blood viscoelastic hemostatic assays have gained acceptance by allowing a rapid and timely identification of coagulopathy along with enabling an individualized, goal-directed transfusion therapy. These strategies joined together seem beneficial for patient outcome, although final evidence on outcome from randomized controlled trials are lacking. We present how we in Copenhagen and Houston, today, manage patients with massive hemorrhage. PMID:25293771
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.
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.
NASA Astrophysics Data System (ADS)
Dixon, John A.
2015-10-01
An action for a complex irreducible massive superspin 1/2 multiplet can be constructed out of two chiral dotted spinor and two chiral undotted spinor superfields. To make this action a sensible one, additional 'reality constraints' are needed, and the notion of BRST recycling is needed to find the supersymmetry transformations of the theory with these additional constraints. This theory possesses three possible mass terms. An earlier paper examined the theory with the first mass term. This paper adds a second mass term and examines the consequences of that. This second mass invariant is 'extraordinary', which means that it is intrinsically dependent on the Zinn sources ('antifields') of the theory. This in turn implies that the action needs to be 'completed' so that it yields zero for the relevant Poisson Bracket. This 'Completion' meets an 'Obstruction', which is a ghost charge one object in the BRST cohomology space. Usually Obstructions arise from a one loop calculation, in which case they form anomalies of the theory. However this Obstruction arises at tree level from the completion. The coefficient of the Obstruction needs to be set to zero. This restores the complex irreducible massive superspin 1/2 multiplet to its usual structure, except that the mass is constructed out of the two mass parameters. The construction suggests interesting possibilities for related interacting theories.
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.
Comments on the Evolution of Massive Stars
NASA Astrophysics Data System (ADS)
El Eid, M. F.; The, L.-S.; Meyer, B. S.
We describe in a brief form present results we have obtained from a careful and up to date study of the evolution of massive stars including their advanced evolutionary phases beyond the oxygen burning phase. We describe the effects of mass loss, treatment of convection in inhomogeneous stellar layers and the rate of the 12C(α,γ)16O reaction on the properties of stellar models in the interesting case of a 25 M⊙ star of solar-like initial metallicity.
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.
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
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.
Massively Parallel Direct Simulation of Multiphase Flow
COOK,BENJAMIN K.; PREECE,DALE S.; WILLIAMS,J.R.
2000-08-10
The authors understanding of multiphase physics and the associated predictive capability for multi-phase systems are severely limited by current continuum modeling methods and experimental approaches. This research will deliver an unprecedented modeling capability to directly simulate three-dimensional multi-phase systems at the particle-scale. The model solves the fully coupled equations of motion governing the fluid phase and the individual particles comprising the solid phase using a newly discovered, highly efficient coupled numerical method based on the discrete-element method and the Lattice-Boltzmann method. A massively parallel implementation will enable the solution of large, physically realistic systems.
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.
Dust in regions of massive star formation
NASA Technical Reports Server (NTRS)
Wolfire, Mark G.; Cassinelli, J. P.
1989-01-01
It is suggested that protostars increase mass by accreting the surrounding gas and dust. Grains are destroyed as they near the central protostar creating a dust shell or cocoon. Radiation pressure acting on the grains can halt the inflow of material thereby limiting the amount of mass accumulated by the protostar. General constraints were considered on the initial dust-to-gas ratio and mass accretion rates that permit inflow. These results were constrained further by constructing a numerical model, including radiative deceleration on grains and grain destruction processes. Also the constraints on dust properties were investigated which allow the formation of massive stars. The obtained results seem to suggest that massive star formation requires rather extreme preconditioning of the grain and gas environment.
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.
Geometric massive gravity in multiconnection framework
NASA Astrophysics Data System (ADS)
Khosravi, Nima
2014-01-01
What is the right way to interpret a massive graviton? We generalize the kinematical framework of general relativity to multiple connections. The average of the connections is itself a connection and plays the role of the canonical connection in standard general relativity. At the level of dynamics, the simplest choice of the Einstein-Hilbert action is indistinguishable from the single-connection case. However, inspired by Weyl geometry, we show how one can construct massive gravity to all orders in perturbation theory compatible with the de Rham-Gabadadze-Tolley ghost-free model. We conclude that the mass of the graviton can be interpreted as a geometrical property of spacetime arising from two connections. Furthermore, in the multiconnection framework there is no ambiguity in the definition of the physical metric and consequently coupling to matter.
The most massive MaxBCG clusters
NASA Astrophysics Data System (ADS)
Murray, Stephen
2014-09-01
Great progress on galaxy clusters has been made in the last several years with SZ and optical surveys. Some new puzzles also emerged and one of them is the mismatch between the stacked Planck SZ fluxes and the model expectations for the MaxBCG clusters. While previous studies regarding this puzzle require the calibration of the true mass and the standard pressure template, we bypass the intermediate steps to directly compare the pressure content derived from the X-ray data with the SZ flux, for massive MaxBCG clusters. This proposal requests Chandra data for 3 clusters to complete a sample of 12 most massive MaxBCG clusters observed with either XMM or Chandra. The results will shed light on the mismatch puzzle and constrain the important scaling relations like Y_X - N_200 and Y_X - Y_SZ.
Massive to gauge field reduction and gravitational wave zone information
NASA Astrophysics Data System (ADS)
Deser, S.
2016-07-01
I analyze the possible relevance of LIGO's gravitational wave detection to the viability of massive gravity models. In GR, a wave zone, where the linearized approximation holds, is guaranteed to exist and the observed wave's amplitude profile can be sufficiently related to the emitting strong field interior to verify that, in this case, it was due to an inspiraling black hole merger. After an excursion to massive spin 1's massless limit, linear massive tensor theory is shown explicitly to propagate only (retarded) maximal, helicity 2, modes to O( m) as m→ 0; however, we don't know if the full theory has a similar "wave zone" governed by the linear model. Even if it does, a much more serious obstacle for massive gravity is to construct a time-varying strong field event to compare with the strong field footprint of LIGO's observed signals.
X(3872) as a molecular DD* state in a potential model
Lee, Ian Woo; Faessler, Amand; Gutsche, Thomas; Lyubovitskij, Valery E.
2009-11-01
We discuss the possibility that the X(3872) can be a hadronic DD* bound state in the framework of a potential model. The potential is generated by the exchange of pseudoscalar, scalar, and vector mesons resulting from the Lagrangian of heavy hadron chiral perturbation theory. The hadronic bound state configuration contains charged and neutral DD* components, while orbital S and D waves are included. Isospin symmetry breaking effects are fully taken into account. We show that binding in the DD* system with J{sup PC}=1{sup ++} already exists for a reasonable value of the meson-exchange regularization parameter of {lambda}{approx}1.2 GeV. We also explore the possibility of hadronic BB* bound states and show that binding can be achieved in the isoscalar limit for J{sup PC}=1{sup ++} or 1{sup +-}.
Study of the η‧→Ve+e- decay with hidden local symmetry model
NASA Astrophysics Data System (ADS)
Yang, Yue-Ling; Huang, Jin-Shu; Lu, Gong-Ru
2015-02-01
Within the hidden local symmetry framework, the Dalitz decay η‧→Ve+e- is studied with the vector meson dominance model. It is found that the partial width Γ(η‧→ωe+e-) ≈ 40 eV and branching ratio β(η‧→ωe+e-) ≈ 2×10-4, and Γ(η‧→ρe+e-) ≈ 10Γ(η‧→ωe+e-) and β(η‧→ρe+e-) ≈ 10β(η‧→ωe+e-). The maximum position of the dilepton distribution is me+e- ≈1.33 MeV. These decays are measurable with the advent of high statistic η‧ experiments. Supported by National Natural Science Foundation of China (11147008, 11275057, U1332103, U1232101) and Program for Science and Technology Innovation Talents in Universities of Henan Province (2012HASTIT030)
NASA Astrophysics Data System (ADS)
Ivanov, M. V.; Megias, G. D.; González-Jiménez, R.; Moreno, O.; Barbaro, M. B.; Caballero, J. A.; Donnelly, T. W.
2016-08-01
Charged current inclusive neutrino-nucleus cross sections are evaluated using the superscaling model for quasielastic scattering and its extension to the pion production region. The contribution of two-particle-two-hole vector meson-exchange current excitations is also considered within a fully relativistic model tested against electron scattering data. The results are compared with the inclusive neutrino-nucleus data from the T2K and SciBooNE experiments. For experiments where < {E}ν > ∼ 0.8 {{GeV}}, the three mechanisms considered in this work provide good agreement with the data. However, when the neutrino energy is larger, effects from beyond the Δ also appear to be playing a role. The results show that processes induced by vector two-body currents play a minor role in the inclusive cross sections at the kinematics considered.
Super-Massive Stars: Dense Star-Gas Systems
NASA Astrophysics Data System (ADS)
Amaro-Seoane, Pau; Spurzem, Rainer; Just, Andreas
We use a gaseous model and a semi-analytical approach to study the evolution of a super-massive central gaseous object (a super-massive star, {SMS} from now on) in an AGN and its evolution by interactions with the surrounding stellar system. Our future work in this field is outlined, which aims at a more detailed study of energy flows in the interstellar medium, stellar evolution and the relation between QSOs and galaxy formation.
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.
f(R) Cosmology and Massive Neutrinos
NASA Astrophysics Data System (ADS)
Motohashi, Hayato; Starobinsky, Alexei A.; Yokoyama, Jun'ichi
2012-02-01
f(R) gravity provides viable cosmology alternative to the ΛCDM model. We discuss the effect of massive neutrinos on matter power spectrum in this theory, to show that the anomalous growth of density fluctuations on small scales due to the scalaron force can be compensated by free streaming of neutrinos. As a result, models which predict observable deviation of the equation-of-state parameter wDE from wDE = -1 may be reconciled with observations of matter clustering if the total neutrino mass is O(0.5 eV).
Extreme parameter sensitivity in quasidilaton massive gravity
NASA Astrophysics Data System (ADS)
Anselmi, Stefano; López Nacir, Diana; Starkman, Glenn D.
2015-10-01
We reanalyze the behavior of Friedmann-Lemaître-Robertson-Walker cosmologies in the recently proposed quasidilaton massive-gravity model, and discover that the background dynamics present hitherto unreported features that require unexpected fine-tuning of the additional fundamental parameters of the theory for an observationally consistent background cosmology. We also identify new allowed regions in the parameter space and exclude some of the previously considered ones. The evolution of the mass of gravitational waves reveals nontrivial behavior, exhibiting a mass-squared that may be negative in the past, and that presently, while positive, is larger than the square of the Hubble parameter, H02 . These properties of the gravity-wave mass have the potential to lead to observational tests of the theory. While quasidilaton massive gravity is known to have issues with stability at short distances, the current analysis is a first step toward the investigation of the more stable extended quasidilaton massive-gravity theory, with some expectation that both the fine-tuning of parameters and the interesting behavior of the gravity-wave mass will persist.
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.
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.
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.
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''.
Warped black holes in 3D general massive gravity
NASA Astrophysics Data System (ADS)
Tonni, Erik
2010-08-01
We study regular spacelike warped black holes in the three dimensional general massive gravity model, which contains both the gravitational Chern-Simons term and the linear combination of curvature squared terms characterizing the new massive gravity besides the Einstein-Hilbert term. The parameters of the metric are found by solving a quartic equation, constrained by an inequality that imposes the absence of closed timelike curves. Explicit expressions for the central charges are suggested by exploiting the fact that these black holes are discrete quotients of spacelike warped AdS 3 and a known formula for the entropy. Previous results obtained separately in topological massive gravity and in new massive gravity are recovered as special cases.
Population synthesis of massive stars
NASA Astrophysics Data System (ADS)
Vanbeveren, Dany
2014-09-01
This review deals with massive star population synthesis with a realistic population of binaries. We focus on the comparison between observed star numbers (as a function of metallicity) and theoretically predicted numbers of stellar populations in regions of continuous star formation and in starburst regions. Special attention is given to the O-type/WR/red supergiant stellar population, the population of blue supergiants, the pulsar and binary pulsar population, and the supernova rates. Finally, we consider massive double compact star mergers and the link with gravitational wave sources (the advanced LIGO II) and r-process element production sites.
Massive Gravitons on Bohmian Congruences
NASA Astrophysics Data System (ADS)
Fathi, Mohsen; Mohseni, Morteza
2016-08-01
Taking a quantum corrected form of Raychaudhuri equation in a geometric background described by a Lorentz-violating massive theory of gravity, we go through investigating a time-like congruence of massive gravitons affected by a Bohmian quantum potential. We find some definite conditions upon which these gravitons are confined to diverging Bohmian trajectories. The respective behaviour of those quantum potentials are also derived and discussed. Additionally, and through a relativistic quantum treatment of a typical wave function, we demonstrate schematic conditions on the associated frequency to the gravitons, in order to satisfy the necessity of divergence.
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
Massive stellar X-ray sources in the Galactic center
NASA Astrophysics Data System (ADS)
Mauerhan, Jon Christian
2008-06-01
The purpose of this thesis is to discover unidentified members of the massive stellar population in the Galactic center, using a novel selection technique: the identification of infrared counterparts to hard X-ray sources. This method provides a means of distinguishing a subset of hot, massive stars from the more numerous cool giants that dominate the stellar population of the central Galaxy, providing potential beacons toward undiscovered regions of massive star formation, and the remains of tidally-disrupted stellar clusters. Hard-X-ray selection also highlights exotic species of massive star, including Wolf-Rayet (WR) binaries with colliding supersonic winds, and wind-accreting neutron stars and black holes in high-mass X-ray binaries (HMXBs). Massive stars were sought in the central 300 pc of the Galaxy by cross- correlating X-ray and IR point-source catalogs. Approximately 1% of the 6067 Chandra X-ray sources near the Galactic center have near-infrared matches with K s < 15.6 mag. A spectroscopic campaign was launched to investigate the most promising candidates; 17 new WR/O stars were discovered throughout the inner 300 pc. Most of the massive stars exhibit infrared excess, attributable to free-free and dust emission. In many cases, mid-IR images exhibit strong interaction of the X-ray sources with the Galactic center medium. Most of the newly found sources have no apparent association with a dense stellar cluster, although several stars lie near the Quintuplet cluster and may have escaped from it. The X-ray emission of the massive stars is consistent with thermal emission from plasma at temperatures above 2 keV, not a ubiquitous feature of single massive stars. The X-ray data are consistent with models of strong WR/O winds colliding with the surfaces of binary companions, but are also consistent with known, low-luminosity HMXBs. Future experiments are discussed, aimed at unambiguously determining the masses of the stellar components, and surveying the
Finite temperature effect in infrared-improved AdS/QCD model with back reaction of bulk vacuum
NASA Astrophysics Data System (ADS)
Cui, Ling-Xiao; Fang, Zhen; Wu, Yue-Liang
2016-06-01
Based on an IR-improved soft-wall AdS/QCD model for mesons, which provides a consistent prediction for the mass spectra of resonance scalar, pseudoscalar, vector and axial-vector mesons, we investigate its finite temperature effect. By analyzing the spectral function of mesons and fitting it with a Breit-Wigner form, we perform an analysis for the critical temperature of mesons. The back-reaction effects of bulk vacuum are considered and the thermal mass spectral function of resonance mesons is calculated based on the back-reaction improved action. A reasonable melting temperature is found to be T c ≈ 150 ± 7 MeV, which is consistent with the recent results from lattice QCD simulations. Supported by National Nature Science Foundation of China (NSFC)(10975170, 10905084, 10821504), and Project of Knowledge Innovation Program (PKIP) of Chinese Academy of Science
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.
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.
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. PMID:27015472
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.
Dipolar dark matter with massive bigravity
NASA Astrophysics Data System (ADS)
Blanchet, Luc; Heisenberg, Lavinia
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.
Massive neutrinos in almost-commutative geometry
NASA Astrophysics Data System (ADS)
Stephan, Christoph A.
2007-02-01
In the noncommutative formulation of the standard model of particle physics by Chamseddine and Connes [Commun. Math. Phys. 182, 155 (1996), e-print hep-th/9606001], one of the three generations of fermions has to possess a massless neutrino. [C. P. Martin et al., Phys. Rep. 29, 363 (1998), e-print hep-th-9605001]. This formulation is consistent with neutrino oscillation experiments and the known bounds of the Pontecorvo-Maki-Nakagawa-Sakata matrix (PMNS matrix). But future experiments which may be able to detect neutrino masses directly and high-precision measurements of the PMNS matrix might need massive neutrinos in all three generations. In this paper we present an almost-commutative geometry which allows for a standard model with massive neutrinos in all three generations. This model does not follow in a straightforward way from the version of Chamseddine and Connes since it requires an internal algebra with four summands of matrix algebras, instead of three summands for the model with one massless neutrino.
Massive neutrinos in almost-commutative geometry
Stephan, Christoph A.
2007-02-15
In the noncommutative formulation of the standard model of particle physics by Chamseddine and Connes [Commun. Math. Phys. 182, 155 (1996), e-print hep-th/9606001], one of the three generations of fermions has to possess a massless neutrino. [C. P. Martin et al., Phys. Rep. 29, 363 (1998), e-print hep-th-9605001]. This formulation is consistent with neutrino oscillation experiments and the known bounds of the Pontecorvo-Maki-Nakagawa-Sakata matrix (PMNS matrix). But future experiments which may be able to detect neutrino masses directly and high-precision measurements of the PMNS matrix might need massive neutrinos in all three generations. In this paper we present an almost-commutative geometry which allows for a standard model with massive neutrinos in all three generations. This model does not follow in a straightforward way from the version of Chamseddine and Connes since it requires an internal algebra with four summands of matrix algebras, instead of three summands for the model with one massless neutrino.
