RNA structure and scalar coupling constants
Tinoco, I. Jr.; Cai, Z.; Hines, J.V.; Landry, S.M.; SantaLucia, J. Jr.; Shen, L.X.; Varani, G.
1994-12-01
Signs and magnitudes of scalar coupling constants-spin-spin splittings-comprise a very large amount of data that can be used to establish the conformations of RNA molecules. Proton-proton and proton-phosphorus splittings have been used the most, but the availability of {sup 13}C-and {sup 15}N-labeled molecules allow many more coupling constants to be used for determining conformation. We will systematically consider the torsion angles that characterize a nucleotide unit and the coupling constants that depend on the values of these torsion angles. Karplus-type equations have been established relating many three-bond coupling constants to torsion angles. However, one- and two-bond coupling constants can also depend on conformation. Serianni and coworkers measured carbon-proton coupling constants in ribonucleosides and have calculated their values as a function of conformation. The signs of two-bond coupling can be very useful because it is easier to measure a sign than an accurate magnitude.
Disentangling scalar coupling patterns by real-time SERF NMR.
Gubensäk, Nina; Fabian, Walter M F; Zangger, Klaus
2014-10-21
Scalar coupling constants and signal splitting patterns in NMR spectra contain a wealth of short-range structural information. The extraction of these parameters from (1)H NMR spectra is often prohibited by simultaneous scalar coupling interactions with several other protons. Here we present a high-resolution NMR experiment where scalar coupling to only one selected signal is visible. All other couplings are removed from the spectrum. This real-time selectively refocused NMR experiment is achieved by spatially selective homonuclear broadband decoupling combined with selective refocusing during acquisition. It allows the unperturbed extraction of scalar coupling constants from the highly resolved acquisition dimension of NMR spectra.
Generating time dependent conformally coupled Einstein-scalar solutions
NASA Astrophysics Data System (ADS)
Sultana, Joseph
2015-07-01
Using the correspondence between a minimally coupled scalar field and an effective stiff perfect fluid with or without a cosmological constant, we present a simple method for generating time dependent Einstein-scalar solutions with a conformally coupled scalar field that has vanishing or non-vanishing potential. This is done by using Bekenstein's transformation on Einstein-scalar solutions with minimally coupled massless scalar fields, and its later generalization by Abreu et al. to massive fields. In particular we obtain two new spherically symmetric time dependent solutions to the coupled system of Einstein's and the conformal scalar field equations, with one of the solutions having a Higgs' type potential for the scalar field, and we study their properties.
Löhr, F; Pérez, C; Köhler, R; Rüterjans, H; Schmidt, J M
2000-09-01
Constant-time 3D heteronuclear relayed E.COSY [Schmidt et al. (1996) J. Biomol. NMR, 7, 142-152], as based on generic 2D small-flip-angle HMQC-COSY [Schmidt et al. (1995) J. Biomol. NMR, 6, 95-105], has been modified to allow for quantitative determination of heteronuclear three-bond 3J(H(alpha),C(gamma)) couplings. The method is applicable to amino acid spin topologies with carbons in the gamma position which lack attached protons, i.e. to asparagine, aspartate, and aromatic residues in uniformly 13C-enriched proteins. The pulse sequence critically exploits heteronuclear triple-quantum coherence (HTQC) of CH2 moieties involving geminal H(beta) proton pairs, taking advantage of improved multiple-quantum relaxation properties, at the same time avoiding scalar couplings between those spins involved in multiple-quantum coherence, thus yielding E.COSY-type multiplets with a splitting structure that is simpler than with the original scheme. Numerical least-squares 2D line-shape simulation is used to extract 3J(H(alpha),C(gamma)) coupling constants which are of relevance to side-chain chi1 dihedral-angle conformations in polypeptides. Methods are demonstrated with recombinant 15N,13C-enriched ribonuclease T1 and Desulfovibrio vulgaris flavodoxin with bound oxidized FMN.
LIPSS results for photons coupling to light neutral scalar bosons
Andrei Afanasev; Oliver K. Baker; Kevin Beard; George Biallas; James Boyce; Minarni Minarni; Roopchan Ramdon; Michelle D. Shinn; Penny Slocum
2008-06-01
The LIPSS search for a light neutral scalar boson coupling to optical photons is reported. The search covers a region of parameter space of approximately 1.0 meV and coupling strength greater than 10^-6 GeV^-1. The LIPSS results show no evidence for scalar coupling in this region of parameter space.
Inflationary solutions in the nonminimally coupled scalar field theory
NASA Astrophysics Data System (ADS)
Koh, Seoktae; Kim, Sang Pyo; Song, Doo Jong
2005-08-01
We study analytically and numerically the inflationary solutions for various type scalar potentials in the nonminimally coupled scalar field theory. The Hamilton-Jacobi equation is used to deal with nonlinear evolutions of inhomogeneous spacetimes and the long-wavelength approximation is employed to find the homogeneous solutions during an inflation period. The constraints that lead to a sufficient number of e-folds, a necessary condition for inflation, are found for the nonminimal coupling constant and initial conditions of the scalar field for inflation potentials. In particular, we numerically find an inflationary solution in the new inflation model of a nonminimal scalar field.
Relativistic stars in scalar-tensor theories with disformal coupling
NASA Astrophysics Data System (ADS)
Minamitsuji, Masato; Silva, Hector O.
2016-06-01
We present a general formulation to analyze the structure of slowly rotating relativistic stars in a broad class of scalar-tensor theories with disformal coupling to matter. Our approach includes theories with generalized kinetic terms, generic scalar field potentials and contains theories with conformal coupling as particular limits. In order to investigate how the disformal coupling affects the structure of relativistic stars, we propose a minimal model of a massless scalar-tensor theory and investigate in detail how the disformal coupling affects the spontaneous scalarization of slowly rotating neutron stars. We show that for negative values of the disformal coupling parameter between the scalar field and matter, scalarization can be suppressed, while for large positive values of the disformal coupling parameter stellar models cannot be obtained. This allows us to put a mild upper bound on this parameter. We also show that these properties can be qualitatively understood by linearizing the scalar field equation of motion in the background of a general-relativistic incompressible star. To address the intrinsic degeneracy between uncertainties in the equation of state of neutron stars and gravitational theory, we also show the existence of universal equation-of-state-independent relations between the moment of inertia and compactness of neutron stars in this theory. We show that in a certain range of the theory's parameter space the universal relation largely deviates from that of general relativity, allowing, in principle, to probe the existence of spontaneous scalarization with future observations.
Transverse relaxation of scalar-coupled protons.
Segawa, Takuya F; Baishya, Bikash; Bodenhausen, Geoffrey
2010-10-25
In a preliminary communication (B. Baishya, T. F. Segawa, G. Bodenhausen, J. Am. Chem. Soc. 2009, 131, 17538-17539), we recently demonstrated that it is possible to obtain clean echo decays of protons in biomolecules despite the presence of homonuclear scalar couplings. These unmodulated decays allow one to determine apparent transverse relaxation rates R(2) (app) of individual protons. Herein, we report the observation of R(2) (app) for three methyl protons, four amide H(N) protons, and all 11 backbone H(α) protons in cyclosporin A. If the proton resonances overlap, their R(2) (app) rates can be measured by transferring their magnetization to neighboring (13)C nuclei, which are less prone to overlap. The R(2) (app) rates of protons attached to (13)C are faster than those attached to (12)C because of (13)C-(1)H dipolar interactions. The differences of these rates allow the determination of local correlation functions. Backbone H(N) and H(α) protons that have fast decay rates R(2) (app) also feature fast longitudinal relaxation rates R(1) and intense NOESY cross peaks that are typical of crowded environments. Variations of R(2) (app) rates of backbone H(α) protons in similar amino acids reflect differences in local environments.
Noncommutative scalar field minimally coupled to nonsymmetric gravity
Kouadik, S.; Sefai, D.
2012-06-27
We construct a non-commutative non symmetric gravity minimally coupled model (the star product only couples matter). We introduce the action for the system considered namely a non-commutative scalar field propagating in a nontrivial gravitational background. We expand the action in powers of the anti-symmetric field and the graviton to second order adopting the assumption that the scalar is weekly coupled to the graviton. We compute the one loop radiative corrections to the self-energy of a scalar particle.
When scalar field is kinetically coupled to the Einstein tensor
Gao, Changjun
2010-06-01
We explore the cosmic evolution of a scalar field with the kinetic term coupled to the Einstein tensor. We find that, in the absence of other matter sources or in the presence of only pressureless matter, the scalar behaves as pressureless matter and the sound speed of the scalar is vanishing. These properties enable the scalar field to be a candidate of cold dark matter. By also considering the scalar potential, we find the scalar field may play the role of both dark matter and dark energy. In this case, the equation of state of the scalar can cross the phantom divide, but this can lead to the sound speed becoming superluminal as it crosses the divide, and so is physically forbidden. Finally, if the kinetic term is coupled to more than one Einstein tensor, we find the equation of state is always approximately equal to -1 whether the potential is flat or not, and so the scalar may also be a candidate for the inflaton.
Inflation from cosmological constant and nonminimally coupled scalar
NASA Astrophysics Data System (ADS)
Glavan, Dražen; Marunović, Anja; Prokopec, Tomislav
2015-08-01
We consider inflation in a universe with a positive cosmological constant and a nonminimally coupled scalar field, in which the field couples both quadratically and quartically to the Ricci scalar. When considered in the Einstein frame and when the nonminimal couplings are negative, the field starts in slow roll and inflation ends with an asymptotic value of the principal slow-roll parameter, ɛE=4 /3 . Graceful exit can be achieved by suitably (tightly) coupling the scalar field to matter, such that at late time the total energy density reaches the scaling of matter, ɛE=ɛm . Quite generically the model produces a red spectrum of scalar cosmological perturbations and a small amount of gravitational radiation. With a suitable choice of the nonminimal couplings, the spectral slope can be as large as ns≃0.955 , which is about one standard deviation away from the central value measured by the Planck satellite. The model can be ruled out by future measurements if any of the following is observed: (a) the spectral index of scalar perturbations is ns>0.960 ; (b) the amplitude of tensor perturbations is above about r ˜10-2 ; (c) the running of the spectral index of scalar perturbations is positive.
Scalar-tensor theory of gravitation with negative coupling constant
NASA Technical Reports Server (NTRS)
Smalley, L. L.; Eby, P. B.
1976-01-01
The possibility of a Brans-Dicke scalar-tensor gravitation theory with a negative coupling constant is considered. The admissibility of a negative-coupling theory is investigated, and a simplified cosmological solution is obtained which allows a negative derivative of the gravitation constant. It is concluded that a Brans-Dicke theory with a negative coupling constant can be a viable alternative to general relativity and that a large negative value for the coupling constant seems to bring the original scalar-tensor theory into close agreement with perihelion-precession results in view of recent observations of small solar oblateness.
N-body simulations for coupled scalar-field cosmology
Li Baojiu; Barrow, John D.
2011-01-15
We describe in detail the general methodology and numerical implementation of consistent N-body simulations for coupled-scalar-field models, including background cosmology and the generation of initial conditions (with the different couplings to different matter species taken into account). We perform fully consistent simulations for a class of coupled-scalar-field models with an inverse power-law potential and negative coupling constant, for which the chameleon mechanism does not work. We find that in such cosmological models the scalar-field potential plays a negligible role except in the background expansion, and the fifth force that is produced is proportional to gravity in magnitude, justifying the use of a rescaled gravitational constant G in some earlier N-body simulation works for similar models. We then study the effects of the scalar coupling on the nonlinear matter power spectra and compare with linear perturbation calculations to see the agreement and places where the nonlinear treatment deviates from the linear approximation. We also propose an algorithm to identify gravitationally virialized matter halos, trying to take account of the fact that the virialization itself is also modified by the scalar-field coupling. We use the algorithm to measure the mass function and study the properties of dark-matter halos. We find that the net effect of the scalar coupling helps produce more heavy halos in our simulation boxes and suppresses the inner (but not the outer) density profile of halos compared with the {Lambda}CDM prediction, while the suppression weakens as the coupling between the scalar field and dark-matter particles increases in strength.
Scalar field conformally coupled to a charged BTZ black hole
NASA Astrophysics Data System (ADS)
Valtancoli, P.
2016-06-01
We study the Klein-Gordon equation of a scalar field conformally coupled to a charged BTZ black hole. The background metric is obtained by coupling a non-linear and conformal invariant Maxwell field to (2 + 1) gravity. We show that the radial part is generally solved by a Heun function and, in the pure gravity limit, by a hypergeometric function.
Loop quantum gravity coupled to a scalar field
NASA Astrophysics Data System (ADS)
Lewandowski, Jerzy; Sahlmann, Hanno
2016-01-01
We consider the model of gravity coupled to the Klein-Gordon time field. We do not deparametrize the theory using the scalar field before quantization, but quantize all degrees of freedom. Several new results for loop quantum gravity are obtained: (i) a Hilbert space for the gravity-matter system and a nonstandard representation of the scalar field thereon is constructed, (ii) a new operator for the scalar constraint of the coupled system is defined and investigated, (iii) methods for solving the constraint are developed. Commutators of the new quantum constraint operators correspond to the quantization of the Poisson bracket. This, however, poses problems for finding solutions. Hence the states we consider—and perhaps the whole setup—still needs some improvement. As a side result we describe a representation of the gravitational degrees of freedom in which the flux is diagonal. This representation is related to the BF theory vacuum of Dittrich and Geiller.
Scalar decay constant and Yukawa coupling in walking gauge theories
Hashimoto, Michio
2011-05-01
We propose an approach for the calculation of the Yukawa coupling through the scalar decay constant and the chiral condensate in the context of the extended technicolor . We perform the nonperturbative computation of the Yukawa coupling based on the improved ladder Schwinger-Dyson equation. It turns out that the Yukawa coupling can be larger or smaller than the standard model value, depending on the number N{sub D} of the weak doublets for each technicolor (TC) index. It is thus nontrivial whether or not the huge enhancement of the production of the scalar via the gluon fusion takes place even for a walking TC model with a colored techni-fermion. For the typical one-family TC model near conformality, it is found that the Yukawa coupling is slightly larger than the standard model one, where the expected mass of the scalar bound state is around 500 GeV. In this case, the production cross section via the gluon fusion is considerably enhanced, as naively expected, and hence such a scalar can be discovered/excluded at the early stage of the LHC.
Quantum entanglement in three accelerating qubits coupled to scalar fields
NASA Astrophysics Data System (ADS)
Dai, Yue; Shen, Zhejun; Shi, Yu
2016-07-01
We consider quantum entanglement of three accelerating qubits, each of which is locally coupled with a real scalar field, without causal influence among the qubits or among the fields. The initial states are assumed to be the GHZ and W states, which are the two representative three-partite entangled states. For each initial state, we study how various kinds of entanglement depend on the accelerations of the three qubits. All kinds of entanglement eventually suddenly die if at least two of three qubits have large enough accelerations. This result implies the eventual sudden death of all kinds of entanglement among three particles coupled with scalar fields when they are sufficiently close to the horizon of a black hole.
Probing scalar coupling differences via long-lived singlet states
NASA Astrophysics Data System (ADS)
DeVience, Stephen J.; Walsworth, Ronald L.; Rosen, Matthew S.
2016-01-01
We probe small scalar coupling differences via the coherent interactions between two nuclear spin singlet states in organic molecules. We show that the spin-lock induced crossing (SLIC) technique enables the coherent transfer of singlet order between one spin pair and another. The transfer is mediated by the difference in syn and anti vicinal or long-range J couplings among the spins. By measuring the transfer rate, we calculate a J coupling difference of 8 ± 2 mHz in phenylalanine-glycine-glycine and 2.57 ± 0.04 Hz in glutamate. We also characterize a coherence between two singlet states in glutamate, which may enable the creation of a long-lived quantum memory.
Improved Measurement of 3J(H αi, N i+1 ) Coupling Constants in H 2O Dissolved Proteins
NASA Astrophysics Data System (ADS)
Löhr, Frank; Schmidt, Jürgen M.; Maurer, Steffen; Rüterjans, Heinz
2001-11-01
A modification to the recently proposed α/β-HN(CO)CA-J TROSY pulse sequence (P. Permi et al., J. Magn. Reson.146, 255-259 (2000)) makes it possible to determine 3J(Hαi, Ni+1) coupling constants from a single E.COSY-type cross-peak pattern rather than from two 1Hα spin-state-edited subspectra. Advantages are increased 15N resolution, critical to extracting accurate 1Hα-15N coupling constants, and minimized differential relaxation due to nested 13Cα and 15N evolution periods. Application of the improved pulse sequence to Desulfovibrio vulgaris flavodoxin results in 3J(Hαi, Ni+1) values being systematically larger than those obtained with the original scheme. Parametrization of the coupling dependence on the protein backbone torsion angle ψ yields the Karplus relation 3J(Hαi, Ni+1)=-1.00 cos2(ψ-120°)+0.65 cos(ψ-120°)-0.15 Hz, with a residual root-mean-square difference of 0.13 Hz between measured and back-calculated coupling constants. The curve compares with data derived from ubiquitin (A. C. Wang and A. Bax, J. Am. Chem. Soc.117, 1810-1813 (1995)), although spanning a slightly larger range of J values in flavodoxin. The orientation of the Ala39/Ser40 peptide link, forming a type-II β-turn in flavodoxin, is twisted against X-ray-derived torsions by approximately 10° in the NMR structure as evident from the analysis of φ- and ψ-related 3J coupling constants. The remaining deviation of some experimental values from the prediction is likely to be due to strong hydrogen bonding, substituent effects, or the additional dependence on the adjacent torsions φ.
Chern-Simons theory coupled to bifundamental scalars
NASA Astrophysics Data System (ADS)
Banerjee, Shamik; Radičević, Đorđe
2014-06-01
We study the three-dimensional theory of two Chern-Simons gauge fields coupled to a scalar field in the bifundamental representation of the SU( N ) k × SU( M )- k gauge group. At small but fixed M ≪ N , this system approaches the theory of a Chern-Simons field coupled to fundamental matter, conjectured to be dual to a parity-violating version of Vasiliev's higher-spin gauge theory in AdS4. At finite M/N and large 't Hooft coupling this theory (or its SUSY version) is expected to be dual to an Einstein-like gravity. We show at two loops that this theory possesses a line of fixed points at any value of M/N . We also prove that turning on a finite but small M/N gaps out the light states that Chern-Simons theory coupled to fundamental matter develops when placed on a torus. We also comment on the higher genus case.
Neutron Star Structure in the Presence of Conformally Coupled Scalar Fields
NASA Technical Reports Server (NTRS)
Sultana, Joseph; Bose, Benjamin; Kazanas, Demosthenes
2014-01-01
Neutron star models are studied in the context of scalar-tensor theories of gravity in the presence of a conformally coupled scalar field, using two different numerical equations of state (EoS) representing different degrees of stiffness. In both cases we obtain a complete solution by matching the interior numerical solution of the coupled Einstein-scalar field hydrostatic equations, with an exact metric on the surface of the star. These are then used to find the effect of the scalar field and its coupling to geometry, on the neutron star structure, particularly the maximum neutron star mass and radius. We show that in the presence of a conformally coupled scalar field, neutron stars are less dense and have smaller masses and radii than their counterparts in the minimally coupled case, and the effect increases with the magnitude of the scalar field at the center of the star.
Galaxy cluster constraints on the coupling to photons of low-mass scalars
NASA Astrophysics Data System (ADS)
Brax, Philippe; Brun, Pierre; Wouters, Denis
2015-10-01
We consider a broad class of interactions between radiation and a light scalar field, including both conformal and disformal couplings. Such a scalar field potentially acts on cosmological scales as dark energy and could also appear in modified gravity theories. We study the consequences of these couplings on the mixing between the scalar field and photons in galaxy clusters in the presence of a magnetic field. In particular we focus on the resulting turbulence-induced irregularities in the x-ray and UV bands. We find new bounds on the photon-to-scalar couplings, both conformal and disformal, which complement laboratory experiments and other astrophysical constraints.
Dynamics of the Bianchi I model with non-minimally coupled scalar field near the singularity
NASA Astrophysics Data System (ADS)
Hrycyna, Orest; Szydłowski, Marek
2013-02-01
Dynamical systems methods are used to study evolution of Bianchi I model with a scalar field. We show that inclusion of non-minimal coupling term between the scalar field and the curvature changes evolution of the model compared with the minimally coupled case. In the model with non-minimally coupled scalar field there is a new type of singularity dominated by the non-minimal coupling term. We examine the impact of non-minimal coupling on the anisotropy evolution and demonstrate the existence of its minimal value in the generic case.
Extended quintessence with nonminimally coupled phantom scalar field
Hrycyna, Orest; Szydlowski, Marek
2007-12-15
We investigate evolutional paths of an extended quintessence with a nonminimally coupled phantom scalar field {psi} to the Ricci curvature. The dynamical system methods are used to investigate typical regimes of dynamics at the late time. We demonstrate that there are two generic types of evolutional scenarios which approach the attractor (a focus or a node type critical point) in the phase space: the quasioscillatory and monotonic trajectories approach the attractor which represents the Friedmann-Robertson-Walker model with the cosmological constant. We demonstrate that the dynamical system admits an invariant two-dimensional submanifold and discuss that which cosmological scenario is realized depends on the behavior of the system on the phase plane ({psi},{psi}{sup '}). We formulate simple conditions on the value of the coupling constant {xi} for which trajectories tend to the focus in the phase plane and hence damping oscillations around the mysterious value w=-1. We describe this condition in terms of slow-roll parameters calculated at the critical point. We discover that the generic trajectories in the focus-attractor scenario come from the unstable node. We also investigate the exact form of the parametrization of the equation of state parameter w(z) (directly determined from dynamics) which assumes a different form for both scenarios.
Visualizing Unresolved Scalar Couplings by Real-Time J-Upscaled NMR
2015-01-01
Scalar coupling patterns contain a wealth of structural information. The determination, especially of small scalar coupling constants, is often prevented by merging the splittings with the signal line width. Here we show that real-time J-upscaling enables the visualization of unresolved coupling constants in the acquisition dimension of one-dimensional (1D) or multidimensional NMR spectra. This technique, which works by introducing additional scalar coupling evolution delays within the recording of the FID (free induction decay), not only stretches the recorded coupling patterns but also actually enhances the resolution of multiplets, by reducing signal broadening by magnetic field inhomogeneities during the interrupted data acquisition. Enlarging scalar couplings also enables their determination in situations where the spectral resolution is limited, such as in the acquisition dimension of heteronuclear broadband decoupled HSQC (heteronuclear single quantum correlation) spectra. PMID:25837306
NASA Astrophysics Data System (ADS)
Gal'Tsov, D. V.; Xanthopoulos, B. C.
1992-01-01
Starting from any solution of the Einstein equations, with cosmological term, coupled to a minimally coupled massless scalar field, a solution of the Einstein equations is constructed, conformally coupled to a massless self-interacting scalar field with the usual Higgs potential. When the cosmological constant vanishes, the Higgs term disappears and the transformation procedure reduces to that obtained by Bekenstein in 1974. As an example, a nonsingular cosmological solution is constructed that describes the restoration of spontaneously broken symmetry.
Bean, J.W.; Briand, J.; Burgess, J.L.; Callahan, J.F.
1994-12-01
The conformations of two diazocine turn mimics, which were later incorporated into GPIIb/IIIa peptide antagonists, were investigated using nuclear magnetic resonance techniques. The two compounds, methyl (2,5-dioxo-3-(S)-(3-{omega}-tosylguanidino-propyl)-4-methyl-octahydro-1,4-dazocin-1-yl)acetate (1) and methyl (2,5-dioxo-3-(S)-(3-{omega}-tosyl-guanidino-propyl)-octahydro-1,5-diazocin-1-yl)acetate (2), differ only in their substituent at the diazocine position 4 nitrogen, yet this substitution results in a marked difference in the affinity of the resulting analogs for the GPIIb/IIIa receptor. It was of interest to determine if the difference observed in the antagonistic potency between these analogs was related to constitutional or, perhaps, conformational differences. The backbone conformations of these two molecules can be determined by measuring vicinal coupling constants along the trimethylene portion of the C8 ring backbone and by measuring interproton NOE intensities between the diazocine methine proton and the protons of the trimethylene group. For compound 1, {sup 3}J{sub HH} values measured from a P.E.COSY spectrum and interproton distances calculated from ROESY buildup curves indicated the presence of a single C8 ring backbone conformation where the trimethylene bridge adopted a staggered conformation and the H{alpha}1 and H{gamma}1 protons of the trimethylene group were 2.2 A from the methine proton. For compound 2, however, partial overlap of the central H{beta}1 and H{beta}2 protons made it impossible to measure {sup 3}J{sub HH} values from the P.E.COSY spectrum. We therefore used a {sup 13}C-filtered TOCSY experiment to measure the {sup 3}J{sub CH} values in both compounds 1 and 2. These heteronuclear vicinal coupling constants measured with {sup 13}C in natural abundance in conjunction with measured interproton NOE intensities indicate that these compounds share a common C8 ring backbone conformation.
Phase space analysis for a scalar-tensor model with kinetic and Gauss-Bonnet couplings
NASA Astrophysics Data System (ADS)
Granda, L. N.; Loaiza, E.
2016-09-01
We study the phase space for a scalar-tensor string inspired model of dark energy with nonminimal kinetic and Gauss-Bonnet couplings. The form of the scalar potential and of the coupling terms is of the exponential type, which gives rise to appealing cosmological solutions. The critical points describe a variety of cosmological scenarios that go from a matter or radiation dominated universe to a dark energy dominated universe. Trajectories were found in the phase space departing from unstable or saddle fixed points and arriving at the stable scalar field dominated point corresponding to late-time accelerated expansion.
Coupled scalar fields in the late Universe: the mechanical approach and the late cosmic acceleration
NASA Astrophysics Data System (ADS)
Burgazli, Alvina; Zhuk, Alexander; Morais, João; Bouhmadi-López, Mariam; Sravan Kumar, K.
2016-09-01
In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a minimally coupled scalar field and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as fluctuations of other perfect fluids are non-relativistic. Such fluids are designated as coupled because they are concentrated around inhomogeneities. In the present paper we investigate the conditions under which a scalar field can become coupled, and show that, at the background level, such coupled scalar field behaves as a two component perfect fluid: a network of frustrated cosmic strings with EoS parameter w=-1/3 and a cosmological constant. The potential of this scalar field is very flat at the present time. Hence, the coupled scalar field can provide the late cosmic acceleration. The fluctuations of the energy density and pressure of this field are concentrated around the galaxies screening their gravitational potentials. Therefore, such scalar fields can be regarded as coupled to the inhomogeneities.
Non-minimally coupled scalar field cosmology on the phase plane
Hrycyna, Orest; Szydlowski, Marek E-mail: uoszydlo@cyf-kr.edu.pl
2009-04-15
In this publication we investigate dynamics of a flat FRW cosmological model with a non-minimally coupled scalar field with the coupling term {xi}R{psi}{sup 2} in the scalar field action. The quadratic potential function V({psi}) {proportional_to} {psi}{sup 2} is assumed. All the evolutional paths are visualized and classified in the phase plane, at which the parameter of non-minimal coupling {xi} plays the role of a control parameter. The fragility of global dynamics with respect to changes of the coupling constant is studied in details. We find that the future big rip singularity appearing in the phantom scalar field cosmological models can be avoided due to non-minimal coupling constant effects. We have shown the existence of a finite scale factor singular point (future or past) where the Hubble function as well as its first cosmological time derivative diverge.
Building a holographic superconductor with a scalar field coupled kinematically to Einstein tensor
NASA Astrophysics Data System (ADS)
Kuang, Xiao-Mei; Papantonopoulos, Eleftherios
2016-08-01
We study the holographic dual description of a superconductor in which the gravity sector consists of a Maxwell field and a charged scalar field which except its minimal coupling to gravity it is also coupled kinematically to Einstein tensor. As the strength of the new coupling is increased, the critical temperature below which the scalar field condenses is lowering, the condensation gap decreases faster than the temperature, the width of the condensation gap is not proportional to the size of the condensate and at low temperatures the condensation gap tends to zero for the strong coupling. These effects which are the result of the presence of the coupling of the scalar field to the Einstein tensor in the gravity bulk, provide a dual description of impurities concentration in a superconducting state on the boundary.
Matter in loop quantum gravity without time gauge: A nonminimally coupled scalar field
Cianfrani, Francesco; Montani, Giovanni
2009-10-15
We analyze the phase space of gravity nonminimally coupled to a scalar field in a generic local Lorentz frame. We reduce the set of constraints to a first class one by fixing a specific hypersurfaces in the phase space. The main issue of our analysis is to extend the features of the vacuum case to the presence of scalar matter by recovering the emergence of an SU(2) gauge structure and the nondynamical role of boost variables. Within this scheme, the supermomentum and the super-Hamiltonian are those ones associated with a scalar field minimally coupled to the metric in the Einstein frame. Hence, the kinematical Hilbert space is defined as in canonical loop quantum gravity with a scalar field, but the differences in the area spectrum are outlined to be the same as in the time-gauge approach.
Cosmological three-coupled scalar theory for the dS/LCFT correspondence
Myung, Yun Soo; Moon, Taeyoon E-mail: tymoon@inje.ac.kr
2015-01-01
We investigate cosmological perturbations generated during de Sitter inflation in the three-coupled scalar theory. This theory is composed of three coupled scalars φ{sub p},p=1,2,3) to give a sixth-order derivative scalar theory for φ{sub 3}, in addition to tensor. Recovering the power spectra between scalars from the LCFT correlators in momentum space indicates that the de Sitter/logarithmic conformal field theory (dS/LCFT) correspondence works in the superhorizon limit. We use LCFT correlators derived from the dS/LCFT differentiate dictionary to compare cosmological correlators (power spectra) and find also LCFT correlators by making use of extrapolate dictionary. This is because the former approach is more conventional than the latter. A bulk version dual to the truncation process to find a unitary CFT in the LCFT corresponds to selecting a physical field φ{sub 2} with positive norm propagating on the dS spacetime.
Inflationary universe from higher derivative quantum gravity coupled with scalar electrodynamics
NASA Astrophysics Data System (ADS)
Myrzakulov, R.; Odintsov, S. D.; Sebastiani, L.
2016-06-01
We study inflation for a quantum scalar electrodynamics model in curved space-time and for higher-derivative quantum gravity (QG) coupled with scalar electrodynamics. The corresponding renormalization-group (RG) improved potential is evaluated for both theories in Jordan frame where non-minimal scalar-gravitational coupling sector is explicitly kept. The role of one-loop quantum corrections is investigated by showing how these corrections enter in the expressions for the slow-roll parameters, the spectral index and the tensor-to-scalar ratio and how they influence the bound of the Hubble parameter at the beginning of the primordial acceleration. We demonstrate that the viable inflation maybe successfully realized, so that it turns out to be consistent with last Planck and BICEP2/Keck Array data.
RESEARCH NOTE FROM COLLABORATION: Dimensionless coupling of bulk scalars at the LHC
NASA Astrophysics Data System (ADS)
Beauchemin, P.-H.; Azuelos, G.; Burgess, C. P.
2004-10-01
We identify the lowest-dimension interaction which is possible between standard model brane fields and bulk scalars in six dimensions. The lowest-dimension interaction is unique and involves a trilinear coupling between the standard model Higgs boson and the bulk scalar. Because this interaction has a dimensionless coupling, it depends only logarithmically on ultraviolet mass scales and heavy physics need not decouple from it. We compute its influence on Higgs physics at ATLAS and identify how large a coupling can be detected at the LHC. Besides providing a potentially interesting signal in Higgs-boson searches, such couplings provide a major observational constraint on 6D large-extra-dimensional models with scalars in the bulk.
Stationary states of fermions in a sign potential with a mixed vector–scalar coupling
Castilho, W.M. Castro, A.S. de
2014-01-15
The scattering of a fermion in the background of a sign potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling under the Sturm–Liouville perspective. When the vector coupling and the scalar coupling have different magnitudes, an isolated solution shows that the fermion under a strong potential can be trapped in a highly localized region without manifestation of Klein’s paradox. It is also shown that the lonely bound-state solution disappears asymptotically as one approaches the conditions for the realization of spin and pseudospin symmetries. -- Highlights: •Scattering of fermions in a sign potential assessed under a Sturm–Liouville perspective. •An isolated bounded solution. •No pair production despite the high localization. •No bounded solution under exact spin and pseudospin symmetries.
Scalar-tensor gravity with a non-minimally coupled Higgs field and accelerating universe
NASA Astrophysics Data System (ADS)
Sim, Jonghyun; Lee, Tae Hoon
2016-03-01
We consider general couplings, including non-minimal derivative coupling, of a Higgs boson field to scalar-tensor gravity and calculate their contributions to the energy density and pressure in Friedmann-Robertson-Walker spacetime. In a special case where the kinetic term of the Higgs field is non-minimally coupled to the Einstein tensor, we seek de Sitter solutions for the cosmic scale factor and discuss the possibility that the late-time acceleration and the inflationary era of our universe can be described by means of scalar fields with self-interactions and the Yukawa potential.
New Experimental limit on Optical Photon Coupling to Neutral, Scalar Bosons
Afanaciev, Andrei; Afanasev, Andrei; Afanaciev, Andrei; Afanasev, Andrei; Baker, O.; Beard, Kevin; Biallas, George; Boyce, James; Minarni, Minarni; Ramdon, Roopchan; Michelle D. Shinn; Slocum, P.
2008-09-01
We report on the first results of a sensitive search for scalar coupling of photons to a light neutral boson in the mass range of approximately 1.0 milli-electron volts and coupling strength greater than 10$^-6$ GeV$^-1$ using optical photons. This was a photon regeneration experiment using the "light shining through a wall" technique in which laser light was passed through a strong magnetic field upstream of an optical beam dump; regenerated laser light was then searched for downstream of a second magnetic field region optically shielded from the former. Our results show no evidence for scalar coupling in this region of parameter space.
Inflation and nonminimal scalar-curvature coupling in gravity and supergravity
Ketov, Sergei V.; Starobinsky, Alexei A. E-mail: alstar@landau.ac.ru
2012-08-01
Inflationary slow-roll dynamics in Einstein gravity with a nonminimal scalar-curvature coupling can be equivalent to that in the certain f(R) gravity theory. We review the correspondence and extend it to N=1 supergravity. The nonminimal coupling in supergravity is rewritten in terms of the standard ('minimal') N=1 matter-coupled supergravity by using curved superspace. The established equivalence between two different inflationary theories means the same inflaton scalar potential, and does not imply the same post-inflationary dynamics and reheating.
Quantization of scalar fields coupled to point masses
NASA Astrophysics Data System (ADS)
Barbero G, J. Fernando; Juárez-Aubry, Benito A.; Margalef-Bentabol, Juan; Villaseñor, Eduardo J. S.
2015-12-01
We study the Fock quantization of a compound classical system consisting of point masses and a scalar field. We consider the Hamiltonian formulation of the model by using the geometric constraint algorithm of Gotay, Nester and Hinds. By relying on this Hamiltonian description, we characterize in a precise way the real Hilbert space of classical solutions to the equations of motion and use it to rigorously construct the Fock space of the system. We finally discuss the structure of this space, in particular the impossibility of writing it in a natural way as a tensor product of Hilbert spaces associated with the point masses and the field, respectively.
Non-minimally coupled scalar fields, Holst action and black hole mechanics
Chatterjee, Ayan
2011-02-15
The paper deals with the extension of the Weak Isolated Horizon (WIH) formulation of black hole horizons to the non-minimally coupled scalar fields. In the early part of the paper, we introduce an appropriate Holst type action to incorporate scalar fields non-minimally coupled to gravity and construct the covariant phase space of the theory. Using this phase space, we proceed to prove the laws of black hole mechanics. Further, we show that with a gauge fixing, the symplectic structure on the horizon reduces to that of a U(1) Chern-Simons theory. The level of the Chern-Simons theory is shown to depend on the non-minimally coupled scalar field.
Born-Infeld Black Holes Coupled to a Massive Scalar Field
NASA Astrophysics Data System (ADS)
Georgieva, Daniela A.; Stefanov, Ivan Zh.; Yazadjiev, Stoytcho S.; Todorov, Michail D.
Born-Infeld black holes in the scalar-tensor theories of gravity with massless scalar field have been recently obtained [I. Stefanov, S. Yazadjiev and M. Todorov, Phys. Rev. D 75 (2007) 084036; Mod. Phys. Lett. A. 23(34) (2008) 2915; Class. Quantum Gravity 26 (2009) 015006]. The aim of the current paper is to study the effect of the inclusion of a potential for the scalar field in the theory, through a combination of analytical techniques and numerical methods. The black holes coupled to a massive scalar field have richer causal structure in comparison to the massless scalar field case. In the former case, the black holes may have a second, inner horizon. The presence of potential for the scalar field allows the existence of extremal black holes for certain values of the mass of the scalar field and the magnetic (electric) charge of the black hole. The solutions are stable against spherically symmetric perturbations. Arguments in favor of the general stability of the solutions coming from the application of the "turning point" method are also presented.
Determination of unresolved heteronuclear scalar coupling constants by J(up)-HSQMBC
NASA Astrophysics Data System (ADS)
Glanzer, Simon; Kunert, Olaf; Zangger, Klaus
2016-07-01
Long-range heteronuclear scalar coupling constants provide important structural information, which is necessary for obtaining stereospecific assignment or dihedral angle information. The measurement of small proton-carbon splittings is particularly difficult due to the low natural abundance of carbon-13 and the presence of homonuclear couplings of similar size. Here we present a real-time J-upscaled HSQMBC, which allows the measurement of heteronuclear coupling constants even if they are hidden in the signal linewidth of a regular spectrum.
Marunovic, Anja; Prokopec, Tomislav
2011-05-15
We calculate the one-loop graviton vacuum polarization induced by a massless, nonminimally coupled scalar field on Minkowski background. We make use of the Schwinger-Keldysh formalism, which allows us to study time dependent phenomena. As an application we compute the leading quantum correction to the Newtonian potential of a point particle. The novel aspect of the calculation is the use of the Schwinger-Keldysh formalism, within which we calculate the time transients induced by switching on the graviton-scalar coupling.
The Hamiltonian formalism for scalar fields coupled to gravity in a cosmological background
Bernardini, A.E. Bertolami, O.
2013-11-15
A novel routine to investigate the scalar fields in a cosmological context is discussed in the framework of the Hamiltonian formalism. Starting from the Einstein–Hilbert action coupled to a Lagrangian density that contains two components–one corresponding to a scalar field Lagrangian, L{sub ϕ}, and another that depends on the scale parameter, L{sub a}–one can identify a generalized Hamiltonian density from which first-order dynamical equations can be obtained. This set up corresponds to the dynamics of Friedmann–Robertson–Walker models in the presence of homogeneous fields embedded into a generalized cosmological background fluid in a system that evolves all together isentropically. Once the generalized Hamiltonian density is properly defined, the constraints on the gravity–matter–field system are straightforwardly obtained through the first-order Hamilton equations. The procedure is illustrated for three examples of cosmological interest for studies of the dark sector: real scalar fields, tachyonic fields and generalized Born–Infeld tachyonic fields. The inclusion of some isentropic fluid component into the Friedmann equation allows for identifying an exact correspondence between the dark sector underlying scalar field and an ordinary real scalar field dynamics. As a final issue, the Hamiltonian formulation is used to set the first-order dynamical equations through which one obtains the exact analytical description of the cosmological evolution of a generalized Chaplygin gas (GCG) with dustlike matter, radiation or curvature contributions. Model stability in terms of the square of the sound velocity, c{sub s}{sup 2}, cosmic acceleration, q, and conditions for inflation are discussed. -- Highlights: •The Hamiltonian formalism for scalar fields coupled to gravity in a cosmological background is constructed. •Real scalar, tachyonic and generalized Born–Infeld tachyonic-type fields are considered. •An extended formulation of the Hamilton
Thermodynamics of Scalar-tensor AdS Black Holes Coupled to Nonlinear Electrodynamics
Doneva, D.; Yazadjiev, S.; Kokkotas, K.; Stefanov, I.; Todorov, M.
2010-11-25
We construct new numerical solutions describing charged anti-de Sitter black holes coupled to nonlinear Born-Infeld electrodynamics within a certain class of scalar-tensor theories and we study their thermodynamic phase structure. It is shown that for certain charge intervals phase transitions of zeroth and first order exist.
Cosmological effects of scalar-photon couplings: dark energy and varying-α Models
Avgoustidis, A.; Martins, C.J.A.P.; Monteiro, A.M.R.V.L.; Vielzeuf, P.E.; Luzzi, G. E-mail: Carlos.Martins@astro.up.pt E-mail: up110370652@alunos.fc.up.pt
2014-06-01
We study cosmological models involving scalar fields coupled to radiation and discuss their effect on the redshift evolution of the cosmic microwave background temperature, focusing on links with varying fundamental constants and dynamical dark energy. We quantify how allowing for the coupling of scalar fields to photons, and its important effect on luminosity distances, weakens current and future constraints on cosmological parameters. In particular, for evolving dark energy models, joint constraints on the dark energy equation of state combining BAO radial distance and SN luminosity distance determinations, will be strongly dominated by BAO. Thus, to fully exploit future SN data one must also independently constrain photon number non-conservation arising from the possible coupling of SN photons to the dark energy scalar field. We discuss how observational determinations of the background temperature at different redshifts can, in combination with distance measures data, set tight constraints on interactions between scalar fields and photons, thus breaking this degeneracy. We also discuss prospects for future improvements, particularly in the context of Euclid and the E-ELT and show that Euclid can, even on its own, provide useful dark energy constraints while allowing for photon number non-conservation.
NASA Astrophysics Data System (ADS)
Coelho, L. A. A.; Skea, J. E. F.; Stuchi, T. J.
2008-02-01
In this paper, we use a nonintegrability theorem by Morales and Ramis to analyse the integrability of Friedmann-Robertson-Walker cosmological models with a conformally coupled massive scalar field. We answer the long-standing question of whether these models with a vanishing cosmological constant and non-self-interacting scalar field are integrable: by applying Kovacic's algorithm to the normal variational equations, we prove analytically and rigorously that these equations and, consequently, the Hamiltonians are nonintegrable. We then address the models with a self-interacting massive scalar field and cosmological constant and show that, with the exception of a set of measure zero, the models are nonintegrable. For the spatially curved cases, we prove that there are no additional integrable cases other than those identified in the previous work based on the non-rigorous Painlevé analysis. In our study of the spatially flat model, we explicitly obtain a new possibly integrable case.
Possible Statistics of Two Coupled Random Fields: Application to Passive Scalar
NASA Technical Reports Server (NTRS)
Dubrulle, B.; He, Guo-Wei; Bushnell, Dennis M. (Technical Monitor)
2000-01-01
We use the relativity postulate of scale invariance to derive the similarity transformations between two coupled scale-invariant random elds at different scales. We nd the equations leading to the scaling exponents. This formulation is applied to the case of passive scalars advected i) by a random Gaussian velocity field; and ii) by a turbulent velocity field. In the Gaussian case, we show that the passive scalar increments follow a log-Levy distribution generalizing Kraichnan's solution and, in an appropriate limit, a log-normal distribution. In the turbulent case, we show that when the velocity increments follow a log-Poisson statistics, the passive scalar increments follow a statistics close to log-Poisson. This result explains the experimental observations of Ruiz et al. about the temperature increments.
Experimental Limit on Optical-Photon Coupling to Light Neutral Scalar Bosons
Afanaciev, Andrei; Afanasev, Andrei; Baker, O.; Beard, Kevin; Biallas, George; Boyce, James; Minarni, Minarni; Ramdon, Roopchan; Michelle D. Shinn; Slocum, P.
2008-09-01
DOI: http://dx.doi.org/10.1103/PhysRevLett.101.120401
We report on the first results of a sensitive search for scalar coupling of photons to a light neutral boson in the mass range of approximately 1.0 meV (milli-electron volts) and coupling strength greater than 10^-6 GeV^-1 using optical photons. This was a photon regeneration experiment using the "light shining through a wall" technique in which laser light was passed through a strong magnetic field upstream of an optical beam dump; regenerated laser light was then searched for downstream of a second magnetic field region optically shielded from the former. Our results show no evidence for scalar coupling in this region of parameter space.
Hairy black holes sourced by a conformally coupled scalar field in D dimensions
NASA Astrophysics Data System (ADS)
Giribet, Gaston; Leoni, Matías; Oliva, Julio; Ray, Sourya
2014-04-01
There exist well-known no-hair theorems forbidding the existence of hairy black hole solutions in general relativity coupled to a scalar conformal field theory in asymptotically flat space. Even in the presence of cosmological constant, where no-hair theorems can usually be circumvented and black holes with conformal scalar hair were shown to exist in D≤4 dimensions, no-go results were reported for D>4. In this paper we prove that these obstructions can be evaded and we answer in the affirmative a question that remained open: Whether hairy black holes do exist in general relativity sourced by a conformally coupled scalar field in arbitrary dimensions. We find the analytic black hole solution in arbitrary dimension D>4, which exhibits a backreacting scalar hair that is regular everywhere outside and on the horizon. The metric asymptotes to (anti-)de Sitter spacetime at large distance and admits spherical horizon as well as horizon of a different topology. We also find analytic solutions when higher-curvature corrections O(Rn) of arbitrary order n are included in the gravity action.
Determination of unresolved heteronuclear scalar coupling constants by J(up)-HSQMBC.
Glanzer, Simon; Kunert, Olaf; Zangger, Klaus
2016-07-01
Long-range heteronuclear scalar coupling constants provide important structural information, which is necessary for obtaining stereospecific assignment or dihedral angle information. The measurement of small proton-carbon splittings is particularly difficult due to the low natural abundance of carbon-13 and the presence of homonuclear couplings of similar size. Here we present a real-time J-upscaled HSQMBC, which allows the measurement of heteronuclear coupling constants even if they are hidden in the signal linewidth of a regular spectrum. PMID:27183090
Scale-invariant scalar spectrum from the nonminimal derivative coupling with fourth-order term
NASA Astrophysics Data System (ADS)
Myung, Yun Soo; Moon, Taeyoon
2015-08-01
In this paper, an exactly scale-invariant spectrum of scalar perturbation generated during de Sitter spacetime is found from the gravity model of the nonminimal derivative coupling with fourth-order term. The nonminimal derivative coupling term generates a healthy (ghost-free) fourth-order derivative term, while the fourth-order term provides an unhealthy (ghost) fourth-order derivative term. The Harrison-Zel’dovich spectrum obtained from Fourier transforming the fourth-order propagator in de Sitter space is recovered by computing the power spectrum in its momentum space directly. It shows that this model provides a truly scale-invariant spectrum, in addition to the Lee-Wick scalar theory.
Detection of scalar coupling at zero magnetic field with an atomic magnetometer
NASA Astrophysics Data System (ADS)
Ledbetter, Micah; Crawford, Charles; Pines, Alex; Wemmer, Dave; Kitching, John; Knappe, Svenja; Budker, Dmitry
2009-05-01
Nuclear magnetic resonance (NMR) is one of the most powerful analytical tools for elucidating molecular structure and function. Conventionally, NMR is detected using inductive pickup coils in high field environments, requiring expensive and immobile superconducting magnets. The signatures for chemical identification are chemical shift and scalar couplings between nuclei of the form JI1I2, which typically lie between 1 Hz and 200 Hz. Here we demonstrate detection of both homonuclear and heteronuclear scalar couplings in a zero field environment (where the Zeeman interaction is entirely absent) using a millimeter scale microfabricated atomic magnetometer. We show that characteristic functional groups produce distinct spectra in a zero field environment and can be used for chemical identification. We obtain NMR linewidths of 0.1 Hz without using spin-echoes and measure scalar coupling parameters with a statistical uncertainty of 4 mHz. We also show that the zero field spectra of certain functional groups is remarkably simple compared to spectra obtained in low (earth) field environments. Progress towards multidimensional spectroscopy will be presented.
Directly Measuring the Tensor Structure of the Scalar Coupling to Gauge Bosons
Stolarski, Daniel; Vega-Morales, Roberto
2012-12-01
Kinematic distributions in the decays of the newly discovered resonance to four leptons can provide a direct measurement of the tensor structure of the particle's couplings to gauge bosons. Even if the particle is shown to be a parity even scalar, measuring this tensor structure is a necessary step in determining if this particle is responsible for giving mass to the Z. We consider a Standard Model like coupling as well as coupling via a dimension five operator to either ZZ or Z\\gamma. We show that using full kinematic information from each event allows discrimination between renormalizable and higher dimensional coupling to ZZ at the 95% confidence level with O(50) signal events, and coupling to Z\\gamma can be distinguished with as few as 20 signal events. This shows that these measurements can be useful even with this year's LHC data.
Asymptotically free scalar curvature-ghost coupling in quantum Einstein gravity
Eichhorn, Astrid; Gies, Holger; Scherer, Michael M.
2009-11-15
We consider the asymptotic-safety scenario for quantum gravity which constructs a nonperturbatively renormalizable quantum gravity theory with the help of the functional renormalization group (RG). We verify the existence of a non-Gaussian fixed point and include a running curvature-ghost coupling as a first step towards the flow of the ghost sector of the theory. We find that the scalar curvature-ghost coupling is asymptotically free and RG relevant in the ultraviolet. Most importantly, the property of asymptotic safety discovered so far within the Einstein-Hilbert truncation and beyond remains stable under the inclusion of the ghost flow.
NASA Astrophysics Data System (ADS)
Mackrory, Jonathan B.; Bhattacharya, Tanmoy; Steck, Daniel A.
2016-10-01
We present a worldline method for the calculation of Casimir energies for scalar fields coupled to magnetodielectric media. The scalar model we consider may be applied in arbitrary geometries, and it corresponds exactly to one polarization of the electromagnetic field in planar layered media. Starting from the field theory for electromagnetism, we work with the two decoupled polarizations in planar media and develop worldline path integrals, which represent the two polarizations separately, for computing both Casimir and Casimir-Polder potentials. We then show analytically that the path integrals for the transverse-electric polarization coupled to a dielectric medium converge to the proper solutions in certain special cases, including the Casimir-Polder potential of an atom near a planar interface, and the Casimir energy due to two planar interfaces. We also evaluate the path integrals numerically via Monte Carlo path-averaging for these cases, studying the convergence and performance of the resulting computational techniques. While these scalar methods are only exact in particular geometries, they may serve as an approximation for Casimir energies for the vector electromagnetic field in other geometries.
Topological black holes dressed with a conformally coupled scalar field and electric charge
Martinez, Cristian; Troncoso, Ricardo; Staforelli, Juan Pablo
2006-08-15
Electrically charged solutions for gravity with a conformally coupled scalar field are found in four dimensions in the presence of a cosmological constant. If a quartic self-interaction term for the scalar field is considered, there is a solution describing an asymptotically locally AdS charged black hole dressed with a scalar field that is regular on and outside the event horizon, which is a surface of negative constant curvature. This black hole can have negative mass, which is bounded from below for the extremal case, and its causal structure shows that the solution describes a ''black hole inside a black hole''. The thermodynamics of the nonextremal black hole is analyzed in the grand canonical ensemble. The entropy does not follow the area law, and there is an effective Newton constant which depends on the value of the scalar field at the horizon. If the base manifold is locally flat, the solution has no electric charge, and the scalar field has a vanishing stress-energy tensor so that it dresses a locally AdS spacetime with a nut at the origin. In the case of vanishing self interaction, the solutions also dress locally AdS spacetimes, and if the base manifold is of negative constant curvature a massless electrically charged hairy black hole is obtained. The thermodynamics of this black hole is also analyzed. It is found that the bounds for the black holes parameters in the conformal frame obtained from requiring the entropy to be positive are mapped into the ones that guarantee cosmic censorship in the Einstein frame.
The universe dominated by oscillating scalar with non-minimal derivative coupling to gravity
Jinno, Ryusuke; Mukaida, Kyohei; Nakayama, Kazunori E-mail: mukaida@hep-th.phys.s.u-tokyo.ac.jp
2014-01-01
We study the expansion law of the universe dominated by the oscillating scalar field with non-minimal derivative coupling to gravity as G{sup μν}∂{sub μ}φ∂{sub ν}φ. In this system the Hubble parameter oscillates with a frequency of the effective mass of the scalar field, which formerly caused a difficulty in analyzing how the universe expands. We find an analytical solution for power law potentials and interpret the solution in an intuitive way by using a new invariant of the system. As a result, we find marginally accelerated expansion for the quadratic potential and no accelerated expansion for the potential with higher power.
Static black hole solutions with a self-interacting conformally coupled scalar field
Dotti, Gustavo; Gleiser, Reinaldo J.; Martinez, Cristian
2008-05-15
We study static, spherically symmetric black hole solutions of the Einstein equations with a positive cosmological constant and a conformally coupled self-interacting scalar field. Exact solutions for this model found by Martinez, Troncoso, and Zanelli were subsequently shown to be unstable under linear gravitational perturbations, with modes that diverge arbitrarily fast. We find that the moduli space of static, spherically symmetric solutions that have a regular horizon--and satisfy the weak and dominant energy conditions outside the horizon--is a singular subset of a two-dimensional space parametrized by the horizon radius and the value of the scalar field at the horizon. The singularity of this space of solutions provides an explanation for the instability of the Martinez, Troncoso, and Zanelli spacetimes and leads to the conclusion that, if we include stability as a criterion, there are no physically acceptable black hole solutions for this system that contain a cosmological horizon in the exterior of its event horizon.
Chen Songbai; Jing Jiliang
2010-10-15
We study the dynamical evolution of a scalar field coupling to Einstein's tensor in the background of a Reissner-Nordstroem black hole. Our results show that the coupling constant {eta} imprints in the wave dynamics of a scalar perturbation. In the weak coupling, we find that with the increase of the coupling constant {eta} the real parts of the fundamental quasinormal frequencies decrease and the absolute values of imaginary parts increase for fixed charge q and multipole number l. In the strong coupling, we find that for l{ne}0 the instability occurs when {eta} is larger than a certain threshold value {eta}{sub c} which deceases with the multipole number l and charge q. However, for the lowest l=0, we find that there does not exist such a threshold value and the scalar field always decays for arbitrary coupling constant.
NASA Astrophysics Data System (ADS)
Jurić, Tajron; Samsarov, Andjelo
2016-05-01
In this work, we consider a noncommutative (NC) massless scalar field coupled to the classical nonrotational BTZ geometry. In a manner of the theories where the gravity emerges from the underlying scalar field theory, we study the effective action and the entropy derived from this noncommutative model. In particular, the entropy is calculated by making use of the two different approaches, the brick-wall method and the heat kernel method designed for spaces with conical singularity. We show that the UV divergent structures of the entropy obtained through these two different methods agree with each other. It is also shown that the same renormalization condition that removes the infinities from the effective action can also be used to renormalize the entanglement entropy for the same system. Besides, the interesting feature of the NC model considered here is that it allows an interpretation in terms of an equivalent system comprising a commutative massive scalar field but in a modified geometry: that of the rotational BTZ black hole, the result that hints at a duality between the commutative and noncommutative systems in the background of a BTZ black hole.
Hamiltonian operator for loop quantum gravity coupled to a scalar field
NASA Astrophysics Data System (ADS)
Alesci, E.; Assanioussi, M.; Lewandowski, J.; Mäkinen, I.
2015-06-01
We present the construction of a physical Hamiltonian operator in the deparametrized model of loop quantum gravity coupled to a free scalar field. This construction is based on the use of the recently introduced curvature operator, and on the idea of so-called special loops. We discuss in detail the regularization procedure and the assignment of the loops, along with the properties of the resulting operator. We compute the action of the squared Hamiltonian operator on spin network states, and close with some comments and outlooks.
NASA Astrophysics Data System (ADS)
Gladwin Pradeep, R.; Chandrasekar, V. K.; Mohanasubha, R.; Senthilvelan, M.; Lakshmanan, M.
2016-07-01
We identify contact transformations which linearize the given equations in the Riccati and Abel chains of nonlinear scalar and coupled ordinary differential equations to the same order. The identified contact transformations are not of Cole-Hopf type and are new to the literature. The linearization of Abel chain of equations is also demonstrated explicitly for the first time. The contact transformations can be utilized to derive dynamical symmetries of the associated nonlinear ODEs. The wider applicability of identifying this type of contact transformations and the method of deriving dynamical symmetries by using them is illustrated through two dimensional generalizations of the Riccati and Abel chains as well.
Fate of three-dimensional black holes coupled to a scalar field and the Bekenstein-Hawking entropy
NASA Astrophysics Data System (ADS)
Park, Mu-In
2004-09-01
Three-dimensional black holes coupled to a self-interacting scalar field is considered. It is known that its statistical entropy à la Strominger does not agree with the Bekenstein-Hawking (BH) entropy. However, I show that, by a careful treatment of the vacuum state in the canonical ensemble with a fixed temperature, which is the same as that of the BTZ black hole without the scalar field, the BH entropy may be exactly produced by the Cardy's formula. I discuss its several implications, including the fate of black holes, no-scalar-hair theorems, stability, mirror black holes, and higher-order corrections to the entropy.
The Scalar-photon Coupling with Mie Invariant Within the Scope of Bianchi Type-I Cosmological Model
NASA Astrophysics Data System (ADS)
Muharlyamov, Ruslan K.; Pankratyeva, Tatiana N.
2016-02-01
We investigate the Bianchi type-I cosmological model with the scalar and electromagnetic fields possessing non-minimal couplings. They contain the Mie invariant that leads to the flat Friedman's cosmological model. We found the lagrangian for interaction, which the isotropization process of the expansion takes place. Two cases are considered, when the Mie invariant is constat or time-dependent. We study the canonical scalar field and the phantom one.
Randall-Sundrum cosmological model with nonminimal derivative coupling of scalar field
Widiyani, Agustina Suroso, Agus Zen, Freddy P.
2015-04-16
Nonminimal derivative coupling (NMDC) of scalar field in time-dependent Randall-Sundrum model is investigated. Firstly, we take a simple relation between the scale factor on the brane, a(t), and the scale factor of the extradimension, b(t), as b = a{sup γ} where γ is a constant. Then, we derive the Einstein equation and find its cosmological solution for a special case of static extra dimension, γ = 0. As the result, we find that de Sitter solution is a typical solution of our model. We also find that the brane tension which is related to cosmological constant on the brane is related to the coupling constant of the model.
Vögeli, Beat; Olsson, Simon; Riek, Roland; Güntert, Peter
2015-01-01
We compiled an NMR data set consisting of exact nuclear Overhauser enhancement (eNOE) distance limits, residual dipolar couplings (RDCs) and scalar (J) couplings for GB3, which forms one of the largest and most diverse data set for structural characterization of a protein to date. All data have small experimental errors, which are carefully estimated. We use the data in the research article Vogeli et al., 2015, Complementarity and congruence between exact NOEs and traditional NMR probes for spatial decoding of protein dynamics, J. Struct. Biol., 191, 3, 306–317, doi:10.1016/j.jsb.2015.07.008 [1] for cross-validation in multiple-state structural ensemble calculation. We advocate this set to be an ideal test case for molecular dynamics simulations and structure calculations. PMID:26504890
Sychrovský, Vladimír; Benda, Ladislav; Prokop, Alexandr; Blechta, Vratislav; Schraml, Jan; Spirko, Vladimír
2008-06-12
The rotation of a trimethylsiloxy (TMSO) group in three silylated phenols (with three different ortho substituents -H, -CH3, and -C(CH3)3) was studied with the NMR (n)J(Si,C), n = 2, 3, 4, 5, scalar spin-spin coupling between the (29)Si nucleus of the TMSO group and the (13)C nuclei of the phenyl ring. The internal rotation potential calculated with the B3LYP and MP2 calculation methods including the effect of a solvent environment (gas phase, chloroform, and water) was used for the calculation of the dynamical averages of the scalar coupling constants in the framework of the rigid-bender formalism. Solvent effects, the quality of the rotational potential, and the applicability of the classical molecular dynamic to the problem is discussed. Quantum effects have a sizable impact on scalar couplings, particularly for the internal rotational states well localized within the wells of the potential surfaces for the TMSO group. The overall difference between the experimental and theoretical scalar couplings calculated for the global energy-minima structures (static model) decreases substantially for both model potentials (B3LYP, MP2) when the molecular motion of the TMSO group is taken into account. The calculated data indicate that the inclusion of molecular motion is necessary for the accurate calculation of the scalar coupling constants and their reliable structural interpretation for any system which possesses a large-amplitude motion. PMID:18491850
Stable coupling between vector and scalar variables for the IDO scheme on collocated grids
NASA Astrophysics Data System (ADS)
Imai, Yohsuke; Aoki, Takayuki
2006-06-01
The Interpolated Differential Operator (IDO) scheme on collocated grids provides fourth-order discretizations for all the terms of the fluid flow equations. However, computations of fluid flows on collocated grids are not guaranteed to produce accurate solutions because of the poor coupling between velocity vector and scalar variables. A stable coupling method for the IDO scheme on collocated grids is proposed, where a new representation of first-order derivatives is adopted. It is important in deriving the representation to refer to the variables at neighboring grid points, keeping fourth-order truncation error. It is clear that accuracy and stability are drastically improved for shallow water equations in comparison with the conventional IDO scheme. The effects of the stable coupling are confirmed in incompressible flow calculations for DNS of turbulence and a driven cavity problem. The introduction of a rational function into the proposed method makes it possible to calculate shock waves with the initial conditions of extreme density and pressure jumps.
Cosmological dynamics with non-minimally coupled scalar field and a constant potential function
NASA Astrophysics Data System (ADS)
Hrycyna, Orest; Szydłowski, Marek
2015-11-01
Dynamical systems methods are used to investigate global behaviour of the spatially flat Friedmann-Robertson-Walker cosmological model in gravitational theory with a non-minimally coupled scalar field and a constant potential function. We show that the system can be reduced to an autonomous three-dimensional dynamical system and additionally is equipped with an invariant manifold corresponding to an accelerated expansion of the universe. Using this invariant manifold we find an exact solution of the reduced dynamics. We investigate all solutions for all admissible initial conditions using theory of dynamical systems to obtain a classification of all evolutional paths. The right-hand sides of the dynamical system depend crucially on the value of the non-minimal coupling constant therefore we study bifurcation values of this parameter under which the structure of the phase space changes qualitatively. We found a special bifurcation value of the non-minimal coupling constant which is distinguished by dynamics of the model and may suggest some additional symmetry in matter sector of the theory.
Cosine Modulated HSQC: A Rapid Determination of 3JHNHα Scalar Couplings in 15N-labeled Proteins
NASA Astrophysics Data System (ADS)
Petit, Audrey; Vincent, Sébastien J. F.; Zwahlen, Catherine
2002-06-01
A two-dimensional HSQC-based NMR method, 15N-COSMO-HSQC, is presented for the rapid determination of homonuclear 3JHNHα couplings in 15N-labeled proteins in solution. Scalar couplings are extracted by comparing the intensity of two separate datasets recorded with and without decoupling of the 3JHNHα during a preparation period. The scalar couplings are introduced through a cosine modulation of the peak intensities. The experiment relies on a BIRD sandwich to selectively invert all amide protons H N and is very simple to implement. 3JHNHα couplings were determined using both the 15N-COSMO-HSQC and quantitative- J on 15N-labeled chemokine RANTES. The two experiments show well-correlated values.
NASA Astrophysics Data System (ADS)
Kanemura, Shinya; Kikuchi, Mariko; Yagyu, Kei
2016-06-01
We calculate renormalized Higgs boson couplings with gauge bosons and fermions at the one-loop level in the model with an additional isospin singlet real scalar field. These coupling constants can deviate from the predictions in the standard model due to tree-level mixing effects and one-loop contributions of the extra neutral scalar boson. We investigate how they can be significant under the theoretical constraints from perturbative unitarity and vacuum stability and also the condition of avoiding the wrong vacuum. Furthermore, comparing with the predictions in the Type I two Higgs doublet model, we numerically demonstrate how the singlet extension model can be distinguished and identified by using precision measurements of the Higgs boson couplings at future collider experiments.
Canonical quantisation via conditional symmetries of the closed FLRW model coupled to a scalar field
NASA Astrophysics Data System (ADS)
Zampeli, Adamantia
2015-09-01
We study the classical, quantum and semiclassical solutions of a Robertson-Walker spacetime coupled to a massless scalar field. The Lagrangian of these minisuperspace models is singular and the application of the theory of Noether symmetries is modified to include the conditional symmetries of the corresponding (weakly vanishing) Hamiltonian. These are found to be the simultaneous symmetries of the supermetric and the superpotential. The quantisation is performed adopting the Dirac proposal for constrained systems. The innovation in the approach we use is that the integrals of motion related to the conditional symmetries are promoted to operators together with the Hamiltonian and momentum constraints. These additional conditions imposed on the wave function render the system integrable and it is possible to obtain solutions of the Wheeler-DeWitt equation. Finally, we use the wave function to perform a semiclassical analysis following Bohm and make contact with the classical solution. The analysis starts with a modified Hamilton-Jacobi equation from which the semiclassical momenta are defined. The solutions of the semiclassical equations are then studied and compared to the classical ones in order to understand the nature and behaviour of the classical singularities.
The self-force on a non-minimally coupled static scalar charge outside a Schwarzschild black hole
NASA Astrophysics Data System (ADS)
Cho, Demian H. J.; Tsokaros, Antonios A.; Wiseman, Alan G.
2007-03-01
The finite part of the self-force on a static, non-minimally coupled scalar test charge outside a Schwarzschild black hole is zero. This result is determined from the work required to slowly raise or lower the charge through an infinitesimal distance. Unlike similar force calculations for minimally-coupled scalar charges or electric charges, we find that we must account for a flux of field energy that passes through the horizon and changes the mass and area of the black hole when the charge is displaced. This occurs even for an arbitrarily slow displacement of the non-minimally coupled scalar charge. For a positive coupling constant, the area of the hole increases when the charge is lowered and decreases when the charge is raised. The fact that the self-force vanishes for a static, non-minimally coupled scalar charge in Schwarzschild spacetime agrees with a simple prediction of the Quinn Wald axioms. However, Zel'nikov and Frolov computed a non-vanishing self-force for a non-minimally coupled charge. Our method of calculation closely parallels the derivation of Zel'nikov and Frolov, and we show that their omission of this unusual flux is responsible for their (incorrect) result. When the flux is accounted for, the self-force vanishes. This correction eliminates a potential counter example to the Quinn Wald axioms. The fact that the area of the black hole changes when the charge is displaced brings up two interesting questions that did not arise in similar calculations for static electric charges and minimally coupled scalar charges. (1) How can we reconcile a decrease in the area of the black hole horizon with the area theorem which concludes that δAreahorizon >= 0? The key hypothesis of the area theorem is that the stress energy tensor must satisfy a null-energy condition Tαβlαlβ >= 0 for any null vector lα. We explicitly show that the stress energy associated with a non-minimally coupled field does not satisfy this condition, and this violation of the
NASA Astrophysics Data System (ADS)
Nakonieczna, Anna; Yeom, Dong-han
2016-05-01
Investigating the dynamics of gravitational systems, especially in the regime of quantum gravity, poses a problem of measuring time during the evolution. One of the approaches to this issue is using one of the internal degrees of freedom as a time variable. The objective of our research was to check whether a scalar field or any other dynamical quantity being a part of a coupled multi-component matter-geometry system can be treated as a `clock' during its evolution. We investigated a collapse of a self-gravitating electrically charged scalar field in the Einstein and Brans-Dicke theories using the 2+2 formalism. Our findings concentrated on the spacetime region of high curvature existing in the vicinity of the emerging singularity, which is essential for the quantum gravity applications. We investigated several values of the Brans-Dicke coupling constant and the coupling between the Brans-Dicke and the electrically charged scalar fields. It turned out that both evolving scalar fields and a function which measures the amount of electric charge within a sphere of a given radius can be used to quantify time nearby the singularity in the dynamical spacetime part, in which the apparent horizon surrounding the singularity is spacelike. Using them in this respect in the asymptotic spacetime region is possible only when both fields are present in the system and, moreover, they are coupled to each other. The only nonzero component of the Maxwell field four-potential cannot be used to quantify time during the considered process in the neighborhood of the whole central singularity. None of the investigated dynamical quantities is a good candidate for measuring time nearby the Cauchy horizon, which is also singular due to the mass inflation phenomenon.
NASA Astrophysics Data System (ADS)
Zumalacárregui, Miguel; García-Bellido, Juan
2014-03-01
We study the structure of scalar-tensor theories of gravity based on derivative couplings between the scalar and the matter degrees of freedom introduced through an effective metric. Such interactions are classified by their tensor structure into conformal (scalar), disformal (vector), and extended disformal (traceless tensor), as well as by the derivative order of the scalar field. Relations limited to first derivatives of the field ensure second-order equations of motion in the Einstein frame and hence the absence of Ostrogradski ghost degrees of freedom. The existence of a mapping to the Jordan frame is not trivial in the general case, and can be addressed using the Jacobian of the frame transformation through its eigenvalues and eigentensors. These objects also appear in the study of different aspects of such theories, including the metric and field redefinition transformation of the path integral in the quantum mechanical description. Although second-order in the Einstein frame, generic disformally coupled theories are described by higher-order equations of motion in the Jordan frame. This apparent contradiction is solved by the use of a hidden constraint: the contraction of the metric equations with a Jacobian eigentensor provides a constraint relation for the higher field derivatives, which allows one to express the dynamical equations in a second-order form. This signals a loophole in Horndeski's theorem and allows one to enlarge the set of scalar-tensor theories which are Ostrogradski stable. The transformed Gauss-Bonnet terms are also discussed for the simplest conformal and disformal relations.
Massive Nordström scalar (density) gravities from universal coupling
NASA Astrophysics Data System (ADS)
Pitts, J. Brian
2011-03-01
Both particle physics and the 1890s Seeliger-Neumann modification of Newtonian gravity suggest considering a “mass term” for gravity, yielding a finite range due to an exponentially decaying Yukawa potential. Unlike Nordström’s “massless” theory, massive scalar gravities are strictly Special Relativistic, being invariant under the Poincaré group but not the conformal group. Geometry is a poor guide to understanding massive scalar gravities: matter sees a conformally flat metric, but gravity also sees the rest of the flat metric, barely, in the mass term. Infinitely many theories exhibit this bimetric ‘geometry,’ all with the total stress-energy’s trace as source. All are new except the Freund-Nambu theory. The smooth massless limit indicates underdetermination of theories by data between massless and massive scalar gravities. The ease of accommodating electrons, protons and other fermions using density-weighted Ogievetsky-Polubarinov spinors in scalar gravity is noted.
NASA Technical Reports Server (NTRS)
Ransom, Jonathan B.
2002-01-01
A multifunctional interface method with capabilities for variable-fidelity modeling and multiple method analysis is presented. The methodology provides an effective capability by which domains with diverse idealizations can be modeled independently to exploit the advantages of one approach over another. The multifunctional method is used to couple independently discretized subdomains, and it is used to couple the finite element and the finite difference methods. The method is based on a weighted residual variational method and is presented for two-dimensional scalar-field problems. A verification test problem and a benchmark application are presented, and the computational implications are discussed.