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.
Massively parallel visualization: Parallel rendering
Hansen, C.D.; Krogh, M.; White, W.
1995-12-01
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 renderer use a MIMD approach. Implementations for these algorithms are presented for the Thinking Machines Corporation CM-5 MPP.
Dark matter in massive galaxies
NASA Astrophysics Data System (ADS)
Gerhard, Ortwin
2013-07-01
The spatial distributions of luminous and dark matter in massive early-type galaxies (ETGs) reflect the formation processes which shaped these systems. This article reviews the predictions of cosmological simulations for the dark and baryonic components of ETGs, and the observational constraints from lensing, hydrostatic X-ray gas atmospheres, and outer halo stellar dynamics.
Sinus histiocytosis with massive lymphadenopathy
Pastakia, B.; Weiss, S.H.
1987-11-01
Gallium uptake corresponding to the extent of the disease in a patient with histologically proven sinus histiocytosis with massive lymphadenopathy (SHML) is reported. Computerized tomography confirmed the presence of bilateral retrobulbar masses, involvement of both lateral recti, erosion of the bony orbital floor with encroachment of tumor into the right maxillary antrum, and retropharyngeal involvement.
Understanding massively open online courses.
Billings, Diane M
2014-02-01
Massively open online courses (MOOCs) are an innovative delivery system for educational offerings. MOOCs have been hailed with optimism for making education accessible to many, but at the same time, they have been criticized for poor participant completion rates. Nurse educators are considering whether and how to use MOOCs; this column explains MOOCs and their advantages and disadvantages for nurse educators. PMID:24494660
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.
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.
Improved analysis of J/{psi} decays into a vector meson and two pseudoscalars
Laehde, Timo A.; Meissner, Ulf-G.
2006-08-01
Recently, the BES collaboration has published an extensive partial-wave analysis of experimental data on J/{psi}{yields}{phi}{pi}{sup +}{pi}{sup -}, J/{psi}{yields}{omega}{pi}{sup +}{pi}{sup -}, J/{psi}{yields}{phi}K{sup +}K{sup -} and J/{psi}{yields}{omega}K{sup +}K{sup -}. These new results are analyzed here, with full account of detection efficiencies, in the framework of a chiral unitary description with coupled-channel final state interactions between {pi}{pi} and KK pairs. The emission of a dimeson pair is described in terms of the strange and nonstrange scalar form factors of the pion and the kaon, which include the final state interaction and are constrained by unitarity and by matching to the next-to-leading-order chiral expressions. This procedure allows for a calculation of the S-wave component of the dimeson spectrum including the f{sub 0}(980) resonance, and for an estimation of the low-energy constants of Chiral Perturbation Theory, in particular, the large N{sub c} suppressed constants L{sub 4}{sup r} and L{sub 6}{sup r}. The decays in question are also sensitive to physics associated with OZI violation in the 0{sup ++} channel. It is found that the S-wave contributions to {phi}{pi}{sup +}{pi}{sup -}, {phi}K{sup +}K{sup -} and {omega}{pi}{sup +}{pi}{sup -} given by the BES partial-wave analysis may be very well fitted up to a dimeson center-of-mass energy of {approx}1.2 GeV, for a large and positive value of L{sub 4}{sup r} and a value of L{sub 6}{sup r} compatible with zero. An accurate determination of the amount of OZI violation in the J/{psi}{yields}{phi}{pi}{sup +}{pi}{sup -} decay is achieved, and the S-wave contribution to {omega}K{sup +}K{sup -} near threshold is predicted.
Medium Modi cation on Vector Mesons Observed in 12 GeV p + A Reactions
NASA Astrophysics Data System (ADS)
Naruki, M.; En'yo, H.; Muto, R.; Tabaru, T.; Yokkaichi, S.; Fukao, Y.; Funahashi, H.; Ishino, M.; Kanda, H.; Kitaguchi, M.; Mihara, S.; Miwa, K.; Miyashita, T.; Murakami, T.; Nakura, T.; Sakuma, F.; Togawa, M.; Yamada, S.; Yoshimura, Y.; Chiba, J.; Ieiri, M.; Sasaki, O.; Sekimoto, M.; Tanaka, K. H.; Hamagaki, H.; Kek-Ps E325 Collaboration
2006-11-01
The invariant mass spectra of e+e- pairs produced in 12 GeV p+A reactions are measured at the KEK-PS. We observed a significant enhancement over the known hadronic sources on the low-mass side of the ω meson peak. The 95 % C.L. allowed parameter regions for ρ/ω ratio are obtained as ρ/ω < 0.15 and ρ/ω < 0.31 for C and Cu targets, respectively. As for the φ meson, the data obtained with a Cu target revealed a significant excess on the low-mass side of the φ meson peak mainly in the βγφ < 1.25 region.
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
Massive Stars in the Quintuplet Cluster
NASA Astrophysics Data System (ADS)
Figer, Donald F.; McLean, Ian S.; Morris, Mark
1999-03-01
We present near-infrared photometry and K-band spectra of newly identified massive stars in the Quintuplet cluster, one of the three massive clusters projected within 50 pc of the Galactic center. We find that the cluster contains a variety of massive stars, including more unambiguously identified Wolf-Rayet stars than any cluster in the Galaxy, and over a dozen stars in earlier stages of evolution, i.e., luminous blue variables (LBVs), Ofpe/WN9, and OB supergiants. One newly identified star is the second luminous blue variable in the cluster, after the ``Pistol star.'' Although we are unable to provide certain spectral classifications for the five enigmatic Quintuplet-proper members, we tentatively propose that they are extremely dusty versions of the WC stars found elsewhere in the cluster and similar to the dozen or so known examples in the Galaxy. Although the cluster parameters are uncertain because of photometric errors and uncertainties in stellar models, i.e., extrapolating initial masses and estimating ionizing fluxes, we have the following conclusions. Given the evolutionary stages of the identified stars, the cluster appears to be about 4+/-1 Myr old, assuming coeval formation. The total mass in observed stars is ~103 Msolar, and the implied mass is ~104 Msolar, assuming a lower mass cutoff of 1 Msolar and a Salpeter initial mass function. The implied mass density in stars is greater than or similar to a few thousand Msolar pc-3. The newly identified stars increase the estimated ionizing flux from this cluster by about an order of magnitude with respect to earlier estimates, to 1050.9 photons s-1, or roughly what is required to ionize the nearby ``Sickle'' H II region (G0.18-0.04). The total luminosity from the massive cluster stars is ~107.5 Lsolar, enough to account for the heating of the nearby molecular cloud, M0.20-0.033. We propose a picture that integrates most of the major features in this part of the sky, excepting the nonthermal filaments. We
Baryogenesis for weakly interacting massive particles
NASA Astrophysics Data System (ADS)
Cui, Yanou; Sundrum, Raman
2013-06-01
We propose a robust, unified framework, in which the similar baryon and dark matter cosmic abundances both arise from the physics of weakly interacting massive particles (WIMPs), with the rough quantitative success of the so-called “WIMP miracle.” In particular the baryon asymmetry arises from the decay of a metastable WIMP after its thermal freeze-out at or below the weak scale. A minimal model and its embedding in R-parity violating supersymmetry are studied as examples. The new mechanism saves R-parity violating supersymmetry from the potential crisis of washing out primordial baryon asymmetry. Phenomenological implications for the LHC and precision tests are discussed.
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.
The Λ2 limit of massive gravity
NASA Astrophysics Data System (ADS)
de Rham, Claudia; Tolley, Andrew J.; Zhou, Shuang-Yong
2016-04-01
Lorentz-invariant massive gravity is usually associated with a strong coupling scale Λ3. By including non-trivial effects from the Stückelberg modes, we show that about these vacua, one can push the strong coupling scale to higher values and evade the linear vDVZ-discontinuity. For generic parameters of the theory and generic vacua for the Stückelberg fields, the Λ2-decoupling limit of the theory is well-behaved and free of any ghost or gradient-like instabilities. We also discuss the implications for nonlinear sigma models with Lorentzian target spaces.
Probing Isolated Massive Star Formation in the LMC
NASA Astrophysics Data System (ADS)
Stephens, Ian
2012-10-01
Whether massive stars can form in isolation is one of the most debated questions in star formation. Observations of main sequence O-stars indicate that 5-10% of them form in isolation, but models of massive star formation suggest that massive stars should form in cluster environments. Isolated massive young stellar objects {YSOs} are better suited to address whether or not massive stars truly form in isolation since YSOs have had less time to disrupt their natal environment or move away from their stellar siblings. We have developed a unique sample of 7 candidates for isolated massive YSOs in the LMC. Within 80 pc, these objects are not associated with 1} other massive and intermediate-mass YSOs, 2} OB associations, and 3} giant molecular clouds {GMCs}. In all cases ground-based H-alpha observations show that they are affiliated with non-elongated, small HII regions and therefore are unlikely to be part of a runaway population. We request WFC3/UVIS and IR observations in the F656N, F555W, F814W, F110W, and F160W bands to examine the interstellar environment and determine the main sequence and pre-main sequence {PMS} populations down to 0.7 solar masses. In addition, coordinated parallel ACS/WFC F555W, F814W, and F658N observations will be used to assess the nearby control-field populations. From these observations we can search for lower-mass PMS stars, infer the local star formation history, and determine whether evidence exists for remnants of a disrupted GMC. With this statistically significant sample, we will have the ability to assess the possibility of massive stars forming in isolation.
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2009-12-01
We study exclusive nonleptonic two-body B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)})+F decays with F (pseudoscalar or vector mesons) factored out in the QCD factorization approach. The nonleptonic decay amplitudes are related to the product of meson decay constants and the form factors for semileptonic B{sub c} decays. As inputs in obtaining the branching ratios for a large set of nonleptonic B{sub c} decays, we use the weak form factors for the semileptonic B{sub c}{yields}(D{sub (s)},{eta}{sub c},B{sub (s)}) decays in the whole kinematical region and the unmeasured meson decay constants obtained from our previous light-front quark model. We compare our results for the branching ratios with those of other theoretical studies.
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.
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. PMID:25146286
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.
Chiral description of massive gravity
NASA Astrophysics Data System (ADS)
Alexandrov, Sergei; Krasnov, Kirill; Speziale, Simone
2013-06-01
We propose and study a new first order version of the ghost-free massive gravity. Instead of metrics or tetrads, it uses a connection together with Plebanski's chiral 2-forms as fundamental variables, rendering the phase space structure similar to that of SU(2) gauge theories. The chiral description simplifies computations of the constraint algebra, and allows us to perform the complete canonical analysis of the system. In particular, we explicitly compute the secondary constraint and carry out the stabilization procedure, thus proving that in general the theory propagates 7 degrees of freedom, consistently with previous claims. Finally, we point out that the description in terms of 2-forms opens the door to an infinite class of ghost-free massive bi-gravity actions. Our results apply directly to Euclidean signature. The reality conditions to be imposed in the Lorentzian signature appear to be more complicated than in the usual gravity case and are left as an open issue.
Efficient, massively parallel eigenvalue computation
NASA Technical Reports Server (NTRS)
Huo, Yan; Schreiber, Robert
1993-01-01
In numerical simulations of disordered electronic systems, one of the most common approaches is to diagonalize random Hamiltonian matrices and to study the eigenvalues and eigenfunctions of a single electron in the presence of a random potential. An effort to implement a matrix diagonalization routine for real symmetric dense matrices on massively parallel SIMD computers, the Maspar MP-1 and MP-2 systems, is described. Results of numerical tests and timings are also presented.
Analytics for Massive Heat Maps
Bohn, Shawn J.; Payne, Deborah A.; Nakamura, Grant C.; Love, Douglas V.
2009-01-19
High throughput instrumentation for genomics is producing data orders of magnitude greater than even a decade before. Biologists often visualize the data of these experiments through the use of heat maps. For large datasets, heat map visualizations do not scale. These visualizations are only capable of displaying a portion of the data, making it difficult for scientists to find and detect patterns that span more than a subsection of the data. We present a novel method that provides an interactive visual display for massive heat maps [O(108)]. Our process shows how a massive heat map can be decomposed into multiple levels of abstraction to represent the underlying macrostructures. We aggregate these abstractions into a framework that can allow real-time navigation of the space. To further assist pattern discovery, we ground our system on the principle of focus+context. Our framework also addresses the issue of balancing the memory and display resolution and heat map size. We will show that this technique for biologists provides a powerful new visual metaphor for analyzing massive datasets.
Analytics for massive heat maps
NASA Astrophysics Data System (ADS)
Bohn, Shawn J.; Payne, Deborah; Nakamura, Grant; Love, Douglass
2009-01-01
High throughput instrumentation for genomics is producing data orders of magnitude greater than even a decade before. Biologists often visualize the data of these experiments through the use of heat maps. For large datasets, heat map visualizations do not scale. These visualizations are only capable of displaying a portion of the data, making it difficult for scientists to find and detect patterns that span more than a subsection of the data. We present a novel method that provides an interactive visual display for massive heat maps [O(108)]. Our process shows how a massive heat map can be decomposed into multiple levels of abstraction to represent the underlying macrostructures. We aggregate these abstractions into a framework that can allow near real-time navigation of the space. To further assist pattern discovery, we ground our system on the principle of focus+context. Our framework also addresses the issue of balancing the memory and display resolution and heat map size. We will show that this technique for biologists provides a powerful new visual metaphor for analyzing massive datasets.
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.
NASA Astrophysics Data System (ADS)
Miah, Khalid; Bellefleur, Gilles
2014-05-01
The global demand for base metals, uranium and precious metals has been pushing mineral explorations at greater depth. Seismic techniques and surveys have become essential in finding and extracting mineral rich ore bodies, especially for deep VMS mining camps. Geophysical parameters collected from borehole logs and laboratory measurements of core samples provide preliminary information about the nature and type of subsurface lithologic units. Alteration halos formed during the hydrothermal alteration process contain ore bodies, which are of primary interests among geologists and mining industries. It is known that the alteration halos are easier to detect than the ore bodies itself. Many 3D geological models are merely projection of 2D surface geology based on outcrop inspections and geochemical analysis of a small number of core samples collected from the area. Since a large scale 3D multicomponent seismic survey can be prohibitively expensive, performance analysis of such geological models can be helpful in reducing exploration costs. In this abstract, we discussed challenges and constraints encountered in geophysical modelling of ore bodies and surrounding geologic structures from the available coarse 3D geological models of the Lalor Lake mining camp, located in northern Manitoba, Canada. Ore bodies in the Lalor lake VMS camp are rich in gold, zinc, lead and copper, and have an approximate weight of 27 Mt. For better understanding of physical parameters of these known ore bodies and potentially unknown ones at greater depth, we constructed a fine resolution 3D seismic model with dimensions: 2000 m (width), 2000 m (height), and 1500 m (vertical depth). Seismic properties (P-wave, S-wave velocities, and density) were assigned based on a previous rock properties study of the same mining camp. 3D finite-difference elastic wave propagation simulation was performed in the model using appropriate parameters. The generated synthetic 3D seismic data was then compared to
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 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
NASA Astrophysics Data System (ADS)
Gasper, F.; Goergen, K.; Shrestha, P.; Sulis, M.; Rihani, J.; Geimer, M.; Kollet, S.
2014-10-01
Continental-scale hyper-resolution simulations constitute a grand challenge in characterizing nonlinear 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 v1.0) 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 using the OASIS suite of external couplers, and require memory and load balancing considerations in the exchange of the coupling fields between different component models and the allocation of computational resources, respectively. Using the advanced profiling and tracing tool Scalasca to determine an optimum load balancing leads to a 19% speedup. In massively parallel supercomputer environments, the coupler OASIS-MCT is recommended, which resolves memory limitations that may be significant in case of very large computational domains and exchange fields as they occur in these specific test cases and in many applications in terrestrial research. However, model I/O and initialization in the petascale range still require major attention, as they constitute true big data challenges in light of future exascale computing resources. Based on a factor-two speedup due to compiler optimizations, a refactored coupling interface using OASIS-MCT and an optimum load balancing, the problem size in a weak scaling study can be increased by a factor of 64 from 512 to 32 768 processes while maintaining parallel efficiencies above 80% for the component models.
The Dynamics of Massive Starless Cores with ALMA
NASA Astrophysics Data System (ADS)
Tan, Jonathan C.; Kong, Shuo; Butler, Michael J.; Caselli, Paola; Fontani, Francesco
2013-12-01
How do stars that are more massive than the Sun form, and thus how is the stellar initial mass function (IMF) established? Such intermediate- and high-mass stars may be born from relatively massive pre-stellar gas cores, which are more massive than the thermal Jeans mass. The turbulent core accretion model invokes such cores as being in approximate virial equilibrium and in approximate pressure equilibrium with their surrounding clump medium. Their internal pressure is provided by a combination of turbulence and magnetic fields. Alternatively, the competitive accretion model requires strongly sub-virial initial conditions that then lead to extensive fragmentation to the thermal Jeans scale, with intermediate- and 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 extinction mapping of infrared dark clouds. Fontani et al. found high deuteration fractions of N2H+ in these objects, which are consistent with them being starless. Here we present ALMA observations of these four clumps that probe the N2D+ (3-2) line at 2.''3 resolution. We find six N2D+ cores and determine their dynamical state. Their observed velocity dispersions and sizes are broadly consistent with the predictions of the turbulent core model of self-gravitating, magnetized (with Alfvén Mach number mA ~ 1) and virialized cores that are bounded by the high pressures of their surrounding clumps. However, in the most massive cores, with masses up to ~60 M ⊙, our results suggest that moderately enhanced magnetic fields (so that mA ~= 0.3) may be needed for the structures to be in virial and pressure equilibrium. Magnetically regulated core formation may thus be important in controlling the formation of massive cores, inhibiting their fragmentation, and thus helping to establish the stellar IMF.