Cadoni, Mariano; Serra, Matteo; Mignemi, Salvatore
2011-10-15
We propose a general method for solving exactly the static field equations of Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field. Our method starts from an ansatz for the scalar field profile, and determines, together with the metric functions, the corresponding form of the scalar self-interaction potential. Using this method we prove a new no-hair theorem about the existence of hairy black-hole and black-brane solutions and derive broad classes of static solutions with radial symmetry of the theory, which may play an important role in applications of the AdS/CFT correspondence to condensed matter and strongly coupled QFTs. These solutions include: (1) four- or generic (d+2)-dimensional solutions with planar, spherical or hyperbolic horizon topology; (2) solutions with anti-de Sitter, domain wall and Lifshitz asymptotics; (3) solutions interpolating between an anti-de Sitter spacetime in the asymptotic region and a domain wall or conformal Lifshitz spacetime in the near-horizon region.
Boson stars in a theory of complex scalar fields coupled to the U(1) gauge field and gravity
NASA Astrophysics Data System (ADS)
Kumar, Sanjeev; Kulshreshtha, Usha; Shankar Kulshreshtha, Daya
2014-08-01
We study boson shells and boson stars in a theory of a complex scalar field coupled to the U(1) gauge field {{A}_{\\mu }} and Einstein gravity with the potential V(|\\Phi |)\\;:=\\frac{1}{2}{{m}^{2}}{{\\left( |\\Phi |+a \\right)}^{2}}. This could be considered either as a theory of a massive complex scalar field coupled to an electromagnetic field and gravity in a conical potential, or as a theory in the presence of a potential that is an overlap of a parabolic and conical potential. Our theory has a positive cosmological constant (\\Lambda :=4\\pi G{{m}^{2}}{{a}^{2}}). Boson stars are found to come in two types, having either ball-like or shell-like charge density. We studied the properties of these solutions and also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.
An Exact Solution of Einstein-Maxwell Gravity Coupled to a Scalar Field
NASA Technical Reports Server (NTRS)
Turyshev, S. G.
1995-01-01
The general solution to low-energy string theory representing static spherically symmetric solution of the Einstein-Maxwell gravity with a massless scalar field has been found. Some of the partial cases appear to coincide with known solutions to black holes, naked singularities, and gravity and electromagnetic fields.
NASA Astrophysics Data System (ADS)
McDonald, John
2016-10-01
The 750 GeV resonance observed by ATLAS and CMS may be explained by a gauge singlet scalar. This would provide an ideal candidate for a gauge singlet scalar alternative to Higgs Inflation, known as S-inflation. Here we discuss the relevant results of S-inflation in the context of the 750 GeV resonance. In particular, we show that a singlet scalar, if it is real, has a major advantage over the Higgs boson with regard to unitarity violation during inflation. This is because it is possible to restrict the large non-minimal coupling required for inflation, ξ ∼105, to the real singlet scalar, with all other scalars having ξ ∼ 1. In this case the scale of unitarity violation Λ is much larger than the inflaton field during inflation. This protects the inflaton effective potential from modification by the new physics or strong coupling which is necessary to restore unitarity, which would otherwise invalidate the perturbative effective potential based on Standard Model physics. This is in contrast to the case of Higgs Inflation or models based on complex singlet scalars, where the unitarity violation scale during inflation is less than or of the order of the inflaton field. Therefore if the 750 GeV resonance is the inflaton, it must be a non-minimally coupled real singlet scalar.
NASA Astrophysics Data System (ADS)
Bouhmadi-López, Mariam; Sravan Kumar, K.; Marto, João; Morais, João; Zhuk, Alexander
2016-07-01
In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we can consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a K-essence scalar field, playing the role of dark energy, and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as the fluctuations of the other perfect fluids are non-relativistic. Such fluids are designated as coupled because they are concentrated around the inhomogeneities. In the present paper, we investigate the conditions under which the K-essence scalar field with the most general form for its action can become coupled. We investigate at the background level three particular examples of the K-essence models: (i) the pure kinetic K-essence field, (ii) a K-essence with a constant speed of sound and (iii) the K-essence model with the Lagrangian bX+cX2‑V(phi). We demonstrate that if the K-essence is coupled, all these K-essence models take the form of multicomponent perfect fluids where one of the component is the cosmological constant. Therefore, they can provide the late-time cosmic acceleration and be simultaneously compatible with the mechanical approach.
NASA Astrophysics Data System (ADS)
Bouhmadi-López, Mariam; Sravan Kumar, K.; Marto, João; Morais, João; Zhuk, Alexander
2016-07-01
In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we can consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a K-essence scalar field, playing the role of dark energy, and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as the fluctuations of the other perfect fluids are non-relativistic. Such fluids are designated as coupled because they are concentrated around the inhomogeneities. In the present paper, we investigate the conditions under which the K-essence scalar field with the most general form for its action can become coupled. We investigate at the background level three particular examples of the K-essence models: (i) the pure kinetic K-essence field, (ii) a K-essence with a constant speed of sound and (iii) the K-essence model with the Lagrangian bX+cX2-V(phi). We demonstrate that if the K-essence is coupled, all these K-essence models take the form of multicomponent perfect fluids where one of the component is the cosmological constant. Therefore, they can provide the late-time cosmic acceleration and be simultaneously compatible with the mechanical approach.
3j Symbols: To Normalize or Not to Normalize?
ERIC Educational Resources Information Center
van Veenendaal, Michel
2011-01-01
The systematic use of alternative normalization constants for 3j symbols can lead to a more natural expression of quantities, such as vector products and spherical tensor operators. The redefined coupling constants directly equate tensor products to the inner and outer products without any additional square roots. The approach is extended to…
NASA Astrophysics Data System (ADS)
Ledbetter, M. P.; Romalis, M. V.; Kimball, D. F. Jackson
2013-01-01
A comparison between existing nuclear magnetic resonance measurements and calculations of the scalar spin-spin interaction (J coupling) in deuterated molecular hydrogen yields stringent constraints on anomalous spin-dependent potentials between nucleons at the atomic scale (˜1Å). The dimensionless coupling constant gPpgPN/4π associated with the exchange of pseudoscalar (axionlike) bosons between nucleons is constrained to be less than 3.6×10-7 for boson masses in the range of 5 keV, representing improvement by a factor of 100 over previous constraints. The dimensionless coupling constant gApgAN/4π associated with the exchange of an axial-vector boson between nucleons is constrained to be gApgAN/4π<1.3×10-19 for bosons of mass ≲1000eV, improving constraints at this distance scale by a factor of 100 for proton-proton couplings and more than 8 orders of magnitude for neutron-proton couplings.
Conformally coupled scalar black holes admit a flat horizon due to axionic charge
NASA Astrophysics Data System (ADS)
Bardoux, Yannis; Caldarelli, Marco M.; Charmousis, Christos
2012-09-01
Static, charged black holes in the presence of a negative cosmological constant and with a planar horizon are found in four dimensions. The solutions have scalar secondary hair. We claim that these constitute the planar version of the Martínez-Troncoso-Zanelli black holes, only known up to now for a curved event horizon in four dimensions. Their planar version is rendered possible due to the presence of two, equal and homogeneously distributed, axionic charges dressing the flat horizon. The solutions are presented in the conformal and minimal frame and their basic properties and thermodynamics analysed. Entertaining recent applications to holographic superconductors, we expose two branches of solutions: the undressed axionic Reissner-Nordström-AdS black hole, and the novel black hole carrying secondary hair. We show that there is a critical temperature at which the (bald) axionic Reissner-Nordström-AdS black hole undergoes a second order phase transition to the hairy black hole spontaneously acquiring scalar hair.
Chu, Yi-Zen
2014-09-15
Motivated by the desire to understand the causal structure of physical signals produced in curved spacetimes – particularly around black holes – we show how, for certain classes of geometries, one might obtain its retarded or advanced minimally coupled massless scalar Green's function by using the corresponding Green's functions in the higher dimensional Minkowski spacetime where it is embedded. Analogous statements hold for certain classes of curved Riemannian spaces, with positive definite metrics, which may be embedded in higher dimensional Euclidean spaces. The general formula is applied to (d ≥ 2)-dimensional de Sitter spacetime, and the scalar Green's function is demonstrated to be sourced by a line emanating infinitesimally close to the origin of the ambient (d + 1)-dimensional Minkowski spacetime and piercing orthogonally through the de Sitter hyperboloids of all finite sizes. This method does not require solving the de Sitter wave equation directly. Only the zero mode solution to an ordinary differential equation, the “wave equation” perpendicular to the hyperboloid – followed by a one-dimensional integral – needs to be evaluated. A topological obstruction to the general construction is also discussed by utilizing it to derive a generalized Green's function of the Laplacian on the (d ≥ 2)-dimensional sphere.
Li, Changhong; Cheung, Yeuk-Kwan E. E-mail: cheung@nju.edu.cn
2014-07-01
We investigate the spectrum of cosmological perturbations in a bounce cosmos modeled by a scalar field coupled to the string tachyon field (CSTB cosmos). By explicit computation of its primordial spectral index we show the power spectrum of curvature perturbations, generated during the tachyon matter dominated contraction phase, to be nearly scale invariant. We propose a unified parameter space for a systematic study of inflationary and bounce cosmologies. The CSTB cosmos is dual-in Wands's sense-to slow-roll inflation as can be visualized with the aid of this parameter space. Guaranteed by the dynamical attractor behavior of the CSTB Cosmos, the scale invariance of its power spectrum is free of the fine-tuning problem, in contrast to the slow-roll inflation model.
NASA Astrophysics Data System (ADS)
Cisterna, Adolfo; Cruz, Miguel; Delsate, Térence; Saavedra, Joel
2015-11-01
We derive the odd-parity perturbation equation for the nonminimal kinetic coupling sector of the general Horndeski theory, where the kinetic term is coupled to the metric and the Einstein tensor. We derive the potential of the perturbation, by identifying a master function and switching to tortoise coordinates. We then prove the mode stability under linear odd-parity perturbations of hairy black holes in this sector of Horndeski theory, when a cosmological constant term in the action is included. Finally, we comment on the existence of slowly rotating black hole solutions in this setup and discuss their implications on the physics of compact object configurations, such as neutron stars.
NASA Astrophysics Data System (ADS)
Gambini, Rodolfo; Pullin, Jorge
2013-01-01
We discuss a gauge fixing of gravity coupled to a scalar field in spherical symmetry such that the Hamiltonian is an integral over space of a local density. In a previous paper, we had presented it using Ashtekar’s new variables. Here we study it in metric variables. We specify completely the initial-boundary value problem for ingoing Gaussian pulses.
NASA Astrophysics Data System (ADS)
Ghosh, Kaushik
2016-01-01
In this article, we will discuss a Lorentzian sector calculation of the entropy of a minimally coupled scalar field in the Schwarzschild black hole background using the brick wall model of 't Hooft. In the original article, the Wentzel-Kramers-Brillouin (WKB) approximation was used for the modes that are globally stationary. In a previous article, we found that the WKB quantization rule together with a proper counting of the states, leads to a new expression of the scalar field entropy which is not proportional to the area of the horizon. The expression of the entropy is logarithmically divergent in the brick wall cut-off parameter in contrast to an inverse power divergence obtained earlier. In this article, we will consider the entropy for a thin shell of matter field of a given thickness surrounding the black hole horizon. The thickness is chosen to be large compared with the Planck length and is of the order of the atomic scale. We will discuss the corresponding boundary conditions and the appropriateness of the WKB approximation using the Regge-Wheeler tortoise coordinates. When expressed in terms of a covariant cut-off parameter, the entropy of a thin shell of matter field of a given thickness and surrounding the horizon in the Schwarzschild black hole background is given by an expression proportional to the area of the black hole horizon. This leading order divergent term in the cut-off parameter remains to be logarithmically divergent. The logarithmic divergence is expected from the nature of the near-horizon geometry and is discussed in detail at the end of Sect. 2. We will find that these discussions are significant in the context of the continuation to the Euclidean sector and the corresponding regularization schemes used to evaluate the thermodynamical properties of matter fields in curved spaces. These are related with to geometric aspects of curved spaces.
Detection of a transient intramolecular hydrogen bond using (1)JNH scalar couplings.
Xiang, ShengQi; Zweckstetter, Markus
2014-06-01
Hydrogen bonds are essential for the structure, stability and folding of proteins. The identification of intramolecular hydrogen bonds, however, is challenging, in particular in transiently folded states. Here we studied the presence of intramolecular hydrogen bonds in the folding nucleus of the coiled-coil structure of the GCN4 leucine zipper. Using one-bond (1)JNH spin-spin coupling constants and hydrogen/deuterium exchange, we demonstrate that a transient intramolecular hydrogen bond is present in the partially helical folding nucleus of GCN(16-31). The data demonstrate that (1)JNH couplings are a sensitive tool for the detection of transient intramolecular hydrogen bonds in challenging systems where the effective/useable protein concentration is low. This includes peptides at natural abundance but also uniformly labeled biomolecules that are limited to low concentrations because of precipitation or aggregation.
Pseudo-scalar pi N coupling and relativistic proton-nucleus scattering
NASA Technical Reports Server (NTRS)
Gross, Franz; Maung, Khin Maung; Tjon, J. A.; Townsend, L. W.; Wallace, S. J.
1988-01-01
Relativistic p-Ca-40 elastic scattering observables are calculated using relativistic NN amplitudes obtained from the solution of a two-body relativistic equation in which one particle is kept on its mass-shell. Results at 200 MeV are presented for two sets of NN amplitudes, one with pure pseudo-vector coupling for the pion and another with a 25 percent admixture of pseudo-scaling coupling. Both give a very good fit to the positive energy on-shell NN data. Differences between the predictions of these two models (which are shown to be due only to the differences in their corresponding negative energy amplitudes) provide a measure of the uncertainty in contructing Dirac optical potentials from NN amplitudes.
Collection of NMR Scalar and Residual Dipolar Couplings Using a Single Experiment.
Gil-Silva, Leandro F; Santamaría-Fernández, Raquel; Navarro-Vázquez, Armando; Gil, Roberto R
2016-01-11
A new DMSO-compatible aligning gel based on cross-linked poly(2-hydroxylethyl methacrylate) (poly-HEMA) has been developed. Due to a significant difference in bulk magnetic susceptibility between the DMSO inside and outside the gel, it is possible to simultaneously collect isotropic and anisotropic NMR data, such as residual dipolar couplings (RDC), in the same NMR tube. RDC-assisted structural analysis of menthol and the alkaloid retrorsine is reported as proof of concept.
Aquino, Fredy W.; Pritchard, Ben; Autschbach, Jochen
2012-02-14
A method is reported by which calculated hyperfine coupling constants (HFCCs) and paramagnetic NMR (pNMR) chemical shifts can be analyzed in a chemically intuitive way by decomposition into contributions from localized molecular orbitals (LMOs). A new module for density functional calculations with nonhybrid functionals, global hybrids, and range-separated hybrids, utilizing the two-component relativistic zeroth-order regular approximation (ZORA), has been implemented in the parallel open-source NWChem quantum chemistry package. Benchmark results are reported for a test set of few-atom molecules with light and heavy elements. Finite nucleus effects on ¹⁹⁹Hg HFCCs are shown to be on the order of -11 to -15%. A proof of concept for the LMO analysis is provided for the metal and fluorine HFCCs of TiF₃ and NpF₆. Calculated pNMR chemical shifts are reported for the 2-methylphenyl-t-butylnitroxide radical and for five cyclopentadienyl (Cp) sandwich complexes with 3d metals. Nickelocene and vanadocene carbon pNMR shifts are analyzed in detail, demonstrating that the large carbon pNMR shifts calculated as +1540 for Ni (exptl.: +1514) and -443 for V (exptl.: -510) are caused by different spin-polarization mechanisms. For Ni, Cp to Ni π back-donation dominates the result, whereas for vanadocene, V to Cp σ donation with relaxation of the carbon 1s shells can be identified as the dominant mechanism.
Near-horizon geometry and the entropy of a minimally coupled scalar field in the Kerr black hole
NASA Astrophysics Data System (ADS)
Ghosh, Kaushik
2016-09-01
In this article we will discuss a Lorentzian sector calculation of the entropy of a minimally coupled scalar field in a Kerr black hole background. We will use the brick wall model of 't Hooft. In a Kerr black hole, complications arise due to the absence of a global timelike Killing field and the presence of the ergosphere. Nevertheless, it is possible to calculate the entropy of a thin shell of matter field in the near-horizon region using the brick wall model. The corresponding leading-order entropy of the nonsuperradiant modes is found to be proportional to the area of the horizon and is logarithmically divergent. Thus, the entropy of a three-dimensional system in the near-horizon region is proportional to the boundary surface. This aspect is also valid in the Schwarzschild black holes and is similar to that of the black hole entropy itself. The corresponding internal energy remains finite if the entropy is chosen to be of the order of the black hole entropy itself. For a fixed value of the brick wall cut-off, the leading order entropy in a Kerr black hole is found to be half of the corresponding term in a Schwarzschild black hole. This is due to rotation and is consistent with the preferential emission of particles in a Kerr black hole with azimuthal angular momentum in the same direction as that of the black hole itself. However, we can obtain the Schwarzschild case expression by including a subleading term and taking the appropriate slow rotation limit.
Scalar limitations of diffractive optical elements
NASA Technical Reports Server (NTRS)
Johnson, Eric G.; Hochmuth, Diane; Moharam, M. G.; Pommet, Drew
1993-01-01
In this paper, scalar limitations of diffractive optic components are investigated using coupled wave analyses. Results are presented for linear phase gratings and fanout devices. In addition, a parametric curve is given which correlates feature size with scalar performance.
NASA Astrophysics Data System (ADS)
Chiavazza, Enrico; Kubala, Eugen; Gringeri, Concetta V.; Düwel, Stephan; Durst, Markus; Schulte, Rolf F.; Menzel, Marion I.
2013-02-01
Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., 79Br-13C), can be a very effective relaxation mechanism. While working on hyperpolarized [5-13C]glutamine, fast liquid-state polarization decay during transfer to the MRI scanner was observed. This behavior could hypothetically be explained by substantial T1 shortening due to a scalar coupling contribution (type II) to the relaxation caused by the fast-relaxing quadrupolar 14N adjacent to the 13C nucleus in the amide group. This contribution is only effective in low magnetic fields (i.e., less than 800 μT) and prevents the use of molecules bearing the 13C-amide group as hyperpolarized MRS/MRI probes. In the present work, this hypothesis is explored both theoretically and experimentally. The results show that high hyperpolarization levels can be retained using either a 15N-labeled amide or by applying a magnetic field during transfer of the sample from the polarizer to the MRI scanner.
Geometric scalar theory of gravity
Novello, M.; Bittencourt, E.; Goulart, E.; Salim, J.M.; Toniato, J.D.; Moschella, U. E-mail: eduhsb@cbpf.br E-mail: egoulart@cbpf.br E-mail: toniato@cbpf.br
2013-06-01
We present a geometric scalar theory of gravity. Our proposal will be described using the ''background field method'' introduced by Gupta, Feynman, Deser and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor — which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models — does not apply to our geometric scalar theory. From the very beginning this is not a special relativistic scalar gravity. The adjective ''geometric'' pinpoints its similarity with general relativity: this is a metric theory of gravity. Some consequences of this new scalar theory are explored.
Electroweak Baryogenesis and Colored Scalars
Cohen, Timothy; Pierce, Aaron; /Michigan U., MCTP
2012-02-15
We consider the 2-loop finite temperature effective potential for a Standard Model-like Higgs boson, allowing Higgs boson couplings to additional scalars. If the scalars transform under color, they contribute 2-loop diagrams to the effective potential that include gluons. These 2-loop effects are perhaps stronger than previously appreciated. For a Higgs boson mass of 115 GeV, they can increase the strength of the phase transition by as much as a factor of 3.5. It is this effect that is responsible for the survival of the tenuous electroweak baryogenesis window of the Minimal Supersymmetric Standard Model. We further illuminate the importance of these 2-loop diagrams by contrasting models with colored scalars to models with singlet scalars. We conclude that baryogenesis favors models with light colored scalars. This motivates searches for pair-produced di-jet resonances or jet(s) + = E{sub T}.
Conformal scalar field wormholes
NASA Technical Reports Server (NTRS)
Halliwell, Jonathan J.; Laflamme, Raymond
1989-01-01
The Euclidian Einstein equations with a cosmological constant and a conformally coupled scalar field are solved, taking the metric to be of the Robertson-Walker type. In the case Lambda = 0, solutions are found which represent a wormhole connecting two asymptotically flat Euclidian regions. In the case Lambda greater than 0, the solutions represent tunneling from a small Tolman-like universe to a large Robertson-Walker universe.
Are stealth scalar fields stable?
Faraoni, Valerio; Moreno, Andres F. Zambrano
2010-06-15
Nongravitating (stealth) scalar fields associated with Minkowski space in scalar-tensor gravity are examined. Analytical solutions for both nonminimally coupled scalar field theory and for Brans-Dicke gravity are studied and their stability with respect to tensor perturbations is assessed using a covariant and gauge-invariant formalism developed for alternative gravity. For Brans-Dicke solutions, the stability with respect to homogeneous perturbations is also studied. There are regions of parameter space corresponding to stability and other regions corresponding to instability.
Slowly rotating neutron stars in scalar-tensor theories with a massive scalar field
NASA Astrophysics Data System (ADS)
Yazadjiev, Stoytcho S.; Doneva, Daniela D.; Popchev, Dimitar
2016-04-01
In the scalar-tensor theories with a massive scalar field, the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper, we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined—the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak-field limit. In the latter case, we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastically compared to the massless case. It turns out that mass, radius, and moment of inertia for neutron stars in massive scalar-tensor theories can differ drastically from the pure general relativistic solutions if sufficiently large masses of the scalar field are considered.
Cheng, Lan
2015-08-14
Quantum-chemical computations of nuclear quadrupole-coupling parameters for 24 open-shell states of small molecules based on non-relativistic and spin-free exact two-component (SFX2C) relativistic equation-of-motion coupled-cluster (EOM-CC) as well as spin-orbital-based restricted open-shell Hartree-Fock coupled-cluster (ROHF-CC) methods are reported. Relativistic effects, the performance of the EOM-CC and ROHF-CC methods for treating electron correlation, as well as basis-set convergence have been carefully analyzed. Consideration of relativistic effects is necessary for accurate calculations on systems containing third-row (K-Kr) and heavier elements, as expected, and the SFX2C approach is shown to be a useful cost-effective option here. Further, it is demonstrated that the EOM-CC methods constitute flexible and accurate alternatives to the ROHF-CC methods in the calculations of nuclear quadrupole-coupling parameters for open-shell states.
Mäntylahti, Sampo; Koskela, Outi; Jiang, Pengju; Permi, Perttu
2010-07-01
We describe a novel pulse sequence, MQ-HNCO-TROSY, for the measurement of scalar and residual dipolar couplings between amide proton and nitrogen in larger proteins. The experiment utilizes the whole 2T(N) polarization transfer delay for labeling of (15)N chemical shift in a constant time manner, which efficiently doubles the attainable resolution in (15)N dimension with respect to the conventional HNCO-TROSY experiment. In addition, the accordion principle is employed for measuring (J + D)(NH)s, and the multiplet components are selected with the generalized version of the TROSY scheme introduced by Nietlispach (J Biomol NMR 31:161-166, 2005). Therefore, cross peak overlap is diminished while the time period during which the (15)N spin is susceptible to fast transverse relaxation associated with the anti-TROSY transition is minimized per attainable resolution unit. The proposed MQ-HNCO-TROSY scheme was employed for measuring RDCs in high molecular weight protein IgFLNa16-21 of 557 residues, resulting in 431 experimental RDCs. Correlations between experimental and back-calculated RDCs in individual domains gave relatively low Q-factors (0.19-0.39), indicative of sufficient accuracy that can be obtained with the proposed MQ-HNCO-TROSY experiment in high molecular weight proteins. PMID:20454834
Electrophobic Scalar Boson and Muonic Puzzles
NASA Astrophysics Data System (ADS)
Liu, Yu-Sheng; McKeen, David; Miller, Gerald A.
2016-09-01
A new scalar boson which couples to the muon and proton can simultaneously solve the proton radius puzzle and the muon anomalous magnetic moment discrepancy. Using a variety of measurements, we constrain the mass of this scalar and its couplings to the electron, muon, neutron, and proton. Making no assumptions about the underlying model, these constraints and the requirement that it solve both problems limit the mass of the scalar to between about 100 keV and 100 MeV. We identify two unexplored regions in the coupling constant-mass plane. Potential future experiments and their implications for theories with mass-weighted lepton couplings are discussed.
Roberts, M.D.
1996-09-01
Static spherically symmetric uncoupled scalar space{endash}times have no event horizon and a divergent Kretschmann singularity at the origin of the coordinates. The singularity is always present so that nonstatic solutions have been sought to see if the singularities can develop from an initially singular free space{endash}time. In flat space{endash}time the Klein{endash}Gordon equation {D`Alembertian}{var_phi}=0 has the nonstatic spherically symmetric solution {var_phi}={sigma}({ital v})/{ital r}, where {sigma}({ital v}) is a once differentiable function of the null coordinate {ital v}. In particular, the function {sigma}({ital v}) can be taken to be initially zero and then grow, thus producing a singularity in the scalar field. A similar situation occurs when the scalar field is coupled to gravity via Einstein{close_quote}s equations; the solution also develops a divergent Kretschmann invariant singularity, but it has no overall energy. To overcome this, Bekenstein{close_quote}s theorems are applied to give two corresponding conformally coupled solutions. One of these has positive ADM mass and has the following properties: (i) it develops a Kretschmann invariant singularity, (ii) it has no event horizon, (iii) it has a well-defined source, (iv) it has well-defined junction condition to Minkowski space{endash}time, and (v) it is asymptotically flat with positive overall energy. This paper presents this solution and several other nonstatic scalar solutions. The properties of these solutions which are studied are limited to the following three: (i) whether the solution can be joined to Minkowski space{endash}time, (ii) whether the solution is asymptotically flat, (iii) and, if so, what the solutions{close_quote} Bondi and ADM masses are. {copyright} {ital 1996 American Institute of Physics.}
Exact computation of the 3-j and 6-j symbols
NASA Astrophysics Data System (ADS)
Lai, Shan-Tao; Chiu, Ying-Nan
1990-12-01
A simple FORTRAN program for the exact computation of 3- j and 6- j symbols has been written for the VAX with VMS version v5.1 in our university's computing center. It goes beyond and contains all of the 3- j and 6- j symbols evaluated in the book by M. Rotenberg, R. Bivins, N. Metropolis and J.K. Wooten Jr. The 3- j symbols up to ( 30m130m2 30 m3)] and 6- j symbols up to { 202020202020} can be computed exactly by this program. Approximate values for larger j's up to 200m1200m2200m3 and { 200200200200200220} can also be computed by this program.
Maximum J Pairing and Asymptotic Behavior of the 3j and 9j Coefficients
NASA Astrophysics Data System (ADS)
Hertz-Kintish, Daniel; Zamick, Larry; Kleszyk, Brian
2014-09-01
We investigate the large j behavior of certain 3 j and 9 j symbols, where j is the total angular momentum of one particle in a given shell. Our motivation is the problem of maximum J pairing in nuclei, along with the more familiar J = 0 pairing. Maximum J pairing leads to an increase in J = 2 coupling of two protons and two neutrons relative to J = 0 . We find that a coupling unitary 9 j symbol (U 9 j) is very weak as j increases, leading to wavefunctions which are to an excellent approximation single U 9 j coefficients. Our study of the large j behavior of coupling unitary 9 j symbols is through the consideration of the case when the total angular momentum I is equal to Imax - 2 n and Imax ≡ 4 j - 2 , where n = 0 , 1 , 2 , ... . We here derive asymptotic approximations of coupling 3 j symbols and find that the 3 j ~j - 3 / 4 in the high j limit. One major analytical tool we used is the Stirling Approximation. Through analytical, numerical, and graphical methods, we show the power law behavior of the coupling unitary 9 j symbols in the n / j << 1 limit, i.e. U 9 j ~j-n . Power-law behavior is evident if there is a linear dependence of ln | U 9 j | vs. ln j . We also present some examples of percent errors in our approximations. We investigate the large j behavior of certain 3 j and 9 j symbols, where j is the total angular momentum of one particle in a given shell. Our motivation is the problem of maximum J pairing in nuclei, along with the more familiar J = 0 pairing. Maximum J pairing leads to an increase in J = 2 coupling of two protons and two neutrons relative to J = 0 . We find that a coupling unitary 9 j symbol (U 9 j) is very weak as j increases, leading to wavefunctions which are to an excellent approximation single U 9 j coefficients. Our study of the large j behavior of coupling unitary 9 j symbols is through the consideration of the case when the total angular momentum I is equal to Imax - 2 n and Imax ≡ 4 j - 2 , where n = 0 , 1 , 2 , ... . We here
Preimesberger, Matthew R; Majumdar, Ananya; Rice, Selena L; Que, Lauren; Lecomte, Juliette T J
2015-11-24
In addition to its well-known roles as an electrophile and general acid, the side chain of histidine often serves as a hydrogen bond (H-bond) acceptor. These H-bonds provide a convenient pH-dependent switch for local structure and functional motifs. In hundreds of instances, a histidine caps the N-terminus of α- and 310-helices by forming a backbone NH···Nδ1 H-bond. To characterize the resilience and dynamics of the histidine cap, we measured the trans H-bond scalar coupling constant, (2h)JNN, in several forms of Group 1 truncated hemoglobins and cytochrome b5. The set of 19 measured (2h)JNN values were between 4.0 and 5.4 Hz, generally smaller than in nucleic acids (~6-10 Hz) and indicative of longer, weaker bonds in the studied proteins. A positive linear correlation between (2h)JNN and the difference in imidazole ring (15)N chemical shift (Δ(15)N = |δ(15)Nδ1 - δ(15)Nε2|) was found to be consistent with variable H-bond length and variable cap population related to the ionization of histidine in the capping and noncapping states. The relative ease of (2h)JNN detection suggests that this parameter can become part of the standard arsenal for describing histidines in helix caps and other key structural and catalytic elements involving NH···N H-bonds. The combined nucleic acid and protein data extend the utility of (2h)JNN as a sensitive marker of local structural, dynamic, and thermodynamic properties in biomolecules. PMID:26523621
NASA Astrophysics Data System (ADS)
Lasukov, V. V.
2012-06-01
It is shown that negative Scalars can claim to be the object referred to as black holes, therefore observation of black holes means observation of Scalars. In contrast to blackholes, negative Scalars contain no singularity inside. Negative Scalars can be observed from the effect of generation of ordinary matter by the Lemaître primordial atom.
Oscillons in dilaton-scalar theories
NASA Astrophysics Data System (ADS)
Fodor, Gyula; Forgács, Péter; Horváth, Zalán; Mezei, Márk
2009-08-01
It is shown by both analytical methods and numerical simulations that extremely long living spherically symmetric oscillons appear in virtually any real scalar field theory coupled to a massless dilaton (DS theories). In fact such ``dilatonic'' oscillons are already present in the simplest non-trivial DS theory — a free massive scalar field coupled to the dilaton. It is shown that in analogy to the previously considered cases with a single nonlinear scalar field, in DS theories there are also time periodic quasibreathers (QB) associated to small amplitude oscillons. Exploiting the QB picture the radiation law of the small amplitude dilatonic oscillons is determined analytically.
Black hole hair in generalized scalar-tensor gravity.
Sotiriou, Thomas P; Zhou, Shuang-Yong
2014-06-27
The most general action for a scalar field coupled to gravity that leads to second-order field equations for both the metric and the scalar--Horndeski's theory--is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories, the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss-Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem which seems to have overlooked the presence of this coupling. PMID:25014801
Black hole hair in generalized scalar-tensor gravity.
Sotiriou, Thomas P; Zhou, Shuang-Yong
2014-06-27
The most general action for a scalar field coupled to gravity that leads to second-order field equations for both the metric and the scalar--Horndeski's theory--is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories, the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss-Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem which seems to have overlooked the presence of this coupling.
Nguyen Lan, Tran; Kurashige, Yuki; Yanai, Takeshi
2015-01-13
We have developed a new computational scheme for high-accuracy prediction of the isotropic hyperfine coupling constant (HFCC) of heavy molecules, accounting for the high-level electron correlation effects, as well as the scalar-relativistic effects. For electron correlation, we employed the ab initio density matrix renormalization group (DMRG) method in conjunction with a complete active space model. The orbital-optimization procedure was employed to obtain the optimized orbitals required for accurately determining the isotropic HFCC. For the scalar-relativistic effects, we initially derived and implemented the Douglas-Kroll-Hess (DKH) hyperfine coupling operators up to the third order (DKH3) by using the direct transformation scheme. A set of 4d transition-metal radicals consisting of Ag atom, PdH, and RhH2 were chosen as test cases. Good agreement between the isotropic HFCC values obtained from DMRG/DKH3 and experiment was archived. Because there are no available gas-phase values for PdH and RhH2 radicals in the literature, the results from the present high-level theory may serve as benchmark data.
Electrophobic Scalar Boson and Muonic Puzzles.
Liu, Yu-Sheng; McKeen, David; Miller, Gerald A
2016-09-01
A new scalar boson which couples to the muon and proton can simultaneously solve the proton radius puzzle and the muon anomalous magnetic moment discrepancy. Using a variety of measurements, we constrain the mass of this scalar and its couplings to the electron, muon, neutron, and proton. Making no assumptions about the underlying model, these constraints and the requirement that it solve both problems limit the mass of the scalar to between about 100 keV and 100 MeV. We identify two unexplored regions in the coupling constant-mass plane. Potential future experiments and their implications for theories with mass-weighted lepton couplings are discussed. PMID:27636468
Inflation in anisotropic scalar-tensor theories
NASA Technical Reports Server (NTRS)
Pimentel, Luis O.; Stein-Schabes, Jaime
1988-01-01
The existence of an inflationary phase in anisotropic Scalar-Tensor Theories is investigated by means of a conformal transformation that allows us to rewrite these theories as gravity minimally coupled to a scalar field with a nontrivial potential. The explicit form of the potential is then used and the No Hair Theorem concludes that there is an inflationary phase in all open or flat anisotropic spacetimes in these theories. Several examples are constructed where the effect becomes manifest.
NEUTRON STAR STRUCTURE IN THE PRESENCE OF SCALAR FIELDS
Crawford, James P.; Kazanas, Demosthenes
2009-08-20
Motivated by the possible presence of scalar fields on cosmological scales, suggested by the recent measurement of the deceleration parameter by supernovae surveys, we present models of neutron star structure under the assumption that a scalar field makes a significant contribution to the stress energy momentum tensor, in addition to that made by the normal matter. To that end we solve the coupled Einstein-scalar field-hydrostatic balance equations to compute the effect of the presence of the scalar field on the neutron star structure. We find that the presence of the scalar field does change the structure of the neutron star, especially in cases of strong coupling between the scalar field and the matter density. We present the neutron star radius as a function of the matter-scalar field coupling constant for different values of the neutron star central density. The presence of the scalar field does affect both the maximum neutron star mass and its radius, the latter increasing with the value of the above coupling constant. Our results can provide limits to the scalar field-matter coupling through spectro-temporal observations of accreting or isolated neutron stars.
29 CFR 451.4 - Labor organizations under section 3(j).
Code of Federal Regulations, 2010 CFR
2010-07-01
...” under Railroad Retirement Act in 20 CFR 201.1(k). (3) Joint or system boards. As mentioned above, in... 29 Labor 2 2010-07-01 2010-07-01 false Labor organizations under section 3(j). 451.4 Section 451.4... 1959 § 451.4 Labor organizations under section 3(j). (a) General. Section 3(j) sets forth...
29 CFR 451.4 - Labor organizations under section 3(j).
Code of Federal Regulations, 2014 CFR
2014-07-01
...” under Railroad Retirement Act in 20 CFR 201.1(k). (3) Joint or system boards. As mentioned above, in... 29 Labor 2 2014-07-01 2014-07-01 false Labor organizations under section 3(j). 451.4 Section 451.4... 1959 § 451.4 Labor organizations under section 3(j). (a) General. Section 3(j) sets forth...
29 CFR 451.4 - Labor organizations under section 3(j).
Code of Federal Regulations, 2012 CFR
2012-07-01
...” under Railroad Retirement Act in 20 CFR 201.1(k). (3) Joint or system boards. As mentioned above, in... 29 Labor 2 2012-07-01 2012-07-01 false Labor organizations under section 3(j). 451.4 Section 451.4... 1959 § 451.4 Labor organizations under section 3(j). (a) General. Section 3(j) sets forth...
29 CFR 451.4 - Labor organizations under section 3(j).
Code of Federal Regulations, 2011 CFR
2011-07-01
...” under Railroad Retirement Act in 20 CFR 201.1(k). (3) Joint or system boards. As mentioned above, in... 29 Labor 2 2011-07-01 2011-07-01 false Labor organizations under section 3(j). 451.4 Section 451.4... 1959 § 451.4 Labor organizations under section 3(j). (a) General. Section 3(j) sets forth...
29 CFR 451.4 - Labor organizations under section 3(j).
Code of Federal Regulations, 2013 CFR
2013-07-01
...” under Railroad Retirement Act in 20 CFR 201.1(k). (3) Joint or system boards. As mentioned above, in... 29 Labor 2 2013-07-01 2013-07-01 false Labor organizations under section 3(j). 451.4 Section 451.4... 1959 § 451.4 Labor organizations under section 3(j). (a) General. Section 3(j) sets forth...
Scalar self-interactions loosen constraints from fifth force searches
Gubser, Steven S.; Khoury, Justin
2004-11-15
The mass of a scalar field mediating a fifth force is tightly constrained by experiments. We show, however, that adding a quartic self-interaction for such a scalar makes most tests much less constraining: the nonlinear equation of motion masks the coupling of the scalar to matter through the chameleon mechanism. We discuss consequences for fifth force experiments. In particular, we find that, with quartic coupling of order unity, a gravitational strength interaction with matter is allowed by current constraints. We show that our chameleon scalar field results in experimental signatures that could be detected through modest improvements of current laboratory set-ups.
Semi-analytic stellar structure in scalar-tensor gravity
NASA Astrophysics Data System (ADS)
Horbatsch, M. W.; Burgess, C. P.
2011-08-01
Precision tests of gravity can be used to constrain the properties of hypothetical very light scalar fields, but these tests depend crucially on how macroscopic astrophysical objects couple to the new scalar field. We study the equations of stellar structure using scalar-tensor gravity, with the goal of seeing how stellar properties depend on assumptions made about the scalar coupling at a microscopic level. In order to make the study relatively easy for different assumptions about microscopic couplings, we develop quasi-analytic approximate methods for solving the stellar-structure equations rather than simply integrating them numerically. (The approximation involved assumes the dimensionless scalar coupling at the stellar center is weak, and we compare our results with numerical integration in order to establish its domain of validity.) We illustrate these methods by applying them to Brans-Dicke scalars, and their generalization in which the scalar-matter coupling slowly runs — or `walks' — as a function of the scalar field: a(phi) simeq as+bsphi. (Such couplings can arise in extra-dimensional applications, for instance.) The four observable parameters that characterize the fields external to a spherically symmetric star are the stellar radius, R, mass, M, scalar `charge', Q, and the scalar's asymptotic value, phi∞. These are subject to two relations because of the matching to the interior solution, generalizing the usual mass-radius, M(R), relation of General Relativity. Since phi∞ is common to different stars in a given region (such as a binary pulsar), all quantities can be computed locally in terms of the stellar masses. We identify how these relations depend on the microscopic scalar couplings, agreeing with earlier workers when comparisons are possible. Explicit analytical solutions are obtained for the instructive toy model of constant-density stars, whose properties we compare to more realistic equations of state for neutron star models.
NASA Astrophysics Data System (ADS)
Mottola, Emil
2016-03-01
General Relativity receives quantum corrections relevant at macroscopic distance scales and near event horizons. These arise from the conformal scalar degree of freedom in the extended effective field theory (EFT) of gravity generated by the trace anomaly of massless quantum fields in curved space. Linearized around flat space this quantum scalar degree of freedom combines with the conformal part of the metric and predicts the existence of scalar spin-0 ``breather'' propagating gravitational waves in addition to the transverse tensor spin-2 waves of classical General Relativity. Estimates of the expected strength of scalar gravitational radiation from compact astrophysical sources are given.
Scalar Mixing In A Vortex Flow
NASA Astrophysics Data System (ADS)
Meunier, P.; Villermaux, E.; Leweke, T.
We present experimental and theoretical results on the evolution of a scalar blob em- bedded in the velocity field of one or two vortices, a configuration relevant to geo- physical mixing in particular. We first follow the evolution of the scalar in one vortex. The scalar blob rolls up into a spiral and then diffuses rapidly, much faster than in the absence of a vortex flow. A simple model predicts that the maximal scalar concentration decreases in time as t-3 , after a mixing time which scales like Pe1 /2 /3 (where Pe = /D is the Peclet number). This hyper-diffusion process is due to the coupled presence of stretching and diffusion, and is in good quantitative agreement with the experimental results. In contrast with this temporal variation of the scalar, the model predicts that the proba- bility distribution functions (PDF) of the scalar are almost stationnary. The agreement between experimental and theoretical PDF is excellent. Finally, we report on the evolution of the PDF of a scalar during the merging of two vortices and on the comparison law of the concentration PDF's associated with each vortices, both in laminar and turbulent situations.
Llinares, Claudio; Mota, David F
2013-04-19
Several extensions of general relativity and high energy physics include scalar fields as extra degrees of freedom. In the search for predictions in the nonlinear regime of cosmological evolution, the community makes use of numerical simulations in which the quasistatic limit is assumed when solving the equation of motion of the scalar field. In this Letter, we propose a method to solve the full equations of motion for scalar degrees of freedom coupled to matter. We run cosmological simulations which track the full time and space evolution of the scalar field, and find striking differences with respect to the commonly used quasistatic approximation. This novel procedure reveals new physical properties of the scalar field and uncovers concealed astrophysical phenomena which were hidden in the old approach. PMID:23679591
Scalar explanation of diphoton excess at LHC
NASA Astrophysics Data System (ADS)
Han, Huayong; Wang, Shaoming; Zheng, Sibo
2016-06-01
Inspired by the diphoton signal excess observed in the latest data of 13 TeV LHC, we consider either a 750 GeV real scalar or pseudo-scalar responsible for this anomaly. We propose a concrete vector-like quark model, in which the vector-like fermion pairs directly couple to this scalar via Yukawa interaction. For this setting the scalar is mainly produced via gluon fusion, then decays at the one-loop level to SM diboson channels gg , γγ , ZZ , WW. We show that for the vector-like fermion pairs with exotic electric charges, such model can account for the diphoton excess and is consistent with the data of 8 TeV LHC simultaneously in the context of perturbative analysis.
A Search for Scalar Chameleons with ADMX
Rybka, G.; Hotz, M.; Rosenberg, L.J.; Asztalos, S.J.; Carosi, G.; Hagmann, C.; Kinion, D.; van Bibber, K.; Hoskins, J.; Martin, C.; Sikivie, P.; Tanner, D.B.; Bradley, R.; Clarke, J.
2010-04-26
Scalar fields with a"chameleon" property, in which the effective particle mass is a function of its local environment, are common to many theories beyond the standard model and could be responsible for dark energy. If these fields couple weakly to the photon, they could be detectable through the afterglow effect of photon-chameleon-photon transitions. The ADMX experiment was used in the first chameleon search with a microwave cavity to set a new limit on scalar chameleon-photon coupling beta_gamma excluding values between 2x109 and 5x1014 for effective chameleon masses between 1.9510 and 1:9525 micro eV.
Santiago, Marcelina; Low, Eddy; Chambournier, Gilles; Gawley, Robert E
2003-10-31
The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction. PMID:14575474
Santiago, Marcelina; Low, Eddy; Chambournier, Gilles; Gawley, Robert E
2003-10-31
The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction.
Black Hole Hair in Generalized Scalar-Tensor Gravity
NASA Astrophysics Data System (ADS)
Sotiriou, Thomas P.; Zhou, Shuang-Yong
2014-06-01
The most general action for a scalar field coupled to gravity that leads to second-order field equations for both the metric and the scalar—Horndeski's theory—is considered, with the extra assumption that the scalar satisfies shift symmetry. We show that in such theories, the scalar field is forced to have a nontrivial configuration in black hole spacetimes, unless one carefully tunes away a linear coupling with the Gauss-Bonnet invariant. Hence, black holes for generic theories in this class will have hair. This contradicts a recent no-hair theorem which seems to have overlooked the presence of this coupling.
Inflation as AN Attractor in Scalar Cosmology
NASA Astrophysics Data System (ADS)
Kim, Hyeong-Chan
2013-06-01
We study an inflation mechanism based on attractor properties in cosmological evolutions of a spatially flat Friedmann-Robertson-Walker spacetime based on the Einstein-scalar field theory. We find a new way to get the Hamilton-Jacobi equation solving the field equations. The equation relates a solution "generating function" with the scalar potential. We analyze its stability and find a later time attractor which describes a Universe approaching to an eternal-de Sitter inflation driven by the potential energy, V0>0. The attractor exists when the potential is regular and does not have a linear and quadratic terms of the field. When the potential has a mass term, the attractor exists if the scalar field is in a symmetric phase and is weakly coupled, λ<9V0/16. We also find that the attractor property is intact under small modifications of the potential. If the scalar field has a positive mass-squared or is strongly coupled, there exists a quasi-attractor. However, the quasi-attractor property disappears if the potential is modified. On the whole, the appearance of the eternal inflation is not rare in scalar cosmology in the presence of an attractor.
Exact scalar-tensor cosmological solutions via Noether symmetry
NASA Astrophysics Data System (ADS)
Belinchón, J. A.; Harko, T.; Mak, M. K.
2016-02-01
In this paper, we investigate the Noether symmetries of a generalized scalar-tensor, Brans-Dicke type cosmological model, in which we consider explicit scalar field dependent couplings to the Ricci scalar, and to the scalar field kinetic energy, respectively. We also include the scalar field self-interaction potential into the gravitational action. From the condition of the vanishing of the Lie derivative of the gravitational cosmological Lagrangian with respect to a given vector field we obtain three cosmological solutions describing the time evolution of a spatially flat Friedman-Robertson-Walker Universe filled with a scalar field. The cosmological properties of the solutions are investigated in detail, and it is shown that they can describe a large variety of cosmological evolutions, including models that experience a smooth transition from a decelerating to an accelerating phase.
NASA Astrophysics Data System (ADS)
Mendes, Raissa F. P.; Ortiz, Néstor
2016-06-01
Scalar-tensor theories of gravity are extensions of general relativity (GR) including an extra, nonminimally coupled scalar degree of freedom. A wide class of these theories, albeit indistinguishable from GR in the weak field regime, predicts a radically different phenomenology for neutron stars, due to a nonperturbative, strong-field effect referred to as spontaneous scalarization. This effect is known to occur in theories where the effective linear coupling β0 between the scalar and matter fields is sufficiently negative, i.e. β0≲-4.35 , and has been strongly constrained by pulsar timing observations. In the test-field approximation, spontaneous scalarization manifests itself as a tachyonic-like instability. Recently, it was argued that, in theories where β0>0 , a similar instability would be triggered by sufficiently compact neutron stars obeying realistic equations of state. In this work we investigate the end state of this instability for some representative coupling functions with β0>0 . This is done both through an energy balance analysis of the existing equilibrium configurations, and by numerically determining the nonlinear Cauchy development of unstable initial data. We find that, contrary to the β0<0 case, the final state of the instability is highly sensitive to the details of the coupling function, varying from gravitational collapse to spontaneous scalarization. In particular, we show, for the first time, that spontaneous scalarization can happen in theories with β0>0 , which could give rise to novel astrophysical tests of the theory of gravity.
Liu Yunhu; Shao Jianxin; Wang Xiaogang; Zhang Ziying; Li Demin
2008-02-01
Based on the main assumption that the D{sub sJ}(2860) belongs to the 2{sup 3}P{sub 0} qq multiplet, the masses of the scalar meson nonet are estimated in the framework of the relativistic independent quark model, Regge phenomenology, and meson-meson mixing. We suggest that the a{sub 0}(1005), K{sub 0}*(1062), f{sub 0}(1103), and f{sub 0}(564) constitute the ground scalar meson nonet; it is supposed that these states would likely correspond to the observed states a{sub 0}(980), {kappa}(900), f{sub 0}(980), and f{sub 0}(600)/{sigma}, respectively. Also a{sub 0}(1516), K{sub 0}*(1669), f{sub 0}(1788), and f{sub 0}(1284) constitute the first radial scalar meson nonet, it is supposed that these states would likely correspond to the observed states a{sub 0}(1450), K{sub 0}*(1430), f{sub 0}(1710), and f{sub 0}(1370), respectively. The scalar state f{sub 0}(1500) may be a good candidate for the ground scalar glueball. The agreement between the present findings and those given by other different approaches is satisfactory.
NASA Astrophysics Data System (ADS)
Ge, Li; Shi, Yu
2012-10-01
Using the approach of low-energy effective field theory, the phase diagram is studied for a mixture of two species of pseudospin-\\frac{1}{2} Bose atoms with interspecies spin exchange. There are four mean-field regimes on the parameter plane of ge and gz, where ge is the interspecies spin-exchange interaction strength, while gz is the difference between the interaction strength of interspecies scattering without spin exchange of equal spins and that of unequal spins. Two regimes, with |gz| > |ge|, correspond to ground states with the total spins of the two species parallel or antiparallel along the z direction, and the low-energy excitations are equivalent to those of two-component spinless bosons. The other two regimes, with |ge| > |gz|, correspond to ground states with the total spins of the two species parallel or antiparallel on the xy plane, and the low-energy excitations are described by a sine-Gordon model coupled with a free scalar field, where the effective fields are combinations of the phases of the original four boson fields. In (1 + 1)-dimension, they are described by Kosterlitz-Thouless renormalization group (RG) equations, and there are three sectors in the phase plane of a scaling dimension and a dimensionless parameter proportional to the strength of the cosine interaction, both depending on the densities. The gaps of these elementary excitations are experimental probes of the underlying many-body ground states.
NASA Astrophysics Data System (ADS)
Iuga, Adriana; Iuga, Dinu; Cross, Albert R.; Gerken, Michael; Hazendonk, Paul
2007-02-01
A method is introduced to select the signal from a spin-1/2 nucleus I specifically bound to another spin-1/2 nucleus S for solid-state magic angle spinning nuclear magnetic resonance (NMR) spectroscopy via correlation through the heteronuclear J coupling. This experiment is analogous to the bilinear rotation decoupling (BIRD) sequence in liquid-state NMR spectroscopy which selects for signals from H1 directly bound to C13. The spin dynamics of this modified BIRD experiment is described using the product-operator formalism, where experimental considerations such as rotor synchronization and the effect of large chemical shielding anisotropies on I and S are discussed. Two experiments are proposed that accommodate large chemical shielding anisotropies on S: (1) by stepping the inversion pulse frequency through the entire S spectral range or (2) by adiabatically inverting the S spins. Both these experiments are shown to successfully select the signal of F19 bound to Xe129 in XeF+ salts, removing the contributions from isotopomers containing non-spin-1/2 Xe isotopes. The feasibility in obtaining isotope-selective F19 spectra of inorganic fluoride compounds is discussed, and further modifications are proposed to expand the application to other chemical systems.
NASA Astrophysics Data System (ADS)
Claeys, Pieter W.; De Baerdemacker, Stijn; Van Raemdonck, Mario; Van Neck, Dimitri
2015-10-01
Starting from integrable su(2) (quasi-)spin Richardson-Gaudin (RG) XXZ models we derive several properties of integrable spin models coupled to a bosonic mode. We focus on the Dicke-Jaynes-Cummings-Gaudin models and the two-channel (p + ip)-wave pairing Hamiltonian. The pseudo-deformation of the underlying su(2) algebra is here introduced as a way to obtain these models in the contraction limit of different RG models. This allows for the construction of the full set of conserved charges, the Bethe ansatz state, and the resulting RG equations. For these models an alternative and simpler set of quadratic equations can be found in terms of the eigenvalues of the conserved charges. Furthermore, the recently proposed eigenvalue-based determinant expressions for the overlaps and form factors of local operators are extended to these models, linking the results previously presented for the Dicke-Jaynes-Cummings-Gaudin models with the general results for RG XXZ models.
Time-dependent scalar fields in modified gravities in a stationary spacetime
NASA Astrophysics Data System (ADS)
Zhong, Yi; Gu, Bao-Ming; Wei, Shao-Wen; Liu, Yu-Xiao
2016-07-01
Most no-hair theorems involve the assumption that the scalar field is independent of time. Recently in Graham and Jha (Phys. Rev. D90: 041501, 2014) the existence of time-dependent scalar hair outside a stationary black hole in general relativity was ruled out. We generalize this work to modified gravities and non-minimally coupled scalar field with the additional assumption that the spacetime is axisymmetric. It is shown that in higher-order gravity such as metric f( R) gravity the time-dependent scalar hair does not exist. In Palatini f( R) gravity and the non-minimally coupled case the time-dependent scalar hair may exist.
Scalar Hair of Global Defect and Black Brane World
NASA Astrophysics Data System (ADS)
Kim, Yoonbai; Park, Dong Hyun
2004-06-01
We consider a complex scalar field in (p+3)-dimensional bulk with a negative cosmological constant and study global vortices in two extra-dimensions. We reexamine carefully the coupled scalar and Einstein equations, and show that the boundary value of scalar amplitude at infinity of the extra-dimensions should be smaller than vacuum expectation value. The brane world has a cigar-like geometry with an exponentially decaying warp factor and a flat thick p-brane is embedded. Since a coordinate transformation identifies the obtained brane world as a black p-brane world bounded by a horizon, this strange boundary condition of the scalar amplitude is understood as existence of a short scalar hair.
Pragmatic Aspects of Scalar Modifiers
ERIC Educational Resources Information Center
Sawada, Osamu
2010-01-01
This dissertation investigates the pragmatic aspects of scalar modifiers from the standpoint of the interface between semantics and pragmatics, focusing on (i) the (non) parallelism between the truth-conditional scalar modifiers and the non-truth-conditional scalar modifiers, (ii) the compositionality and dimensionality of non-truth-conditional…
Growth of spherical overdensities in scalar-tensor cosmologies
NASA Astrophysics Data System (ADS)
Nazari-Pooya, N.; Malekjani, M.; Pace, F.; Jassur, D. Mohammad-Zadeh
2016-06-01
The accelerated expansion of the universe is a rather established fact in cosmology and many different models have been proposed as a viable explanation. Many of these models are based on the standard general relativistic framework of non-interacting fluids or more recently of coupled (interacting) dark energy models, where dark energy (the scalar field) is coupled to the dark matter component giving rise to a fifth-force. An interesting alternative is to couple the scalar field directly to the gravity sector via the Ricci scalar. These models are dubbed non-minimally coupled models and give rise to a time-dependent gravitational constant. In this work, we study few models falling into this category and describe how observables depend on the strength of the coupling. We extend recent work on the subject by taking into account also the effects of the perturbations of the scalar field and showing their relative importance on the evolution of the mass function. By working in the framework of the spherical collapse model, we show that perturbations of the scalar field have a limited impact on the growth factor (for small coupling constant) and on the mass function with respect to the case where perturbations are neglected.
Antibiofilm Activity of the Marine Bacterium Pseudoalteromonas sp. Strain 3J6▿
Dheilly, Alexandra; Soum-Soutéra, Emmanuelle; Klein, Géraldine L.; Bazire, Alexis; Compère, Chantal; Haras, Dominique; Dufour, Alain
2010-01-01
Biofilm formation results in medical threats or economic losses and is therefore a major concern in a variety of domains. In two-species biofilms of marine bacteria grown under dynamic conditions, Pseudoalteromonas sp. strain 3J6 formed mixed biofilms with Bacillus sp. strain 4J6 but was largely predominant over Paracoccus sp. strain 4M6 and Vibrio sp. strain D01. The supernatant of Pseudoalteromonas sp. 3J6 liquid culture (SN3J6) was devoid of antibacterial activity against free-living Paracoccus sp. 4M6 and Vibrio sp. D01 cells, but it impaired their ability to grow as single-species biofilms and led to higher percentages of nonviable cells in 48-h biofilms. Antibiofilm molecules of SN3J6 were able to coat the glass surfaces used to grow biofilms and reduced bacterial attachment about 2-fold, which might partly explain the biofilm formation defect but not the loss of cell viability. SN3J6 had a wide spectrum of activity since it affected all Gram-negative marine strains tested except other Pseudoalteromonas strains. Biofilm biovolumes of the sensitive strains were reduced 3- to 530-fold, and the percentages of nonviable cells were increased 3- to 225-fold. Interestingly, SN3J6 also impaired biofilm formation by three strains belonging to the human-pathogenic species Pseudomonas aeruginosa, Salmonella enterica, and Escherichia coli. Such an antibiofilm activity is original and opens up a variety of applications for Pseudoalteromonas sp. 3J6 and/or its active exoproducts in biofilm prevention strategies. PMID:20363799
Scalar and Pseudoscalar Glueballs
NASA Astrophysics Data System (ADS)
Cheng, Hai-Yang
We employ two simple and robust results to constrain the mixing matrix of the isosinglet scalar mesons f0(1710), f0(1500), f0(1370): one is the approximate SU(3) symmetry empirically observed in the scalar sector above 1 GeV and confirmed by lattice QCD, and the other is the scalar glueball mass at 1710 MeV in the quenched approximation. In the SU(3) symmetry limit, f0(1500) becomes a pure SU(3) octet and is degenerate with a0(1450), while f0(1370) is mainly an SU(3) singlet with a slight mixing with the scalar glueball which is the primary component of f0(1710). These features remain essentially unchanged even when SU(3) breaking is taken into account. The observed enhancement of ωf0(1710) production over ɸf0(1710) in hadronic J/ψ decays and the copious f0(1710) production in radiative J/ψ decays lend further support to the prominent glueball nature of f0(1710). We deduce the mass of the pseudoscalar glueball G from an η-η‧-G mixing formalism based on the anomalous Ward identity for transition matrix elements. With the inputs from the recent KLOE experiment, we find a solution for the pseudoscalar glueball mass around (1.4±0.1) GeV, which is fairly insensitive to a range of inputs with or without Okubo-Zweig-Iizuka-rule violating effects. This affirms that η(1405), having a large production rate in the radiative J/ψ decay and not seen in γγ reactions, is indeed a leading candidate for the pseudoscalar glueball. It is much lower than the results from quenched lattice QCD (> 2.0 GeV) due to the dynamic fermion effect. It is thus urgent to have a full QCD lattice calculation of pseudoscalar glueball masses.
NASA Astrophysics Data System (ADS)
Egorov, A. I.; Kashargin, P. E.; Sushkov, Sergey V.
2016-09-01
In 1921 Bach and Weyl derived the method of superposition to construct new axially symmetric vacuum solutions of general relativity. In this paper we extend the Bach–Weyl approach to non-vacuum configurations with massless scalar fields. Considering a phantom scalar field with the negative kinetic energy, we construct a multi-wormhole solution describing an axially symmetric superposition of N wormholes. The solution found is static, everywhere regular and has no event horizons. These features drastically tell the multi-wormhole configuration from other axially symmetric vacuum solutions which inevitably contain gravitationally inert singular structures, such as ‘struts’ and ‘membranes’, that keep the two bodies apart making a stable configuration. However, the multi-wormholes are static without any singular struts. Instead, the stationarity of the multi-wormhole configuration is provided by the phantom scalar field with the negative kinetic energy. Anther unusual property is that the multi-wormhole spacetime has a complicated topological structure. Namely, in the spacetime there exist 2 N asymptotically flat regions connected by throats.
NASA Astrophysics Data System (ADS)
Egorov, A. I.; Kashargin, P. E.; Sushkov, Sergey V.
2016-09-01
In 1921 Bach and Weyl derived the method of superposition to construct new axially symmetric vacuum solutions of general relativity. In this paper we extend the Bach-Weyl approach to non-vacuum configurations with massless scalar fields. Considering a phantom scalar field with the negative kinetic energy, we construct a multi-wormhole solution describing an axially symmetric superposition of N wormholes. The solution found is static, everywhere regular and has no event horizons. These features drastically tell the multi-wormhole configuration from other axially symmetric vacuum solutions which inevitably contain gravitationally inert singular structures, such as ‘struts’ and ‘membranes’, that keep the two bodies apart making a stable configuration. However, the multi-wormholes are static without any singular struts. Instead, the stationarity of the multi-wormhole configuration is provided by the phantom scalar field with the negative kinetic energy. Anther unusual property is that the multi-wormhole spacetime has a complicated topological structure. Namely, in the spacetime there exist 2 N asymptotically flat regions connected by throats.
Scalar perturbations in conformal rolling scenario with intermediate stage
Libanov, M.; Ramazanov, S.; Rubakov, V. E-mail: sabir@ms2.inr.ac.ru
2011-06-01
Scalar cosmological perturbations with nearly flat power spectrum may originate from perturbations of the phase of a scalar field conformally coupled to gravity and rolling down negative quartic potential. We consider a version of this scenario whose specific property is a long intermediate stage between the end of conformal rolling and horizon exit of the phase perturbations. Such a stage is natural, e.g., in cosmologies with ekpyrosis or genesis. Its existence results in small negative scalar tilt, statistical anisotropy of all even multipoles starting from quardupole of general structure (in contrast to the usually discussed single quadrupole of special type) and non-Gaussianity of a peculiar form.
Gauge invariant perturbations of scalar-tensor cosmologies: The vacuum case
Carloni, Sante; Dunsby, Peter K. S.; Rubano, Claudio
2006-12-15
The covariant gauge-invariant perturbation theory of scalar cosmological perturbations is developed for a general scalar-tensor Friedmann-Lemaitre-Robertson-Walker cosmology in a vacuum. The perturbation equations are then solved exactly in the long wavelength limit for a specific coupling, potential, and background. Differences with the minimally coupled case are briefly discussed.
Kerr black holes with scalar hair.
Herdeiro, Carlos A R; Radu, Eugen
2014-06-01
We present a family of solutions of Einstein's gravity minimally coupled to a complex, massive scalar field, describing asymptotically flat, spinning black holes with scalar hair and a regular horizon. These hairy black holes (HBHs) are supported by rotation and have no static limit. Besides mass M and angular momentum J, they carry a conserved, continuous Noether charge Q measuring the scalar hair. HBHs branch off from the Kerr metric at the threshold of the superradiant instability and reduce to spinning boson stars in the limit of vanishing horizon area. They overlap with Kerr black holes for a set of (M, J) values. A single Killing vector field preserves the solutions, tangent to the null geodesic generators of the event horizon. HBHs can exhibit sharp physical differences when compared to the Kerr solution, such as J/M^{2}>1, a quadrupole moment larger than J^{2}/M, and a larger orbital angular velocity at the innermost stable circular orbit. Families of HBHs connected to the Kerr geometry should exist in scalar (and other) models with more general self-interactions.
Cosmological simulations: the role of scalar fields
Rodriguez-Meza, M. A.
2009-04-20
We present numerical N-body simulation studies of large-scale structure formation. The main purpose of these studies is to analyze the several models of dark matter and the role they played in the process of large-scale structure formation. We analyze the standard and more successful case, i.e., the cold dark matter with cosmological constant ({lambda}CDM). We compare the results of this model with the corresponding results of other alternative models, in particular, the models that can be built from the Newtonian limit of alternative theories of gravity like scalar-tensor theories. An specific model is the one that considers that the scalar field is non-minimally coupled to the Ricci scalar in the Einstein-Hilbert Lagrangian that gives, in the Newtonian limit an effective gravitational force that is given by two contributions: the standard Newtonian potential plus a Yukawa potential that comes from a massive scalar field. Comparisons of the models are done by analyzing the snapshots of the N-body system at z = 0 for several values of the SF parameters.
All one-loop scalar vertices in the effective potential approach
NASA Astrophysics Data System (ADS)
Camargo-Molina, José Eliel; Morais, António P.; Pasechnik, Roman; Sampaio, Marco O. P.; Wessén, Jonas
2016-08-01
Using the one-loop Coleman-Weinberg effective potential, we derive a general analytic expression for all the derivatives of the effective potential with respect to any number of classical scalar fields. The result is valid for a renormalisable theory in four dimensions with any number of scalars, fermions or gauge bosons. This result corresponds to the zero-external momentum contribution to a general one-loop diagram with N scalar external legs. We illustrate the use of the general result in two simple scalar singlet extensions of the Standard Model, to obtain the dominant contributions to the triple couplings of light scalar particles under the zero external momentum approximation.
Frisch, E.; Johnson, C.G.
1962-05-15
A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)
Scalar meson spectroscopy with lattice staggered fermions
Bernard, Claude; DeTar, Carleton; Fu Ziwen; Prelovsek, Sasa
2007-11-01
With sufficiently light up and down quarks the isovector (a{sub 0}) and isosinglet (f{sub 0}) scalar meson propagators are dominated at large distance by two-meson states. In the staggered-fermion formulation of lattice quantum chromodynamics, taste-symmetry breaking causes a proliferation of two-meson states that further complicates the analysis of these channels. Many of them are unphysical artifacts of the lattice approximation. They are expected to disappear in the continuum limit. The staggered-fermion fourth-root procedure has its purported counterpart in rooted staggered chiral perturbation theory (rS{chi}PT). Fortunately, the rooted theory provides a strict framework that permits the analysis of scalar meson correlators in terms of only a small number of low-energy couplings. Thus the analysis of the point-to-point scalar meson correlators in this context gives a useful consistency check of the fourth-root procedure and its proposed chiral realization. Through numerical simulation we have measured correlators for both the a{sub 0} and f{sub 0} channels in the 'Asqtad' improved staggered-fermion formulation in a lattice ensemble with lattice spacing a=0.12 fm. We analyze those correlators in the context of rS{chi}PT and obtain values of the low-energy chiral couplings that are reasonably consistent with previous determinations.
Constructing scalar-photon three point vertex in massless quenched scalar QED
NASA Astrophysics Data System (ADS)
Fernández-Rangel, L. Albino; Bashir, Adnan; Gutiérrez-Guerrero, L. X.; Concha-Sánchez, Y.
2016-03-01
Nonperturbative studies of Schwinger-Dyson equations require their infinite, coupled tower to be truncated in order to reduce them to a practically solvable set. In this connection, a physically acceptable Ansatz for the three point vertex is the most favorite choice. Scalar quantum electrodynamics (sQED) provides a simple and neat platform to address this problem. The most general form of the three point scalar-photon vertex can be expressed in terms of only two independent form factors, a longitudinal and a transverse one. Ball and Chiu have demonstrated that the longitudinal vertex is fixed by requiring the Ward-Fradkin-Green-Takahashi identity while the transverse vertex remains undetermined. In massless quenched sQED, we construct the transverse part of the nonperturbative scalar-photon vertex. This construction (i) ensures multiplicative renormalizability of the scalar propagator in keeping with the Landau-Khalatnikov-Fradkin transformations, (ii) has the same transformation properties as the bare vertex under charge conjugation, parity and time reversal, (iii) has no kinematic singularities and (iv) reproduces the one-loop asymptotic result in the weak coupling regime of the theory.
Fermion-scalar conformal blocks
Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran
2016-04-13
In this study, we compute the conformal blocks associated with scalar-scalar-fermionfermion 4-point functions in 3D CFTs. Together with the known scalar conformal blocks, our result completes the task of determining the so-called ‘seed blocks’ in three dimensions. In addition, conformal blocks associated with 4-point functions of operators with arbitrary spins can now be determined from these seed blocks by using known differential operators.
Anisotropic inflation from charged scalar fields
Emami, Razieh; Firouzjahi, Hassan; Movahed, S.M. Sadegh; Zarei, Moslem E-mail: firouz@ipm.ir E-mail: m.zarei@cc.iut.ac.ir
2011-02-01
We consider models of inflation with U(1) gauge fields and charged scalar fields including symmetry breaking potential, chaotic inflation and hybrid inflation. We show that there exist attractor solutions where the anisotropies produced during inflation becomes comparable to the slow-roll parameters. In the models where the inflaton field is a charged scalar field the gauge field becomes highly oscillatory at the end of inflation ending inflation quickly. Furthermore, in charged hybrid inflation the onset of waterfall phase transition at the end of inflation is affected significantly by the evolution of the background gauge field. Rapid oscillations of the gauge field and its coupling to inflaton can have interesting effects on preheating and non-Gaussianities.
Detecting chameleons: The astronomical polarization produced by chameleonlike scalar fields
Burrage, Clare; Davis, Anne-Christine; Shaw, Douglas J.
2009-02-15
We show that a coupling between chameleonlike scalar fields and photons induces linear and circular polarization in the light from astrophysical sources. In this context chameleonlike scalar fields include those of the Olive-Pospelov (OP) model, which describes a varying fine structure constant. We determine the form of this polarization numerically and give analytic expressions in two useful limits. By comparing the predicted signal with current observations we are able to improve the constraints on the chameleon-photon coupling and the coupling in the OP model by over 2 orders of magnitude. It is argued that, if observed, the distinctive form of the chameleon induced circular polarization would represent a smoking gun for the presence of a chameleon. We also report a tentative statistical detection of a chameleonlike scalar field from observations of starlight polarization in our galaxy.
Outburst of CV ROTSE3 J031031.4+431115.0
NASA Astrophysics Data System (ADS)
Dhungana, G.; Ferrante, F. V.; Staten, R.; Kehoe, R.
2015-02-01
Further to ATel#1272, we report observations of an outburst of the U Geminorum-type CV ROTSE3 J031031.4+431115.0 in unfiltered CCD images taken by the 0.45 m ROTSE-IIIb telescope at McDonald Observatory, Texas.
Scalar field in the anisotropic universe
Kim, Hyeong-Chan; Minamitsuji, Masato
2010-04-15
We discuss the primordial spectrum of a massless and minimally coupled scalar field, produced during the initial anisotropic epoch before the onset of inflation. We consider two models of the anisotropic cosmology, the (planar) Kasner-de Sitter solution (Bianchi I) and the Taub-NUT-de Sitter solution (Bianchi IX), where the 3-space geometry is initially anisotropic, followed by the de Sitter phase due to the presence of a positive cosmological constant. We discuss the behavior of a quantized, massless and minimally coupled scalar field in the anisotropic stage. This scalar field is not the inflaton and hence does not contribute to the background dynamics. We focus on the quantization procedure and evolution in the preinflationary anisotropic background. Also, in this paper for simplicity the metric perturbations are not taken into account. The initial condition is set by the requirement that the scalar field is initially in an adiabatic state. Usually, in a quantum harmonic oscillator system, an adiabatic process implies the one where the potential changes slowly enough compared to its size, and the time evolution can be obtained from the zeroth order WKB approximation. In our case, such a vacuum state exists only for limited solutions of the anisotropic universe, whose spacetime structure is regular in the initial times. In this paper, we call our adiabatic vacuum state the anisotropic vacuum. In the Kasner-de Sitter model, for one branch of planar solutions there is an anisotropic vacuum unless k{sub 3{ne}}0, where k{sub 3} is the comoving momentum along the third direction, while in the other branch there is no anisotropic vacuum state. In the first branch, for the moderate modes, k{sub 3{approx}}k, where k is the total comoving momentum, the scalar power spectrum has an oscillatory behavior and its direction dependence is suppressed. For the planar modes, k{sub 3}<
Morphine analgesic tolerance in 129P3/J and 129S6/SvEv mice
Bryant, Camron D.; Roberts, Kristofer W.; Byun, Janet S.; Fanselow, Michael S.; Evans, Christopher J.