Massive Compact Stars as Quark Stars
NASA Astrophysics Data System (ADS)
Rodrigues, Hilário; Barbosa Duarte, Sérgio; de Oliveira, José Carlos T.
2011-03-01
High-mass compact stars have been reported recently in the literature, providing strong constraints on the properties of the ultra dense matter beyond the saturation nuclear density. In view of these results, the calculations of quark star or hybrid star equilibrium structure must be compatible with the provided observational data. But since the equations of state used in describing quark matter are in general too soft in comparison with the equation of states used to describe the hadronic or nuclear matter, the calculated quark star models presented in the literature are in general not suitable to explain the stability of highly-compact massive objects. In this work, we present the calculations of a spherically symmetric quark star structure by using an equation of state that takes into account the superconducting color-flavor locked phase of the strange quark matter. In addition, some fundamental aspects of QCD (asymptotic freedom and confinement) are considered by means of a phenomenological description of the deconfined quark phase, the density-dependent quark mass model. The quark matter behavior introduced by this model stiffens the corresponding equation of state. We thus investigate the influence of this model on the mass-radius diagram of quark stars. We obtain massive quark stars due to the stiffness of the equation of state, when a reasonable parameterization of the color superconducting gap is used. Models of quark stars enveloped by a nucleonic crust composed of a nuclear lattice embedded in an electron gas, with nuclei close to neutron drip line, are also discussed.
Casas, Caty; Sergeant, Nicolas; Itier, Jean-Michel; Blanchard, Véronique; Wirths, Oliver; van der Kolk, Nicolien; Vingtdeux, Valérie; van de Steeg, Evita; Ret, Gwenaëlle; Canton, Thierry; Drobecq, Hervé; Clark, Allan; Bonici, Bruno; Delacourte, André; Benavides, Jesús; Schmitz, Christoph; Tremp, Günter; Bayer, Thomas A.; Benoit, Patrick; Pradier, Laurent
2004-01-01
Alzheimer’s disease (AD) is characterized by a substantial degeneration of pyramidal neurons and the appearance of neuritic plaques and neurofibrillary tangles. Here we present a novel transgenic mouse model, APPSLPS1KI that closely mimics the development of AD-related neuropathological features including a significant hippocampal neuronal loss. This transgenic mouse model carries M233T/L235P knocked-in mutations in presenilin-1 and overexpresses mutated human β-amyloid (Aβ) precursor protein. Aβx-42 is the major form of Aβ species present in this model with progressive development of a complex pattern of N-truncated variants and dimers, similar to those observed in AD brain. At 10 months of age, an extensive neuronal loss (>50%) is present in the CA1/2 hippocampal pyramidal cell layer that correlates with strong accumulation of intraneuronal Aβ and thioflavine-S-positive intracellular material but not with extracellular Aβ deposits. A strong reactive astrogliosis develops together with the neuronal loss. This loss is already detectable at 6 months of age and is PS1KI gene dosage-dependent. Thus, APPSLPS1KI mice further confirm the critical role of intraneuronal Aβ42 in neuronal loss and provide an excellent tool to investigate therapeutic strategies designed to prevent AD neurodegeneration. PMID:15466394
Formation and Assembly of Massive Star Clusters
NASA Astrophysics Data System (ADS)
McMillan, Stephen
The formation of stars and star clusters is a major unresolved problem in astrophysics. It is central to modeling stellar populations and understanding galaxy luminosity distributions in cosmological models. Young massive clusters are major components of starburst galaxies, while globular clusters are cornerstones of the cosmic distance scale and represent vital laboratories for studies of stellar dynamics and stellar evolution. Yet how these clusters form and how rapidly and efficiently they expel their natal gas remain unclear, as do the consequences of this gas expulsion for cluster structure and survival. Also unclear is how the properties of low-mass clusters, which form from small-scale instabilities in galactic disks and inform much of our understanding of cluster formation and star-formation efficiency, differ from those of more massive clusters, which probably formed in starburst events driven by fast accretion at high redshift, or colliding gas flows in merging galaxies. Modeling cluster formation requires simulating many simultaneous physical processes, placing stringent demands on both software and hardware. Simulations of galaxies evolving in cosmological contexts usually lack the numerical resolution to simulate star formation in detail. They do not include detailed treatments of important physical effects such as magnetic fields, radiation pressure, ionization, and supernova feedback. Simulations of smaller clusters include these effects, but fall far short of the mass of even single young globular clusters. With major advances in computing power and software, we can now directly address this problem. We propose to model the formation of massive star clusters by integrating the FLASH adaptive mesh refinement magnetohydrodynamics (MHD) code into the Astrophysical Multi-purpose Software Environment (AMUSE) framework, to work with existing stellar-dynamical and stellar evolution modules in AMUSE. All software will be freely distributed on-line, allowing
The Evolution and Stability of Massive Stars
NASA Astrophysics Data System (ADS)
Shiode, Joshua Hajime
Massive stars are the ultimate source for nearly all the elements necessary for life. The first stars forge these elements from the sparse set of ingredients supplied by the Big Bang, and distribute enriched ashes throughout their galactic homes via their winds and explosive deaths. Subsequent generations follow suit, assembling from the enriched ashes of their predecessors. Over the last several decades, the astrophysics community has developed a sophisticated theoretical picture of the evolution of these stars, but it remains an incomplete accounting of the rich set of observations. Using state of the art models of massive stars, I have investigated the internal processes taking place throughout the life-cycles of stars spanning those from the first generation ("Population III") to the present-day ("Population I"). I will argue that early-generation stars were not highly unstable to perturbations, contrary to a host of past investigations, if a correct accounting is made for the viscous effect of convection. For later generations, those with near solar metallicity, I find that this very same convection may excite gravity-mode oscillations that produce observable brightness variations at the stellar surface when the stars are near the main sequence. If confirmed with modern high-precision monitoring experiments, like Kepler and CoRoT, the properties of observed gravity modes in massive stars could provide a direct probe of the poorly constrained physics of gravity mode excitation by convection. Finally, jumping forward in stellar evolutionary time, I propose and explore an entirely new mechanism to explain the giant eruptions observed and inferred to occur during the final phases of massive stellar evolution. This mechanism taps into the vast nuclear fusion luminosity, and accompanying convective luminosity, in the stellar core to excite waves capable of carrying a super-Eddington luminosity out to the stellar envelope. This energy transfer from the core to the
Awareness-based communication management in the MASSIVE systems
NASA Astrophysics Data System (ADS)
Greenhalgh, Chris
1998-09-01
The MASSIVE-1 and MASSIVE-2 distributed virtual environment systems are based on an explicit model of user communication requirements known as the spatial model of interaction; this model addresses the general issue of managing communication in large space-based systems such as DVEs. The goals of the spatial model are to guide the distribution and presentation of information in a way which facilitates collaboration between participants (based on observed patterns of interaction in real-world environments) and which is also efficient and appropriate. The MASSIVE-1 system emphasized the spatial model's `aura' concept as the basis for a distinct shared service in an otherwise wholly unicast peer-to-peer system. This approach was effective for relatively small systems but could not be extended to make general use of multicast communication (to reduce total bandwidth requirements). The MASSIVE-2 system added the concept of `third-party objects' which support the definition and management of multiple multicast groups for updates and continuous media distribution.
Combining magnetic and seismic studies to constrain processes in massive stars
NASA Astrophysics Data System (ADS)
Neiner, Coralie; Degroote, Pieter; Coste, Blanche; Briquet, Maryline; Mathis, Stéphane
2014-08-01
The presence of pulsations influences the local parameters at the surface of massive stars and thus it modifies the Zeeman magnetic signatures. Therefore it makes the characterisation of a magnetic field in pulsating stars more difficult and the characterisation of pulsations is thus required for the study of magnetic massive stars. Conversely, the presence of a magnetic field can inhibit differential rotation and mixing in massive stars and thus provides important constraints for seismic modelling based on pulsation studies. As a consequence, it is necessary to combine spectropolarimetric and seismic studies for all massive classical pulsators. Below we show examples of such combined studies and the interplay between physical processes.
Spontaneous Scalarization of Massive Fields
NASA Astrophysics Data System (ADS)
Ramazanoglu, Fethi M.; Pretorius, Frans
2014-03-01
Spontaneous scalarization is a phenomenon in certain scalar-tensor theories where large deviations from general relativity can be observed inside compact stars, while the known observational bounds can also be satisfied far away. This scenario has been investigated for massless scalars and binary neutron stars using numerical relativity, but the parameter space for such theories have been severely restricted by recent observations. Here, we present our results on the spontaneous scalarization of massive scalars. We simulate cases with different equations of state and scalar field parameters, and comment on the detectability of the scalar field effects from the gravitational wave signal.
Detecting weakly interacting massive particles.
NASA Astrophysics Data System (ADS)
Drukier, A. K.; Gelmini, G. B.
The growing synergy between astrophysics, particle physics, and low background experiments strengthens the possibility of detecting astrophysical non-baryonic matter. The idea of direct detection is that an incident, massive weakly interacting particle could collide with a nucleus and transfer an energy that could be measured. The present low levels of background achieved by the PNL/USC Ge detector represent a new technology which yields interesting bounds on Galactic cold dark matter and on light bosons emitted from the Sun. Further improvements require the development of cryogenic detectors. The authors analyse the practicality of such detectors, their optimalization and background suppression using the "annual modulation effect".
Quantum aspects of massive gravity
NASA Astrophysics Data System (ADS)
Park, Minjoon
2011-05-01
We consider the effect of quantum interactions on Pauli-Fierz massive gravity. With generic graviton cubic interactions, we observe that the 1-loop counterterms do not conform to the tree level structure of Pauli-Fierz action, resulting in the reappearance of the sixth mode ghost. Then to explore the quantum effects to the full extent, we calculate the resummed graviton propagator with an arbitrary interaction and analyze its complete structure, from which a minimal condition for the absence of the ghost is obtained.
Cosmological stability bound in massive gravity and bigravity
Fasiello, Matteo; Tolley, Andrew J. E-mail: andrew.j.tolley@case.edu
2013-12-01
We give a simple derivation of a cosmological bound on the graviton mass for spatially flat FRW solutions in massive gravity with an FRW reference metric and for bigravity theories. This bound comes from the requirement that the kinetic term of the helicity zero mode of the graviton is positive definite. The bound is dependent only on the parameters in the massive gravity potential and the Hubble expansion rate for the two metrics. We derive the decoupling limit of bigravity and FRW massive gravity, and use this to give an independent derivation of the cosmological bound. We recover our previous results that the tension between satisfying the Friedmann equation and the cosmological bound is sufficient to rule out all observationally relevant FRW solutions for massive gravity with an FRW reference metric. In contrast, in bigravity this tension is resolved due to different nature of the Vainshtein mechanism. We find that in bigravity theories there exists an FRW solution with late-time self-acceleration for which the kinetic terms for the helicity-2, helicity-1 and helicity-0 are generically nonzero and positive making this a compelling candidate for a model of cosmic acceleration. We confirm that the generalized bound is saturated for the candidate partially massless (bi)gravity theories but the existence of helicity-1/helicity-0 interactions implies the absence of the conjectured partially massless symmetry for both massive gravity and bigravity.
Consistent quantization of massive chiral electrodynamics in four dimensions
Andrianov, A. ); Bassetto, A.; Soldati, R.
1989-10-09
We discuss the quantization of a four-dimensional model in which a massive Abelian vector field interacts with chiral massless fermions. We show that, by introducing extra scalar fields, a renormalizable unitary {ital S} matrix can be obtained in a suitably defined Hilbert space of physical states.
Superluminal Propagation and Acausality of Nonlinear Massive Gravity
NASA Astrophysics Data System (ADS)
Deser, S.; Izumi, K.; Ong, Y. C.; Waldron, A.
2014-04-01
Massive gravity is an old idea: trading geometry for mass. Much effort has been expended on establishing a healthy model, culminating in the current ghost-free version. We summarize here our recent findings -- that it is still untenable -- because it likely admits local acausalities: solutions with CTCs in a small neighborhood of any event.
A New Framework for Massive Open Online Courses (MOOCs)
ERIC Educational Resources Information Center
Schoenack, Lindsie
2013-01-01
The challenges that massive open online courses (MOOCs) bring to the learning arena spur adult educators to improve delivery. A framework for a new type of MOOC is presented to address some of the challenges presented by earlier models. This new MOOC, called a mesoMOOC, can bridge several challenges that hinder current effective delivery of MOOCs…
Massive neutrinos and the pancake theory of galaxy formation
NASA Technical Reports Server (NTRS)
Schaeffer, R.; Silk, J.
1984-01-01
Three problems encountered by the pancake theory of galaxy formation in a massive neutrino-dominated universe are discussed. A nonlinear model for pancakes is shown to reconcile the data with the predicted coherence length and velocity field, and minimal predictions are given of the contribution from the large-scale matter distribution.
Holographic renormalization of 3D minimal massive gravity
NASA Astrophysics Data System (ADS)
Alishahiha, Mohsen; Qaemmaqami, Mohammad M.; Naseh, Ali; Shirzad, Ahmad
2016-01-01
We study holographic renormalization of 3D minimal massive gravity using the Chern-Simons-like formulation of the model. We explicitly present Gibbons- Hawking term as well as all counterterms needed to make the action finite in terms of dreibein and spin-connection. This can be used to find correlation functions of stress tensor of holographic dual field theory.
Matter coupling in 3D ‘minimal massive gravity’
NASA Astrophysics Data System (ADS)
Arvanitakis, Alex S.; Routh, Alasdair J.; Townsend, Paul K.
2014-12-01
The ‘minimal massive gravity’ model of massive gravity in three spacetime dimensions (which has the same anti-de Sitter (AdS) bulk properties as ‘topologically massive gravity’ but improved boundary properties) is coupled to matter. Consistency requires a particular matter source tensor, which is quadratic in the stress tensor. The consequences are explored for an ideal fluid in the context of asymptotically de Sitter (dS) cosmological solutions, which bounce smoothly from contraction to expansion. Various vacuum solutions are also found, including warped (A)dS, and (for special values of parameters) static black holes and an (A)dS2× {{S}1} vacuum.
The Deuteration Clock for Massive Starless Cores
NASA Astrophysics Data System (ADS)
Kong, S.; Tan, J. C.; Caselli, P.; Fontani, F.
2016-05-01
To understand massive star formation requires study of its initial conditions. Two massive starless core candidates, C1-N & C1-S, have been detected in IRDC G028.37+00.07 in N2D+(3-2) with ALMA. From their line widths, either the cores are subvirial and are thus young structures on the verge of near free-fall collapse, or they are threaded by ˜1 mG B-fields that help support them in near virial equilibrium and potentially have older ages. We modeled the deuteration rate of N2H+ to constrain collapse rates of the cores. First, to measure their current deuterium fraction, D≡ [N2D+]/[N2H+], we observed multiple transitions of N2H+ and N2D+ with CARMA, SMA, JCMT, NRO 45 m and IRAM 30 m, to complement the ALMA data. For both cores we derived D ˜ 0.3, several orders of magnitude above the cosmic [D]/[H] ratio. We then carried out chemodynamical modeling, exploring how collapse rate relative to free-fall, αff, affects the level of D that is achieved from a given initial condition. To reach the observed D, most models require slow collapse with αff˜0.1, i.e., ˜1/10th of free-fall. This makes it more likely that the cores have been able to reach a near virial equilibrium state and we predict that strong B-fields will eventually be detected. The methods developed here will be useful for measurement of the pre-stellar core mass function.
[Treatment alternatives in massive hemorrhage].
Fernández-Hinojosa, E; Murillo-Cabezas, F; Puppo-Moreno, A; Leal-Noval, S R
2012-10-01
Massive hemorrhage is the main cause of mortality and morbidity in trauma patients, and is one of the most important causes in any patient following major surgery. Conventional treatment consists of volume replacement, including the transfusion of blood products, so that tissue perfusion and oxygenation may be maintained. Associated hypothermia, acidosis and coagulopathy is a lethal triad. This review focuses on the latest therapeutic management of massive hemorrhage. The authors advocate the use of crystalloids as per protocol (controlled volumes) in order to achieve a systolic blood pressure of 85mmHg. The administration of the three blood products (red cells, plasma, and platelets) should be on a 1:1:1 basis. Where possible, this in turn should be guided by thromboelastography performed at point of care near the patient. Coagulopathy can occur early and late. With the exception of tranexamic acid, the cost-benefit relationships of the hemostatic agents, such as fibrinogen, prothrombin complex, and recombinant F VII, are subject to discussion. PMID:22321860
Sinus histiocytosis with massive lymphadenopathy: a "massive" misnomer.