2007-01-01
Morphine analgesic tolerance is heritable in both humans and rodents, with some individuals and strains exhibiting little and others exhibiting robust tolerance. 129S6/SvEv and 129P3/J mice reportedly do not demonstrate tolerance to morphine analgesia. Using our laboratory's standard morphine tolerance regimen and a between-subjects design, tolerance developed in the hot plate and tail withdrawal assays as indicated by a change in analgesic efficacy following a morphine challenge dose. Furthermore, the non-competitive NMDA receptor antagonist MK-801 (dizocilipine) blocked morphine tolerance in 129S6/SvEv and CD-1 mice in the hot plate assay. As previously reported, when a within-subjects design and cumulative dosing was employed, no tolerance was observed in the 129P3/J strain. However, using the same morphine regimen and a between-subjects design, comparable tolerance developed between 129P3/J and C57BL/6J strains following a single challenge dose of morphine. Spontaneous hyperalgesia was observed in the tail withdrawal assay following chronic morphine in C57BL/6J, but not 129P3/J mice. Additionally, morphine-tolerant C57BL/6J mice, but not 129P3/J mice, exhibited a large increase in the frequency of tail flicks during the first second following the baseline nociceptive response which may facilitate detection of the response during the tolerant state. We conclude that the method of tolerance assessment affects the ability to detect tolerance and thus, may affect the degree and pattern of heritability of this trait and this could have implications for gene mapping studies. PMID:17196637
Fermion damping in a fermion-scalar plasma
Boyanovsky, D.; Wang, S.; de Vega, H.J.; Lee, D.; Ng, Y.J.
1999-05-01
In this article we study the dynamics of fermions in a fermion-scalar plasma. We begin by obtaining the effective in-medium Dirac equation in real time which is fully renormalized and causal and leads to the initial value problem. For a heavy scalar we find the novel result that the {ital decay} of the scalar into fermion pairs in the medium leads to damping of the fermionic excitations and their in-medium propagation as quasiparticles. That is, the fermions acquire a width due to the decay of the heavier scalar in the medium. We find the damping rate to lowest order in the Yukawa coupling for arbitrary values of scalar and fermion masses, temperature and fermion momentum. An all-order expression for the damping rate in terms of the exact quasiparticle wave functions is established. A kinetic Boltzmann approach to the relaxation of the fermionic distribution function confirms the damping of fermionic excitations as a consequence of the induced decay of heavy scalars in the medium. A linearization of the Boltzmann equation near equilibrium clearly displays the relationship between the damping rate of fermionic mean fields and the fermion interaction rate to lowest order in the Yukawa coupling directly in real time. {copyright} {ital 1999} {ital The American Physical Society}
General analytic solutions of scalar field cosmology with arbitrary potential
NASA Astrophysics Data System (ADS)
Dimakis, N.; Karagiorgos, A.; Zampeli, Adamantia; Paliathanasis, Andronikos; Christodoulakis, T.; Terzis, Petros A.
2016-06-01
We present the solution space for the case of a minimally coupled scalar field with arbitrary potential in a Friedmann-Lemaître-Robertson-Walker metric. This is made possible due to the existence of a nonlocal integral of motion corresponding to the conformal Killing field of the two-dimensional minisuperspace metric. Both the spatially flat and nonflat cases are studied first in the presence of only the scalar field and subsequently with the addition of noninteracting perfect fluids. It is verified that this addition does not change the general form of the solution, but only the particular expressions of the scalar field and the potential. The results are applied in the case of parametric dark energy models where we derive the scalar field equivalence solution for some proposed models in the literature.
Composite (pseudo) scalar contributions to muon g - 2
NASA Astrophysics Data System (ADS)
Hong, Deog Ki; Kim, Du Hwan
2016-07-01
We have calculated the composite (pseudo) scalar contributions to the anomalous magnetic moment of muons in models of walking technicolor. By the axial or scale anomaly the light scalars such as techni-dilaton, techni-pions or techni-eta have anomalous couplings to two-photons, which make them natural candidates for the recent 750 GeV resonance excess, observed at LHC. Due to the anomalous couplings, their contributions to muon (g - 2) are less suppressed and might explain the current deviation in muon (g - 2) measurements from theory.
On the stability and causality of scalar-vector theories
Fleury, Pierre; Pitrou, Cyril; Uzan, Jean-Philippe; Almeida, Juan P. Beltrán E-mail: juanpbeltran@uan.edu.co E-mail: uzan@iap.fr
2014-11-01
Various extensions of standard inflationary models have been proposed recently by adding vector fields. Because they are generally motivated by large-scale anomalies, and the possibility of statistical anisotropy of primordial fluctuations, such models require to introduce non-standard couplings between vector fields on the one hand, and either gravity or scalar fields on the other hand. In this article, we study models involving a vector field coupled to a scalar field. We derive restrictive necessary conditions for these models to be both stable (Hamiltonian bounded by below) and causal (hyperbolic equations of motion)
Gravity quantized: Loop quantum gravity with a scalar field
Domagala, Marcin; Kaminski, Wojciech; Giesel, Kristina; Lewandowski, Jerzy
2010-11-15
...''but we do not have quantum gravity.'' This phrase is often used when analysis of a physical problem enters the regime in which quantum gravity effects should be taken into account. In fact, there are several models of the gravitational field coupled to (scalar) fields for which the quantization procedure can be completed using loop quantum gravity techniques. The model we present in this paper consists of the gravitational field coupled to a scalar field. The result has similar structure to the loop quantum cosmology models, except that it involves all the local degrees of freedom of the gravitational field because no symmetry reduction has been performed at the classical level.
Scalar-tensor theories with an external scalar
NASA Astrophysics Data System (ADS)
Chauvineau, Bertrand; Rodrigues, Davi C.; Fabris, Júlio C.
2016-06-01
Scalar-tensor (ST) gravity is considered in the case where the scalar is an external field. We show that general relativity (GR) and usual ST gravity are particular cases of the external scalar-tensor (EST) gravity. It is shown with a particular cosmological example that it is possible to join a part of a GR solution to a part of a ST one such that the complete solution neither belongs to GR nor to ST, but fully satisfies the EST field equations. We argue that external fields may effectively work as a type of screening mechanism for ST theories.
Higgs and gravitational scalar fields together induce Weyl gauge
NASA Astrophysics Data System (ADS)
Scholz, Erhard
2015-02-01
A common biquadratic potential for the Higgs field and an additional scalar field , non minimally coupled to gravity, is considered in a locally scale symmetric approach to standard model fields in curved spacetime. A common ground state of the two scalar fields exists and couples both fields to gravity, more precisely to Weyl geometric scalar curvature . In Einstein gauge (, often called "Einstein frame"), also is scaled to a constant. This condition makes perfect sense, even in the general case, in the Weyl geometric approach. There it has been called Weyl gauge, because it was first considered by Weyl in the different context of his original scale geometric theory of gravity of 1918. Now it may get new meaning as a combined effect of electroweak theory and gravity, and their common influence on atomic frequencies.
Scalar mode propagation in modified gravity with a scalar field
De Felice, Antonio; Suyama, Teruaki
2009-10-15
We study the propagation of the scalar modes around a Friedmann-Lemaitre-Robertson-Walker universe for general modifications of gravity in the presence of a real scalar field. In general, there will be two propagating scalar perturbation fields, which will have in total 4 degrees of freedom. Two of these degrees will have a superluminal propagation - with k-dependent speed of propagation - whereas the other two will have the speed of light. Therefore, the scalar degrees of freedom do not modify the general feature of modified gravity models: the appearance of modes whose frequency depends on the second power of the modulus of the wave vector. Constraints are given and special cases are discussed.
Chiba, Takeshi; Yamaguchi, Masahide E-mail: gucci@phys.aoyama.ac.jp
2009-01-15
As an extension of our previous study, we derive slow-roll conditions for multiple scalar fields which are non-minimally coupled with gravity and for generalized gravity theories of the form f({phi}, R). We provide simple formulae of the spectral indices of scalar/tensor perturbations in terms of the slow-roll parameters.
Scalar cosmological perturbations
NASA Astrophysics Data System (ADS)
Uggla, Claes; Wainwright, John
2012-05-01
Scalar perturbations of Friedmann-Lemaitre cosmologies can be analyzed in a variety of ways using Einstein’s field equations, the Ricci and Bianchi identities, or the conservation equations for the stress-energy tensor, and possibly introducing a timelike reference congruence. The common ground is the use of gauge invariants derived from the metric tensor, the stress-energy tensor, or from vectors associated with a reference congruence, as basic variables. Although there is a complication in that there is no unique choice of gauge invariants, we will show that this can be used to advantage. With this in mind our first goal is to present an efficient way of constructing dimensionless gauge invariants associated with the tensors that are involved, and of determining their inter-relationships. Our second goal is to give a unified treatment of the various ways of writing the governing equations in dimensionless form using gauge-invariant variables, showing how simplicity can be achieved by a suitable choice of variables and normalization factors. Our third goal is to elucidate the connection between the metric-based approach and the so-called 1 + 3 gauge-invariant approach to cosmological perturbations. We restrict our considerations to linear perturbations, but our intent is to set the stage for the extension to second-order perturbations.
Impact of other scalar fields on oscillons after hilltop inflation
NASA Astrophysics Data System (ADS)
Antusch, Stefan; Orani, Stefano
2016-03-01
Oscillons are spatially localized and relatively stable field fluctuations which can form after inflation under suitable conditions. In order to reheat the universe, the fields which dominate the energy density after inflation have to couple to other degrees of freedom and finally produce the matter particles present in the universe today. In this study, we use lattice simulations in 2+1 dimensions to investigate how such couplings can affect the formation and stability of oscillons. We focus on models of hilltop inflation, where we have recently shown that hill crossing oscillons generically form, and consider the coupling to an additional scalar field which, depending on the value of the coupling parameter, can get resonantly enhanced from the inhomogeneous inflaton field. We find that three cases are realized: without a parametric resonance, the additional scalar field has no effects on the oscillons. For a fast and strong parametric resonance of the other scalar field, oscillons are strongly suppressed. For a delayed parametric resonance, on the other hand, the oscillons get imprinted on the other scalar field and their stability is even enhanced compared to the single-field oscillons.
Symmetry inheritance of scalar fields
NASA Astrophysics Data System (ADS)
Smolić, Ivica
2015-07-01
Matter fields do not necessarily have to share the symmetries with the spacetime they live in. When this happens, we speak of the symmetry inheritance of fields. In this paper we classify the obstructions of symmetry inheritance by the scalar fields, both real and complex, and look more closely at the special cases of stationary and axially symmetric spacetimes. Since the symmetry noninheritance is present in the scalar fields of boson stars and may enable the existence of the black hole scalar hair, our results narrow the possible classes of such solutions. Finally, we define and analyse the symmetry noninheritance contributions to the Komar mass and angular momentum of the black hole scalar hair.
Scalar graviton as dark matter
Pirogov, Yu. F.
2015-06-15
The basics of the theory of unimodular bimode gravity built on the principles of unimodular gauge invariance/relativity and general covariance are exposed. Besides the massless tensor graviton of General Relativity, the theory includes an (almost) massless scalar graviton treated as the gravitational dark matter. A spherically symmetric vacuum solution describing the coherent scalar-graviton field for the soft-core dark halos, with the asymptotically flat rotation curves, is demonstrated as an example.
Tensor-multi-scalar theories: relativistic stars and 3 + 1 decomposition
NASA Astrophysics Data System (ADS)
Horbatsch, Michael; Silva, Hector O.; Gerosa, Davide; Pani, Paolo; Berti, Emanuele; Gualtieri, Leonardo; Sperhake, Ulrich
2015-10-01
Gravitational theories with multiple scalar fields coupled to the metric and each other—a natural extension of the well studied single-scalar-tensor theories—are interesting phenomenological frameworks to describe deviations from general relativity in the strong-field regime. In these theories, the N-tuple of scalar fields takes values in a coordinate patch of an N-dimensional Riemannian target-space manifold whose properties are poorly constrained by weak-field observations. Here we introduce for simplicity a non-trivial model with two scalar fields and a maximally symmetric target-space manifold. Within this model we present a preliminary investigation of spontaneous scalarization for relativistic, perfect fluid stellar models in spherical symmetry. We find that the scalarization threshold is determined by the eigenvalues of a symmetric scalar-matter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the target-space curvature radius. In preparation for numerical relativity simulations, we also write down the 3 + 1 decomposition of the field equations for generic tensor-multi-scalar theories.
Scalar field cosmology via non-local integrals of motion
NASA Astrophysics Data System (ADS)
Dimakis, N.
2016-08-01
In re-parametrization invariant systems, such as mini-superspace Lagrangians, the existence of constraints can lead to the emergence of additional non-local integrals of motion defined in phase space. In the case of a FLRW flat/non-flat space-time minimally coupled to an arbitrary scalar field, we manage to use such conserved quantities to completely integrate the system of equations of motion. This is achieved without constraining the potential in any way. Thus, obtaining the most general solution that encompasses all possible cosmological scenarios which can be based on the existence of a scalar field.
Very light cosmological scalar fields from a tiny cosmological constant
Calmet, Xavier
2007-10-15
I discuss a mechanism which generates a mass term for a scalar field in an expanding universe. The mass of this field turns out to be generated by the cosmological constant and can be naturally small if protected by a conformal symmetry which is, however, broken in the gravitational sector. The mass is comparable today to the Hubble time. This scalar field could thus impact our Universe today and, for example, be at the origin of a time variation of the couplings and masses of the parameters of the standard model.
Braneworld inflation with a complex scalar field from Planck 2015
NASA Astrophysics Data System (ADS)
Mounzi, Z.; Ferricha-Alami, M.; Chakir, H.; Bennai, M.
2016-06-01
We study an inflationary model with a single complex scalar field in the framework of braneworld Randall-Sundrum model type 2. From the scalar curvature perturbation constrained by the recent observation values, and for specific choice of parameters, we can reduce the values of the coupling constant to take the natural values, and we found that the phase theta θ of the inflation field can take the narrow interval. We have also derived all known inflationary parameters (ns, r and dns/d ln (k)), which are widely consistent with the recent Planck data for a suitable choice of brane tension value λ.
Color Sextet Scalars in Early LHC Experiments
Berger, Edmond L.; Cao Qinghong; Chen, Chuan-Ren; Shaughnessy, Gabe; Zhang Hao
2010-10-29
We explore the potential for discovery of an exotic color sextet scalar in same-sign top quark pair production in early running at the LHC. We present the first phenomenological analysis at colliders of color sextet scalars with full top quark spin correlations included. We demonstrate that one can measure the scalar mass, the top quark polarization, and confirm the scalar resonance with 1 fb{sup -1} of integrated luminosity. The top quark polarization can distinguish gauge triplet and singlet scalars.
Decay of massive scalar hair in the background of a dilaton gravity black hole
Rogatko, Marek
2007-05-15
We investigate analytically both the intermediate and late-time behavior of the massive scalar field in the background of the static spherically symmetric black hole solution in dilaton gravity with an arbitrary coupling constant. The intermediate asymptotic behavior of the scalar field depends on the field's parameter mass as well as the multiple number l. On its turn, the late-time behavior has the power-law decay rate independent on the coupling constant in the theory under consideration.
NASA Astrophysics Data System (ADS)
Berberian, John Edwin
1999-01-01
matching interface, and scalar-tensor coupling function) to which they can be joined. The screening procedure is independent of the particular spherically symmetric coordinate system in which the candidate solution is expressed. Scalar field coordinates are also used to examine succinctly the problem of perturbative expansion of scalar-tensor vacuum solutions about the vacuum solution of general relativity. All solutions are shown to fall into three categories: perturbation about the Schwarzschild solution, perturbation about a two dimensional metric, and non-perturbative solutions. In the process of classification, the Birkhoff theorem for vacuum solutions of general relativity is explicitly shown. In the final section, future directions are discussed. They are: exploiting Lie-theoretic methods to find new solution families which may lead to an explicit matched solution, searching for the Choptuik critical solution, and application of scalar field coordinates to relativistic perfect fluids (T = 0) in order to find exact solutions. Finally, a re-examination of classical gravitational collapse of a scalar field is advocated using matched solutions.
Big bang nucleosynthesis constraints on scalar-tensor theories of gravity
Coc, Alain; Olive, Keith A.; Uzan, Jean-Philippe; Vangioni, Elisabeth
2006-04-15
We investigate Big bang nucleosynthesis (BBN) in scalar-tensor theories of gravity with arbitrary matter couplings and self-interaction potentials. We first consider the case of a massless dilaton with a quadratic coupling to matter. We perform a full numerical integration of the evolution of the scalar field and compute the resulting light element abundances. We demonstrate in detail the importance of particle mass thresholds on the evolution of the scalar field in a radiation dominated universe. We also consider the simplest extension of this model including a cosmological constant in either the Jordan or Einstein frame.
Asymptotic cosmological regimes in scalar-torsion gravity with a perfect fluid
NASA Astrophysics Data System (ADS)
Skugoreva, Maria A.; Toporensky, Alexey V.
2016-06-01
We consider the cosmological dynamics of a nonminimally coupled scalar field in scalar-torsion gravity in the presence of hydrodynamical matter. The potential of the scalar field have been chosen as power law with negative index, this type of potentials is usually used in quintessence scenarios. We identify several asymptotic regimes, including de Sitter, kinetic dominance, kinetic tracker, and tracker solutions and study the conditions for their existence and stability. We show that for each combination of coupling constant and potential power index one of the regimes studied in the present paper is stable to the future.
Dynamical Characteristics of a Non-canonical Scalar-Torsion Model of Dark Energy
NASA Astrophysics Data System (ADS)
Banijamali, A.; Ghasemi, E.
2016-08-01
In this paper, we analyze the phase-space of a model of dark energy in which a non-canonical scalar field (tachyon) non-minimally coupled to torsion scalar in the framework of teleparallelism. Scalar field potential and non-minimal coupling function are chosen as V( ϕ) = V 0 ϕ n and f( ϕ) = ϕ N , respectively. We obtain a critical point that behaves like a stable or saddle point depending on the values of N and n. Additionally we find an unstable critical line. We have shown such a behavior of critical points using numerical computations and phase-space trajectories explicitly.
Screening of scalar fields in Dirac-Born-Infeld theory
NASA Astrophysics Data System (ADS)
Burrage, Clare; Khoury, Justin
2014-07-01
We study a new screening mechanism which is present in Dirac-Born-Infeld (DBI)-like theories. A scalar field with a DBI-like Lagrangian is minimally coupled to matter. In the vicinity of sufficiently dense sources, nonlinearities in the scalar dominate and result in an approximately constant acceleration on a test particle, thereby suppressing the scalar force relative to gravity. Unlike generic P(X) or chameleon theories, screening happens within the regime of validity of the effective field theory thanks to the DBI symmetry. We derive an exact form for the field profile around multiple sources and determine the constraints on the theory parameters from tests of gravity. Perturbations around the spherically-symmetric background propagate superluminally, but we argue for a chronology protection analogous to Galileons. This is the first example of a screening mechanism for which quantum corrections to the theory are under control and exact solutions to cosmological N-body problems can be found.
Thick branes from self-gravitating scalar fields
Novikov, Oleg O.; Andrianov, Vladimir A.; Andrianov, Alexander A.
2014-07-23
The formation of a domain wall ('thick brane') induced by scalar matter dynamics and triggered by a thin brane defect is considered in noncompact five-dimensional space-time with warped AdS type geometry. The scalar matter is composed of two fields with softly broken O(2) symmetry and minimal coupling to gravity. The nonperturbative effects in the invariant mass spectrum of light localized scalar states are investigated for different values of the tension of the thin brane defect. Especially interesting is the case of the thin brane with negative tension when the singular barriers form a potential well with two infinitely tall walls and the discrete spectrum of localized states arises completely isolated from the bulk.
Color sextet scalars at the CERN Large Hadron Collider
Chen, C.-R.; Klemm, William; Rentala, Vikram; Wang Kai
2009-03-01
Taking a phenomenological approach, we study a color sextet scalar at the LHC. We focus on the QCD production of a color sextet pair {phi}{sub 6}{phi}{sub 6} through gg fusion and qq annihilation. Its unique coupling to {psi}{sup c}{psi} allows the color sextet scalar to decay into same-sign diquark states, such as {phi}{sub 6}{yields}tt/tt*. We propose a new reconstruction in the multijet plus same-sign dilepton with missing transverse energy samples (bb+l{sup {+-}}l{sup {+-}}+Ee{sub T}+Nj, N{>=}6) to search for on-shell tttt final states from sextet scalar pair production. Thanks to the large QCD production, the search covers the sextet mass range up to 1 TeV for 100 fb{sup -1} integrated luminosity.
Scalar field dark matter and the Higgs field
NASA Astrophysics Data System (ADS)
Bertolami, O.; Cosme, Catarina; Rosa, João G.
2016-08-01
We discuss the possibility that dark matter corresponds to an oscillating scalar field coupled to the Higgs boson. We argue that the initial field amplitude should generically be of the order of the Hubble parameter during inflation, as a result of its quasi-de Sitter fluctuations. This implies that such a field may account for the present dark matter abundance for masses in the range 10-6-10-4eV, if the tensor-to-scalar ratio is within the range of planned CMB experiments. We show that such mass values can naturally be obtained through either Planck-suppressed non-renormalizable interactions with the Higgs boson or, alternatively, through renormalizable interactions within the Randall-Sundrum scenario, where the dark matter scalar resides in the bulk of the warped extra-dimension and the Higgs is confined to the infrared brane.
An inflationary model with small scalar and large tensor nongaussianities
Cook, Jessica L.; Sorbo, Lorenzo E-mail: sorbo@physics.umass.edu
2013-11-01
We study a model of inflation where the scalar perturbations are almost gaussian while there is sizable (equilateral) nongaussianity in the tensor sector. In this model, a rolling pseudoscalar gravitationally coupled to the inflaton amplifies the vacuum fluctuations of a vector field. The vector sources both scalar and tensor metric perturbations. Both kinds of perturbations are nongaussian, but, due to helicity conservation, the tensors have a larger amplitude, so that nongaussianity in the scalar perturbations is negligible. Moreover, the tensors produced this way are chiral. We study, in the flat sky approximation, how constraints on tensor nongaussianities affect the detectability of parity violation in the Cosmic Microwave Background. We expect the model to feature interesting patterns on nongaussianities in the polarization spectra of the CMB.
Astrophysical effects of scalar dark matter miniclusters
NASA Astrophysics Data System (ADS)
Zurek, Kathryn M.; Hogan, Craig J.; Quinn, Thomas R.
2007-02-01
We model the formation, evolution and astrophysical effects of dark compact Scalar Miniclusters (“ScaMs”). These objects arise when a scalar field, with an axion-like or Higgs-like potential, undergoes a second-order phase transition below the QCD scale. Such a scalar field may couple too weakly to the standard model to be detectable directly through particle interactions, but may still be detectable by gravitational effects, such as lensing and baryon accretion by large, gravitationally bound miniclusters. The masses of these objects are shown to be constrained by the Lyα power spectrum to be less than ˜104M⊙, but they may be as light as classical axion miniclusters, of the order of 10-12M⊙. We simulate the formation and nonlinear gravitational collapse of these objects around matter-radiation equality using an N-body code, estimate their gravitational lensing properties, and assess the feasibility of studying them using current and future lensing experiments. Future MACHO-type variability surveys of many background sources can reveal either high-amplification, strong-lensing events, or measure density profiles directly via weak-lensing variability, depending on ScaM parameters and survey depth. However, ScaMs, due to their low internal densities, are unlikely to be responsible for apparent MACHO events already detected in the Galactic halo. As a result, in the entire window between 10-7M⊙ and 102M⊙ covered by the galactic scale lensing experiments, ScaMs may in fact compose all the dark matter. A simple estimate is made of parameters that would give rise to early structure formation; in principle, early stellar collapse could be triggered by ScaMs as early as recombination, and significantly affect cosmic reionization.
Astrophysical effects of scalar dark matter miniclusters
Zurek, Kathryn M.; Hogan, Craig J.; Quinn, Thomas R.
2007-02-15
We model the formation, evolution and astrophysical effects of dark compact Scalar Miniclusters ('ScaMs'). These objects arise when a scalar field, with an axion-like or Higgs-like potential, undergoes a second-order phase transition below the QCD scale. Such a scalar field may couple too weakly to the standard model to be detectable directly through particle interactions, but may still be detectable by gravitational effects, such as lensing and baryon accretion by large, gravitationally bound miniclusters. The masses of these objects are shown to be constrained by the Ly{alpha} power spectrum to be less than {approx}10{sup 4}M{sub {center_dot}}, but they may be as light as classical axion miniclusters, of the order of 10{sup -12}M{sub {center_dot}}. We simulate the formation and nonlinear gravitational collapse of these objects around matter-radiation equality using an N-body code, estimate their gravitational lensing properties, and assess the feasibility of studying them using current and future lensing experiments. Future MACHO-type variability surveys of many background sources can reveal either high-amplification, strong-lensing events, or measure density profiles directly via weak-lensing variability, depending on ScaM parameters and survey depth. However, ScaMs, due to their low internal densities, are unlikely to be responsible for apparent MACHO events already detected in the Galactic halo. As a result, in the entire window between 10{sup -7}M{sub {center_dot}} and 10{sup 2}M{sub {center_dot}} covered by the galactic scale lensing experiments, ScaMs may in fact compose all the dark matter. A simple estimate is made of parameters that would give rise to early structure formation; in principle, early stellar collapse could be triggered by ScaMs as early as recombination, and significantly affect cosmic reionization.
The emergence of scalar meanings
Etxeberria, Urtzi; Irurtzun, Aritz
2015-01-01
This paper analyzes the emergence of scalar additive meanings. We show that in Basque the same particle ere can obtain both the “simple additive” reading (akin to English too) and the “scalar additive” reading (akin to English even) but we argue that we do not have to distinguish two types of ere. We provide evidence, by means of a production and a perception experiment, that the reading is disambiguated by means of prosody (the placement of nuclear stress), which is a correlate of focus. We argue that the scalarity effect is generated by the combination of two presuppositions (a focus-induced one and a lexical one) and the assertion of the sentence. PMID:25745405
Scalar-tensor cosmological models
NASA Astrophysics Data System (ADS)
Serna, A.; Alimi, J. M.
1996-03-01
We analyze the qualitative behavior of scalar-tensor cosmologies with an arbitrary monotonic $\\omega(\\Phi)$ function. In particular, we are interested in scalar-tensor theories distinguishable at early epochs from general relativity (GR) but leading to predictions compatible with solar-system experiments. After extending the method developed by Lorentz-Petzold and Barrow, we establish the conditions required for convergence towards GR at $t \\rightarrow \\infty$. Then, we obtain all the asymptotic analytical solutions at early times which are possible in the framework of these theories. The subsequent qualitative evolution, from these asymptotic solutions until their later convergence towards GR, is analyzed by means of numerical computations. From this analysis, we are able to establish a classification of the different qualitative behaviors of scalar-tensor cosmological models with an arbitrary monotonic $\\omega(\\Phi)$ function
Scalar transport by planktonic swarms
NASA Astrophysics Data System (ADS)
Martinez-Ortiz, Monica; Dabiri, John O.
2012-11-01
Nutrient and energy transport in the ocean is primarily governed by the action of physical phenomena. In previous studies it has been suggested that aquatic fauna may significantly contribute to this process through the action of the induced drift mechanism. In this investigation, the role of planktonic swarms as ecosystem engineers is assessed through the analysis of scalar transport within a stratified water column. The vertical migration of Artemia salina is controlled via luminescent signals on the top and bottom of the column. The scalar transport of fluorescent dye is visualized and quantified through planar laser induced fluorescence (PLIF). Preliminary results show that the vertical movement of these organisms enhances scalar transport relative to control cases in which only buoyancy forces and diffusion are present. Funded by the BSF program (2011553).
Long-lived, colour-triplet scalars from unnaturalness
Barnard, James; Cox, Peter; Gherghetta, Tony; Spray, Andrew
2016-03-01
We study that long-lived, colour-triplet scalars are a generic prediction of unnatural, or split, composite Higgs models where the spontaneous global-symmetry breaking scale f ≳ 10TeV and an unbroken SU(5) symmetry is preserved. Since the triplet scalars are pseudo Nambu- Goldstone bosons they are split from the much heavier composite-sector resonances and are the lightest exotic, coloured states. This makes them ideal to search for at colliders. Due to discrete symmetries the triplet scalar decays via a dimension-six term and given the large suppression scale f is often metastable. We show that existing searches for collider-stable R-hadrons from Run-I atmore » the LHC forbid a triplet scalar mass below 845 GeV, whereas with 300 fb-1 at 13TeV triplet scalar masses up to 1.4TeV can be discovered. For shorter lifetimes displaced-vertex searches provide a discovery reach of up to 1.8TeV. Also, we present exclusion and discovery reaches of future hadron colliders as well as indirect limits that arise from modi cations of the Higgs couplings.« less
Late time solution for interacting scalar in accelerating spaces
Prokopec, Tomislav
2015-11-01
We consider stochastic inflation in an interacting scalar field in spatially homogeneous accelerating space-times with a constant principal slow roll parameter ε. We show that, if the scalar potential is scale invariant (which is the case when scalar contains quartic self-interaction and couples non-minimally to gravity), the late-time solution on accelerating FLRW spaces can be described by a probability distribution function (PDF) ρ which is a function of φ/H only, where φ=φ( x-vector ) is the scalar field and H=H(t) denotes the Hubble parameter. We give explicit late-time solutions for ρarrow ρ{sub ∞}(φ/H), and thereby find the order ε corrections to the Starobinsky-Yokoyama result. This PDF can then be used to calculate e.g. various n-point functions of the (self-interacting) scalar field, which are valid at late times in arbitrary accelerating space-times with ε= constant.
Electroweak baryogenesis in a scalar-assisted vectorlike fermion model
NASA Astrophysics Data System (ADS)
Xiao, Ming-Lei; Yu, Jiang-Hao
2016-07-01
We extend the standard model to a scalar-assisted vectorlike fermion model to realize electroweak baryogenesis. The extended Cabibbo-Kobayashi-Maskawa matrix, due to the mixing among the vectorlike quark and the standard model quarks, provides additional sources of the C P violation. Together with the enhancement from a large vectorlike quark mass, a large enough baryon-to-photon ratio could be obtained. The strongly first-order phase transition could be realized via the potential barrier which separates the broken minimum and the symmetric minimum in the scalar potential. We investigate in detail the one loop temperature-dependent effective potential and perform a random parameter scan to study the allowed parameter region that satisfies the strongly first order phase transition criteria vc≥Tc. Several distinct patterns of phase transition are classified and discussed. Among these patterns, a large trilinear mass term between the Higgs boson and the scalar is preferred, for it controls the width of the potential barrier. Our results indicate large quartic scalar couplings and a moderate mixing angle between the Higgs boson and the new scalar. This parameter region could be further explored at the Run 2 LHC.
Effect of dilatation on scalar dissipation in turbulent premixed flames
Swaminathan, N.; Bray, K.N.C.
2005-12-01
The scalar dissipation rate signifies the local mixing rate and thus plays a vital role in the modeling of reaction rate in turbulent flames. The local mixing rate is influenced by the turbulence, the chemical, and the molecular diffusion processes which are strongly coupled in turbulent premixed flames. Thus, a model for the mean scalar dissipation rate, and hence the mean reaction rate, should include the contributions of these processes. Earlier models for the scalar dissipation rate include only a turbulence time scale. In this study, we derive exact transport equations for the instantaneous and the mean scalar dissipation rates. Using these equations, a simple algebraic model for the mean scalar dissipation rate is obtained. This model includes a chemical as well as a turbulence time scale and its prediction compares well with direct numerical simulation results. Reynolds-averaged Navier-Stokes calculations of a test flame using the model obtained here show that the contribution of dilatation to local turbulent mixing rate is important to predict the propagation phenomenon.
Survival of scalar zero modes in warped extra dimensions
George, Damien P.
2011-05-15
Models with an extra dimension generally contain background scalar fields in a nontrivial configuration, whose stability must be ensured. With gravity present, the extra dimension is warped by the scalars, and the spin-0 degrees of freedom in the metric mix with the scalar perturbations. Where possible, we formally solve the coupled Schroedinger equations for the zero modes of these spin-0 perturbations. When specializing to the case of two scalars with a potential generated by a superpotential, we are able to fully solve the system. We show how these zero modes can be used to construct a solution matrix, whose eigenvalues tell whether a normalizable zero mode exists, and how many negative mass modes exist. These facts are crucial in determining stability of the corresponding background configuration. We provide examples of the general analysis for domain-wall models of an infinite extra dimension and domain-wall soft-wall models. For five-dimensional models with two scalars constructed using a superpotential, we show that a normalizable zero mode survives, even in the presence of warped gravity. Such models, which are widely used in the literature, are therefore phenomenologically unacceptable.
Iron Kα line of Kerr black holes with scalar hair
NASA Astrophysics Data System (ADS)
Ni, Yueying; Zhou, Menglei; Cárdenas-Avendaño, Alejandro; Bambi, Cosimo; Herdeiro, Carlos A. R.; Radu, Eugen
2016-07-01
Recently, a family of hairy black holes in 4-dimensional Einstein gravity minimally coupled to a complex, massive scalar field was discovered [1]. Besides the mass M and spin angular momentum J, these objects are characterized by a Noether charge Q, measuring the amount of scalar hair, which is not associated to a Gauss law and cannot be measured at spatial infinity. Introducing a dimensionless scalar hair parameter q, ranging from 0 to 1, we recover (a subset of) Kerr black holes for q = 0 and a family of rotating boson stars for q = 1. In the present paper, we explore the possibility of measuring q for astrophysical black holes with current and future X-ray missions. We study the iron Kα line expected in the reflection spectrum of such hairy black holes and we simulate observations with Suzaku and eXTP. As a proof of concept, we point out, by analyzing a sample of hairy black holes, that current observations can already constrain the scalar hair parameter q, because black holes with q close to 1 would have iron lines definitively different from those we observe in the available data. We conclude that a detailed scanning of the full space of solutions, together with data from the future X-ray missions, like eXTP, will be able to put relevant constraints on the astrophysical realization of Kerr black holes with scalar hair.
A Riccati equation based approach to isotropic scalar field cosmologies
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lobo, Francisco S. N.; Mak, M. K.
2014-05-01
Gravitationally coupled scalar fields ϕ, distinguished by the choice of an effective self-interaction potential V(ϕ), simulating a temporarily nonvanishing cosmological term, can generate both inflation and late time acceleration. In scalar field cosmological models the evolution of the Hubble function is determined, in terms of the interaction potential, by a Riccati type equation. In the present work, we investigate scalar field cosmological models that can be obtained as solutions of the Riccati evolution equation for the Hubble function. Four exact integrability cases of the field equations are presented, representing classes of general solutions of the Riccati evolution equation. The solutions correspond to cosmological models in which the Hubble function is proportional to the scalar field potential plus a linearly decreasing function of time, models with the time variation of the scalar field potential proportional to the potential minus its square, models in which the potential is the sum of an arbitrary function and the square of the function integral, and models in which the potential is the sum of an arbitrary function and the derivative of its square root, respectively. The cosmological properties of all models are investigated in detail, and it is shown that they can describe the inflationary or the late accelerating phase in the evolution of the universe.
DFT analysis of NMR scalar interactions across the glycosidic bond in DNA.