Sardana, Divesh; Goyal, Ashima; Gauba, Krishan
2015-04-01
Sinus histiocytosis with massive lymphadenopathy also known as Rosai-Dorfman disease is a rare, benign, histiocytic disorder of unknown origin characterized by lymphadenopathy. Since its original description by Rosai and Dorfman in 1969, small number of cases has been reported; hence no specific diagnostic criteria and treatment guidelines have been suggested. The purpose of this article is to present and discuss a case of Rosai Dorfman Syndrome in 4-year-old child diagnosed with the help of Fine Needle Aspiration Cytology. The swelling resolved over a period of 18 months without any recurrence in 2-year follow-up period. This case report highlights the role of Fine Needle Aspiration Cytology in the diagnosis of Rosai-Dorfman disease and the importance of regular follow ups using a careful wait and watch approach in its management. The report also briefly discusses the various dilemmas associated with its diagnosis and treatment. PMID:25088489
Sakai, Tadakatsu; Sugimoto, Shigeki
2005-12-02
We propose a holographic dual of QCD with massless flavors on the basis of a D4/D8-brane configuration within a probe approximation. We are led to a five-dimensional Yang-Mills theory on a curved space-time along with a Chern-Simons five-form on it, both of which provide us with a unifying framework to study the massless pion and an infinite number of massive vector mesons. We make sample computations of the physical quantities that involve the mesons and compare them with the experimental data. It is found that most of the results of this model are compatible with the experiments.
NASA Astrophysics Data System (ADS)
Sakai, Tadakatsu; Sugimoto, Shigeki
2005-12-01
We propose a holographic dual of QCD with massless flavors on the basis of a D4/D8-brane configuration within a probe approximation. We are led to a five-dimensional Yang-Mills theory on a curved space-time along with a Chern-Simons five-form on it, both of which provide us with a unifying framework to study the massless pion and an infinite number of massive vector mesons. We make sample computations of the physical quantities that involve the mesons and compare them with the experimental data. It is found that most of the results of this model are compatible with the experiments.
Rb and Zr abundances in massive Galactic AGB stars revisited
NASA Astrophysics Data System (ADS)
Pérez-Mesa, V.; Zamora, O.; García-Hernández, D. A.; Plez, B.; Manchado, A.; Karakas, A. I.; Lugaro, M.
2016-07-01
We report new abundances of Rb and Zr in a sample of massive Galactic asymptotic giant branch (AGB) stars that were previously studied with hydrostatic models by using more realistic dynamical model atmospheres. We use a modified version of the spectral synthesis code Turbospectrum, and consider the presence of a circumstellar envelope and a radial wind in the modelling of these Galactic AGB stars. The Rb and Zr are determined from the 7800 Å Rb I resonant line and the 6474 Å ZrO bandhead, respectively, and they are compared with the AGB nucleosynthesis theoretical predictions. The derived Rb abundances are much lower (∼⃒1-2 dex) with the new dynamical models, while the Zr abundances, however, are closer to the hydrostatic values. The new model atmospheres can help to resolve the problem of the mismatch between the observations and the nucleosynthesis theoretical predictions of massive AGB stars.
Massive Binaries in the Galactic Center
NASA Astrophysics Data System (ADS)
Figer, D. F.; Kim, S. S.
We review the status of massive-star interaction research in the Galactic center (GC). Given the short lifetimes of massive stars, massive binaries will necessarily be located near their formation sites in starburst clusters. The GC contains three recently formed clusters having a very high stellar density, as high as 106 stars pc-3. We discuss these extreme environments, and possible massive binaries therein. In addition, we argue that they may host the products of massive stellar mergers and collisions. In particular, we predict that at least one massive star in the Arches cluster has already experienced stellar merger events in its short lifetime. Further, the Pistol Star, in the nearby Quintuplet cluster, might owe its apparent relative youth to a rejuvinating stellar merger. Finally, the apparently young stars in the central arcsecond could be products of either collisions, inducing atmospheric stripping, or mergers.
Holographic Josephson junction from massive gravity
NASA Astrophysics Data System (ADS)
Hu, Ya-Peng; Li, Huai-Fan; Zeng, Hua-Bi; Zhang, Hai-Qing
2016-05-01
We study the holographic superconductor-normal metal-superconductor (SNS) Josephson junction in de Rham-Gabadadze-Tolley massive gravity. If the boundary theory is independent of spatial directions, i.e., if the chemical potential is homogeneous in spatial directions, we find that the graviton mass parameter will make it more difficult for the normal metal-superconductor phase transition to take place. In the holographic model of the Josephson junction, it is found that the maximal tunneling current will decrease according to the graviton mass parameter. Besides, the coherence length of the junction decreases as well with respect to the graviton mass parameter. If one interprets the graviton mass parameter as the effect of momentum dissipation in the boundary field theory, this indicates that the stronger the momentum dissipation is, the smaller the coherence length is.
SATELLITE FORMATION from ancient massive rings
NASA Astrophysics Data System (ADS)
Crida, Aurélien; Charnoz, Sébastien
2013-07-01
When a planetary tidal disk - like Saturn's rings - spreads beyond the Roche radius (inside which planetary tides prevent aggregation), satellites form and migrate away. Here, we show that most regular satellites in the solar system probably formed in this way. According to our analytical model, when the spreading is slow, a retinue of satellites appear with masses increasing with distance to the Roche radius, in excellent agreement with Saturn's, Uranus', and Neptune's satellite systems. This suggests that Uranus and Neptune used to have massive rings that disappeared to give birth to most of their regular satellites. In contrast, when the spreading is fast, only one large satellite forms, as was the case for Pluto and Earth. This conceptually bridges the gap between terrestrial and giant planet systems. (Ref: Crida & Charnoz 2012, Science, 338, 1196-1199)
Massive Open Online Courses in Public Health
Gooding, Ira; Klaas, Brian; Yager, James D.; Kanchanaraksa, Sukon
2013-01-01
Massive open online courses (MOOCs) represent a new and potentially transformative model for providing educational opportunities to learners not enrolled in a formal educational program. The authors describe the experience of developing and offering eight MOOCs on a variety of public health topics. Existing institutional infrastructure and experience with both for-credit online education and open educational resources mitigated the institutional risk and resource requirements. Although learners are able to enroll easily and freely and do so in large numbers, there is considerable variety in the level of participation and engagement among enrollees. As a result, comprehensive and accurate assessment of meaningful learning progress remains a major challenge for evaluating the effectiveness of MOOCs for providing public health education. PMID:24350228
Massive open online courses in public health.
Gooding, Ira; Klaas, Brian; Yager, James D; Kanchanaraksa, Sukon
2013-01-01
Massive open online courses (MOOCs) represent a new and potentially transformative model for providing educational opportunities to learners not enrolled in a formal educational program. The authors describe the experience of developing and offering eight MOOCs on a variety of public health topics. Existing institutional infrastructure and experience with both for-credit online education and open educational resources mitigated the institutional risk and resource requirements. Although learners are able to enroll easily and freely and do so in large numbers, there is considerable variety in the level of participation and engagement among enrollees. As a result, comprehensive and accurate assessment of meaningful learning progress remains a major challenge for evaluating the effectiveness of MOOCs for providing public health education. PMID:24350228
Energetic Supernovae of Very Massive Primordial Stars
NASA Astrophysics Data System (ADS)
Chen, Ke-Jung; Woosley, Stan
2015-08-01
Current models of the formation of the first stars in the universe suggest that these stars were very massive, having a typical mass scale of hundreds of solar masses. Some of them would die as pair instability supernovae (PSNe) which might be the biggest explosions of the universe. We present the results from multidimensional numerical studies of PSNe with a new radiation-hydrodynamics code, CASTRO and with realistic nuclear reaction networks. We simulate the fluid instabilities that occur in multiple spatial dimensions and discuss how the resulting mixing affects the explosion, mixing, and nucleosynthesis of these supernovae. Our simulations provide useful predictions for the observational signatures of PSNe, which might soon be examined by the James Webb Space Telescope.
The Massive Star Population in M101
NASA Astrophysics Data System (ADS)
Grammer, Skyler H.
An increasing number of non-terminal giant eruptions are being observed by modern supernova and transient surveys. Very little is known about the origin of these giant eruptions and their progenitors which are presumably very-massive, evolved stars such as luminous blue variables, hypergiants, and supergiants. Motivated by the small number of progenitors positively associated with these giant eruptions, we have begun a survey of the luminous and evolved massive star populations in several nearby galaxies. We aim to identify the likely progenitors of the giant eruptions, study the spatial variations in the stellar populations, and examine the relationship between massive star populations and their environment. The work presented here is focused on stellar populations in the relatively nearby, giant, spiral galaxy M101 from sixteen archival BVI HST/ACS images. We create a catalog of stars in the direction to M101 with photometric errors < 10% for V < 24.5 and 50% completeness down to V ˜ 26.5 even in regions of high stellar crowding. Using color and magnitude criteria we have identified candidate luminous OB type stars and blue supergiants, yellow supergiants, and red supergiants for future observation. We examine their spatial distributions across the face of M101 and find that the ratio of blue to red supergiants decreases by two orders of magnitude over the radial extent. From our catalog, we derive the star formation history (SFH) for the stellar populations in five 2' wide annuli by fitting the color-magnitude diagrams. Binning the SFH into time frames corresponding to populations traced by Halpha, far ultraviolet (FUV), and near ultraviolet (NUV) emission, we show that the fraction of stellar populations young enough to contribute in Halpha is 15% " 35% in the inner regions, compared to less than 5% in the outer regions. This provides a sufficient explanation for the lack of Halpha emission at large radii. We also model the blue to red supergiant ratio in our
Cosmic expansion in extended quasidilaton massive gravity
NASA Astrophysics Data System (ADS)
Kahniashvili, Tina; Kar, Arjun; Lavrelashvili, George; Agarwal, Nishant; Heisenberg, Lavinia; Kosowsky, Arthur
2015-02-01
Quasidilaton massive gravity offers a physically well-defined gravitational theory with nonzero graviton mass. We present the full set of dynamical equations governing the expansion history of the Universe, valid during radiation domination, matter domination, and a late-time self-accelerating epoch related to the graviton mass. The existence of self-consistent solutions constrains the amplitude of the quasidilaton field and the graviton mass, as well as other model parameters. We point out that the effective mass of gravitational waves can be significantly larger than the graviton mass, opening the possibility that a single theory can explain both the late-time acceleration of cosmic expansion and modifications of structure growth leading to the suppression of large-angle correlations observed in the cosmic microwave background.
A Search for charged massive stable particles
Nunnemann, Thomas; /Munich U.
2006-02-01
A search for charged massive (quasi-) stable particles with the D0 detector at the Tevatron collider based on 390 pb{sup -1} of data is presented. The search is performed in the frameworks of gauge-mediated supersymmetry breaking and the minimal supersymmetric extension of the standard model. The hypothetical particles are assumed to be pair-produced in p{bar p} collisions giving a signature of two reconstructed muon-like objects with high invariant mass and time-of-flights indicative of heavy particles. Since no excess over background is observed, cross-section limits for the pair-production of stable staus and charginos are set. Mass limits of 140 GeV for a higgsino-like chargino and 174 GeV for a gaugino-like chargino are set.
Massive gravity with N=1 local supersymmetry
NASA Astrophysics Data System (ADS)
Malaeb, O.
2013-09-01
A consistent theory of massive gravity, where the graviton acquires mass by spontaneously breaking diffeomorphism invariance, is now well established. We supersymmetrize this construction using N=1 fields. Coupling to N=1 supergravity is done by applying the rules of tensor calculus to construct an action invariant under local N=1 supersymmetry. The supersymmetric action is shown, at the quadratic level, to be free of ghosts and have as its spectrum a massive graviton, two gravitinos (with different masses) and a massive vector.
MY Camelopardalis, a very massive merger progenitor
NASA Astrophysics Data System (ADS)
Lorenzo, J.; Negueruela, I.; Baker, A. K. F. Val; García, M.; Simón-Díaz, S.; Pastor, P.; Méndez Majuelos, M.
2014-12-01
Context. The early-type binary MY Cam belongs to the young open cluster Alicante 1, embedded in Cam OB3. Aims: MY Cam consists of two early-O type main-sequence stars and shows a photometric modulation suggesting an orbital period slightly above one day. We intend to confirm this orbital period and derive orbital and stellar parameters. Methods: Timing analysis of a very exhaustive (4607 points) light curve indicates a period of 1.1754514 ± 0.0000015 d. High-resolution spectra and the cross-correlation technique implemented in the todcor program were used to derive radial velocities and obtain the corresponding radial velocity curves for MY Cam. Modelling with the stellar atmosphere code fastwind was used to obtain stellar parameters and create templates for cross-correlation. Stellar and orbital parameters were derived using the Wilson-Devinney code, such that a complete solution to the binary system could be described. Results: The determined masses of the primary and secondary stars in MY Cam are 37.7 ± 1.6 and 31.6 ± 1.4M⊙, respectively. The corresponding temperatures, derived from the model atmosphere fit, are 42 000 and 39 000 K, with the more massive component being hotter. Both stars are overfilling their Roche lobes, sharing a common envelope. Conclusions: MY Cam contains the most massive dwarf O-type stars found so far in an eclipsing binary. Both components are still on the main sequence, and probably not far from the zero-age main sequence. The system is a likely merger progenitor, owing to its very short period. Tables 1 and 3 are available in electronic form at http://www.aanda.orgPhotometric data (Table 2) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A110
Finding evidence for massive neutrinos using 3D weak lensing
Kitching, T. D.; Heavens, A. F.; Verde, L.; Serra, P.; Melchiorri, A.
2008-05-15
In this paper we investigate the potential of 3D cosmic shear to constrain massive neutrino parameters. We find that if the total mass is substantial (near the upper limits from large scale structure, but setting aside the Ly alpha limit for now), then 3D cosmic shear+Planck is very sensitive to neutrino mass and one may expect that a next generation photometric redshift survey could constrain the number of neutrinos N{sub {nu}} and the sum of their masses m{sub {nu}}=im{sub i} to an accuracy of {delta}N{sub {nu}}{approx}0.08 and {delta}m{sub {nu}}{approx}0.03 eV, respectively. If in fact the masses are close to zero, then the errors weaken to {delta}N{sub {nu}}{approx}0.10 and {delta}m{sub {nu}}{approx}0.07 eV. In either case there is a factor 4 improvement over Planck alone. We use a Bayesian evidence method to predict joint expected evidence for N{sub {nu}} and m{sub {nu}}. We find that 3D cosmic shear combined with a Planck prior could provide 'substantial' evidence for massive neutrinos and be able to distinguish 'decisively' between many competing massive neutrino models. This technique should 'decisively' distinguish between models in which there are no massive neutrinos and models in which there are massive neutrinos with |N{sub {nu}}-3| > or approx. 0.35 and m{sub {nu}} > or approx. 0.25 eV. We introduce the notion of marginalized and conditional evidence when considering evidence for individual parameter values within a multiparameter model.
Merlin - Massively parallel heterogeneous computing
NASA Technical Reports Server (NTRS)
Wittie, Larry; Maples, Creve
1989-01-01
Hardware and software for Merlin, a new kind of massively parallel computing system, are described. Eight computers are linked as a 300-MIPS prototype to develop system software for a larger Merlin network with 16 to 64 nodes, totaling 600 to 3000 MIPS. These working prototypes help refine a mapped reflective memory technique that offers a new, very general way of linking many types of computer to form supercomputers. Processors share data selectively and rapidly on a word-by-word basis. Fast firmware virtual circuits are reconfigured to match topological needs of individual application programs. Merlin's low-latency memory-sharing interfaces solve many problems in the design of high-performance computing systems. The Merlin prototypes are intended to run parallel programs for scientific applications and to determine hardware and software needs for a future Teraflops Merlin network.
PRISM Polarimetry of Massive Stars
NASA Astrophysics Data System (ADS)
Kerkstra, Brennan; Lomax, Jamie R.; Bjorkman, Karen S.; Bjorkman, Jon Eric; Skiff, Brian; Covey, Kevin R.; Wisniewski, John P.
2016-01-01
We present the early results from our long-term, multi-epoch filter polarization survey of massive stars in and around young Galactic clusters. These BVRI polarization data were obtained using the PRISM instrument mounted on the 1.8m Perkins Telescope at Lowell Observatory. We first detail the creation of our new semi-automated polarization data reduction pipeline that we developed to process these data. Next, we present our analysis of the instrumental polarization properties of the PRISM instrument, via observations of polarized and unpolarized standard stars. Finally, we present early results on the total and intrinsic polarization behavior of several isolated, previously suggested classical Be stars, and discuss these results in the context of the larger project.BK acknowledges support from a NSF/REU at the University of Oklahoma. This program was also supported by NSF-AST 11411563, 1412110, and 1412135.
Massively parallel quantum computer simulator
NASA Astrophysics Data System (ADS)
De Raedt, K.; Michielsen, K.; De Raedt, H.; Trieu, B.; Arnold, G.; Richter, M.; Lippert, Th.; Watanabe, H.; Ito, N.
2007-01-01
We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.