Munzarová, Markéta L; Sklenár, Vladimír
2003-03-26
The relationship between the glycosidic torsion angle chi, the three-bond couplings (3)J(C2/4-H1') and (3)J(C6/8-H1'), and the one-bond coupling (1)J(C1'-H1') in deoxyribonucleosides and a number of uracil cyclo-nucleosides has been analyzed using density functional theory. The influence of the sugar pucker and the hydroxymethyl conformation has also been considered. The parameters of the Karplus relationships between the three-bond couplings and chi depend strongly on the aromatic base. (3)J(C2/4-H1') reveals different behavior for deoxyadenosine, deoxyguanosine, and deoxycytidine as compared to deoxythymidine and deoxyuridine. In the case of (3)J(C6/8-H1'), an opposite trans to cis ratio of couplings is obtained for pyrimidine nucleosides in contrast to purine nucleosides. The extremes of the Karplus curves are shifted by ca. 10 degrees with respect to syn and anti-periplanar orientations of the coupled nuclei. The change in the sugar pucker from S to N decreases (3)J(C2/4-H1') and (3)J(C6/8-H1'), while increasing (1)J(C1'-H1') for the syn rotamers, whereas all of the trends are reversed for the anti rotamers. The influence of the sugar pucker on (1)J(C1'-H1') is interpreted in terms of interactions between the n(O4'), sigma*(C1'-H1') orbitals. The (1)J(C1'-H1') are related to chi through a generalized Karplus relationship, which combines cos(chi) and cos(2)(chi) functions with mutually different phase shifts that implicitly accounts for a significant portion of the related sugar pucker effects. Most of theoretical (3)J(C2/4-H1') and (3)J(C6/8-H1') for uracil cyclo-nucleosides compare well with available experimental data. (3)J(C6/8-H1') couplings for all C2-bridged nucleosides are up to 3 Hz smaller than in the genuine nucleosides with the corresponding chi, revealing a nonlocal aspect of the spin-spin interactions across the glycosidic bond. Theoretical (1)J(C1'-H1') are underestimated with respect to the experiment by ca. 10% but reproduce the trends in (1)J
ROTSE3 J133033.0-313427 is a Type Ia Supernova
NASA Astrophysics Data System (ADS)
Quimby, R. M.
2010-03-01
A spectrum (340-760 nm) of ROTSE3 J133033.0-313427 (Zheng et al., ATel #2468) obtained on Mar 14.58 UT with the 10-m Keck I (+ Low Resolution Imaging Spectrometer) shows it to be a normal Type Ia supernova. The spectra are similar to SN 1992A a few days after maximum light (Kirshner et al. 1993, ApJ 415,589). Adopting the redshift of the apparent host (z=0.048; Katgert et al. 1998, A&AS 129, 399), the expansion velocity derived from the minimum of the SiII (rest 635.5 nm) line is about 12,000 km/s.
Kinetic mixing in scalar-tensor theories of gravity
NASA Astrophysics Data System (ADS)
Bettoni, Dario; Zumalacárregui, Miguel
2015-05-01
Kinetic mixing between the metric and scalar degrees of freedom is an essential ingredient in contemporary scalar-tensor theories. This often makes it hard to understand their physical content, especially when derivative mixing is present, as is the case for Horndeski action. In this work we develop a method that allows us to write a Ricci-curvature-free scalar field equation, and we discuss some of the advantages of such a rephrasing in the study of stability issues in the presence of matter, the existence of an Einstein frame, and the generalization of the disformal screening mechanism. For quartic Horndeski theories, such a procedure leaves, in general, a residual coupling to the curvature, given by the Weyl tensor. This gives rise to a binary classification of scalar-tensor theories into stirred theories, in which the curvature can be substituted, and shaken theories, in which a residual coupling to the curvature remains. Quite remarkably, we have found that generalized Dirac-Born-Infeld Galileons belong to the first class. Finally, we discuss kinetic mixing in quintic theories, in which nonlinear mixing terms appear, and in the recently proposed theories beyond Horndeski that display a novel form of kinetic mixing, in which the field equation is sourced by derivatives of the energy-momentum tensor.
Global structure of exact scalar hairy dynamical black holes
NASA Astrophysics Data System (ADS)
Fan, Zhong-Ying; Chen, Bin; Lü, H.
2016-05-01
We study the global structure of some exact scalar hairy dynamical black holes which were constructed in Einstein gravity either minimally or non-minimally coupled to a scalar field. We find that both the apparent horizon and the local event horizon (measured in luminosity coordinate) monotonically increase with the advanced time as well as the Vaidya mass. At late advanced times, the apparent horizon approaches the event horizon and gradually becomes future outer. Correspondingly, the space-time arrives at stationary black hole states with the relaxation time inversely proportional to the 1/( n-1) power of the final black hole mass, where n is the space-time dimension. These results strongly support the solutions describing the formation of black holes with scalar hair. We also obtain new charged dynamical solutions in the non-minimal theory by introducing an Maxwell field which is non-minimally coupled to the scalar. The presence of the electric charge strongly modifies the dynamical evolution of the space-time.
Scalar fields and particle accelerators
NASA Astrophysics Data System (ADS)
Sultana, Joseph; Bose, Benjamin
2015-06-01
The phenomenon discovered in 2009 by Bañados, Silk and West where particle collisions can achieve arbitrary high center-of-mass (c.m.) energies close to the event horizon of an extreme Kerr black hole, has generated a lot of interest. Although rotation seemed to be an essential requirement, it was later shown that arbitrary high energies can also be achieved for collisions between radially moving particles near the horizon of the electrically charged extreme Reissner-Nordström black hole. Recently Patil and Joshi claimed that instead of spinning up the black hole one can also crank up the c.m. energy of particle collisions by "charging up" a static black hole with a massless scalar field. In this regard they showed that infinite energies can be attained in the vicinity of the naked singularity of the Janis-Newman-Wincour (JNW) spacetime, which contains a massless scalar field that also becomes infinite at the position of the curvature singularity. In this study we show that Patil and Joshi's claim does not apply for other static black hole systems endowed with a massless scalar field. In particular we consider the well-known Bekenstein black hole and the recently discovered Martínez-Troncoso-Zanelli black hole, and show that the expression of the c.m. energy for particle collisions near the event horizons of these black holes is no different than the corresponding case with vanishing scalar field represented by the Schwarzschild solution. Moreover by studying the motion of scalar test charges that interact with the background scalar field in these black hole spacetimes we show that the resulting c.m. energies are even smaller than in the case of free particles. This shows that the infinite energies obtained by Patil and Joshi may not be due to the fact that the black hole contains a massless scalar field, but may be instead related to the geometry of the naked singularity in the JNW spacetime. An analogous case of infinite c.m. energy in the vicinity of a naked
MAGSAT scalar and vector anomaly data analysis
NASA Technical Reports Server (NTRS)
1982-01-01
Efforts on the analysis of MAGSAT scalar anomaly data, the application of the scalar analysis results to three component vector data, and the comparison of MAGSAT data with corresponding MAGNET aeromagnetic and free air gravity anomaly data are briefly described.
NASA Astrophysics Data System (ADS)
van de Bruck, Carsten; Koivisto, Tomi; Longden, Chris
2016-03-01
A disformal coupling between two scalar fields is considered in the context of cosmological inflation. The coupling introduces novel derivative interactions mixing the kinetic terms of the fields but without introducing superluminal or unstable propagation of the two scalar fluctuation modes. Though the typical effect of the disformal coupling is to inhibit one of the fields from inflating the universe, the energy density of the other field can drive viable near Sitter -inflation in the presence of nontrivial disformal dynamics, in particular when one assumes exponential instead of power-law form for the couplings. The linear perturbation equations are written for the two-field system, its canonical degrees of freedom are quantised, their spectra are derived and the inflationary predictions are reported for numerically solved exponential models. A generic prediction is low tensor-to-scalar ratio.
The trace anomaly and massless scalar degrees of freedom
Gianotti, Maurizio; Mottola, Emil
2008-01-01
The trace anomaly of quantum fields in electromagnetic or gravitational backgrounds implies the existence of massless scalar poles in physical amplitudes involving the stress-energy tensor. Considering first the axial anomaly and using QED as an example, we compute the full one-loop triangle amplitude of the fermionic stress tensor with two current vertices, {open_square}T{sup {mu}{nu}}J{sup {alpha}}J{sup {beta}}, and exhibit the scalar pole in this amplitude associated with the trace anomaly, in the limit of zero electron mass m{yields}0. To emphasize the infrared aspect of the anomaly, we use a dispersive approach and show that this amplitude and the existence of the massless scalar pole is determined completely by its ultraviolet finite terms, together with the requirements of Poincare invariance of the vacuum, Bose symmetry under interchange of J{sup {alpha}} and J{sup {beta}}, and vector current and stress-tensor conservation. We derive a sum rule for the appropriate positive spectral function corresponding to the discontinuity of the triangle amplitude, showing that it becomes proportional to {delta}(k{sup 2}) and therefore contains a massless scalar intermediate state in the conformal limit of zero electron mass. The effective action corresponding to the trace of the triangle amplitude can be expressed in local form by the introduction of two scalar auxiliary fields which satisfy massless wave equations. These massless scalar degrees of freedom couple to classical sources, contribute to gravitational scattering processes, and can have long range gravitational effects.
Bianchi I in scalar and scalar-tensor cosmologies
NASA Astrophysics Data System (ADS)
Belinchón, José
2012-08-01
We study how the constants G and Λ may vary in different theoretical models (general relativity (GR) with a perfect fluid, scalar cosmological models (SM) ("quintessence") with and without interacting scalar and matter fields and three scalar-tensor theories (STT) with a dynamical Λ) in order to explain some observational results. We apply the program outlined in section II to study the Bianchi I models, under the self-similarity hypothesis. We put special emphasis on calculating exact power-law solutions which allow us to compare the different models. In all the studied cases we conclude that the solutions are isotropic and noninflationary. We also arrive at the conclusion that in the GR model with time-varying constants, Λ vanishes while G is constant. In the SM all the solutions are massless i.e. the potential vanishes and all the interacting models are inconsistent from the thermodynamical point of view. The solutions obtained in the STT collapse to the perfect fluid one obtained in the GR model where G is a true constant and Λ vanishes as in the GR and SM frameworks.
Instabilities in neutrino systems induced by interactions with scalars
Sawyer, R. F.
2011-03-15
If there are scalar particles of small or moderate mass coupled very weakly to Dirac neutrinos, in a minimal way, then neutrino-anti-neutrino clouds of sufficient number density can experience an instability in which helicities are suddenly reversed. The predicted collective evolution is many orders of magnitude faster than given by cross section calculations. The instabilities are the analogue of the 'flavor-angle' instabilities (enabled by the Z exchange force) that may drive very rapid flavor exchange among the neutrinos that emerge from a supernova. These exchanges do require a tiny seed in addition to the scalar couplings, but the transition time is proportional to the negative of the logarithm of the seed strength, so that the size of this parameter is comparatively unimportant. For our actual estimates we use a tiny nonconservation of leptons; an alternative would be a neutrino magnetic moment in a small magnetic field. The possibility of a quantum fluctuation as a seed is also discussed. Operating in the mode of putting limits on the coupling constant of the scalar field, for the most minimal coupling scheme, with independent couplings to all three {nu}, we find a rough limit on the dimensionless coupling constant for a neutrino-flavor independent coupling of G<10{sup -10}, to avoid the effective number of light neutrinos in the early universe being essentially six. If, on the other hand, we wish to fine-tune the model to give a more modest excess (over three) in the effective neutrino number, as may be needed according to recent WMAP analyses, it is easy to do so.
Endlessly flat scalar potentials and α-attractors
NASA Astrophysics Data System (ADS)
Artymowski, Michał; Rubio, Javier
2016-10-01
We consider a minimally-coupled inflationary theory with a general scalar potential V (f (φ)) = V (ξ∑k=1nλkφk) containing a stationary point of maximal order m. We show that asymptotically flat potentials can be associated to stationary points of infinite order and discuss the relation of our approach to the theory of α-attractors.
Weak Gravitational Wave and Casimir Energy of a Scalar Field
NASA Astrophysics Data System (ADS)
Tavakoli, F.; Pirmoradian, R.; Parsabod, I.
2016-09-01
In this paper, we calculate the effect of a weak gravitational field on the Casimir force between two ideal plates subjected to a massless minimally coupled field. It is the aim of this work to study the Casimir energy under a weak perturbation of gravity. Moreover, the fluctuations of the stress-energy tensor for a scalar field in de Sitter space-time are computed as well.
GravitoMagnetic Field in Tensor-Vector-Scalar Theory
Exirifard, Qasem
2013-04-01
We study the gravitomagnetism in the TeVeS theory. We compute the gravitomagnetic field that a slow moving mass distribution produces in its Newtonian regime. We report that the consistency between the TeVeS gravitomagnetic field and that predicted by the Einstein-Hilbert theory leads to a relation between the vector and scalar coupling constants of the theory. We translate the Lunar Laser Ranging measurement's data into a constraint on the deviation from this relation.
Sweetener preference of C57BL/6ByJ and 129P3/J mice.
Bachmanov, A A; Tordoff, M G; Beauchamp, G K
2001-09-01
Previous studies have shown large differences in taste responses to several sweeteners between mice of the C57BL/6ByJ (B6) and 129P3/J (129) inbred strains. The goal of this study was to compare behavioral responses of B6 and 129 mice to a wider variety of sweeteners. Seventeen sweeteners were tested using two-bottle preference tests with water. Three main patterns of strain differences were evident. First, sucrose, maltose, saccharin, acesulfame-K, sucralose and SC-45647 were preferred by both strains, but the B6 mice had lower preference thresholds and higher solution intakes. Second, the amino acids D-phenylalanine, D-tryptophan, L-proline and glycine were highly preferred by B6 mice, but not by 129 mice. Third, glycyrrhizic acid, neohesperidin dihydrochalcone, thaumatin and cyclamate did not evoke strong preferences in either strain. Aspartame was neutral to all 129 and some B6 mice, but other B6 mice strongly preferred it. Thus, compared with the 129 mice the B6 mice had higher preferences for sugars, sweet tasting amino acids and several but not all non-caloric sweeteners. Glycyrrhizic acid, neohesperidin, thaumatin and cyclamate are not palatable to B6 or 129 mice.
Early-time cosmological solutions in Einstein-scalar-Gauss-Bonnet theory
NASA Astrophysics Data System (ADS)
Kanti, Panagiota; Gannouji, Radouane; Dadhich, Naresh
2015-10-01
In this work, we consider a generalized gravitational theory that contains the Einstein term, a scalar field, and the quadratic Gauss-Bonnet (GB) term. We focus on the early-universe dynamics, and demonstrate that a simple choice of the coupling function between the scalar field and the Gauss-Bonnet term and a simplifying assumption regarding the role of the Ricci scalar can lead to new, analytical, elegant solutions with interesting characteristics. We first argue, and demonstrate in the context of two different models, that the presence of the Ricci scalar in the theory at early times (when the curvature is strong) does not affect the actual cosmological solutions. By considering therefore a pure scalar-GB theory with a quadratic coupling function we derive a plethora of interesting, analytic solutions: for a negative coupling parameter, we obtain inflationary, de Sitter-type solutions or expanding solutions with a de Sitter phase in their past and a natural exit mechanism at later times; for a positive coupling function, we find instead singularity-free solutions with no big bang singularity. We show that the aforementioned solutions arise only for this particular choice of coupling function, a result that may hint at some fundamental role that this coupling function may hold in the context of an ultimate theory.
Constrained inflaton due to a complex scalar
Budhi, Romy H. S.; Kashiwase, Shoichi; Suematsu, Daijiro
2015-09-14
We reexamine inflation due to a constrained inflaton in the model of a complex scalar. Inflaton evolves along a spiral-like valley of special scalar potential in the scalar field space just like single field inflation. Sub-Planckian inflaton can induce sufficient e-foldings because of a long slow-roll path. In a special limit, the scalar spectral index and the tensor-to-scalar ratio has equivalent expressions to the inflation with monomial potential φ{sup n}. The favorable values for them could be obtained by varying parameters in the potential. This model could be embedded in a certain radiative neutrino mass model.
Scalar speed limits and cosmology: Acceleration from D-cceleration
Silverstein, Eva
2004-11-15
Causality on the gravity side of the AdS/CFT correspondence restricts motion on the moduli space of the N=4 super Yang-Mills theory by imposing a speed limit on how fast the scalar field may roll. This effect can be traced to higher-derivative operators arising from integrating out light degrees of freedom near the origin. In the strong coupling limit of the theory, the dynamics is well approximated by the Dirac-Born-Infeld Lagrangian for a probe D3-brane moving toward the horizon of the AdS Poincare patch, combined with an estimate of the (ultimately suppressed) rate of particle and string production in the system. We analyze the motion of a rolling scalar field explicitly in the strong coupling regime of the field theory and extend the analysis to cosmological systems obtained by coupling this type of field theory to four-dimensional gravity. This leads to a mechanism for slow roll inflation for a massive scalar at sub-Planckian vacuum expectation value without need for a flat potential (realizing a version of k inflation in a microphysical framework). It also leads to a variety of novel Friedman-Roberston-Walker cosmologies, some of which are related to those obtained with tachyon matter.
Radiation patterns of 'scalar' lightpipes
NASA Astrophysics Data System (ADS)
Padman, Rachael; Murphy, J. A.
At long wavelengths, diffraction effects cause condensing lightpipes to have a significant response in directions within the geometric-optics shadow zone. Here, using an analogy with the corrugated 'scalar' horns often used in antenna engineering, it is suggested that a lightpipe with anisotropic surface impedance on its interior surfaces can have substantially reduced sidelobe levels. This may be important for measurements requiring high dynamic range, particularly in the far-IR.
NASA Astrophysics Data System (ADS)
Fodor, Gyula; Forgács, Péter; Mezei, Márk
2010-03-01
Spherically symmetric oscillatons (also referred to as oscillating soliton stars) i.e. gravitationally bound oscillating scalar lumps are considered in theories containing a massive self-interacting real scalar field coupled to Einstein’s gravity in 1+D dimensional spacetimes. Oscillations are known to decay by emitting scalar radiation with a characteristic time scale which is, however, extremely long, it can be comparable even to the lifetime of our universe. In the limit when the central density (or amplitude) of the oscillaton tends to zero (small-amplitude limit) a method is introduced to compute the transcendentally small amplitude of the outgoing waves. The results are illustrated in detail on the simplest case, a single massive free scalar field coupled to gravity.
Slow-roll inflation in loop quantum cosmology of scalar-tensor theories of gravity
NASA Astrophysics Data System (ADS)
Han, Yu
2015-07-01
The slow-roll inflation of scalar-tensor theories (STTs) of gravity in the context of loop quantum cosmology (LQC) is investigated in this paper. After deriving the effective Hamiltonian, we obtain the semiclassical equations of motion for the background variables in both Jordan frame and Einstein frame of STTs. Then we apply these equations in the slow-roll limit and derive the LQC corrections to the scalar spectral index ns and the tensor-to-scalar ratio r in the two frames of STTs. Finally, we take two special sectors of STTs as specific examples, namely the Starobinsky model and the non-minimally coupled scalar field model (with the coupling function ξϕ2R and the potential λ 4 ϕ4). We derive the detailed expressions of the LQC corrections to ns and r in terms of the e-folding number for these two models in both frames.
CP-even scalar boson production via gluon fusion at the LHC
NASA Astrophysics Data System (ADS)
Anastasiou, Charalampos; Duhr, Claude; Dulat, Falko; Furlan, Elisabetta; Gehrmann, Thomas; Herzog, Franz; Lazopoulos, Achilleas; Mistlberger, Bernhard
2016-09-01
In view of the searches at the LHC for scalar particle resonances in addition to the 125 GeV Higgs boson, we present the cross-section for a CP-even scalar produced via gluon fusion at N3LO in perturbative QCD assuming that it couples directly to gluons in an effective theory approach. We refine our prediction by taking into account the possibility that the scalar couples to the top-quark and computing the corresponding contributions through NLO in perturbative QCD. We assess the theoretical uncertainties of the crosssection due to missing higher-order QCD effects and we provide the necessary information for obtaining the cross-section value and uncertainty from our results in specific scenarios beyond the Standard Model. We also give detailed results for the case of a 750 GeV scalar, which will be the subject of intense experimental studies.
Multiscale renormalization group methods for effective potentials with multiple scalar fields
NASA Astrophysics Data System (ADS)
Wang, Zhi-Wei; Steele, Tom; McKeon, Gerry
2015-04-01
Conformally symmetric scalar extensions of the Standard Model are particular appealing to reveal the underlying mechanism for electroweak symmetry breaking and to provide dark matter candidates. The Gildener & Weinberg (GW) method is widely used in these models, but is limited to weakly coupled theories. In this talk, multi-scale renormalization group (RG) methods are reviewed and applied to the analysis of the effective potential for radiative symmetry breaking with multiple scalar fields, allowing an extension of the GW method beyond the weak coupling limit. A model containing two interacting real scalar fields is used as an example to illustrate these multi-scale RG methods. Extensions of these multi-scale methods for effective potentials in models containing multiple scalars with O(M) × O(N) symmetry will also be discussed. Reseach funded by NSERC (Natural Sciences and Engineering Research Council of Canada).
Fodor, Gyula; Forgacs, Peter; Mezei, Mark
2010-03-15
Spherically symmetric oscillatons (also referred to as oscillating soliton stars) i.e. gravitationally bound oscillating scalar lumps are considered in theories containing a massive self-interacting real scalar field coupled to Einstein's gravity in 1+D dimensional spacetimes. Oscillations are known to decay by emitting scalar radiation with a characteristic time scale which is, however, extremely long, it can be comparable even to the lifetime of our universe. In the limit when the central density (or amplitude) of the oscillaton tends to zero (small-amplitude limit) a method is introduced to compute the transcendentally small amplitude of the outgoing waves. The results are illustrated in detail on the simplest case, a single massive free scalar field coupled to gravity.
Vacuum stability of a general scalar potential of a few fields
NASA Astrophysics Data System (ADS)
Kannike, Kristjan
2016-06-01
We calculate analytical vacuum stability or bounded from below conditions for general scalar potentials of a few fields. After a brief review of copositivity, we show how to find positivity conditions for more complicated potentials. We discuss the vacuum stability conditions of the general potential of two real scalars, without and with the Higgs boson included in the potential. As further examples, we give explicit vacuum stability conditions for the two Higgs doublet model with no explicit CP breaking, and for the mathbb {Z}3 scalar dark matter with an inert doublet and a complex singlet. We give a short overview of positivity conditions for tensors of quartic couplings via tensor eigenvalues.
Spinning boson stars and Kerr black holes with scalar hair: The effect of self-interactions
NASA Astrophysics Data System (ADS)
Herdeiro, Carlos A. R.; Radu, Eugen; Rúnarsson, Helgi F.
2016-05-01
Self-interacting boson stars (BSs) have been shown to alleviate the astrophysically low maximal mass of their nonself-interacting counterparts. We report some physical features of spinning self-interacting BSs, namely their compactness, the occurrence of ergo-regions and the scalar field profiles, for a sample of values of the coupling parameter. The results agree with the general picture that these BSs are comparatively less compact than the nonself-interacting ones. We also briefly discuss the effect of scalar self-interactions on the properties of Kerr black holes with scalar hair.
Quantum tunneling from rotating black holes with scalar hair in three dimensions
NASA Astrophysics Data System (ADS)
Sakalli, I.; Gursel, H.
2016-06-01
We study the Hawking radiation of scalar and Dirac particles (fermions) emitted from a rotating scalar hair black hole (RSHBH) within the context of three dimensional (3 D) Einstein gravity using non-minimally coupled scalar field theory. Amalgamating the quantum tunneling approach with the Wentzel-Kramers-Brillouin approximation, we obtain the tunneling rates of the outgoing particles across the event horizon. Inserting the resultant tunneling rates into the Boltzmann formula, we then obtain the Hawking temperature (T_H) of the 3 D RSHBH.
Symmetry breaking and restoration for interacting scalar and gauge fields in Lifshitz type theories
NASA Astrophysics Data System (ADS)
Farakos, K.; Metaxas, D.
2012-05-01
We consider the one-loop effective potential at zero and finite temperature in field theories with anisotropic space-time scaling, with critical exponent z = 2, including both scalar and gauge fields. Depending on the relative strength of the coupling constants for the gauge and scalar interactions, we find that there is a symmetry breaking term induced at one loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature.
Scalar triplet flavored leptogenesis: a systematic approach
Sierra, D. Aristizabal; Dhen, Mikaël; Hambye, Thomas E-mail: mikadhen@ulb.ac.be
2014-08-01
Type-II seesaw is a simple scenario in which Majorana neutrino masses are generated by the exchange of a heavy scalar electroweak triplet. When endowed with additional heavy fields, such as right-handed neutrinos or extra triplets, it also provides a compelling framework for baryogenesis via leptogenesis. We derive in this context the full network of Boltzmann equations for studying leptogenesis in the flavored regime. To this end we determine the relations which hold among the chemical potentials of the various particle species in the thermal bath. This takes into account the standard model Yukawa interactions of both leptons and quarks as well as sphaleron processes which, depending on the temperature, may be classified as faster or slower than the Universe Hubble expansion. We find that when leptogenesis is enabled by the presence of an extra triplet, lepton flavor effects allow the production of the B-L asymmetry through lepton number conserving CP asymmetries. This scenario becomes dominant as soon as the triplets couple more to leptons than to standard model scalar doublets. In this case, the way the B-L asymmetry is created through flavor effects is novel: instead of invoking the effect of L-violating inverse decays faster than the Hubble rate, it involves the effect of L-violating decays slower than the Hubble rate. We also analyze the more general situation where lepton number violating CP asymmetries are present and actively participate in the generation of the B-L asymmetry, pointing out that as long as L-violating triplet decays are still in thermal equilibrium when the triplet gauge scattering processes decouple, flavor effects can be striking, allowing to avoid all washout suppression effects from seesaw interactions. In this case the amount of B-L asymmetry produced is limited only by a universal gauge suppression effect, which nevertheless goes away for large triplet decay rates.
Cosmological tests of the disformal coupling to radiation
Brax, Philippe; Davis, Anne-Christine; Gubitosi, Giulia E-mail: Clare.Burrage@nottingham.ac.uk E-mail: giulia.gubitosi@roma1.infn.it
2013-11-01
Light scalar fields can naturally couple disformally to Standard Model fields without giving rise to the unacceptably large fifth forces usually associated with light scalars. We show that these scalar fields can still be studied and constrained through their interaction with photons, and focus particularly on changes to the Cosmic Microwave Background spectral distortions and violations of the distance duality relation. We then specialise our constraints to scalars which could play the role of pseudo-Goldstone quintessence.
Entropic quantization of scalar fields
Ipek, Selman; Caticha, Ariel
2015-01-13
Entropic Dynamics is an information-based framework that seeks to derive the laws of physics as an application of the methods of entropic inference. The dynamics is derived by maximizing an entropy subject to constraints that represent the physically relevant information that the motion is continuous and non-dissipative. Here we focus on the quantum theory of scalar fields. We provide an entropic derivation of Hamiltonian dynamics and using concepts from information geometry derive the standard quantum field theory in the Schrödinger representation.
Dissipation coefficients from scalar and fermion quantum field interactions
Bastero-Gil, Mar; Berera, Arjun; Ramos, Rudnei O. E-mail: ab@ph.ed.ac.uk
2011-09-01
Dissipation coefficients are calculated in the adiabatic, near thermal equilibrium regime for a large class of renormalizable interaction configurations involving a two-stage mechanism, where a background scalar field is coupled to heavy intermediate scalar or fermion fields which in turn are coupled to light scalar or fermion radiation fields. These interactions are typical of warm inflation microscopic model building. Two perturbative regimes are shown where well defined approximations for the spectral functions apply. One regime is at high temperature, when the masses of both intermediate and radiation fields are less than the temperature scale and where the poles of the spectral functions dominate. The other regime is at low temperature, when the intermediate field masses are much bigger than the temperature and where the low energy and low three-momentum regime dominate the spectral functions. The dissipation coefficients in these two regimes are derived. However, due to resummation issues for the high temperature case, only phenomenological approximate estimates are provided for the dissipation in this regime. In the low temperature case, higher loop contributions are suppressed and so no resummation is necessary. In addition to inflationary cosmology, the application of our results to cosmological phase transitions is also discussed.
Embedding DBI inflation in scalar-tensor theory
Bruck, Carsten van de; Weller, Joel M.; Mota, David F. E-mail: d.f.mota@astro.uio.no
2011-03-01
The Dirac-Born-Infeld (DBI) action has been widely studied as an interesting example of a model of k-inflation in which the sound speed of the cosmological perturbations differs from unity. In this article we consider a scalar-tensor theory in which the matter component is a field with a DBI action. Transforming to the Einstein frame, we explore the effect of the resulting coupling on the background dynamics of the fields and the first-order perturbations. We find that the coupling forces the scalar field into the minimum of its effective potential. While the additional scalar field contributes significantly to the energy density during inflation, the dynamics are determined by the DBI field, which has the interesting effect of increasing the number of efolds of inflation and decreasing the boost factor of the DBI field. Focusing on this case, we show, with the benefit of numerical examples, that the power spectrum of the primordial perturbations is determined by the behaviour of the perturbations of the modified DBI field.
Lepton-flavored scalar dark matter with minimal flavor violation
NASA Astrophysics Data System (ADS)
Lee, Chao-Jung; Tandean, Jusak
2015-04-01
We explore scalar dark matter that is part of a lepton flavor triplet satisfying symmetry requirements under the hypothesis of minimal flavor violation. Beyond the standard model, the theory contains in addition three right-handed neutrinos that participate in the seesaw mechanism for light neutrino mass generation. The dark-matter candidate couples to standard-model particles via Higgs-portal renormalizable interactions as well as to leptons through dimension-six operators, all of which have minimal flavor violation built-in. We consider restrictions on the new scalars from the Higgs boson measurements, observed relic density, dark-matter direct detection experiments, LEP II measurements on e + e - scattering into a photon plus missing energy, and searches for flavor-violating lepton decays. The viable parameter space can be tested further with future data. Also, we investigate the possibility of the new scalars' couplings accounting for the tentative hint of Higgs flavor-violating decay h → μτ recently detected in the CMS experiment. They are allowed by constraints from other Higgs data to produce a rate of this decay roughly compatible with the CMS finding.
A hybrid scalar model for sooting turbulent flames
Aksit, I.M.; Moss, J.B.
2006-04-15
A Lagrangian Monte Carlo solution of the joint scalar pdf transport equation for mixture fraction and representative soot properties, coupled with an Eulerian solution for the turbulent flow field and here described as a 'hybrid model,' has been developed. The modeling of soot formation and destruction employs an existing description of the key processes based on two soot variables-the soot volume fraction (or mass concentration) and the particle number density. The gas-phase chemistry is introduced through flamelet-state relationships. The simulation strategy is based on tracing the evolution of reactive stochastic particles within the computational domain. The ensemble of these particles at a fixed location and time then describes the joint scalar pdf. Soot rate equations, represented as functions of mixture fraction, soot mass concentration, and number density, are solved exactly in terms of the scalar values of each individual stochastic particle and the associated gas-phase properties derived from laminar flamelet-state relationships. The solution for the turbulent flow field provides the mean velocity and mixing frequency required for the transport of the stochastic particles in both physical and compositional space, while the Monte Carlo simulation returns the computed mean density field to the CFD code. Density-weighted mean values are approximated by ensemble averages over the scalar values of the stochastic particles in individual computational cells. The principal objective of the hybrid model is the improved treatment of nonlinear soot formation and oxidation, in particular, the capture of the intermittency in the oxidation process associated with the noncoexistence of soot and the principal oxidizing species. Significant computational economies accompany the adoption of the laminar flamelet approach for the source terms in the soot rate equations and the reduced number of scalars computed stochastically. (author)
Two Higgs doublet models augmented by a scalar colour octet
NASA Astrophysics Data System (ADS)
Cheng, Li; Valencia, German
2016-09-01
The LHC is now studying in detail the couplings of the Higgs boson in order to determine if there is new physics. Many recent studies have examined the available fits to Higgs couplings from the perspective of constraining two Higgs doublet models (2HDM). In this paper we extend those studies to include constraints on the one loop couplings of the Higgs to gluons and photons. These couplings are particularly sensitive to the existence of new coloured particles that are hard to detect otherwise and we use them to constrain a 2HDM augmented with a colour-octet scalar, a possibility motivated by minimal flavour violation. We first study theoretical constraints on this model and then compare them with LHC measurements.
Disformal scalars as dark matter candidates — Branon phenomenology
NASA Astrophysics Data System (ADS)
Cembranos, Jose A. R.; Maroto, Antonio L.
2016-05-01
Scalar particles coupled to the Standard Model fields through a disformal coupling arise in different theories, such as massive gravity or braneworld models. We will review the main phenomenology associated with such particles. Distinctive disformal signatures could be measured at colliders and with astrophysical observations. The phenomenological relevance of the disformal coupling demands the introduction of a set of symmetries, which may ensure the stability of these new degrees of freedom. In such a case, they constitute natural dark matter candidates since they are generally massive and weakly coupled. We will illustrate these ideas by paying particular attention to the branon case, since these questions arise naturally in braneworld models with low tension, where they were first discussed.
Dark matter relic density in scalar-tensor gravity revisited
Meehan, Michael T.; Whittingham, Ian B. E-mail: Ian.Whittingham@jcu.edu.au
2015-12-01
We revisit the calculation of dark matter relic abundances in scalar-tensor gravity using a generic form A(φ{sub *}) = e{sup βφ{sub *}{sup 2/2}} for the coupling between the scalar field φ{sub *} and the metric, for which detailed Big Bang Nucleosynthesis constraints are available. We find that BBN constraints restrict the modified expansion rate in these models to be almost degenerate with the standard expansion history at the time of dark matter decoupling. In this case the maximum level of enhancement of the dark matter relic density was found to be a factor of ∼ 3, several orders of magnitude below that found in previous investigations.
Baryogenesis from baryon-number-violating scalar interactions
NASA Astrophysics Data System (ADS)
Bowes, J. P.; Volkas, R. R.
1997-03-01
In the following work we consider the possibility of explaining the observed baryon-number asymmetry in the universe from simple baryon-number-violating modifications, involving massive scalar bosons, to the standard model. In these cases baryon-number violation is mediated through a combination of Yukawa and scalar self-coupling interactions. Starting with a previously compiled catalogue of baryon-number-violating extensions of the standard model, we identify the minimal subsets which can induce a B-L asymmetry and thus be immune to sphaleron washout. For each of these models, we identify the region of parameter space that leads to the production of a baryon number asymmetry of the correct order of magnitude.
The scalar singlet-triplet dark matter model
Fischer, O.; Van der Bij, J.J. E-mail: vdbij@physik.uni-freiburg.de
2014-01-01
We consider a model for cold dark matter, which combines a real scalar singlet and a real scalar SU(2){sub L} triplet field, both of which are residing in the odd representation of a global Z{sub 2} symmetry. The parameter space of the model is constrained by the inferred dark matter abundance from the WMAP and Planck data, the most recent results from the direct dark matter search experiment LUX, the Z boson decay width from LEP-I and perturbativity of the coupling parameters. The phenomenology of the remaining parameter space is studied. We find that the model allows for DM masses near the electroweak scale and a variety of decay scenarios.
Scalar field theory in the strong self-interaction limit
NASA Astrophysics Data System (ADS)
Frasca, Marco
2014-06-01
The Standard Model with a classical conformal invariance holds the promise to lead to a better understanding of the hierarchy problem and could pave the way beyond the Standard Model physics. Thus, we give here a mathematical treatment of a massless quartic scalar field theory with a strong self-coupling both classically and for quantum field theory. We use a set of classical solutions recently found and show that there exist an infinite set of infrared trivial scalar theories with a mass gap. Free particles have superimposed a harmonic oscillator set of states. The classical solution is displayed through a current expansion and the next-to-leading order quantum correction is provided. Application to the Standard Model would entail the existence of higher excited states of the Higgs particle and reduced decay rates to WW and ZZ that could already be measured.
Schwarzschild black holes can wear scalar wigs.
Barranco, Juan; Bernal, Argelia; Degollado, Juan Carlos; Diez-Tejedor, Alberto; Megevand, Miguel; Alcubierre, Miguel; Núñez, Darío; Sarbach, Olivier
2012-08-24
We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultralight scalar field dark matter around supermassive black holes and axionlike scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic in the sense that fairly arbitrary initial data evolve, at late times, as a combination of those long-lived configurations.