The Embedded Phase of Massive Star Formation
NASA Astrophysics Data System (ADS)
van der Tak, Floris
2000-11-01
This thesis studies the physical and chemical structure of a set of massive young stars which are surrounded by a thick envelope of dust and gas, the earliest known phase of massive star formation. The primary scientific questions addressed are: (i) What is the evolutionary order of the phenomena associated with massive star formation? (ii) What is the physical and chemical structure of the envelopes of massive young stars? How do they compare to those of low-mass stars? Do specific molecules trace different stages? (iii) What are the masses of any circumstellar disks, and on what time scales are they dispersed? To answer these questions, a sample of infrared and submillimeter sources has been selected on high luminosity, close distance, isolated location and high mid-infrared flux. We present observations of these sources with single-dish submillimeter antennas, millimeter interferometers and near-infrared spectroscopy, and also discuss ISO spectra. For the interpretation, we have developed models with a detailed physical structure, combined with chemical differentiation, which is strongly coupled to the temperature. Some of the conclusions are: The envelopes of massive young stars are well described by centrally heated spherical models, with masses of ~ 100-1000 Modot within radii of ~0.1 pc. For a power-law density structure n(r) = n0 (r / r0)-α, we find α = 1.0-1.5 for the younger sources, significantly lower than α ≅ 2 found for the envelopes of low-mass stars at a comparable stage of evolution. This difference may indicate that the support against gravitational collapse in high-mass cores is by nonthermal (e.g., turbulent) pressure, and in low-mass cores by thermal pressure. For the more evolved sources, α = 1.5-2.0 fits the data best. Unlike in low-mass star formation, the near-infrared emission decreases as the envelope warms up, indicates that the hot dust close to the star is destroyed and/or pushed out by stellar radiation or mass loss. The
Requiem for a fractionally charged, massive particle
NASA Astrophysics Data System (ADS)
Langacker, Paul; Steigman, Gary
2011-09-01
Fractionally charged massive particles (FCHAMPs) appear in extensions of the standard model, especially those with superstring constructions. The lightest FCHAMP would be absolutely stable and any of them produced during the early evolution of the Universe would be present today. The thermal production, annihilation and, survival of an FCHAMP, a lepton L with electroweak (i.e., U(1)Y) but no strong interactions, of mass mL and charge QL (in units of the charge on the electron) are explored. The FCHAMP relic abundance is determined by the total annihilation cross section which depends on mL, QL and on the available annihilation channels. Since massive (mL≳1GeV) charged particles (QL≳0.01) behave like baryons (heavy ions), primordial nucleosynthesis and the cosmic background radiation temperature anisotropies limit the FCHAMP relic density. Requiring that ΩL≲ΩB/5 leads to a constraint on the QL-mL relation. Further constraints on QL and mL are provided by the invisible width of the Z (QL>0.16 for mL≤MZ/2) and by accelerator searches for massive, charged particles. Our key result is to exploit the fact that in the early Universe, after L± freeze-out but prior to e± recombination, the negatively charged L- will combine with the more abundant alpha particles and protons to form tightly bound, positively charged states (fractionally charged heavy ions). The Coulomb barriers between these positively charged L-α and L-p (L-pp, L-αα, …) bound states and the free L+ suppresses late-time FCHAMP annihilation in the interstellar medium (ISM) of the Galaxy and on Earth, limiting significantly the late-time reduction of the FCHAMP abundance compared to its relic value. The surviving FCHAMP abundance on Earth is orders of magnitude higher than the limits from terrestrial searches for fractionally charged particles, closing the window on FCHAMPs with QL≳0.01. However, as QL approaches an integer (e.g., |QL-n|≲0.25) these searches become increasingly insensitive
Stability and Coalescence of Massive Twin Binaries
NASA Astrophysics Data System (ADS)
Hwang, J.; Lombardi, J. C., Jr.; Rasio, F. A.; Kalogera, V.
2015-06-01
Massive stars are usually found in binaries, and binaries with periods less than 10 days may have a preference for near equal component masses (“twins”). In this paper we investigate the evolution of massive twin binaries all the way to contact and the possibility that these systems can be progenitors of double neutron star binaries. The small orbital separations of observed double neutron star binaries suggest that the progenitor systems underwent a common envelope phase at least once during their evolution. Bethe & Brown proposed that massive binary twins will undergo a common envelope evolution while both components are ascending the red giant branch (RGB) or asymptotic giant branch (AGB) simultaneously, also known as double-core evolution. Using models generated from the stellar evolution code EZ (evolve zero-age main sequence), we determine the range of mass ratios resulting in a contact binary with both components simultaneously ascending the RGB or AGB as a function of the difference in birth times, Δτ. We find that, even for a generous Δτ = 5 Myr, the minimum mass ratio {{q}min }=0.933 for an 8 {{M}⊙ } primary and increases for larger mass primaries. We use a smoothed particle hydrodynamics code, StarSmasher, to study specifically the evolution of q = 1 common envelope systems as a function of initial component mass, age, and orbital separation. We also consider a q = 0.997 system to test the effect of relaxing the constraint of strictly identical components. We find the dynamical stability limit, the largest orbital separation where the binary becomes dynamically unstable, as a function of the component mass and age. Finally, we calculate the efficiency of ejecting matter during the inspiral phase to extrapolate the properties of the remnant binary from our numerical results, assuming the common envelope is completely ejected. We find that for the nominal core masses, there is a minimum orbital separation for a given component mass such that the
The formation of massive stars: A 30 MO case study
NASA Astrophysics Data System (ADS)
Beech, Martin
1993-07-01
Pre-main sequence evolutionary tracks have been calculated for a series of massive star models under Hayashi's canonical theory and Stahler's mass accretion paradigm. Canonical pre-main sequence tracks for 15-60 solar mass (SM) stars were calculated with both Cox-Stewart (CS) and Rogers-Iglesias (RI) opacities. The differences between the two sequences were systematically explored. The final pre-main sequence phase of the canonical evolution and the onset of central hydrogen burning is discussed. Arrival of a massive star on the zero age main sequence (ZAMS) is defined and the characteristics of the upper ZAMS models are determined. A systematic investigation of pre-main sequence tracks revealed a boundary in the central density versus central temperature plane, beyond which the models always had a central convective core. In a study of a sequence of accretion models, beyond about 17 SM their characteristics became increasingly more luminous and cooler compared to the same-mass canonical ZAMS models. In the main sequence phase, the accretion build model evolved at essentially the same effective temperature as the canonical model but at a lower luminosity. An upper stellar birthline is proposed, defining a boundary in the Hertzsprung Russell diagram beyond which massive stars first become optically visible.
Completing Lorentz violating massive gravity at high energies
Blas, D.; Sibiryakov, S.
2015-03-15
Theories with massive gravitons are interesting for a variety of physical applications, ranging from cosmological phenomena to holographic modeling of condensed matter systems. To date, they have been formulated as effective field theories with a cutoff proportional to a positive power of the graviton mass m{sub g} and much smaller than that of the massless theory (M{sub P} ≈ 10{sup 19} GeV in the case of general relativity). In this paper, we present an ultraviolet completion for massive gravity valid up to a high energy scale independent of the graviton mass. The construction is based on the existence of a preferred time foliation combined with spontaneous condensation of vector fields. The perturbations of these fields are massive and below their mass, the theory reduces to a model of Lorentz violating massive gravity. The latter theory possesses instantaneous modes whose consistent quantization we discuss in detail. We briefly study some modifications to gravitational phenomenology at low-energies. The homogeneous cosmological solutions are the same as in the standard cosmology. The gravitational potential of point sources agrees with the Newtonian one at distances small with respect to m{sub g}{sup −1}. Interestingly, it becomes repulsive at larger distances.
New Frontiers in Stellar Astrophysics: Massive Stars as Cosmological Tools
NASA Astrophysics Data System (ADS)
Levesque, Emily M.
2015-01-01
Massive stars are crucial building blocks in the study of star-forming galaxies, stellar evolution, and transient events, and their applications as fundamental astrophysical tools span a broad range of subfields. Unfortunately, many key traits of massive stars - from their physical properties and ionizing radiation to their evolution and core-collapse deaths - remain poorly understood. I will discuss several current research programs focused on developing a comprehensive picture of massive stars across the cosmos. These include observational surveys and population synthesis models of star-forming galaxies; progenitor and host environment studies of transient phenomena such as supernovae and gamma-ray bursts; and the remarkable reach of extragalactic stellar observations, which recently led to the discovery of the first Thorne-Zytkow object candidate. With cutting-edge theoretical models and the capabilities of current ground-based and orbital observatories, we are ideally poised to make substantial progress in our understanding of massive stars over the coming decade. This in turn will equip us with the tools we need to take full advantage of the frontiers opened up by new observational facilities such as JWST, the ELTs, and LSST, allowing us to immediately begin probing the new corners of the universe that they reveal.
Compound nucleus formation in reactions between massive nuclei: Fusion barrier
Antonenko, N.V.; Cherepanov, E.A.; Nasirov, A.K.; Permjakov, V.P.; Volkov, V.V.
1995-05-01
The evaporation residue cross sections {sigma}{sub ER} in reactions between massive nuclei have been analyzed within different models of complete fusion. The calculations in the framework of the optical model, the surface friction model, and the macroscopic dynamic model can give the results which are by few orders of magnitude different from experimental data. This takes place due to neglect of the competition between complete fusion and quasifission. A possible mechanism of compound nucleus formation in heavy-ion-induced reactions has been suggested. The analysis of the complete fusion of nuclei on the basis of dinuclear system approach has allowed one to reveal an important feature of the fusion process of massive nuclei, that is, the appearance of the fusion barrier during dinuclear system evolution to a compound nucleus. As a result, the competition between complete fusion and quasifission arises and strongly reduces the cross section of the compound nucleus formation. A model is proposed for calculation of this competition in a massive symmetric dinuclear system. This model is applied for collision energies above the Coulomb barrier. The {sigma}{sub ER} values calculated in the framework of dinuclear system approach seem to be close to the experimental data. For illustration the reactions {sup 100}Mo+{sup 100}Mo, {sup 110}Pd+{sup 110}Pd, and {sup 124}Sn+{sup 96}Zr have been considered.
NASA Astrophysics Data System (ADS)
Popov, Anton; Kaus, Boris
2015-04-01
This software project aims at bringing the 3D lithospheric deformation modeling to a qualitatively different level. Our code LaMEM (Lithosphere and Mantle Evolution Model) is based on the following building blocks: * Massively-parallel data-distributed implementation model based on PETSc library * Light, stable and accurate staggered-grid finite difference spatial discretization * Marker-in-Cell pedictor-corector time discretization with Runge-Kutta 4-th order * Elastic stress rotation algorithm based on the time integration of the vorticity pseudo-vector * Staircase-type internal free surface boundary condition without artificial viscosity contrast * Geodynamically relevant visco-elasto-plastic rheology * Global velocity-pressure-temperature Newton-Raphson nonlinear solver * Local nonlinear solver based on FZERO algorithm * Coupled velocity-pressure geometric multigrid preconditioner with Galerkin coarsening Staggered grid finite difference, being inherently Eulerian and rather complicated discretization method, provides no natural treatment of free surface boundary condition. The solution based on the quasi-viscous sticky-air phase introduces significant viscosity contrasts and spoils the convergence of the iterative solvers. In LaMEM we are currently implementing an approximate stair-case type of the free surface boundary condition which excludes the empty cells and restores the solver convergence. Because of the mutual dependence of the stress and strain-rate tensor components, and their different spatial locations in the grid, there is no straightforward way of implementing the nonlinear rheology. In LaMEM we have developed and implemented an efficient interpolation scheme for the second invariant of the strain-rate tensor, that solves this problem. Scalable efficient linear solvers are the key components of the successful nonlinear problem solution. In LaMEM we have a range of PETSc-based preconditioning techniques that either employ a block factorization of
Stefan-Boltzmann Law for Massive Photons
NASA Astrophysics Data System (ADS)
Moreira, E. S.; Ribeiro, T. G.
2016-08-01
This paper generalizes the Stefan-Boltzmann law to include massive photons. A crucial ingredient to obtain the correct formula for the radiance is to realize that a massive photon does not travel at the speed of (massless) light. It follows that, contrary to what could be expected, the radiance is not proportional to the energy density times the speed of light.
Gravitational massive modes from extended gravity
NASA Astrophysics Data System (ADS)
Basini, Giuseppe; Capozziello, Salvatore; de Laurentis, Mariafelicia
2016-02-01
Further gravitational massive modes emerge by extending the geometrical sector of Hilbert-Einstein theory in the most general theory including curvature invariants. Besides massless spin-2, also spin-0 and spin-2 massive and ghost fields have to be considered. We investigate the possible detectability of such additional modes by the Large Hadron Collider and calculate the detectable energy density of the spectrum.
NASA Astrophysics Data System (ADS)
Herrero, A.; Garcia, M.; Simón-Díaz, S.; Camacho, I.; Sabín-Sanjulián, C.; Castro, N.
2015-01-01
Massive stars play a key role in environments with very different metallicities. To interpret the role of massive stars in these systems we have to know their properties at different metallicities. The Local Group offers an excellent laboratory to this aim.
Stefan-Boltzmann Law for Massive Photons
NASA Astrophysics Data System (ADS)
Moreira, E. S.; Ribeiro, T. G.
2016-04-01
This paper generalizes the Stefan-Boltzmann law to include massive photons. A crucial ingredient to obtain the correct formula for the radiance is to realize that a massive photon does not travel at the speed of (massless) light. It follows that, contrary to what could be expected, the radiance is not proportional to the energy density times the speed of light.
Remark on massive particle's de Sitter tunneling
Jiang, Qing-Quan; Chen, De-You; Wen, Dan E-mail: deyouchen@126.com
2013-11-01
In the work [J. Y. Zhang and Z. Zhao, Massive particles's black hole tunneling and de Sitter tunneling, Nucl. Phys. B 725 (2005) 173.], the Hawking radiation of the massive particle via tunneling from the de Sitter cosmological horizon has been first described in the tunneling framework. However, the geodesic equation of the massive particle was unnaturally and awkwardly defined there by investigating the relation between the group and phase velocity. In this paper, we start from the Lagrangian analysis on the action to naturally produce the geodesic equation of the tunneling massive particle. Then, based on the new definition for the geodesic equation, we revisit the Hawking radiation of the massive particle via tunneling from the de Sitter cosmological horizon. It is noteworthy that, the highlight of our work is a new and important development of the Parikh-Wilczek's tunneling method, which can make it more physical.
Lagrangians for massive Dirac chiral superfields
NASA Astrophysics Data System (ADS)
Jiménez, Enrique; Vaquera-Araujo, C. A.
2016-06-01
A variant for the superspin one-half massive superparticle in 4D, N = 1, based on Dirac superfields, is offered. As opposed to the current known models that use spinor chiral superfields, the propagating fields of the supermultiplet are those of the lowest mass dimensions possible: scalar, Dirac and vector fields. Besides the supersymmetric chiral condition, the Dirac superfields are not further constrained, allowing a very straightforward implementation of the path-integral method. The corresponding superpropagators are presented. In addition, an interaction super Yukawa potential, formed by Dirac and scalar chiral superfields, is given in terms of their component fields. The model is first presented for the case of two superspin one-half superparticles related by the charged conjugation operator, but in order to treat the case of neutral superparticles, the Majorana condition on the Dirac superfields is also studied. We compare our proposal with the known models of spinor superfields for the one-half superparticle and show that it is equivalent to them.
Spiderwebs and Flies: Observing Massive Galaxy Formation in Action
NASA Astrophysics Data System (ADS)
Miley, George
2009-07-01
Distant luminous radio galaxies are among the brightest known galaxies in the early Universe, pinpoint likely progenitors of dominant cluster galaxies and are unique laboratories for studying massive galaxy formation. Spectacular images with the ACS and NICMOS of one such object, the "Spiderweb Galaxy" at z = 2.2, show in exquisite detail, hierarchical merging occurring 11 Gyr ago. By imaging 3 additional Spiderweb-like galaxies we wish to study this potentially crucial phase of massive galaxy evolution, when hierarchical merging, galaxy downsizing and AGN feedback are all likely to be occurring. Properties of the complete sample of Spiderweb galaxies will be used to {i} constrain models for the formation and evolution of the most massive galaxies that dominate rich clusters and {ii} investigate the nature of chain and tadpole galaxies, a fundamental but poorly understood constituent of the early Universe. We shall image rest-frame UV and optical continuum emission from 3 radio galaxies with 2.4 < z < 3.8 that appear clumpy and large in shallow WFPC/PC observations. The new observations will typically reach 2 magnitudes fainter over 20-40 times larger area than previously. Photometric and morphological parameters will be measured for satellite galaxies {"flies"} in the clumpy massive hosts and for galaxies in 1.5 Mpc x 1.5 Mpc regions of surrounding protoclusters. Locations, sizes, elongations, clumpiness, masses, and star formation rates of the merging satellite and protocluster galaxies will be compared with new state of the art simulations. Combination of ACS and WFC3 images will help disentangle the properties of the young and old populations.Specific goals include: {i} investigating star formation histories of the satellite galaxies and the extended emission, {ii} studying "downsizing" and merging scenarios and {iii} measuring the statistics of linear galaxies and relating them to models for the formation of massive galaxies and to the properties of the
ON THE ASSEMBLY HISTORY OF STELLAR COMPONENTS IN MASSIVE GALAXIES
Lee, Jaehyun; Yi, Sukyoung K.
2013-03-20
Matsuoka and Kawara showed that the number density of the most massive galaxies (log M/M{sub Sun} = 11.5-12.0) increases faster than that of the next massive group (log M/M{sub Sun} = 11.0-11.5) during 0 < z < 1. This appears to be in contradiction to the apparent 'downsizing effect'. We attempt to understand the two observational findings in the context of the hierarchical merger paradigm using semi-analytic techniques. Our models closely reproduce the result of Matsuoka and Kawara. Downsizing can also be understood as larger galaxies have, on average, smaller assembly ages but larger stellar ages. Our fiducial models further reveal details of the history of the stellar mass growth of massive galaxies. The most massive galaxies (log M/M{sub Sun} = 11.5-12.0 at z = 0), which are mostly the brightest cluster galaxies, obtain roughly 70% of their stellar components via merger accretion. The role of merger accretion monotonically declines with galaxy mass: 40% for log M/M{sub Sun} = 11.0-11.5 and 20% for log M/M{sub Sun} = 10.5-11.0 at z = 0. The specific accreted stellar mass rates via galaxy mergers decline very slowly during the whole redshift range, while specific star formation rates sharply decrease with time. In the case of the most massive galaxies, merger accretion becomes the most important channel for the stellar mass growth at z {approx} 2. On the other hand, in situ star formation is always the dominant channel in L{sub *} galaxies.
The properties of low-metallicity massive stars
NASA Astrophysics Data System (ADS)
Tramper, F.
2014-11-01
My thesis has two main topics: the study of low-metallicity massive stars, and the study of the suspected final stage of massive stars from a certain initial mass range, the WO stars. All the data that has been used in this thesis has been obtained with the X-Shooter spectrograph on ESO's Very Large Telescope. As the formation of massive stars was favored in the metal-free early universe, the properties and evolution of low-metallicity massive stars gives insight in the influence of these stars in the young universe. I have quantitatively analyzed six O-type stars in the low-metallicity dwarf galaxies IC1613, WLM and NGC3109. These stars appear to have surprisingly strong winds, and do not agree with theoretical predictions. The analysis of four more O stars confirms this finding. The low-metallicity temperature scale, recent star formation history of the galaxies and the evolutionary state of the O stars are also discussed. The enigmatic WO stars are very rare (only 9 are known), and are thought to represent the final stage of some of the most massive stars. The spectra of most of these stars have never been modeled in detailed using expanding atmosphere codes. I have modeled the spectrum of the low-metallicity WO star DR1 and find abundances comparable to carbon Wolf-Rayet stars, but a much higher stellar temperature. The study of the other known single WO stars (5 in total) shows that most of them show very high carbon and oxygen abundances, and have less then 40% of helium left (by mass). The found stellar abundances will be used to constrain the initial masses of the stars and their evolutionary path. They are also used to constrain the illusive carbon to oxygen thermonuclear reaction rate.
The formation of massive, quiescent galaxies at cosmic noon
NASA Astrophysics Data System (ADS)
Feldmann, Robert; Hopkins, Philip F.; Quataert, Eliot; Faucher-Giguère, Claude-André; Kereš, Dušan
2016-05-01
The cosmic noon (z ˜ 1.5-3) marked a period of vigorous star formation for most galaxies. However, about a third of the more massive galaxies at those times were quiescent in the sense that their observed stellar populations are inconsistent with rapid star formation. The reduced star formation activity is often attributed to gaseous outflows driven by feedback from supermassive black holes, but the impact of black hole feedback on galaxies in the young Universe is not yet definitively established. We analyse the origin of quiescent galaxies with the help of ultrahigh resolution, cosmological simulations that include feedback from stars but do not model the uncertain consequences of black hole feedback. We show that dark matter haloes with specific accretion rates below ˜0.25-0.4 Gyr-1 preferentially host galaxies with reduced star formation rates and red broad-band colours. The fraction of such haloes in large dark matter only simulations matches the observed fraction of massive quiescent galaxies (˜1010-1011 M⊙). This strongly suggests that halo accretion rate is the key parameter determining which massive galaxies at z ˜ 1.5-3 become quiescent. Empirical models that connect galaxy and halo evolution, such as halo occupation distribution or abundance matching models, assume a tight link between galaxy properties and the masses of their parent haloes. These models will benefit from adding the specific accretion rate of haloes as a second model parameter.
Pre-Supernova Mass Loss Predictions for Massive Stars
NASA Astrophysics Data System (ADS)
Vink, J. S.; de Koter, A.; Kotak, R.
2008-06-01
Massive stars and supernovae (SNe) have a huge impact on their environment. Despite their importance, a comprehensive knowledge of which massive stars produce which SNe is hitherto lacking. We use a Monte Carlo method to predict the mass-loss rates of massive stars in the Hertzsprung-Russell Diagram (HRD) covering all phases from the OB main sequence, the unstable Luminous Blue Variable (LBV) stage, to the final Wolf-Rayet (WR) phase. Although WR produce their own metals, a strong dependence of the mass-loss rate on the initial iron abundance is found at sub-solar metallicities (1/10 -- 1/100 solar). This may present a viable mechanism to prevent the loss of angular momentum by stellar winds, which could inhibit GRBs occurring at solar metallicities -- providing a significant boost to the collapsar model. Furthermore, we discuss recently reported quasi-sinusoidal modulations in the radio lightcurves of SN 2001ig and SNe 2003bg. We show that both the sinusoidal behaviour and the recurrence timescale of these modulations are consistent with the predicted mass-loss behaviour of LBVs. We discuss potential ramifications for the ``Conti'' scenario for massive star evolution.
Massively parallel femtosecond laser processing.
Hasegawa, Satoshi; Ito, Haruyasu; Toyoda, Haruyoshi; Hayasaki, Yoshio
2016-08-01
Massively parallel femtosecond laser processing with more than 1000 beams was demonstrated. Parallel beams were generated by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The key to this technique is to optimize the CGH in the laser processing system using a scheme called in-system optimization. It was analytically demonstrated that the number of beams is determined by the horizontal number of pixels in the SLM N_{SLM} that is imaged at the pupil plane of an objective lens and a distance parameter p_{d} obtained by dividing the distance between adjacent beams by the diffraction-limited beam diameter. A performance limitation of parallel laser processing in our system was estimated at N_{SLM} of 250 and p_{d} of 7.0. Based on these parameters, the maximum number of beams in a hexagonal close-packed structure was calculated to be 1189 by using an analytical equation. PMID:27505815
Massive Protostars In Young Dense Clusters: Disk Disruption And Binary Capture
NASA Astrophysics Data System (ADS)
Moeckel, Nickolas
2007-12-01
Massive stars are typically found in the centers of young, dense clusters. Encounters between massive protostars and their less-massive cluster siblings are frequent enough to impact their formation processes. We present the results of numerical studies concerning the interaction of a massive-star disk system and an impacting star, which suggest that disk-assisted capture can contribute significantly to the high multiplicity of massive stars. We discuss the results of N-body simulations of this process, as well as the observational clues that point to this scenario. A potential example of a capture process in Cepheus A is presented along with modeling of this system. This work was supported by NASA grant NNA04CC11A to the CU Center for Astrobiology.
Massive vector multiplet inflation with Dirac-Born-Infeld type action
NASA Astrophysics Data System (ADS)
Abe, Hiroyuki; Sakamura, Yutaka; Yamada, Yusuke
2015-06-01
We investigate the inflation model with a massive vector multiplet in a case that the action of the vector multiplet is extended to the Dirac-Born-Infeld (DBI) type one. We show the massive DBI action in four-dimensional N =1 supergravity and find that the higher-order corrections associated with the DBI extension make the scalar potential flat with a simple choice of the matter couplings. We also discuss the DBI extension of the new minimal Starobinsky model and find that it is dual to a special class of the massive DBI action.
On the spectra of scalar mesons from HQCD models
NASA Astrophysics Data System (ADS)
Mintakevich, Oded; Sonnenschein, Jacob
2008-08-01
We determine the holographic spectra of scalar mesons from the fluctuations of the embedding of flavor D-brane probes in HQCD models. The models we consider include a generalization of the Sakai Sugimoto model at zero temperature and at the ``high-temperature intermediate phase", where the system is in a deconfining phase while admitting chiral symmetry breaking and a non-critical 6d model at zero temperature. All these models are based on backgrounds associated with near extremal Nc D4 branes and a set of Nf << Nc flavor probe branes that admit geometrical chiral symmetry breaking. We point out that the spectra of these models include a 0-- branch which does not show up in nature. At zero temperature we found that the masses of the mesons Mn depend on the ``constituent quark mass" parameter mcq and on the excitation number n as Mn2 ~ mcq and M2n ~ n1.7 for the ten dimensional case and as Mn ~ mcq and Mn ~ n0.75 in the non-critical case. At the high temperature intermediate phase we detect a decrease of the masses of low spin mesons as a function of the temperature similar to holographic vector mesons and to lattice calculations.
FAST TRACK COMMUNICATION The Bel-Robinson tensor for topologically massive gravity
NASA Astrophysics Data System (ADS)
Deser, S.; Franklin, J.
2011-02-01
We construct, and establish the (covariant) conservation of, a 4-index 'super stress tensor' for topologically massive gravity. Separately, we discuss its invalidity in quadratic curvature models and suggest a generalization.
The Role of the Magnetorotational Instability in Massive Stars
NASA Astrophysics Data System (ADS)
Wheeler, J. Craig; Kagan, Daniel; Chatzopoulos, Emmanouil
2015-01-01
The magnetorotational instability (MRI) is key to physics in accretion disks and is widely considered to play some role in massive star core collapse. Models of rotating massive stars naturally develop very strong shear at composition boundaries, a necessary condition for MRI instability, and the MRI is subject to triply diffusive destabilizing effects in radiative regions. We have used the MESA stellar evolution code to compute magnetic effects due to the Spruit-Tayler (ST) mechanism and the MRI, separately and together, in a sample of massive star models. We find that the MRI can be active in the later stages of massive star evolution, leading to mixing effects that are not captured in models that neglect the MRI. The MRI and related magnetorotational effects can move models of given zero-age main sequence mass across "boundaries" from degenerate CO cores to degenerate O/Ne/Mg cores and from degenerate O/Ne/Mg cores to iron cores, thus affecting the final evolution and the physics of core collapse. The MRI acting alone can slow the rotation of the inner core in general agreement with the observed "initial" rotation rates of pulsars. The MRI analysis suggests that localized fields ~1012 G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M ⊙ model, we find that the helium shell mixes entirely out into the envelope. Enhanced mixing could yield a population of yellow or even blue supergiant supernova progenitors that would not be standard SN IIP.
THE ROLE OF THE MAGNETOROTATIONAL INSTABILITY IN MASSIVE STARS
Wheeler, J. Craig; Kagan, Daniel; Chatzopoulos, Emmanouil
2015-01-20
The magnetorotational instability (MRI) is key to physics in accretion disks and is widely considered to play some role in massive star core collapse. Models of rotating massive stars naturally develop very strong shear at composition boundaries, a necessary condition for MRI instability, and the MRI is subject to triply diffusive destabilizing effects in radiative regions. We have used the MESA stellar evolution code to compute magnetic effects due to the Spruit-Tayler (ST) mechanism and the MRI, separately and together, in a sample of massive star models. We find that the MRI can be active in the later stages of massive star evolution, leading to mixing effects that are not captured in models that neglect the MRI. The MRI and related magnetorotational effects can move models of given zero-age main sequence mass across ''boundaries'' from degenerate CO cores to degenerate O/Ne/Mg cores and from degenerate O/Ne/Mg cores to iron cores, thus affecting the final evolution and the physics of core collapse. The MRI acting alone can slow the rotation of the inner core in general agreement with the observed ''initial'' rotation rates of pulsars. The MRI analysis suggests that localized fields ∼10{sup 12} G may exist at the boundary of the iron core. With both the ST and MRI mechanisms active in the 20 M {sub ☉} model, we find that the helium shell mixes entirely out into the envelope. Enhanced mixing could yield a population of yellow or even blue supergiant supernova progenitors that would not be standard SN IIP.
The formation of slow-massive-wide jets
NASA Astrophysics Data System (ADS)
Soker, Noam
2008-07-01
I propose a model for the formation of slow-massive-wide (SMW) jets by accretion disks around compact objects. This study is motivated by claims for the existence of SMW jets in some astrophysical objects such as in planetary nebulae (PNs) and in some active galactic nuclei in galaxies and in cooling flow clusters. In this model the energy still comes from accretion onto a compact object. The accretion disk launches two opposite jets with velocity of the order of the escape velocity from the accreting object and with mass outflow rate of ˜1-20% of the accretion rate as in most popular models for jet launching; in the present model these are termed fast-first-stage (FFS) jets. However, the FFS jets encounter surrounding gas that originates in the mass accretion process, and are terminated by strong shocks close to their origin. Two hot bubbles are formed. These bubbles accelerate the surrounding gas to form two SMW jets that are more massive and slower than the FFS jets. There are two conditions for this mechanism to work. Firstly, the surrounding gas should be massive enough to block the free expansion of the FFS jets. Most efficiently this condition is achieved when the surrounding gas is replenished. Secondly, the radiative energy losses must be small.
Linear growth of structure in massive bigravity
Solomon, Adam R.; Akrami, Yashar; Koivisto, Tomi S. E-mail: yashar.akrami@astro.uio.no
2014-10-01
The ghost-free theory of massive gravity with two dynamical metrics has been shown to produce viable cosmological expansion, where the late-time acceleration of the Universe is due to the finite range of the gravitational interaction rather than a nonzero cosmological constant. Here the cosmological perturbations are studied in this theory. The full perturbation equations are presented in a general gauge and analyzed, focusing on subhorizon scales in the quasistatic limit during the matter-dominated era. An evolution equation for the matter inhomogeneities and the parameters quantifying the deviations from general relativistic structure formation are expressed in terms of five functions whose forms are determined directly by the coupling parameters in the theory. The evolution equation has a similar structure to Horndeski-type scalar-tensor theories, exhibiting a modified growth rate and scale-dependence at intermediate wavenumbers. Predictions of the theory are confronted with observational data on both background expansion and large-scale structure, although care must be taken to ensure a model is stable. It is found that while the stable models fit the data well, they feature deviations from the standard cosmology that could be detected or ruled out by near-future experiments.
The dynamics of massive starless cores with ALMA
Tan, Jonathan C.; Kong, Shuo; Butler, Michael J.; Caselli, Paola; Fontani, Francesco
2013-12-20
How do stars that are more massive than the Sun form, and thus how is the stellar initial mass function (IMF) established? Such intermediate- and high-mass stars may be born from relatively massive pre-stellar gas cores, which are more massive than the thermal Jeans mass. The turbulent core accretion model invokes such cores as being in approximate virial equilibrium and in approximate pressure equilibrium with their surrounding clump medium. Their internal pressure is provided by a combination of turbulence and magnetic fields. Alternatively, the competitive accretion model requires strongly sub-virial initial conditions that then lead to extensive fragmentation to the thermal Jeans scale, with intermediate- and high-mass stars later forming by competitive Bondi-Hoyle accretion. To test these models, we have identified four prime examples of massive (∼100 M {sub ☉}) clumps from mid-infrared extinction mapping of infrared dark clouds. Fontani et al. found high deuteration fractions of N{sub 2}H{sup +} in these objects, which are consistent with them being starless. Here we present ALMA observations of these four clumps that probe the N{sub 2}D{sup +} (3-2) line at 2.''3 resolution. We find six N{sub 2}D{sup +} cores and determine their dynamical state. Their observed velocity dispersions and sizes are broadly consistent with the predictions of the turbulent core model of self-gravitating, magnetized (with Alfvén Mach number m{sub A} ∼ 1) and virialized cores that are bounded by the high pressures of their surrounding clumps. However, in the most massive cores, with masses up to ∼60 M {sub ☉}, our results suggest that moderately enhanced magnetic fields (so that m{sub A} ≅ 0.3) may be needed for the structures to be in virial and pressure equilibrium. Magnetically regulated core formation may thus be important in controlling the formation of massive cores, inhibiting their fragmentation, and thus helping to establish the stellar IMF.
No hair theorem in quasi-dilaton massive gravity
NASA Astrophysics Data System (ADS)
Wu, De-Jun; Zhou, Shuang-Yong
2016-06-01
We investigate the static, spherically symmetric black hole solutions in the quasi-dilaton model and its generalizations, which are scalar extended dRGT massive gravity with a shift symmetry. We show that, unlike generic scalar extended massive gravity models, these theories do not admit static, spherically symmetric black hole solutions until the theory parameters in the dRGT potential are fine-tuned. When fine-tuned, the geometry of the static, spherically symmetric black hole is necessarily that of general relativity and the quasi-dilaton field is constant across the spacetime. The fine-tuning and the no hair theorem apply to black holes with flat, anti-de Sitter or de Sitter asymptotics.
Massive pulmonary embolism: the place for embolectomy
Buckels, N J; Mulholland, C; Galvin, I; Gladstone, D; Cleland, J
1988-01-01
Untreated massive pulmonary embolism is associated with a high mortality. Pulmonary embolectomy has been largely superceded by thrombolytic therapy, but there are cases in which pulmonary embolectomy remains the treatment of choice. We present three case reports and discuss the merits of the various treatments available for massive pulmonary embolism. The primary treatment of massive pulmonary embolism should be thrombolytic therapy, but for patients who are at risk of haemorrhage following surgery, who are in cardiogenic shock despite medical treatment, or fail to improve following cardiac arrest, then pulmonary embolectomy remains the treatment of choice. ImagesFig 1Fig 2Fig 3 PMID:3232251
Massive star archeology in globular clusters
NASA Astrophysics Data System (ADS)
Chantereau, W.; Charbonnel, C.; Meynet, G.