Schwarzschild Black Holes can Wear Scalar Wigs
NASA Astrophysics Data System (ADS)
Barranco, Juan; Bernal, Argelia; Degollado, Juan Carlos; Diez-Tejedor, Alberto; Megevand, Miguel; Alcubierre, Miguel; Núñez, Darío; Sarbach, Olivier
2012-08-01
We study the evolution of a massive scalar field surrounding a Schwarzschild black hole and find configurations that can survive for arbitrarily long times, provided the black hole or the scalar field mass is small enough. In particular, both ultralight scalar field dark matter around supermassive black holes and axionlike scalar fields around primordial black holes can survive for cosmological times. Moreover, these results are quite generic in the sense that fairly arbitrary initial data evolve, at late times, as a combination of those long-lived configurations.
Scalar and Pseudoscalar Glueballs Revisited
Cheng Haiyang
2010-08-05
Using two simple and robust inputs to constrain the mixing matrix of the isosinglet scalar mesons f{sub 0}(1710), f{sub 0}(1500), f{sub 0}(1370), we have shown that in the SU(3) symmetry limit, f{sub 0}(1500) becomes apure SU(3) octet and is degenerate with a{sub 0}(1450), while f{sub 0}(1370) is mainly an SU(3) singlet with a slight mixing with the scalar glueball which is the primary component of f{sub 0}(1710). These features remain essentially unchanged even when SU(3) breaking is taken into account. We have deduced the mass of the pseudoscalar glueball G from an {eta}-{eta}{sup '}-G mixing formalism based on the anomalous Ward identity for transition matrix elements. With the inputs from the recent KLOE experiment, we found a solution for the pseudoscalar glueball mass around (1.4{+-}0.1) GeV. This affirms that 77 (1405), having a large production rate in the radiative J/{Psi} decay and not seen in {gamma}{gamma} reactions, is indeed a leading candidate for the pseudoscalar glueball. It is much lower than the results from quenched lattice QCD (> 2.0 GeV).
Relativistic three-body bound states in scalar QFT: Variational basis-state approach
Emami-Razavi, Mohsen; Bergeron, Nantel; Darewych, Jurij W.; Kowalski, Marian
2009-10-15
We use the Hamiltonian formalism of quantum field theory and the variational basis-state method to derive relativistic three-body wave equations for scalar particles interacting via a massive or massless mediating scalar field (the scalar Yukawa model). A variational trial state comprised of three and five Fock-space states is used to derive coupled wave equations for a relativistic three- (and five-) body system. Approximate variational three-body ground-state solutions of the relativistic equations are obtained for various strengths of coupling, for both massive and massless mediating fields. The results show that the inclusion of virtual pairs has a large effect on the three-body binding energy at strong coupling.
Quasinormal modes, bifurcations, and nonuniqueness of charged scalar-tensor black holes
Doneva, Daniela D.; Yazadjiev, Stoytcho S.; Kokkotas, Kostas D.; Stefanov, Ivan Zh.
2010-09-15
In the present paper, we study the scalar sector of the quasinormal modes of charged general relativistic, static, and spherically symmetric black holes coupled to nonlinear electrodynamics and embedded in a class of scalar-tensor theories. We find that for a certain domain of the parametric space, there exists unstable quasinormal modes. The presence of instabilities implies the existence of scalar-tensor black holes with primary hair that bifurcate from the embedded general relativistic black-hole solutions at critical values of the parameters corresponding to the static zero modes. We prove that such scalar-tensor black holes really exist by solving the full system of scalar-tensor field equations for the static, spherically symmetric case. The obtained solutions for the hairy black holes are nonunique, and they are in one-to-one correspondence with the bounded states of the potential governing the linear perturbations of the scalar field. The stability of the nonunique hairy black holes is also examined, and we find that the solutions for which the scalar field has zeros are unstable against radial perturbations. The paper ends with a discussion of possible formulations of a new classification conjecture.
NASA Astrophysics Data System (ADS)
Gardner, Carl L.
2003-08-01
Cosmological variation of the fine structure constant α due to the evolution of a spatially homogeneous ultralight scalar field (m˜H0) during the matter and Λ dominated eras is analyzed. Agreement of Δα/α with the value suggested by recent observations of quasar absorption lines is obtained by adjusting a single parameter, the coupling of the scalar field to matter. Asymptotically α(t) in this model goes to a constant value α¯≈α0 in the early radiation and the late Λ dominated eras. The coupling of the scalar field to (nonrelativistic) matter drives α slightly away from α¯ in the epochs when the density of matter is important. Simultaneous agreement with the more restrictive bounds on the variation |Δα/α| from the Oklo natural fission reactor and from meteorite samples can be achieved if the mass of the scalar field is on the order of 0.5 0.6 HΛ, where HΛ=Ω1/2ΛH0. Depending on the scalar field mass, α may be slightly smaller or larger than α0 at the times of big bang nucleosynthesis, the emission of the cosmic microwave background, the formation of early solar system meteorites, and the Oklo reactor. The effects on the evolution of α due to nonzero mass for the scalar field are emphasized. An order of magnitude improvement in the laboratory technique could lead to a detection of (α˙/α)0.
Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy.
Van Tilburg, Ken; Leefer, Nathan; Bougas, Lykourgos; Budker, Dmitry
2015-07-01
We report new limits on ultralight scalar dark matter (DM) with dilatonlike couplings to photons that can induce oscillations in the fine-structure constant α. Atomic dysprosium exhibits an electronic structure with two nearly degenerate levels whose energy splitting is sensitive to changes in α. Spectroscopy data for two isotopes of dysprosium over a two-year span are analyzed for coherent oscillations with angular frequencies below 1 rad s-1. No signal consistent with a DM coupling is identified, leading to new constraints on dilatonlike photon couplings over a wide mass range. Under the assumption that the scalar field comprises all of the DM, our limits on the coupling exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3×10(-18) eV. Excess oscillatory power, inconsistent with fine-structure variation, is detected in a control channel, and is likely due to a systematic effect. Our atomic spectroscopy limits on DM are the first of their kind, and leave substantial room for improvement with state-of-the-art atomic clocks.
Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy.
Van Tilburg, Ken; Leefer, Nathan; Bougas, Lykourgos; Budker, Dmitry
2015-07-01
We report new limits on ultralight scalar dark matter (DM) with dilatonlike couplings to photons that can induce oscillations in the fine-structure constant α. Atomic dysprosium exhibits an electronic structure with two nearly degenerate levels whose energy splitting is sensitive to changes in α. Spectroscopy data for two isotopes of dysprosium over a two-year span are analyzed for coherent oscillations with angular frequencies below 1 rad s-1. No signal consistent with a DM coupling is identified, leading to new constraints on dilatonlike photon couplings over a wide mass range. Under the assumption that the scalar field comprises all of the DM, our limits on the coupling exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3×10(-18) eV. Excess oscillatory power, inconsistent with fine-structure variation, is detected in a control channel, and is likely due to a systematic effect. Our atomic spectroscopy limits on DM are the first of their kind, and leave substantial room for improvement with state-of-the-art atomic clocks. PMID:26182090
Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy
NASA Astrophysics Data System (ADS)
Van Tilburg, Ken; Leefer, Nathan; Bougas, Lykourgos; Budker, Dmitry
2015-07-01
We report new limits on ultralight scalar dark matter (DM) with dilatonlike couplings to photons that can induce oscillations in the fine-structure constant α . Atomic dysprosium exhibits an electronic structure with two nearly degenerate levels whose energy splitting is sensitive to changes in α . Spectroscopy data for two isotopes of dysprosium over a two-year span are analyzed for coherent oscillations with angular frequencies below 1 rad s-1 . No signal consistent with a DM coupling is identified, leading to new constraints on dilatonlike photon couplings over a wide mass range. Under the assumption that the scalar field comprises all of the DM, our limits on the coupling exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3 ×10-18 eV . Excess oscillatory power, inconsistent with fine-structure variation, is detected in a control channel, and is likely due to a systematic effect. Our atomic spectroscopy limits on DM are the first of their kind, and leave substantial room for improvement with state-of-the-art atomic clocks.
Study of earthquakes and related phenomena using a satellite scalar magnetometer
NASA Astrophysics Data System (ADS)
Schwingenschuh, Konrad; Magnes, Werner; Xuhui, Shen; Wang, Jindong; Pollinger, Andreas; Hagen, Christian; Lammegger, Roland; Ellmeier, Michaela; Prattes, Gustav; Eichelberger, Hans-Ulrich; Wolbang, Daniel; Boudjada, Mohammed Y.; Besser, Bruno P.; Rozhnoi, Alexander A.; Zhang, Tielong
2016-04-01
A new type of scalar magnetometer for space applications has been developed (see Lammegger 2008). A first instrument of this type will be flown aboard the upcoming Chinese Seismo-Electromagnetic Satellite (CSES). The scalar magnetometer can measure the total magnetic field with an accuracy of about 50 pT/sqrt(Hz) in the frequency range between 0 and 30 Hz. In order to minimize the stray field of the satellite, the sensor of the scalar magnetometer is mounted at the tip of a five meter boom. The main scientific objective of the scalar magnetometer aboard the Chinese satellite is the investigation of seismic phenomena before, during and after earthquakes or volcanic activity. The expected variations of the total magnetic field above seismic active regions, are presented, using a model based on the groundbased tectonomagnetic measurements and are simplified lithospheric-ionospheric coupling coefficient. Patent: Lammegger, R., WO 2008/151344 A3, Method and Device for Measuring Magnetic Fields
Polarized lepton-nucleon elastic scattering and a search for a light scalar boson
NASA Astrophysics Data System (ADS)
Liu, Yu-Sheng; Miller, Gerald A.
2015-09-01
Lepton-nucleon elastic scattering, using the one-photon and one-scalar-boson exchange mechanisms considering all possible polarizations, is used to study searches for a new scalar boson and suggest new measurements of the nucleon form factors. A new light scalar boson, which feebly couples to leptons and nucleons, may account for the proton radius and muon g -2 puzzles. We show that the scalar boson produces relatively large effects in a certain kinematic region when using sufficient control of lepton and nucleon spin polarization. We generalize current techniques to measure the ratio GE:GM and present a new method to separately measure GM2 and GE2 using polarized incoming and outgoing muons.
Scalar Mesons and Chiral States
NASA Astrophysics Data System (ADS)
Ishida, M.; Ishida, S.
2004-08-01
The essential points and physical backgrounds of the covariant level-classification scheme, based on Ū(12)SF⊗O(3, 1)L, are reviewed: This scheme is extended from the non-relativistic SU(6)SF⊗O(3)L scheme by introducing the new SU(2)-spin (ρ-spin) degree of freedom, which is necessary for covariant description of composite hadrons. Our scheme predicts the existence of new type of chiral mesons and baryons (Chiralons) out of the conventional SU(6)SF⊗O(3)L scheme. The σ nonet is a typical example of chiralons to be assigned to the (qq¯) relativistic S-wave state. The new narrow mesons Ds(2317)/Ds(2463) are naturally assigned as the ground-state scalar and axial-vector chiralons in the (cs¯) system.
Cross Sections From Scalar Field Theory
NASA Technical Reports Server (NTRS)
Norbury, John W.; Dick, Frank; Norman, Ryan B.; Nasto, Rachel
2008-01-01
A one pion exchange scalar model is used to calculate differential and total cross sections for pion production through nucleon- nucleon collisions. The collisions involve intermediate delta particle production and decay to nucleons and a pion. The model provides the basic theoretical framework for scalar field theory and can be applied to particle production processes where the effects of spin can be neglected.
A note on perfect scalar fields
NASA Astrophysics Data System (ADS)
Unnikrishnan, Sanil; Sriramkumar, L.
2010-05-01
We derive a condition on the Lagrangian density describing a generic, single, noncanonical scalar field, by demanding that the intrinsic, nonadiabatic pressure perturbation associated with the scalar field vanishes identically. Based on the analogy with perfect fluids, we refer to such fields as perfect scalar fields. It is common knowledge that models that depend only on the kinetic energy of the scalar field (often referred to as pure kinetic models) possess no nonadiabatic pressure perturbation. While we are able to construct models that seemingly depend on the scalar field and also do not contain any nonadiabatic pressure perturbation, we find that all such models that we construct allow a redefinition of the field under which they reduce to pure kinetic models. We show that, if a perfect scalar field drives inflation, then, in such situations, the first slow roll parameter will always be a monotonically decreasing function of time. We point out that this behavior implies that these scalar fields cannot lead to features in the inflationary, scalar perturbation spectrum.
Psycholinguistic and Neurolinguistic Investigations of Scalar Implicature
ERIC Educational Resources Information Center
Politzer-Ahles, Stephen
2013-01-01
The present study examines the representation and composition of meaning in scalar implicatures. Scalar implicature is the phenomenon whereby the use of a less informative term (e.g., "some") is inferred to mean the negation of a more informative term (e.g., to mean "not all"). The experiments reported here investigate how the…
Scalar gain interpretation of large order filters
NASA Technical Reports Server (NTRS)
Mason, Paul A. C.; Mook, D. Joseph
1993-01-01
A technique is developed which demonstrates how to interpret a large fully-populated filter gain matrix as a set of scalar gains. The inverse problem is also solved, namely, how to develop a large-order filter gain matrix from a specified set of scalar gains. Examples are given to illustrate the method.
Scalar Fields via Causal Tapestries
NASA Astrophysics Data System (ADS)
Sulis, William
2012-02-01
Causal tapestries provide a framework for implementing an explicit Process Theory approach to quantum foundations which models information flow within a physical system. We consider event-transition tapestry pairs. An event tapestry O is a 4-tuple (L, K, M, Ip ) where K is an index set of cardinality κ, M = M x F(M) x D x P(M') a mathematical structure with M a causal space, F(M) a function space, D a descriptor space, P(M') either a Lie algebra or tangent space on a manifold M', Ip an event tapestry. L consists of elements of the form [n]<α>G, n in K, α in M and G an acyclic directed graph whose vertex set is a subset of Lp Likewise, a transition tapestry π is a 4-tuple (L', K', M', I'p ) where M' = M' x F(M') x D' x P'(M). The dynamic generates a consistent succession of O-π pairs by means of a game based on the technique of forcing used in logic to generate models. This dynamic has previously been shown to be compatible with Lorentz invariance. An application of this approach to model scalar fields is presented in which each informon is associated with a function of the form f(πk1 /σ1 ,,πkN /σN )sin ( σ1 t1 --πk1 )/ ( σ1 t1 --πk1 ) .sin ( σN tN --πkN )/ ( σN tN --πkN ) and the WSK interpolation theorem is used to generate the resulting scalar field on the causal manifold.
García-Fontana, Cristina; Vílchez, Juan Ignacio; Narváez-Reinaldo, Juan Jesús; González-López, Jesús
2015-01-01
The genome sequence for Microbacterium sp. strain 3J1, a desiccation-tolerant organism isolated from the Nerium oleander rhizosphere, is reported here. The genome is estimated to be approximately 3.5 Mb in size, with an average G+C content of 67.7% and a predicted number of protein-coding sequences of 3,310. PMID:26316631
Einstein-Born-Infeld black holes with a scalar hair in three dimensions
NASA Astrophysics Data System (ADS)
Mazharimousavi, S. Habib; Halilsoy, M.
2015-09-01
We present black hole solutions in (2+1)-dimensional Einstein’s theory of gravity coupled with Born-Infeld (BI) nonlinear electrodynamic and a massless self-interacting scalar field. The model has five free parameters: mass M, cosmological constant ℓ, electric q and scalar r0 charges and BI parameter β. To attain exact solution for such a highly nonlinear system we adjust, i.e. finely tune, the parameters of the theory with the integration constants. In the limit β → 0, we recover the results of Einstein-Maxwell-Scalar theory, obtained before. The self-interacting potential admits finite minima apt for the vacuum contribution. Hawking temperature of the model is investigated versus properly tuned parameters. By employing this tuned-solution as basis, we obtain also a dynamic solution which in the proper limit admits the known solution in Einstein gravity coupled with self-interacting scalar field. Finally, we establish the equations of a general scalar-tensor field coupled to nonlinear electrodynamics (NED) field in 2+1 dimensions without searching for exact solutions.
Quantization of massive scalar fields over static black string backgrounds
Fernandez Piedra, Owen Pavel; Montes de Oca, Alejandro Cabo
2007-05-15
The renormalized mean value of the corresponding components of the energy-momentum tensor for massive scalar fields coupled to an arbitrary gravitational field configuration having cylindrical symmetry are analytically evaluated using the Schwinger-DeWitt approximation, up to second order in the inverse mass value. The general results are employed to explicitly derive compact analytical expressions for the energy-momentum tensor in the particular background of the black-string space-time. In the case of the black string considered in this work, we prove that a violation of the weak energy condition occurs at the horizon of the space-time for values of the coupling constant, which include as particular cases the most interesting of minimal and conformal coupling.
New charged black holes with conformal scalar hair
Anabalon, Andres; Maeda, Hideki
2010-02-15
A new class of four-dimensional, hairy, stationary solutions of the Einstein-Maxwell-{Lambda} system with a conformally coupled scalar field is obtained. The metric belongs to the Plebanski-Demianski family and hence its static limit has the form of the charged (A)dS C metric. It is shown that, in the static case, a new family of hairy black holes arises. They turn out to be cohomogeneity-two, with horizons that are neither Einstein nor homogenous manifolds. The conical singularities in the C metric can be removed due to the backreaction of the scalar field providing a new kind of regular, radiative spacetime. The scalar field carries a continuous parameter proportional to the usual acceleration present in the C metric. In the zero-acceleration limit, the static solution reduces to the dyonic Bocharova-Bronnikov-Melnikov-Bekenstein solution or the dyonic extension of the Martinez-Troncoso-Zanelli black holes, depending on the value of the cosmological constant.
Effects of a scalar scaling field on quantum mechanics
NASA Astrophysics Data System (ADS)
Benioff, Paul
2016-07-01
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.
Cosmological density perturbations in a conformal scalar field theory
NASA Astrophysics Data System (ADS)
Libanov, M. V.; Rubakov, V. A.
2012-02-01
We consider a scenario in which primordial scalar perturbations are generated when a complex conformal scalar field rolls down its negative quartic potential. Initially, these are perturbations of the phase of this field, which are then converted into adiabatic perturbations of the density. The existence of perturbations in the radial field direction, which have a red power spectrum, is a potentially dangerous feature of this scenario. But we show that in the linear order in the small parameter, the self-coupling, the infrared effects are completely nullified by an appropriate field redefinition. We evaluate the statistical anisotropy inherent in the model because of the presence of the long-wave perturbations of the radial field component. In the linear order in the self-coupling, the infrared effects do not affect the statistical anisotropy. They are manifested only at the quadratic order in the self-coupling, weakly (logarithmically) enhancing the corresponding contribution to the statistical anisotropy. The resulting statistical anisotropy is a combination of a large term, which decreases as the momentum increases, and a momentum-independent nonamplified term.
Extra neutral scalars with vectorlike fermions at the LHC
NASA Astrophysics Data System (ADS)
Gopalakrishna, Shrihari; Mukherjee, Tuhin Subhra; Sadhukhan, Soumya
2016-03-01
Many theories beyond the standard model (BSM) contain new C P -odd and C P -even neutral scalars ϕ ={A ,H } , and new vectorlike fermions (ψV L). The couplings of the C P -odd scalar A to two standard model (SM) gauge bosons cannot occur from renormalizable operators in a C P -conserving sector, but can be induced at the quantum loop level. We compute these effective couplings at the 1-loop level induced by the SM fermions and vectorlike fermions, present analytical expressions for them, and plot them numerically. Using the 8 TeV Large Hadron Collider (LHC) γ γ , τ+τ- and t t ¯ channel data, we derive constraints on the effective couplings of the ϕ to standard model gauge bosons and fermions. We present the gluon-fusion channel cross sections of the ϕ at the 8 and 14 TeV LHC, and its branching ratios into SM fermion and gauge-boson pairs. We first present our results in a model independent manner, and then we provide results for some simple models containing ϕ and ψV L in the singlet and doublet representations of S U (2 ). In the doublet case, we focus on the two-Higgs-doublet (2HDM) Type-II and Type-X models in the alignment limit.
Diphoton excess and running couplings
NASA Astrophysics Data System (ADS)
Bae, Kyu Jung; Endo, Motoi; Hamaguchi, Koichi; Moroi, Takeo
2016-06-01
The recently observed diphoton excess at the LHC may suggest the existence of a singlet (pseudo-)scalar particle with a mass of 750 GeV which couples to gluons and photons. Assuming that the couplings to gluons and photons originate from loops of fermions and/or scalars charged under the Standard Model gauge groups, we show that there is a model-independent upper bound on the cross section σ (pp → S → γγ) as a function of the cutoff scale Λ and masses of the fermions and scalars in the loop. Such a bound comes from the fact that the contribution of each particle to the diphoton event amplitude is proportional to its contribution to the one-loop β functions of the gauge couplings. We also investigate the perturbativity of running Yukawa couplings in models with fermion loops, and show the upper bounds on σ (pp → S → γγ) for explicit models.
Searching for chameleon-like scalar fields with the ammonia method
NASA Astrophysics Data System (ADS)
Levshakov, S. A.; Molaro, P.; Lapinov, A. V.; Reimers, D.; Henkel, C.; Sakai, T.
2010-03-01
Aims: We probe the dependence of the electron-to-proton mass ratio, μ = me/mp, on the ambient matter density by means of radio astronomical observations. Methods: The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependences of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH3 (J,K) = (1,1), HC_3N J = 2-1, and N_2H^+ J = 1-0 were performed at three radio telescopes to measure the radial velocity offsets, Δ V ≡ Vrot - Vinv, between the inversion transition of NH_3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter Δμ/μ ≡ (μ_obs - μ_lab)/μ_lab. Results: The measured values of Δ V exhibit a statistically significant velocity offset of 23±4_stat ± 3_sys m s-1 . When interpreted in terms of the electron-to-proton mass ratio variation, this infers that Δμ/μ = (2.2±0.4_stat ± 0.3_sys) × 10-8. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |Δ V| ≤ 30 m s-1 . This provides the most accurate reference point at z = 0 for Δμ/μ of |Δ μ/μ| ≤ 3×10-8. Based on observations obtained with the Medicina 32-m telescope operated by INAF - Istituto di Radioastronomia, the 100-m telescope of the Max-Planck Institut für Radioastronomie at Effelsberg, and the Nobeyama Radio Observatory 45-m telescope of the National Astronomical Observatory of Japan.
Minimal semi-annihilating Bbb ZN scalar dark matter
NASA Astrophysics Data System (ADS)
Bélanger, Geneviève; Kannike, Kristjan; Pukhov, Alexander; Raidal, Martti
2014-06-01
We study the dark matter from an inert doublet and a complex scalar singlet stabilized by Bbb ZN symmetries. This field content is the minimal one that allows dimensionless semi-annihilation couplings for N > 2. We consider explicitly the Bbb Z3 and Bbb Z4 cases and take into account constraints from perturbativity, unitarity, vacuum stability, necessity for the electroweak Bbb ZN preserving vacuum to be the global minimum, electroweak precision tests, upper limits from direct detection and properties of the Higgs boson. Co-annihilation and semi-annihilation of dark sector particles as well as dark matter conversion significantly modify the cosmic abundance and direct detection phenomenology.
Nonuniversal scalar-tensor theories and big bang nucleosynthesis
Coc, Alain; Olive, Keith A.; Uzan, Jean-Philippe; Vangioni, Elisabeth
2009-05-15
We investigate the constraints that can be set from big bang nucleosynthesis on two classes of models: extended quintessence and scalar-tensor theories of gravity in which the equivalence principle between standard matter and dark matter is violated. In the latter case, and for a massless dilaton with quadratic couplings, the phase space of theories is investigated. We delineate those theories where attraction toward general relativity occurs. It is shown that big bang nucleosynthesis sets more stringent constraints than those obtained from Solar System tests.
Asymptotic safety in Einstein gravity and scalar-fermion matter.
Vacca, G P; Zanusso, O
2010-12-01
Within the functional renormalization group approach we study the effective quantum field theory of Einstein gravity and one self-interacting scalar coupled to N(f) Dirac fermions. We include in our analysis the matter anomalous dimensions induced by all the interactions and analyze the highly nonlinear beta functions determining the renormalization flow. We find the existence of a nontrivial fixed point structure both for the gravity and the matter sector, besides the usual Gaussian matter one. This suggests that asymptotic safety could be realized in the gravitational sector and in the standard model. Nontriviality in the Higgs sector might involve gravitational interactions.
Gauss-Bonnet Brane World Gravity with a Scalar Field
Davis, Stephen C.
2004-11-17
The effective four-dimensional, linearised gravity of a brane world model with one extra dimension and a single brane is analysed. The model includes higher order curvature terms (such as the Gauss-Bonnet term) and a conformally coupled scalar field. Large and small distance gravitational laws are derived. In contrast to the corresponding Einstein gravity models, it is possible to obtain solutions with localised gravity which are compatible with observations. Solutions with non-standard large distance Newtonian potentials are also described.
Local energy-momentum conservation in scalar-tensor-like gravity with generic curvature invariants
NASA Astrophysics Data System (ADS)
Tian, David Wenjie
2016-08-01
For a large class of scalar-tensor-like gravity whose action contains nonminimal couplings between a scalar field φ (x^α ) and generic curvature invariants R beyond the Ricci scalar R=R^α _{α }, we prove the covariant invariance of its field equation and confirm/prove the local energy-momentum conservation. These φ (x^α )- R coupling terms break the symmetry of diffeomorphism invariance under an active transformation, which implies that the solutions to the field equation should satisfy the consistency condition R ≡ 0 when φ (x^α ) is nondynamical and massless. Following this fact and based on the accelerated expansion of the observable Universe, we propose a primary test to check the viability of the modified gravity to be an effective dark energy, and a simplest example passing the test is the "Weyl/conformal dark energy".
Updated axial meson spectrum and scalar-glueball mixing in AdS/QCD
NASA Astrophysics Data System (ADS)
Bartz, Sean; Rollag, Joshua
2016-03-01
AdS/QCD is a proposed duality between strongly-coupled quantum chromodynamics and weakly-coupled 5D gravity that can offer new insight to hadronic physics. Previous work accurately models confinement and chiral symmetry breaking in the light hadron spectrum. We improve this model by incorporating new experimental data and making predictions for the scalar glueball sector. Recent COMPASS results indicate a new light axial-vector resonance between the ground state and the currently-accepted value for the first excited state. Incorporating this data lessens the model's dependence on unphysical short length scales. In addition, we analyze the mixing between scalar mesons and glueball by computing to first approximation the radial excitation spectra of these particles. We find good experimental agreement for the scalar mesons and show that predictions for the excited glueball spectrum differ from lattice results.
Refining inflation using non-canonical scalars
Unnikrishnan, Sanil; Sahni, Varun; Toporensky, Aleksey E-mail: varun@iucaa.ernet.in
2012-08-01
This paper revisits the Inflationary scenario within the framework of scalar field models possessing a non-canonical kinetic term. We obtain closed form solutions for all essential quantities associated with chaotic inflation including slow roll parameters, scalar and tensor power spectra, spectral indices, the tensor-to-scalar ratio, etc. We also examine the Hamilton-Jacobi equation and demonstrate the existence of an inflationary attractor. Our results highlight the fact that non-canonical scalars can significantly improve the viability of inflationary models. They accomplish this by decreasing the tensor-to-scalar ratio while simultaneously increasing the value of the scalar spectral index, thereby redeeming models which are incompatible with the cosmic microwave background (CMB) in their canonical version. For instance, the non-canonical version of the chaotic inflationary potential, V(φ) ∼ λφ{sup 4}, is found to agree with observations for values of λ as large as unity! The exponential potential can also provide a reasonable fit to CMB observations. A central result of this paper is that steep potentials (such as V∝φ{sup −n}) usually associated with dark energy, can drive inflation in the non-canonical setting. Interestingly, non-canonical scalars violate the consistency relation r = −8n{sub T}, which emerges as a smoking gun test for this class of models.
Static scalar field solutions in symmetric gravity
NASA Astrophysics Data System (ADS)
Hossenfelder, S.
2016-09-01
We study an extension of general relativity with a second metric and an exchange symmetry between the two metrics. Such an extension might help to address some of the outstanding problems with general relativity, for example the smallness of the cosmological constant. We here derive a family of exact solutions for this theory. In this two-parameter family of solutions the gravitational field is sourced by a time-independent massless scalar field. We find that the only limit in which the scalar field entirely vanishes is flat space. The regular Schwarzschild-solution is left with a scalar field hidden in the second metric’s sector.
Scalar-isoscalar states in the large-N{sub c} Regge approach
Ruiz Arriola, Enrique; Broniowski, Wojciech
2010-03-01
Scalar-isoscalar states (J{sup PC}=0{sup ++}) are investigated within the large-N{sub c} Regge approach. We elaborate on the consequences of including the lightest f{sub 0}(600) scalar-isoscalar state into such an analysis, where the position of f{sub 0}(600) fits very well into the pattern of the radial Regge trajectory. Furthermore, we point out that the pion and nucleon spin-0 gravitational form factors, recently measured on the lattice, provide valuable information on the low-mass spectrum of the scalar-isoscalar states on the basis of the scalar-meson dominance in the spin-0 channel. Through the fits to these data we find m{sub {sigma}=}450-600 MeV. We compare the predictions of various fits and methods. An analysis of the QCD condensates in the two-point correlators provides further constraints on the parameters of the scalar-isoscalar sector. We find that a simple two-state model suggests a meson nature of f{sub 0}(600), and a glueball nature of f{sub 0}(980), which naturally explains the ratios of various coupling constants. Finally, we note that the fine-tuned condition of the vanishing dimension-two condensate in the Regge approach with infinitely many scalar-isoscalar states yields a reasonable value for the mass of the lightest glueball state.
Two-dimensionally-periodic diffractive optical elements: limitations of scalar analysis.
Glytsis, Elias N
2002-04-01
The range of validity of the scalar diffraction analysis is quantified for the case of two-dimensionally-periodic diffractive optical elements (crossed gratings). Three canonical classes of two-dimensionally-periodic grating structures are analyzed by using the rigorous coupled-wave analysis as well as the scalar diffraction analysis. In all cases the scalar-analysis diffraction efficiencies are compared with the exact diffraction efficiencies. The error in using the scalar analysis is then determined as a function of the grating-period(s)-to-wavelength ratio(s), the minimum feature size, the grating depth, the refractive index of the grating, the incident polarization, and the number of phase levels. The three classes of two-dimensional (2-D) unit cells are as follows: (1) a rectangular pillar, (2) an elliptical pillar, and (3) an arbitrarily pixellated multilevel 2-D unit cell that is representative of more complicated diffractive optical elements such as computer-generated holograms. In all cases a normally incident electromagnetic plane wave is considered. It is shown that the error of the scalar diffraction analysis in the case of two-dimensionally-periodic diffractive optical elements is greater than that for the corresponding one-dimensionally-periodic counterparts. In addition, the accuracy of the scalar diffraction analysis degrades with increasing refractive index, grating thickness, and asymmetry of the 2-D unit cell and with decreasing grating-period-to-wavelength ratio and feature size.
Properties and uncertainties of scalar field models of dark energy with barotropic equation of state
Novosyadlyj, Bohdan; Sergijenko, Olga; Apunevych, Stepan; Pelykh, Volodymyr
2010-11-15
The dynamics of expansion and large scale structure formation in the multicomponent Universe with dark energy modeled by the minimally coupled scalar field with generalized linear barotropic equation of state are analyzed. It is shown that the past dynamics of expansion and future of the Universe - eternal accelerated expansion or turnaround and collapse - are completely defined by the current energy density of a scalar field and relation between its current and early equation of state parameters. The clustering properties of such models of dark energy and their imprints in the power spectrum of matter density perturbations depend on the same relation and, additionally, on the 'effective sound speed' of a scalar field, defined by its Lagrangian. It is concluded that such scalar fields with different values of these parameters are distinguishable in principle. This gives the possibility to constrain them by confronting the theoretical predictions with the corresponding observational data. For that we have used the 7-year Wilkinson Microwave Anisotropy Probe data on cosmic microwave background anisotropies, the Union2 data set on Supernovae Ia and the seventh data release of the Sloan Digital Sky Survey data on luminous red galaxies space distribution. Using the Markov Chain Monte Carlo technique the marginalized posterior and mean likelihood distributions are computed for the scalar fields with two different Lagrangians: Klein-Gordon and Dirac-Born-Infeld ones. The properties of such scalar field models of dark energy with best fitting parameters and uncertainties of their determination are also analyzed in the paper.
Searching for the Scalar Glueball
Ochs, Wolfgang
2008-08-31
Existence of gluonic resonances is among the early expectations of QCD. Today, QCD calculations predict the lightest glueball to be a scalar state with mass within a range of about 900-1700 MeV but there is no consensus about its experimental evidence. In a re-analysis of the phase shifts for {pi}{pi} scattering up to 1800 MeV where such states should show up we find the broad resonance f{sub 0}(600)/{sigma} contributing to the full mass range and the narrow f{sub 0}(980) and f{sub 0}(1500) but no evidence for f{sub 0}(1370). Phenomenological arguments for the broad state to be a glueball are recalled. It is argued that the large radiative width of f{sub 0}(600)/{sigma} reported recently is not in contradiction to this hypothesis but is mainly due to {pi}{pi}-rescattering. The small 'direct' radiative component is consistent with QCD sum rule predictions for the light glueball.
Hees, A; Guéna, J; Abgrall, M; Bize, S; Wolf, P
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed. PMID:27541455
Hees, A; Guéna, J; Abgrall, M; Bize, S; Wolf, P
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.
NASA Astrophysics Data System (ADS)
Hees, A.; Guéna, J.; Abgrall, M.; Bize, S.; Wolf, P.
2016-08-01
We use 6 yrs of accurate hyperfine frequency comparison data of the dual rubidium and caesium cold atom fountain FO2 at LNE-SYRTE to search for a massive scalar dark matter candidate. Such a scalar field can induce harmonic variations of the fine structure constant, of the mass of fermions, and of the quantum chromodynamic mass scale, which will directly impact the rubidium/caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine structure constant and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed.
Bastero-Gil, Mar; Berera, Arjun; Jackson, Brendan M. E-mail: ab@ph.ed.ac.uk
2011-07-01
A scalar potential coupled to other fields of large disparate masses will exhibit power suppression of the quantum loop corrections from these massive fields. Quintessence fields in the dark energy regime and inflaton fields during inflation often have a very large background field value. Thus any other field with its mass dependent on the quintessence/inflaton background field value through a moderate coupling will become very massive during the dark energy/inflation phase and its quantum corrections to the scalar effective potential will be suppressed. This concept is developed in this paper using the decoupling theorem. The problem then reduces to a quantitative question of the size of suppression effects within the parameter space of coupling constants, scalar field background value and renormalization scale. Some numerical examples are presented both for inflation and quintessence, but the approach is general and can be applied to any scalar field effective potential. The consequences to dark energy of the decoupling effect developed here is that the quintessence field need not just be an incredibly weakly interacting field, often included as an add-on to generate dark energy and having no other purpose. Instead, this quintessence field could play a central role in the particle physics dynamics at early times and then the other fields simply decouple from it at late times before the onset of the dark energy phase. For inflation a consequence is coupling of the inflaton to other heavy fields can be much larger.
The 1+1+2 formalism for scalar-tensor gravity
NASA Astrophysics Data System (ADS)
Carloni, Sante; Dunsby, Peter K. S.
2016-10-01
We use the 1+1+2 covariant approach to clarify a number of aspects of spherically symmetric solutions of non-minimally coupled scalar tensor theories. Particular attention is focused on the extension of Birkhoff's theorem and the nature of quasi-local horizons in this context.