2015-01-01
Globular clusters are among the oldest structures in the Universe and they host today low-mass stars and no gas. However, there has been a time when they formed as gaseous objects hosting a large number of short-lived, massive stars. Many details on this early epoch have been depicted recently through unprecedented dissection of low-mass globular cluster stars via spectroscopy and photometry. In particular, multiple populations have been identified, which bear the nucleosynthetic fingerprints of the massive hot stars disappeared a long time ago. Here we discuss how massive star archeology can be done through the lense of these multiple populations.
Venus - Volcano With Massive Landslides
NASA Technical Reports Server (NTRS)
1992-01-01
This Magellan full-resolution mosaic which covers an area 143 by 146 kilometers (89 by 91 miles) is centered at 55 degrees north latitude, 266 degrees east longitude. The bright feature, slightly south of center is interpreted to be a volcano, 15-20 kilometers (9.3 to 12.4 miles) in diameter with a large apron of blocky debris to its right and some smaller aprons to its left. A preferred explanation is that several massive catastrophic landslides dropped down steep slopes and were carried by their momentum out into the smooth, dark lava plains. At the base of the east-facing or largest scallop on the volcano is what appears to be a large block of coherent rock, 8 to 10 kilometers (5 to 6 miles) in length. The similar margin of both the scallop and block and the shape in general is typical of terrestrial slumped blocks (masses of rock which slide and rotate down a slope instead of breaking apart and tumbling). The bright lobe to the south of the volcano may either be a lava flow or finer debris from other landslides. This volcanic feature, characterized by its scalloped flanks is part of a class of volcanoes called scalloped or collapsed domes of which there are more than 80 on Venus. Based on the chute-like shapes of the scallops and the existence of a spectrum of intermediate to well defined examples, it is hypothesized that all of the scallops are remnants of landslides even though the landslide debris is often not visible. Possible explanations for the missing debris are that it may have been covered by lava flows, the debris may have weathered or that the radar may not be recognizing it because the individual blocks are too small
Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction
NASA Astrophysics Data System (ADS)
Rijken, Th. A.; Yamamoto, Y.
2006-04-01
The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the 3P0 quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the 3P0 model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the Λp and Λn channels, which is an SU(2) isospin breaking, is included in the
Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction
Rijken, Th.A.; Yamamoto, Y.
2006-04-15
The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the {sup 3}P{sub 0} quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the {sup 3}P{sub 0} model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the {lambda}p and {lambda}n channels, which is an SU(2
Constraints on massive gravity theory from big bang nucleosynthesis
Lambiase, G.
2012-10-01
The massive gravity cosmology is studied in the scenario of big bang nucleosynthesis. By making use of current bounds on the deviation from the fractional mass, we derive the constraints on the free parameters of the theory. The cosmological consequences of the model are also analyzed in the framework of the PAMELA experiment, i.e. an excess of positron events, that the conventional cosmology and particle physics cannot explain.
Nonperturbative construction of massive Yang-Mills fields without the Higgs field
NASA Astrophysics Data System (ADS)
Kondo, Kei-Ichi
2013-01-01
In order to understand the so-called decoupling solution for gluon and ghost propagators in QCD, we give a nonperturbative construction of a massive vector field describing a non-Abelian massive spin-one particle, which has the correct physical degrees of freedom and is invariant under a modified Becchi-Rouet-Stora-Tyutin transformation, in a massive Yang-Mills model without the Higgs field, i.e., the Curci-Ferrari model. The resulting non-Abelian massive vector boson field is written by using a nonlinear but local transformation from the original fields in the Curci-Ferrari model. As an application, we write down a local mass term for the Yang-Mills field and a dimension-two condensate, which are exactly invariant under the modified Becchi-Rouet-Stora-Tyutin transformation, Lorentz transformation, and color rotation.
JD13 - Eta Carinae in the Context of the Most Massive Stars
NASA Astrophysics Data System (ADS)
Gull, Theodore R.; Damineli, Augusto
2010-11-01
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, η 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 γ-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, η Car behaved both predictably and unpredictably during this most recent periastron, spurring timely discussions.
Massive and massless higher spinning particles in odd dimensions
NASA Astrophysics Data System (ADS)
Bastianelli, Fiorenzo; Bonezzi, Roberto; Corradini, Olindo; Latini, Emanuele
2014-09-01
We study actions for massive bosonic particles of higher spins by dimensionally reducing an action for massless particles. For the latter we take a model with a SO( N) extended local supersymmetry on the worldline, that is known to describe massless (conformal) particles of higher spins in flat spacetimes of even dimensions. Dimensional reduction produces an action for massive spinning particles in odd dimensions. The field equations that emerge in a quantization à la Dirac are shown to be equivalent to the Fierz-Pauli ones. The massless limit generates a multiplet of massless states with higher spins, whose first quantized field equations have a geometric form with fields belonging to various types of Young tableaux. These geometric equations can be partially integrated to show their equivalence with the standard Fronsdal-Labastida equations. We covariantize our model to check whether an extension to curved spacetimes can be achieved. Restricting to (A)dS spaces, we find that the worldline gauge algebra becomes nonlinear, but remains first class. This guarantees consistency on such backgrounds. A light cone analysis confirms the presence of the expected propagating degrees of freedom. A covariant analysis is worked out explicitly for the massive case, which is seen to give rise to the Fierz-Pauli equations extended to (A)dS spaces. It is worth noting that in D = 3 the massless limit of our model with N → ∞ has the same field content of the Vasiliev's theory that accommodates each spin exactly once.
Microscopically constrained mean-field models from chiral nuclear thermodynamics
NASA Astrophysics Data System (ADS)
Rrapaj, Ermal; Roggero, Alessandro; Holt, Jeremy W.
2016-06-01
We explore the use of mean-field models to approximate microscopic nuclear equations of state derived from chiral effective field theory across the densities and temperatures relevant for simulating astrophysical phenomena such as core-collapse supernovae and binary neutron star mergers. We consider both relativistic mean-field theory with scalar and vector meson exchange as well as energy density functionals based on Skyrme phenomenology and compare to thermodynamic equations of state derived from chiral two- and three-nucleon forces in many-body perturbation theory. Quantum Monte Carlo simulations of symmetric nuclear matter and pure neutron matter are used to determine the density regimes in which perturbation theory with chiral nuclear forces is valid. Within the theoretical uncertainties associated with the many-body methods, we find that select mean-field models describe well microscopic nuclear thermodynamics. As an additional consistency requirement, we study as well the single-particle properties of nucleons in a hot/dense environment, which affect e.g., charged-current weak reactions in neutron-rich matter. The identified mean-field models can be used across a larger range of densities and temperatures in astrophysical simulations than more computationally expensive microscopic models.
Evolution of Massive Stars at Low Metallicity
NASA Astrophysics Data System (ADS)
Meynet, Georges; Walborn, Nolan R.; Hunter, Ian; Martayan, Christophe; van Marle, Allard Jan; Marchenko, Sergey; Vink, Jorick S.; Limongi, Marco; Levesque, Emily M.; Modjaz, Maryam
2008-06-01
This paper reports the contributions made on the occasion of the Special Session entitled “Evolution of Massive Stars at Low Metallicity” which was held on Sunday, December 9, 2007 in Kauai (USA).
Recovering General Relativity from Massive Gravity
Babichev, E.; Deffayet, C.; Ziour, R.
2009-11-13
We obtain static, spherically symmetric, and asymptotically flat numerical solutions of massive gravity with a source. Those solutions show, for the first time explicitly, a recovery of the Schwarzschild solution of general relativity via the so-called Vainshtein mechanism.
Management of massive and nonmassive pulmonary embolism
Sekhri, Vishal; Mehta, Nimeshkumar; Rawat, Naveen; Lehrman, Stuart G.
2012-01-01
Massive pulmonary embolism (PE) is characterized by systemic hypotension (defined as a systolic arterial pressure < 90 mm Hg or a drop in systolic arterial pressure of at least 40 mm Hg for at least 15 min which is not caused by new onset arrhythmias) or shock (manifested by evidence of tissue hypoperfusion and hypoxia, including an altered level of consciousness, oliguria, or cool, clammy extremities). Massive pulmonary embolism has a high mortality rate despite advances in diagnosis and therapy. A subgroup of patients with nonmassive PE who are hemodynamically stable but with right ventricular (RV) dysfunction or hypokinesis confirmed by echocardiography is classified as submassive PE. Their prognosis is different from that of others with non-massive PE and normal RV function. This article attempts to review the evidence-based risk stratification, diagnosis, initial stabilization, and management of massive and nonmassive pulmonary embolism. PMID:23319967
Dwarf Galaxies with Active Massive Black Holes
NASA Astrophysics Data System (ADS)
Reines, Amy E.; Greene, J. E.; Geha, M. C.
2014-01-01
Supermassive black holes (BHs) live at the heart of essentially all massive galaxies with bulges, power AGN, and are thought to be important agents in the evolution of their hosts. However, the birth and growth of the first supermassive BH "seeds" is far from understood. While direct observations of these distant BHs in the infant Universe are unobtainable with current capabilities, massive BHs in present-day dwarf galaxies can place valuable constraints on the masses, formation path, and hosts of supermassive BH seeds. Using optical spectroscopy from the SDSS, we have systematically assembled the largest sample of dwarf galaxies hosting active massive BHs to date. These dwarf galaxies have stellar masses comparable to the Magellanic Clouds and contain some of the least-massive supermassive BHs known.
The origin of massive clusters: from hyper-massive clouds to mini-bursts of star formation
NASA Astrophysics Data System (ADS)
Motte, Frederique; Louvet, Fabien; Nguyen Luong, Quang
2015-08-01
Herschel revealed high-density cloud filaments of several pc^3, which are forming clusters of OB-type stars. Counting Herschel protostars gives a direct measure of the mass of stars forming in a period of ~10^5 yrs, the ``instantaneous'' star formation activity. Given their activity, these so-called mini-starburst cloud ridges could be seen as "miniature and instant models" of starburst galaxies. Their characteristics could shed light on the origin of massive clusters.
Self-protection of massive cosmological gravitons
Berkhahn, Felix; Dietrich, Dennis D.; Hofmann, Stefan E-mail: dietrich@cp3.sdu.dk
2010-11-01
Relevant deformations of gravity present an exciting window of opportunity to probe the rigidity of gravity on cosmological scales. For a single-graviton theory, the leading relevant deformation constitutes a graviton mass term. In this paper, we investigate the classical and quantum stability of massive cosmological gravitons on generic Friedman backgrounds. For a Universe expanding towards a de Sitter epoch, we find that massive cosmological gravitons are self-protected against unitarity violations by a strong coupling phenomenon.
Primordial Li abundance and massive particles
NASA Astrophysics Data System (ADS)
ðapo, H.
2012-10-01
The problem of the observed lithium abundance coming from the Big Bang Nucleosynthesis is as of yet unsolved. One of the proposed solutions is including relic massive particles into the Big Bang Nucleosynthesis. We investigated the effects of such particles on 4HeX-+2H-->6Li+X-, where the X- is the negatively charged massive particle. We demonstrate the dominance of long-range part of the potential on the cross-section.
Radiative ablation of disks around massive stars
NASA Astrophysics Data System (ADS)
Kee, Nathaniel Dylan
Hot, massive stars (spectral types O and B) have extreme luminosities (10. 4 -10. 6 L?) that drive strong stellar winds through UV line-scattering.Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar rotation to launch material into orbiting Keplerian disks of Be-like densities. In contrast to such Be decretion disks, star-forming accretion disks are much denser and so are generally optically thick to continuum processes. To circumvent the computational challenges associated with radiation hydrodynamics through optically thick media, we develop an approximate method for treating continuum absorption in the limit of geometrically thin disks. The comparison of ablation with and without continuum absorption shows that accounting for disk optical thickness leads to less than a 50% reduction in ablation rate, implying that ablation rate depends mainly on stellar properties like luminosity. Finally, we discuss the role of "thin-shell mixing" in reducing X-rays from colliding wind binaries. Laminar, adiabatic shocks produce well understood X-ray emission, but the emission from radiatively cooled shocks is more complex due to thin-shell instabilities. The parameter
Massive hybrid parallelism for fully implicit multiphysics
Gaston, D. R.; Permann, C. J.; Andrs, D.; Peterson, J. W.
2013-07-01
As hardware advances continue to modify the supercomputing landscape, traditional scientific software development practices will become more outdated, ineffective, and inefficient. The process of rewriting/retooling existing software for new architectures is a Sisyphean task, and results in substantial hours of development time, effort, and money. Software libraries which provide an abstraction of the resources provided by such architectures are therefore essential if the computational engineering and science communities are to continue to flourish in this modern computing environment. The Multiphysics Object Oriented Simulation Environment (MOOSE) framework enables complex multiphysics analysis tools to be built rapidly by scientists, engineers, and domain specialists, while also allowing them to both take advantage of current HPC architectures, and efficiently prepare for future supercomputer designs. MOOSE employs a hybrid shared-memory and distributed-memory parallel model and provides a complete and consistent interface for creating multiphysics analysis tools. In this paper, a brief discussion of the mathematical algorithms underlying the framework and the internal object-oriented hybrid parallel design are given. Representative massively parallel results from several applications areas are presented, and a brief discussion of future areas of research for the framework are provided. (authors)
Massive Dataset Analysis for Geoscience Data (Invited)
NASA Astrophysics Data System (ADS)
Braverman, A. J.
2013-12-01
Many large datasets in the geosciences manifest a fundamental problem in massive data set analysis: to understand and quantify local, fine-scale structure in a global context. One approach is to reduce data in a way that preserves spatial, temporal, and inter-scale structures via discrete probability distribution estimates associated with cells of space-time grids at different resolutions. It is then possible to study relationships between cells at different scales. This talk describes the theory and implementation of such a data reduction method developed for NASA satellite missions. Data are stratified on a monthly, five-degree, latitude-longitude space-time grid to form subsets. Each subset is reduced using a clustering algorithm for which the loss function includes an information-theoretic penalty term to help choose the number of clusters and the assignment of observations to them. The clusters' centroids and populations define a set of discrete probability distributions, which become the fundamental units for data analysis. Since the cluster representatives are centroids of original data points, the distributions can be aggregated in time and space, allowing us build statistical models that relate phenomena across scales. These ideas are illustrated with datasets produced through the application of this algorithm for the Multi-angle Imaging SpectroRadiometer (MISR) instrument.
Dark aspects of massive spinor electrodynamics
NASA Astrophysics Data System (ADS)
Kim, Edward J.; Kouwn, Seyen; Oh, Phillial; Park, Chan-Gyung
2014-07-01
We investigate the cosmology of massive spinor electrodynamics when torsion is non-vanishing. A non-minimal interaction is introduced between the torsion and the vector field and the coupling constant between them plays an important role in subsequential cosmology. It is shown that the mass of the vector field and torsion conspire to generate dark energy and pressureless dark matter, and for generic values of the coupling constant, the theory effectively provides an interacting model between them with an additional energy density of the form ~ 1/a6. The evolution equations mimic ΛCDM behavior up to 1/a3 term and the additional term represents a deviation from ΛCDM. We show that the deviation is compatible with the observational data, if it is very small. We find that the non-minimal interaction is responsible for generating an effective cosmological constant which is directly proportional to the mass squared of the vector field and the mass of the photon within its current observational limit could be the source of the dark energy.
MASSIVE BLACK HOLES IN CENTRAL CLUSTER GALAXIES
Volonteri, Marta; Ciotti, Luca
2013-05-01
We explore how the co-evolution of massive black holes (MBHs) and galaxies is affected by environmental effects, addressing in particular MBHs hosted in the central cluster galaxies (we will refer to these galaxies in general as ''CCGs''). Recently, the sample of MBHs in CCGs with dynamically measured masses has increased, and it has been suggested that these MBH masses (M{sub BH}) deviate from the expected correlations with velocity dispersion ({sigma}) and mass of the bulge (M{sub bulge}) of the host galaxy: MBHs in CCGs appear to be ''overmassive''. This discrepancy is more pronounced when considering the M{sub BH}-{sigma} relation than the M{sub BH}-M{sub bulge} one. We show that this behavior stems from a combination of two natural factors: (1) CCGs experience more mergers involving spheroidal galaxies and their MBHs and (2) such mergers are preferentially gas poor. We use a combination of analytical and semi-analytical models to investigate the MBH-galaxy co-evolution in different environments and find that the combination of these two factors is in accordance with the trends observed in current data sets.
Measuring Massive Black Hole Binaries with LISA
NASA Technical Reports Server (NTRS)
Lang, Ryan N.; Hughes, Scott A.; Cornish, Neil J.
2009-01-01
The coalescence of two massive black holes produces gravitational waves (GWs) which can be detected by the space-based detector LISA. By measuring these waves, LISA can determine the various parameters which characterize the source. Measurements of the black hole masses and spins will provide information about the growth of black holes and their host galaxies over time. Measurements of a source's sky position and distance may help astronomers identify an electromagnetic counterpart to the GW event. The counterpart's redshift, combined with the GW-measured luminosity distance, can then be used to measure the Hubble constant and the dark energy parameter $w$. Because the potential science output is so high, it is useful to know in advance how well LISA can measure source parameters for a wide range of binaries. We calculate expected parameter estimation errors using the well-known Fisher matrix method. Our waveform model includes the physics of spin precession, as well as subleading harmonics. When these higher-order effects are not included, strong degeneracies between some parameters cause them to be poorly determined by a GW measurement. When precession and subleading harmonics are properly included, the degeneracies are broken, reducing parameter errors by one to several orders of magnitude.
MASSIVE HYBRID PARALLELISM FOR FULLY IMPLICIT MULTIPHYSICS
Cody J. Permann; David Andrs; John W. Peterson; Derek R. Gaston
2013-05-01
As hardware advances continue to modify the supercomputing landscape, traditional scientific software development practices will become more outdated, ineffective, and inefficient. The process of rewriting/retooling existing software for new architectures is a Sisyphean task, and results in substantial hours of development time, effort, and money. Software libraries which provide an abstraction of the resources provided by such architectures are therefore essential if the computational engineering and science communities are to continue to flourish in this modern computing environment. The Multiphysics Object Oriented Simulation Environment (MOOSE) framework enables complex multiphysics analysis tools to be built rapidly by scientists, engineers, and domain specialists, while also allowing them to both take advantage of current HPC architectures, and efficiently prepare for future supercomputer designs. MOOSE employs a hybrid shared-memory and distributed-memory parallel model and provides a complete and consistent interface for creating multiphysics analysis tools. In this paper, a brief discussion of the mathematical algorithms underlying the framework and the internal object-oriented hybrid parallel design are given. Representative massively parallel results from several applications areas are presented, and a brief discussion of future areas of research for the framework are provided.
Dark aspects of massive spinor electrodynamics
Kim, Edward J.; Kouwn, Seyen; Oh, Phillial; Park, Chan-Gyung E-mail: seyen@ewha.ac.kr E-mail: parkc@jbnu.ac.kr
2014-07-01
We investigate the cosmology of massive spinor electrodynamics when torsion is non-vanishing. A non-minimal interaction is introduced between the torsion and the vector field and the coupling constant between them plays an important role in subsequential cosmology. It is shown that the mass of the vector field and torsion conspire to generate dark energy and pressureless dark matter, and for generic values of the coupling constant, the theory effectively provides an interacting model between them with an additional energy density of the form ∼ 1/a{sup 6}. The evolution equations mimic ΛCDM behavior up to 1/a{sup 3} term and the additional term represents a deviation from ΛCDM. We show that the deviation is compatible with the observational data, if it is very small. We find that the non-minimal interaction is responsible for generating an effective cosmological constant which is directly proportional to the mass squared of the vector field and the mass of the photon within its current observational limit could be the source of the dark energy.
New Bi-Gravity from New Massive Gravity
NASA Astrophysics Data System (ADS)
Akhavan, A.; Alishahiha, M.; Naseh, A.; Nemati, A.; Shirzad, A.
2016-05-01
Using the action of three dimensional New Massive Gravity (NMG) we construct a new bi-gravity in three dimensions. This can be done by promoting the rank two auxiliary field appearing in the expression of NMG's action into a dynamical field. We show that small fluctuations around the AdS vacuum of the model are non-tachyonic and ghost free within certain range of the parameters of the model. We study central charges of the dual field theory and observe that in this range they are positive too. This suggests that the proposed model might be a consistent three dimensional bi-gravity.
Massive spin-2 fields of geometric origin in curved spacetimes
Nair, V. P.; Randjbar-Daemi, S.; Rubakov, V.
2009-11-15
We study the consistency of a model which includes torsion as well as the metric as dynamical fields and has massive spin-2 particle in its spectrum. It is known that this model is tachyon free and ghost free in Minkowski background. We show that this property remains valid and no other pathologies emerge in de Sitter and anti-de Sitter backgrounds, with some of our results extending to arbitrary Einstein space backgrounds. This suggests that the model is consistent, at least at the classical level, unlike, e.g., the Fierz-Pauli theory.
VizieR Online Data Catalog: Fermi sources with massive YSO associations (Munar-Adrover+, 2011)
NASA Astrophysics Data System (ADS)
Munar-Adrover, P.; Paredes, J. M.; Romero, G. E.
2011-09-01
Massive protostars have associated bipolar outflows that can produce strong shocks when they interact with the surrounding medium. At these shocks, particles can be accelerated up to relativistic energies. Relativistic electrons and protons can then produce gamma-ray emission, as some theoretical models predict. To identify young galactic objects that may emit gamma rays, we crossed the Fermi First Year Catalog with some catalogs of known massive young stellar objects (MYSOs), early type stars, and OB associations, and we implemented Monte Carlo simulations to find the probability of chance coincidences. We obtained a list of massive MYSOs that are spatially coincident with Fermi sources. (4 data files).
Nuclear ρ meson transparency in a relativistic Glauber model
NASA Astrophysics Data System (ADS)
Cosyn, W.; Ryckebusch, J.
2013-06-01
Background: The recent Jefferson Laboratory data for the nuclear transparency in ρ0 electroproduction have the potential to settle the scale for the onset of color transparency (CT) in vector meson production.Purpose: To compare the data to calculations in a relativistic and quantum-mechanical Glauber model and to investigate whether they are in accordance with results including color transparency given that the computation of ρ-nucleus attenuations is subject to some uncertainties.Method: We compute the nuclear transparencies in a multiple-scattering Glauber model and account for effects stemming from color transparency, from ρ-meson decay, and from short-range correlations (SRC) in the final-state interactions (FSI).Results: The robustness of the model is tested by comparing the mass dependence and the hard-scale dependence of the A(e,e'p) nuclear transparencies with the data. The hard-scale dependence of the (e,e'ρ0) nuclear transparencies for 12C and 56Fe are only moderately affected by SRC and by ρ0 decay.Conclusions: The RMSGA calculations confirm the onset of CT at four-momentum transfers of a few (GeV/c)2 in ρ meson electroproduction data. A more precise determination of the scale for the onset of CT is hampered by the lack of precise input in the FSI and ρ-meson decay calculations.
Shifting from Stewardship to Analytics of Massive Science Data
NASA Astrophysics Data System (ADS)
Crichton, D. J.; Doyle, R.; Law, E.; Hughes, S.; Huang, T.; Mahabal, A.
2015-12-01
Currently, the analysis of large data collections is executed through traditional computational and data analysis approaches, which require users to bring data to their desktops and perform local data analysis. Data collection, archiving and analysis from future remote sensing missions, be it from earth science satellites, planetary robotic missions, or massive radio observatories may not scale as more capable instruments stress existing architectural approaches and systems due to more continuous data streams, data from multiple observational platforms, and measurements and models from different agencies. A new paradigm is needed in order to increase the productivity and effectiveness of scientific data analysis. This paradigm must recognize that architectural choices, data processing, management, analysis, etc are interrelated, and must be carefully coordinated in any system that aims to allow efficient, interactive scientific exploration and discovery to exploit massive data collections. Future observational systems, including satellite and airborne experiments, and research in climate modeling will significantly increase the size of the data requiring new methodological approaches towards data analytics where users can more effectively interact with the data and apply automated mechanisms for data reduction, reduction and fusion across these massive data repositories. This presentation will discuss architecture, use cases, and approaches for developing a big data analytics strategy across multiple science disciplines.
Relativistic stars in de Rham-Gabadadze-Tolley massive gravity
NASA Astrophysics Data System (ADS)
Katsuragawa, Taishi; Nojiri, Shin'ichi; Odintsov, Sergei D.; Yamazaki, Masashi
2016-06-01
We study relativistic stars in the simplest model of the de Rham-Gabadadze-Tolley massive gravity which describes the massive graviton without a ghost propagating mode. We consider the hydrostatic equilibrium and obtain the modified Tolman-Oppenheimer-Volkoff equation and the constraint equation coming from the potential terms in the gravitational action. We give analytical and numerical results for quark and neutron stars and discuss the deviations compared with general relativity and F (R ) gravity. It is shown that the theory under investigation leads to a small deviation from general relativity in terms of density profiles and mass-radius relation. Nevertheless, such a deviation may be observable in future astrophysical probes.
UH cosmic rays: Possible origin in massive stars
NASA Technical Reports Server (NTRS)
Wefel, J. P.; Schramm, D. N.; Blake, J. B.
1977-01-01
The origin of the Z greater than 28, ultraheavy, cosmic rays in supernova explosions of massive stars is considered. For Z greater than 70, the UH data is dominated by an r-process source distribution, but for the elements just beyond iron, 29 or = Z less than 36, the data cannot be explained by any single process of nucleosynthesis. This problem is solved naturally in a massive star model by secondary neutron capture reactions occuring during core helium burning and during explosive carbon burning. Interstellar propagation calculations were performed with these episodes of synthesis as source distributions, and the results offer an explanation for the current UH cosmic-ray data. The heavy element synthesis during explosive carbon burning is reexamined using more realistic initial conditions given by the post-helium-burning configuration of the star. Effects of preferential acceleration are considered, and experimental tests are discussed.
Cosmological perturbations in massive gravity and the Higuchi bound
Fasiello, Matteo; Tolley, Andrew J. E-mail: andrew.j.tolley@case.edu
2012-11-01
In de Sitter spacetime there exists an absolute minimum for the mass of a spin-2 field set by the Higuchi bound m{sup 2} ≥ 2H{sup 2}. We generalize this bound to arbitrary spatially flat FRW geometries in the context of the recently proposed ghost-free models of Massive Gravity with an FRW reference metric, by performing a Hamiltonian analysis for cosmological perturbations. We find that the bound generically indicates that spatially flat FRW solutions in FRW massive gravity, which exhibit a Vainshtein mechanism in the background as required by consistency with observations, imply that the helicity zero mode is a ghost. In contradistinction to previous works, the tension between the Higuchi bound and the Vainshtein mechanism is equally strong regardless of the equation of state for matter.
New evolutionary tracks of massive stars with PARSEC
NASA Astrophysics Data System (ADS)
Chen, Yang; Bressan, Alessandro; Girardi, Leo; Marigo, Paola
2015-08-01
We present new evolutionary tracks of massive stars that complement the already published PARSEC database and supersede the old Padova evolutionary tracks of massive stars, which are more than 20 years old. We consider a broad range of metallicities, from Z=0.0001 to Z=0.04, and initial masses up to M=350 M⊙. The evolution is computed from the pre-main sequence phase up to the central carbon ignition. We supplement the new tracks with new tables of theoretical bolometric corrections in several photometric systems, obtained by homogenizing stellar atmosphere models of hot and cool stars, PoWR, WM-basic, ATLAS9 and Phoenix.The mass, age and metallicity grids are fully adequate to perform detailed investigations of the properties of very young stellar systems, in local and distant galaxies.
The massive star population of Cygnus OB2
NASA Astrophysics Data System (ADS)
Wright, Nicholas J.; Drew, Janet E.; Mohr-Smith, Michael
2015-05-01
We have compiled a significantly updated and comprehensive census of massive stars in the nearby Cygnus OB2 association by gathering and homogenizing data from across the literature. The census contains 169 primary OB stars, including 52 O-type stars and 3 Wolf-Rayet stars. Spectral types and photometry are used to place the stars in a Hertzsprung-Russell diagram, which is compared to both non-rotating and rotating stellar evolution models, from which stellar masses and ages are calculated. The star formation history and mass function of the association are assessed, and both are found to be heavily influenced by the evolution of the most massive stars to their end states. We find that the mass function of the most massive stars is consistent with a `universal' power-law slope of Γ = 1.3. The age distribution inferred from stellar evolutionary models with rotation and the mass function suggest the majority of star formation occurred more or less continuously between 1 and 7 Myr ago, in agreement with studies of low- and intermediate-mass stars in the association. We identify a nearby young pulsar and runaway O-type star that may have originated in Cyg OB2 and suggest that the association has already seen its first supernova. Finally we use the census and mass function to calculate the total mass of the association of 16 500^{+3800}_{-2800} M⊙, at the low end, but consistent with, previous estimates of the total mass of Cyg OB2. Despite this Cyg OB2 is still one of the most massive groups of young stars known in our Galaxy making it a prime target for studies of star formation on the largest scales.
Massive relic galaxies prefer dense environments
NASA Astrophysics Data System (ADS)
Peralta de Arriba, Luis; Quilis, Vicent; Trujillo, Ignacio; Cebrián, María; Balcells, Marc
2016-09-01
We study the preferred environments of z ˜ 0 massive relic galaxies (M⋆ ≳ 1010 M⊙ galaxies with little or no growth from star formation or mergers since z ˜ 2). Significantly, we carry out our analysis on both a large cosmological simulation and an observed galaxy catalogue. Working on the Millennium I-WMAP7 simulation we show that the fraction of today massive objects which have grown less than 10 per cent in mass since z ˜ 2 is ˜0.04 per cent for the whole massive galaxy population with M⋆ > 1010 M⊙. This fraction rises to ˜0.18 per cent in galaxy clusters, confirming that clusters help massive galaxies remain unaltered. Simulations also show that massive relic galaxies tend to be closer to cluster centres than other massive galaxies. Using the New York University Value-Added Galaxy Catalogue, and defining relics as M⋆ ≳ 1010 M⊙ early-type galaxies with colours compatible with single-stellar population ages older than 10 Gyr, and which occupy the bottom 5-percentile in the stellar mass-size distribution, we find 1.11 ± 0.05 per cent of relics among massive galaxies. This fraction rises to 2.4 ± 0.4 per cent in high-density environments. Our findings point in the same direction as the works by Poggianti et al. and Stringer et al. Our results may reflect the fact that the cores of the clusters are created very early on, hence the centres host the first cluster members. Near the centres, high-velocity dispersions and harassment help cluster core members avoid the growth of an accreted stellar envelope via mergers, while a hot intracluster medium prevents cold gas from reaching the galaxies, inhibiting star formation.
Multigrid on massively parallel architectures
Falgout, R D; Jones, J E
1999-09-17
The scalable implementation of multigrid methods for machines with several thousands of processors is investigated. Parallel performance models are presented for three different structured-grid multigrid algorithms, and a description is given of how these models can be used to guide implementation. Potential pitfalls are illustrated when moving from moderate-sized parallelism to large-scale parallelism, and results are given from existing multigrid codes to support the discussion. Finally, the use of mixed programming models is investigated for multigrid codes on clusters of SMPs.
Dark matter via massive bigravity
NASA Astrophysics Data System (ADS)
Blanchet, Luc; Heisenberg, Lavinia
2015-05-01
In this work we investigate the existence of relativistic models for dark matter in the context of bimetric gravity, used here to reproduce the modified Newtonian dynamics (MOND) at galactic scales. For this purpose we consider two different species of dark matter particles that separately couple to the two metrics of bigravity. These two sectors are linked together via an internal U (1 ) vector field, and some effective composite metric built out of the two metrics. Among possible models only certain classes of kinetic and interaction terms are allowed without invoking ghost degrees of freedom. Along these lines we explore the number of allowed kinetic terms in the theory and point out the presence of ghosts in a previous model. Finally, we propose a promising class of ghost-free candidate theories that could provide the MOND phenomenology at galactic scales while reproducing the standard cold dark matter model at cosmological scales.
OT1_tgull_3: The Homunculus: Clues to Massive Ejection from the Most Massive Stars
NASA Astrophysics Data System (ADS)
Gull, T.
2010-07-01
Eta Carinae is a lynchpin between mass ejection by highly evolved massive stars and the enriched ISM. The Homunculus, a very dusty, neutral bipolar shell ejected in the 1840s, is known to contain at least 12 solar masses, based upon gas/dust=100. But this ejecta is very N-rich with C and O being 0.02 that of solar abundance. What dust formed and how much total mass was ejected? Our ultimate goal is to obtain the total ejected mass. We propose to obtain full spectral scans of the Homunculus with PACS and SPIRES and selected scans with HIFI. We will use these spectra to identify molecules and atomic species associated with this C- and O-depleted gas. While most of this depletion is due to CNO processing and conduction in stars > 60 solar masses, additional depletion is likely due to the first molecules and dust formed at high temperatures during the 1840s eruption. In line of sight we see overabundances of metals not ordinarily seen in the ISM: Sr, Sc, V. These metals have been trapped in atomic state due to limited O and C being available to form molecules. Yet dust has still formed. But what kind of dust? Through existing HST/STIS and VLT/UVES spectra combined with the proposed Herschel spectra and detailed modeling, we will gain much better insight on how molecules and dust can formed in depleted C,O conditions, and in turn provide an improved estimate of the total mass loss. Implications from this study apply to the first massive stars and the earliest dust in the Universe.
NASA Astrophysics Data System (ADS)
Bastian, N.; Hollyhead, K.; Cabrera-Ziri, I.
2014-11-01
One of the leading models for the formation of multiple stellar populations within globular clusters is the `fast rotating massive star' (FRMS) scenario, where the ejecta of rapidly rotating massive stars is mixed with primordial material left over from the star formation process, to form a second generation of stars within the decretion discs of the high-mass stars. A requirement of this model, at least in its current form, is that young massive (i.e. proto-globular) clusters are not able to eject the unused gas and dust from the star formation process from the cluster for 20-30 Myr after the formation of the first generation of stars, i.e. the cluster remains embedded within the gas cloud in which it forms. Here, we test this prediction by performing a literature search for young massive clusters in nearby galaxies, which have ages less than 20 Myr that are not embedded. We report that a number of such clusters exist, with masses near or significantly above 106 M⊙, with ages between a few Myr and ˜15 Myr, suggesting that even high-mass clusters are able to clear any natal gas within them within a few Myr after formation. Additionally, one cluster, Cluster 23 in ESO 338-IG04, has a metallicity below that of some Galactic globular clusters that have been found to host multiple stellar populations, mitigating any potential effect of differences in metallicity in the comparison. The clusters reported here are in contradiction to the expectations of the FRMS scenario, at least in its current form.