Grand unification and light color-octet scalars at the LHC
NASA Astrophysics Data System (ADS)
Pérez, Pavel Fileviez; Gavin, Ryan; McElmurry, Thomas; Petriello, Frank
2008-12-01
We study the properties and production mechanisms of color-octet scalars at the Large Hadron Collider. We focus on the single production of both charged and neutral members of an (8,2)1/2 doublet through bottom-quark initial states. These channels provide a window to the underlying Yukawa structure of the scalar sector. Color-octet scalars naturally appear in grand unified theories based on the SU(5) gauge symmetry. In the context of adjoint SU(5) these fields are expected to be light to satisfy constraints coming from unification and proton decay, and may have TeV-scale masses. One combination of their couplings is defined by the relation between the down-quark and charged-lepton Yukawa couplings. Observation of these states at the LHC gives an upper bound on the proton lifetime if they truly arise from this grand unified theory. We demonstrate that TeV-mass scalars can be observed over background at the LHC using boosted top-quark final states, and study how well the scalar Yukawa parameters can be measured.
Preferred frame parameters in the tensor-vector-scalar theory of gravity and its generalization
Sagi, Eva
2009-08-15
The tensor-vector-scalar theory of gravity, which was designed as a relativistic implementation to the modified dynamics paradigm, has fared quite well as an alternative to dark matter, on both galactic and cosmological scales. However, its performance in the Solar System, as embodied in the post-Newtonian formalism, has not yet been fully investigated. We calculate the post-Newtonian parameters for TeVeS with the cosmological value of the scalar field taken into account, and show that in this situation the cosmological value of the scalar field is tightly linked to the vector field coupling constant K, preventing the former from evolving as predicted by its equation of motion. We show that generalizing TeVeS to have an Aether-type vector action, as suggested by Skordis, removes the aforesaid link, and this generalized version of TeVes has its {beta}, {gamma}, and {xi} parameterized post-Newtonian parameters identical to those in GR, while solar system constraints on the preferred frame parameters {alpha}{sub 1} and {alpha}{sub 2} can be satisfied within a modest range of small values of the scalar and vector fields coupling parameters, and for cosmological values of the scalar field consistent with evolution within the framework of existing cosmological models.
Probing a light CP-odd scalar in di-top-associated production at the LHC
NASA Astrophysics Data System (ADS)
Casolino, Mirkoantonio; Farooque, Trisha; Juste, Aurelio; Liu, Tao; Spannowsky, Michael
2015-10-01
CP-odd scalars are an integral part of many extensions of the Standard Model. Recently, electroweak-scale pseudoscalars have received increased attention in explaining the diffuse gamma-ray excess from the Galactic Centre. Elusive due to absence of direct couplings to gauge bosons, these particles receive only weak constraints from direct searches at LEP or searches performed during the first LHC runs. We investigate the LHC's sensitivity in probing a CP-odd scalar in the mass range 20 ≤ m_A ≤ 100 GeV via di-top-associated production using jet-substructure-based reconstruction techniques. We parameterise the scalar's interactions using a simplified model approach and relate the obtained upper limits to couplings within type-I and type-II 2HDMs as well as the NMSSM. We find that in di-top-associated production, experiments at the LHC can set tight limits on CP-odd scalars that fit the Galactic Centre excess. However, direct sensitivity to light CP-odd scalars from the NMSSM remains challenging.
AdS and Lifshitz scalar hairy black holes in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Chen, Bin; Fan, Zhong-Ying; Zhu, Lu-Yao
2016-09-01
We consider Gauss-Bonnet (GB) gravity in general dimensions, which is nonminimally coupled to a scalar field. By choosing a scalar potential of the type V (ϕ )=2 Λ0+1/2 m2ϕ2+γ4ϕ4 , we first obtain large classes of scalar hairy black holes with spherical/hyperbolic/planar topologies that are asymptotic to locally anti- de Sitter (AdS) space-times. We derive the first law of black hole thermodynamics using Wald formalism. In particular, for one class of the solutions, the scalar hair forms a thermodynamic conjugate with the graviton and nontrivially contributes to the thermodynamical first law. We observe that except for one class of the planar black holes, all these solutions are constructed at the critical point of GB gravity where there exist unique AdS vacua. In fact, a Lifshitz vacuum is also allowed at the critical point. We then construct many new classes of neutral and charged Lifshitz black hole solutions for an either minimally or nonminimally coupled scalar and derive the thermodynamical first laws. We also obtain new classes of exact dynamical AdS and Lifshitz solutions which describe radiating white holes. The solutions eventually become AdS or Lifshitz vacua at late retarded times. However, for one class of the solutions, the final state is an AdS space-time with a globally naked singularity.
Grand unification and light color-octet scalars at the LHC
Perez, Pavel Fileviez; Gavin, Ryan; McElmurry, Thomas; Petriello, Frank
2008-12-01
We study the properties and production mechanisms of color-octet scalars at the Large Hadron Collider. We focus on the single production of both charged and neutral members of an (8,2){sub 1/2} doublet through bottom-quark initial states. These channels provide a window to the underlying Yukawa structure of the scalar sector. Color-octet scalars naturally appear in grand unified theories based on the SU(5) gauge symmetry. In the context of adjoint SU(5) these fields are expected to be light to satisfy constraints coming from unification and proton decay, and may have TeV-scale masses. One combination of their couplings is defined by the relation between the down-quark and charged-lepton Yukawa couplings. Observation of these states at the LHC gives an upper bound on the proton lifetime if they truly arise from this grand unified theory. We demonstrate that TeV-mass scalars can be observed over background at the LHC using boosted top-quark final states, and study how well the scalar Yukawa parameters can be measured.
Gao, Hong; Sneha, Mahima; Bouakline, Foudhil; Althorpe, Stuart C; Zare, Richard N
2015-12-17
We report rovibrationally selected differential cross sections (DCSs) of the benchmark reaction H + D2 → HD(v' = 3, j' = 4-10) + D at a collision energy of 3.26 eV, which exceeds the conical intersection of the H3 potential energy surface at 2.74 eV. We use the PHOTOLOC technique in which a fluorine excimer laser at 157.64 nm photodissociates hydrogen bromide (HBr) molecules to generate fast H atoms and the HD product is detected in a state-specific manner by resonance-enhanced multiphoton ionization. Fully converged quantum wave packet calculations were performed for this reaction at this high collision energy without inclusion of the geometric phase (GP) effect, which takes into account coupling to the first excited state of the H3 potential energy surface. Multimodal structures can be observed in most of the DCSs up to j' = 10, which is predicted by theory and also well-reproduced by experiment. The theoretically calculated DCSs are in good overall agreement with the experimental measurements, which indicates that the GP effect is not large enough that its existence can be verified experimentally at this collision energy.
Extra vectorlike matter and the lightest Higgs scalar boson mass in low-energy supersymmetry
Martin, Stephen P.
2010-02-01
The lightest Higgs scalar boson mass in supersymmetry can be raised significantly by extra vectorlike quark and lepton supermultiplets with large Yukawa couplings but dominantly electroweak-singlet masses. I consider models of this type that maintain perturbative gauge coupling unification. The impact of the new particles on precision electroweak observables is found to be moderate, with the fit to Z-pole data as good or better than that of the standard model even if the new Yukawa couplings are as large as their fixed-point values and the extra vectorlike quark masses are as light as 400 GeV. I study the size of corrections to the lightest Higgs boson mass, taking into account the fixed-point behavior of the scalar trilinear couplings. I also discuss the decay branching ratios of the lightest new quarks and leptons and general features of the resulting collider signatures.
Quantum corrections in Higgs inflation: the real scalar case
George, Damien P.; Mooij, Sander; Postma, Marieke E-mail: sander.mooij@ing.uchile.cl
2014-02-01
We present a critical discussion of quantum corrections, renormalisation, and the computation of the beta functions and the effective potential in Higgs inflation. In contrast with claims in the literature, we find no evidence for a disagreement between the Jordan and Einstein frames, even at the quantum level. For clarity of discussion we concentrate on the case of a real scalar Higgs. We first review the classical calculation and then discuss the back reaction of gravity. We compute the beta functions for the Higgs quartic coupling and non-minimal coupling constant. Here, the mid-field regime is non-renormalisable, but we are able to give an upper bound on the 1-loop corrections to the effective potential. We show that, in computing the effective potential, the Jordan and Einstein frames are compatible if all mass scales are transformed between the two frames. As such, it is consistent to take a constant cutoff in either the Jordan or Einstein frame, and both prescriptions yield the same result for the effective potential. Our results are extended to the case of a complex scalar Higgs.
Stability of a collapsed scalar field and cosmic censorship
Abe, S.
1988-08-15
The static and asymptotically flat solution to the Einstein-massless-scalar model with spherical symmetry describes the spacetime with a naked singularity when it has a nonvanishing scalar charge. We show that such a solution is unstable against the spherical scalar monopole perturbation. This suggests the validity of the cosmic censorship hypothesis in the spherical collapse of the scalar field.
General relativity as an attractor for scalar-torsion cosmology
NASA Astrophysics Data System (ADS)
Järv, Laur; Toporensky, Alexey
2016-01-01
We study flat Friedmann-Lemaître-Robertson-Walker cosmological models for a scalar field coupled nonminimally to teleparallel gravity with generic coupling and potential functions. The goal in this paper is to determine the conditions under which cosmological evolution tends to the limit where the variation of the gravitational "constant" ceases and the system evolves close to general relativity (GR). These conditions can be read off from the approximate analytical solutions describing the process in matter and potential domination eras. Only those models where the GR limit exists and is an attractor can be considered viable. We expect the results to hold in the original "pure tetrad" formulation as well as in the recently suggested covariant formulation of the teleparallel theory. In the former case the GR attractor simultaneously provides a mechanism for how cosmological evolution suppresses the problematic degrees of freedom stemming from the lack of local Lorentz invariance.
Rodrigues, Sophie; Paillard, Christine; Dufour, Alain; Bazire, Alexis
2015-03-01
Vibrio tapetis CECT4600 is a pathogenic Gram-negative bacterium causing the brown ring disease in the Manila clam Ruditapes philippinarum. This vibriosis is induced by bacterial attachment on the periostracal lamina, yielding a decalcification of the bivalve shell. As in many bacterial species, pathogenesis is likely related to biofilm formation. The proteinaceous exoproducts of the marine bacterium Pseudoalteromonas sp. 3J6 inhibit the formation of biofilm by most of the tested marine bacteria without affecting their planktonic growth. In the present work, we examined the sensitivity of V. tapetis to Pseudoalteromonas sp. 3J6 and its exoproducts. In V. tapetis CECT4600-GFP-Pseudoalteromonas sp. 3J6 co-cultures, the latter outcompeted V. tapetis whatever the growth mode (planktonic or biofilm), which could result from a slower growth of V. tapetis. Biofilms containing only V. tapetis were grown in vitro on a glass substratum under dynamic conditions. When the glass was coated with a culture supernatant of Pseudoalteromonas sp. 3J6 (SN(3J6)) prior to inoculating V. tapetis CECT4600-GFP, the bacterial attachment was about fivefold lower than in control experiment without SN3J6 and the biofilm formation was delayed by about 24 h: A full biofilm was obtained at 48 versus 24 h for the control. Moreover, a preformed V. tapetis biofilm (grown on SN(3J6)-free glass substratum) could be disrupted by incubating it with SN3J6. This data suggest that Pseudoalteromonas sp. 3J6 is a good candidate to set up an anti-V. tapetis strategy usable in aquaculture to grow V. tapetis-free Manila clam spats.
Bouncing universes in scalar-tensor gravity models admitting negative potentials
Boisseau, B.; Giacomini, H.; Starobinsky, A.A. E-mail: hector.giacomini@lmpt.univ-tours.fr E-mail: alstar@landau.ac.ru
2015-07-01
We consider the possibility to produce a bouncing universe in the framework of scalar-tensor gravity models in which the scalar field potential may be negative, and even unbounded from below. We find a set of viable solutions with nonzero measure in the space of initial conditions passing a bounce, even in the presence of a radiation component, and approaching a constant gravitational coupling afterwards. Hence we have a model with a minimal modification of gravity in order to produce a bounce in the early universe with gravity tending dynamically to general relativity (GR) after the bounce.
Sub-eV scalar dark matter through the super-renormalizable Higgs portal
NASA Astrophysics Data System (ADS)
Piazza, Federico; Pospelov, Maxim
2010-08-01
The Higgs portal of the standard model provides the opportunity for coupling to a very light scalar field ϕ via the super-renormalizable operator ϕ(H†H). This allows for the existence of a very light scalar dark matter that has coherent interaction with the standard model particles and yet has its mass protected against radiative corrections. We analyze ensuing constraints from the fifth force measurements, along with the cosmological requirements. We find that the detectable level of the fifth force can be achieved in models with low inflationary scales, and by a certain amount of fine-tuning in the initial deviation of ϕ from its minimum.
Light scalar as the messenger of electroweak and flavor symmetry breaking
Lykken, J. D.; Murdock, Z.; Nandi, S.
2009-04-01
We propose a new framework for understanding the hierarchies of fermion masses and mixings. The masses and mixings of all standard model (SM) charged fermions other than top arise from higher dimensional operators involving a messenger scalar S and flavon scalars F{sub i}. The flavons spontaneously break SM flavor symmetries at around the TeV scale. The SM singlet scalar S couples directly to the Higgs H and spontaneously breaks another U(1) at the electroweak scale. At the TeV scale, SM quarks and charged leptons have renormalizable couplings to S, but not to H or F{sub i}. These couplings involve new heavy vectorlike fermions. Integrating out these fermions produces a pattern of higher dimensional operators that reproduce the observed hierarchies of the SM masses and mixings in terms of powers of the 'little hierarchy': the ratio of the electroweak scale to the flavor-breaking scale. The framework has important phenomenological implications. Flavor-changing neutral currents are within experimental limits but D{sup 0}-D{sup 0} mixing and B{sub s}{yields}{mu}{sup +}{mu}{sup -} could be close to current sensitivities. The neutral scalar s of the messenger field mixes with the light Higgs of the SM, which can have strong effects on Higgs decay branching fractions. The s mass eigenstate may be lighter than the Higgs, and could be detected at the Tevatron or the LHC.
Can dark matter be a scalar field?
NASA Astrophysics Data System (ADS)
Jesus, J. F.; Pereira, S. H.; Malatrasi, J. L. G.; Andrade-Oliveira, F.
2016-08-01
In this paper we study a real scalar field as a possible candidate to explain the dark matter in the universe. In the context of a free scalar field with quadratic potential, we have used Union 2.1 SN Ia observational data jointly with a Planck prior over the dark matter density parameter to set a lower limit on the dark matter mass as m>=0.12H0‑1 eV (c=hbar=1). For the recent value of the Hubble constant indicated by the Hubble Space Telescope, namely H0=73±1.8 km s‑1Mpc‑1, this leads to m>=1.56×10‑33 eV at 99.7% c.l. Such value is much smaller than m~ 10‑22 eV previously estimated for some models. Nevertheless, it is still in agreement with them once we have not found evidences for a upper limit on the scalar field dark matter mass from SN Ia analysis. In practice, it confirms free real scalar field as a viable candidate for dark matter in agreement with previous studies in the context of density perturbations, which include scalar field self interaction.
Can dark matter be a scalar field?
NASA Astrophysics Data System (ADS)
Jesus, J. F.; Pereira, S. H.; Malatrasi, J. L. G.; Andrade-Oliveira, F.
2016-08-01
In this paper we study a real scalar field as a possible candidate to explain the dark matter in the universe. In the context of a free scalar field with quadratic potential, we have used Union 2.1 SN Ia observational data jointly with a Planck prior over the dark matter density parameter to set a lower limit on the dark matter mass as m>=0.12H0-1 eV (c=hbar=1). For the recent value of the Hubble constant indicated by the Hubble Space Telescope, namely H0=73±1.8 km s-1Mpc-1, this leads to m>=1.56×10-33 eV at 99.7% c.l. Such value is much smaller than m~ 10-22 eV previously estimated for some models. Nevertheless, it is still in agreement with them once we have not found evidences for a upper limit on the scalar field dark matter mass from SN Ia analysis. In practice, it confirms free real scalar field as a viable candidate for dark matter in agreement with previous studies in the context of density perturbations, which include scalar field self interaction.
Light scalar field constraints from gravitational-wave observations of compact binaries
NASA Astrophysics Data System (ADS)
Berti, Emanuele; Gualtieri, Leonardo; Horbatsch, Michael; Alsing, Justin
2012-06-01
Scalar-tensor theories are among the simplest extensions of general relativity. In theories with light scalars, deviations from Einstein’s theory of gravity are determined by the scalar mass ms and by a Brans-Dicke-like coupling parameter ωBD. We show that gravitational-wave observations of nonspinning neutron star-black hole binary inspirals can be used to set lower bounds on ωBD and upper bounds on the combination ms/ωBD. We estimate via a Fisher matrix analysis that individual observations with signal-to-noise ratio ρ would yield (ms/ωBD)(ρ/10)≲10-15, 10-16, and 10-19eV for Advanced LIGO, ET, and eLISA, respectively. A statistical combination of multiple observations may further improve these bounds.
A New Two-Faced Scalar Solution and Cosmological SUSY Breaking
Shmakova, Marina; Burov, Valentin; /Moscow State U.
2010-08-27
We propose a possible new way to resolve the long standing problem of strong supersymmetry breaking coexisting with a small cosmological constant. We consider a scalar component of a minimally coupled N = 1 supermultiplet in a general Friedmann-Robertson-Walker (FRW) expanding universe. We argue that a tiny term, proportional to H{sup 2} {approx} 10{sup -122} in Plank's units, appearing in the field equations due to this expansion will provide both, the small vacuum energy and the heavy mass of the scalar supersymmetric partner. We present a non-perturbative solution for the scalar field with an unusual dual-frequency behavior. This solution has two characteristic mass scales related to the Hubble parameter as H{sup 1/4} and H{sup 1/2} measured in Plank's units.
WIMP dark matter and unitarity-conserving inflation via a gauge singlet scalar
Kahlhoefer, Felix; McDonald, John E-mail: j.mcdonald@lancaster.ac.uk
2015-11-01
A gauge singlet scalar with non-minimal coupling to gravity can drive inflation and later freeze out to become cold dark matter. We explore this idea by revisiting inflation in the singlet direction (S-inflation) and Higgs Portal Dark Matter in light of the Higgs discovery, limits from LUX and observations by Planck. We show that large regions of parameter space remain viable, so that successful inflation is possible and the dark matter relic abundance can be reproduced. Moreover, the scalar singlet can stabilise the electroweak vacuum and at the same time overcome the problem of unitarity-violation during inflation encountered by Higgs Inflation, provided the singlet is a real scalar. The 2-σ Planck upper bound on n{sub s} imposes that the singlet mass is below 2 TeV, so that almost the entire allowed parameter range can be probed by XENON1T.
FAST TRACK COMMUNICATION: Phenomenology of the equivalence principle with light scalars
NASA Astrophysics Data System (ADS)
Damour, Thibault; Donoghue, John F.
2010-10-01
Light scalar particles with couplings of sub-gravitational strength, which can generically be called 'dilatons', can produce violations of the equivalence principle. However, in order to understand experimental sensitivities one must know the coupling of these scalars to atomic systems. We report here on a study of the required couplings. We give a general Lagrangian with five independent dilaton parameters and calculate the 'dilaton charge' of atomic systems for each of these. Two combinations are particularly important. One is due to the variations in the nuclear binding energy, with a sensitivity scaling with the atomic number as A-1/3. The other is due to electromagnetism. We compare limits on the dilaton parameters from existing experiments.
Extended scalar-tensor theories of gravity
NASA Astrophysics Data System (ADS)
Crisostomi, Marco; Koyama, Kazuya; Tasinato, Gianmassimo
2016-04-01
We study new consistent scalar-tensor theories of gravity recently introduced by Langlois and Noui with potentially interesting cosmological applications. We derive the conditions for the existence of a primary constraint that prevents the propagation of an additional dangerous mode associated with higher order equations of motion. We then classify the most general, consistent scalar-tensor theories that are at most quadratic in the second derivatives of the scalar field. In addition, we investigate the possible connection between these theories and (beyond) Horndeski through conformal and disformal transformations. Finally, we point out that these theories can be associated with new operators in the effective field theory of dark energy, which might open up new possibilities to test dark energy models in future surveys.
Recent progress on light scalar mesons
Peláez, J. R.
2014-07-23
This is a brief account of the recent developments on the determination of the mass and widths of the much debated scalar mesons, paying particular attention to the causes of major revision of the σ or f{sub 0}(500) meson in the last edition of the Review of Particle Physics, which has finally acknowledged that the situation concerning the mass and width of this controversial state has been settled, although this was already well-known to scalar meson practitioners for about a decade. I will briefly comment on the dispersive approach, followed by several groups, which seems to have been the most decisive in support of the existence and precise determinations of scalar meson properties.
The Neural Computation of Scalar Implicature
Hartshorne, Joshua K.; Snedeker, Jesse; Azar, Stephanie Yen-Mun Liem; Kim, Albert E.
2014-01-01
Language comprehension involves not only constructing the literal meaning of a sentence but also going beyond the literal meaning to infer what was meant but not said. One widely-studied test case is scalar implicature: The inference that, e.g., Sally ate some of the cookies implies she did not eat all of them. Research is mixed on whether this is due to a rote, grammaticalized procedure or instead a complex, contextualized inference. We find that in sentences like If Sally ate some of the cookies, then the rest are on the counter, that the rest triggers a late, sustained positivity relative to Sally ate some of the cookies, and the rest are on the counter. This is consistent with behavioral results and linguistic theory suggesting that the former sentence does not trigger a scalar implicature. This motivates a view on which scalar implicature is contextualized but dependent on grammatical structure. PMID:25914890
Exploring scalar field dynamics with Gaussian processes
Nair, Remya; Jhingan, Sanjay; Jain, Deepak E-mail: sanjay.jhingan@gmail.com
2014-01-01
The origin of the accelerated expansion of the Universe remains an unsolved mystery in Cosmology. In this work we consider a spatially flat Friedmann-Robertson-Walker (FRW) Universe with non-relativistic matter and a single scalar field contributing to the energy density of the Universe. Properties of this scalar field, like potential, kinetic energy, equation of state etc. are reconstructed from Supernovae and BAO data using Gaussian processes. We also reconstruct energy conditions and kinematic variables of expansion, such as the jerk and the slow roll parameter. We find that the reconstructed scalar field variables and the kinematic quantities are consistent with a flat ΛCDM Universe. Further, we find that the null energy condition is satisfied for the redshift range of the Supernovae data considered in the paper, but the strong energy condition is violated.
Entanglement from longitudinal and scalar photons
Franson, J. D
2011-09-15
The covariant quantization of the electromagnetic field in the Lorentz gauge gives rise to longitudinal and scalar photons in addition to the usual transverse photons. It is shown here that the exchange of longitudinal and scalar photons can produce entanglement between two distant atoms or harmonic oscillators. The form of the entangled states produced in this way is very different from that obtained in the Coulomb gauge, where the longitudinal and scalar photons do not exist. A generalized gauge transformation is used to show that all physically observable effects are the same in the two gauges, despite the differences in the form of the entangled states. An approach of this kind may be useful for a covariant description of the dynamics of quantum information processing.
Dimensionality influence on passive scalar transport
NASA Astrophysics Data System (ADS)
Iovieno, M.; Ducasse, L.; Tordella, D.
2011-12-01
We numerically investigate the advection of a passive scalar through an interface placed inside a decaying shearless turbulent mixing layer. We consider the system in both two and three dimensions. The dimensionality produces a different time scaling of the diffusion, which is faster in the two-dimensional case. Two intermittent fronts are generated at the margins of the mixing layer. During the decay these fronts present a sort of propagation in both the direction of the scalar flow and the opposite direction. In two dimensions, the propagation of the fronts exhibits a significant asymmetry with respect to the initial position of the interface and is deeper for the front merged in the high energy side of the mixing. In three dimensions, the two fronts remain nearly symmetrically placed. Results concerning the scalar spectra exponents are also presented.
A priori study of subgrid-scale flux of a passive scalar in isotropic homogeneous turbulence
Chumakov, Sergei
2008-01-01
We perform a direct numerical simulation (DNS) of forced homogeneous isotropic turbulence with a passive scalar that is forced by mean gradient. The DNS data are used to study the properties of subgrid-scale flux of a passive scalar in the framework of large eddy simulation (LES), such as alignment trends between the flux, resolved, and subgrid-scale flow structures. It is shown that the direction of the flux is strongly coupled with the subgrid-scale stress axes rather than the resolved flow quantities such as strain, vorticity, or scalar gradient. We derive an approximate transport equation for the subgrid-scale flux of a scalar and look at the relative importance of the terms in the transport equation. A particular form of LES tensor-viscosity model for the scalar flux is investigated, which includes the subgrid-scale stress. Effect of different models for the subgrid-scale stress on the model for the subgrid-scale flux is studied.
Stability of Gauss-Bonnet black holes in anti-de Sitter space-time against scalar field condensation
Brihaye, Yves; Hartmann, Betti
2011-10-15
We study the stability of static, hyperbolic Gauss-Bonnet black holes in (4+1)-dimensional anti-de Sitter (AdS) space-time against the formation of scalar hair. Close to extremality the black holes possess a near-horizon topology of AdS{sub 2}xH{sup 3} such that within a certain range of the scalar field mass one would expect that they become unstable to the condensation of an uncharged scalar field. We confirm this numerically and observe that there exists a family of hairy black hole solutions labeled by the number of nodes of the scalar field function. We construct explicit examples of solutions with a scalar field that possesses zero nodes, one node, and two nodes, respectively, and show that the solutions with nodes persist in the limit of Einstein gravity, i.e. for vanishing Gauss-Bonnet coupling. We observe that the interval of the mass for which scalar field condensation appears decreases with increasing Gauss-Bonnet coupling and/or with increasing node number.
Scalar discrete nonlinear multipoint boundary value problems
NASA Astrophysics Data System (ADS)
Rodriguez, Jesus; Taylor, Padraic
2007-06-01
In this paper we provide sufficient conditions for the existence of solutions to scalar discrete nonlinear multipoint boundary value problems. By allowing more general boundary conditions and by imposing less restrictions on the nonlinearities, we obtain results that extend previous work in the area of discrete boundary value problems [Debra L. Etheridge, Jesus Rodriguez, Periodic solutions of nonlinear discrete-time systems, Appl. Anal. 62 (1996) 119-137; Debra L. Etheridge, Jesus Rodriguez, Scalar discrete nonlinear two-point boundary value problems, J. Difference Equ. Appl. 4 (1998) 127-144].
Scalar operators in solid-state NMR
Sun, Boqin
1991-11-01
Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.
Halos of unified dark matter scalar field
Bertacca, Daniele; Bartolo, Nicola; Matarrese, Sabino E-mail: nicola.bartolo@pd.infn.it
2008-05-15
We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with a non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription to obtain solutions (dark halos) whose rotation curve v{sub c}(r) is in good agreement with observational data. We show that there exist suitable scalar field Lagrangians that allow us to describe the cosmological background evolution and the static solutions with a single dark fluid.
On causality in polymer scalar field theory
NASA Astrophysics Data System (ADS)
García-Chung, Angel A.; Morales-Técotl, Hugo A.
2011-10-01
The properties of spacetime corresponding to a proposed quantum gravity theory might modify the high energy behavior of quantum fields. Motivated by loop quantum gravity, recently, Hossain et al [1] have considered a polymer field algebra that replaces the standard canonical one in order to calculate the propagator of a real scalar field in flat spacetime. This propagator features Lorentz violations. Motivated by the relation between Lorentz invariance and causality in standard Quantum Field Theory, in this work we investigate the causality behavior of the polymer scalar field.
Disformal scalar fields and the dark sector of the universe
NASA Astrophysics Data System (ADS)
Zumalacárregui, M.; Koivisto, T. S.; Mota, D. F.; Ruiz-Lapuente, P.
2010-05-01
Disformal transformations have proven to be very useful to devise models of the dark sector. In the present paper we apply such transformation to a single scalar field theory as a way to drive the field into a slow roll phase. The canonical scalar field Lagrangian, when coupled to a disformal metric, turns out to have relations to bimetric dark matter theories and to describe many specific dark energy models at various limits, thus providing a surprisingly simple parametrisation of a wide variety of models including tachyon, Chaplygin gas, K-essence and dilatonic ghost condensate. We investigate the evolution of the background and linear perturbations in disformal quintessence in order to perform a full comparison of the predictions with the cosmological data. The dynamics of the expansion, in particular the mechanism of the transition to accelerating phase, is described in detail. We then study the effects of disformal quintessence on cosmic microwave background (CMB) anisotropies and large scale structures (LSS). A likelihood analysis using the latest data on wide-ranging SNIa, CMB and LSS observations is performed allowing variations in six cosmological parameters and the two parameters specifying the model. We find that while a large region of parameter space remains compatible with observations, models featuring either too much early dark energy or too slow transition to acceleration are ruled out.
Instability of charged wormholes supported by a ghost scalar field
Gonzalez, J. A.; Guzman, F. S.; Sarbach, O.
2009-07-15
In previous work, we analyzed the linear and nonlinear stability of static, spherically symmetric wormhole solutions to Einstein's field equations coupled to a massless ghost scalar field. Our analysis revealed that all these solutions are unstable with respect to linear and nonlinear spherically symmetric perturbations and showed that the perturbation causes the wormholes to either decay to a Schwarzschild black hole or undergo a rapid expansion. Here, we consider charged generalization of the previous models by adding to the gravitational and ghost scalar field an electromagnetic one. We first derive the most general static, spherically symmetric wormholes in this theory and show that they give rise to a four-parameter family of solutions. This family can be naturally divided into subcritical, critical and supercritical solutions depending on the sign of the sum of the asymptotic masses. Then, we analyze the linear stability of these solutions. We prove that all subcritical and all critical solutions possess one exponentially in time growing mode. It follows that all subcritical and critical wormholes are linearly unstable. In the supercritical case we provide numerical evidence for the existence of a similar unstable mode.
Scalar Contribution to the Graviton Self-Energy During Inflation
Park, Sohyun
2012-01-01
We use dimensional regularization to evaluate the one loop contribution to the graviton self-energy from a massless, minimally coupled scalar on a locally de Sitter background. For noncoincident points our result agrees with the stress tensor correlators obtained recently by Perez-Nadal, Roura and Verdaguer. We absorb the ultraviolet divergences using the R^{2} and C^{2} counterterms first derived by ’t Hooft and Veltman, and we take the D = 4 limit of the finite remainder. The renormalized result is expressed as the sum of two transverse, 4th order differential operators acting on nonlocal, de Sitter invariant structure functions. In this form it can be used to quantum-correct the linearized Einstein equations so that one can study how the inflationary production of infrared scalars affects the propagation of dynamical gravitons and the force of gravity. We have seen that they have no effect on the propagation of dynamical gravitons. Our computation motivates a conjecture for the first correction to the vacuum state wave functional of gravitons. We comment as well on performing the same analysis for the more interesting contribution from inflationary gravitons, and on inferring one loop corrections to the force of gravity.
Gravitational waves and scalar perturbations from spectator fields
Biagetti, Matteo; Dimastrogiovanni, Emanuela; Peloso, Marco; Fasiello, Matteo E-mail: emanuela1573@gmail.com E-mail: peloso@physics.umn.edu
2015-04-01
The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate H. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio r ∼ 0.1) would indicate an inflationary expansion rate close to 10{sup 14} GeV. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [1], where a spectator field σ with a sound speed c{sub s} || 1 acts as a source for gw during inflation. In our formulation σ is described by a so-called P(X) Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by σ and find that, in our realization, r is not enhanced with respect to the standard result but it is strongly sensitive to c{sub s}, thus breaking the direct r ↔ H connection.
A simplified approach to general scalar-tensor theories
Bloomfield, Jolyon
2013-12-01
The most general covariant action describing gravity coupled to a scalar field with only second order equations of motion, Horndeski's theory (also known as ''Generalized Galileons''), provides an all-encompassing model in which single scalar dark energy models may be constrained. However, the generality of the model makes it cumbersome to manipulate. In this paper, we demonstrate that when considering linear perturbations about a Friedmann-Robertson-Walker background, the theory is completely specified by only six functions of time, two of which are constrained by the background evolution. We utilise the ideas of the Effective Field Theory of Inflation/Dark Energy to explicitly construct these six functions of time in terms of the free functions appearing in Horndeski's theory. These results are used to investigate the behavior of the theory in the quasistatic approximation. We find that only four functions of time are required to completely specify the linear behavior of the theory in this limit, which can further be reduced if the background evolution is fixed. This presents a significantly reduced parameter space from the original presentation of Horndeski's theory, giving hope to the possibility of constraining the parameter space. This work provides a cross-check for previous work on linear perturbations in this theory, and also generalizes it to include spatial curvature.
Vector and scalar charmonium resonances with lattice QCD
Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa
2015-09-15
We perform an exploratory lattice QCD simulation of DD¯ scattering, aimed at determining the masses as well as the decay widths of charmonium resonances above open charm threshold. Neglecting coupling to other channels, the resulting phase shift for DD¯ scattering in p-wave yields the well-known vector resonance ψ(3770). For m_{π} = 156 MeV, the extracted resonance mass and the decay width agree with experiment within large statistical uncertainty. The scalar charmonium resonances present a puzzle, since only the ground state _{Χc0}(1P) is well understood, while there is no commonly accepted candidate for its first excitation. We simulate DD¯ scattering in s-wave in order to shed light on this puzzle. The resulting phase shift supports the existence of a yet-unobserved narrow resonance with a mass slightly below 4 GeV. A scenario with this narrow resonance and a pole at _{Χc0}(1P) agrees with the energy-dependence of our phase shift. In addition, further lattice QCD simulations and experimental efforts are needed to resolve the puzzle of the excited scalar charmonia.
Vector and scalar charmonium resonances with lattice QCD
Lang, C. B.; Leskovec, Luka; Mohler, Daniel; Prelovsek, Sasa
2015-09-15
We perform an exploratory lattice QCD simulation of DD¯ scattering, aimed at determining the masses as well as the decay widths of charmonium resonances above open charm threshold. Neglecting coupling to other channels, the resulting phase shift for DD¯ scattering in p-wave yields the well-known vector resonance ψ(3770). For mπ = 156 MeV, the extracted resonance mass and the decay width agree with experiment within large statistical uncertainty. The scalar charmonium resonances present a puzzle, since only the ground state Χc0(1P) is well understood, while there is no commonly accepted candidate for its first excitation. We simulate DD¯ scattering inmore » s-wave in order to shed light on this puzzle. The resulting phase shift supports the existence of a yet-unobserved narrow resonance with a mass slightly below 4 GeV. A scenario with this narrow resonance and a pole at Χc0(1P) agrees with the energy-dependence of our phase shift. In addition, further lattice QCD simulations and experimental efforts are needed to resolve the puzzle of the excited scalar charmonia.« less
An improved mixing model providing joint statistics of scalar and scalar dissipation
Meyer, Daniel W.; Jenny, Patrick
2008-11-15
For the calculation of nonpremixed turbulent flames with thin reaction zones the joint probability density function (PDF) of the mixture fraction and its dissipation rate plays an important role. The corresponding PDF transport equation involves a mixing model for the closure of the molecular mixing term. Here, the parameterized scalar profile (PSP) mixing model is extended to provide the required joint statistics. Model predictions are validated using direct numerical simulation (DNS) data of a passive scalar mixing in a statistically homogeneous turbulent flow. Comparisons between the DNS and the model predictions are provided, which involve different initial scalar-field lengthscales. (author)
Swarm Absolute Scalar Magnetometers first in-orbit results
NASA Astrophysics Data System (ADS)
Fratter, Isabelle; Léger, Jean-Michel; Bertrand, François; Jager, Thomas; Hulot, Gauthier; Brocco, Laura; Vigneron, Pierre
2016-04-01
The ESA Swarm mission will provide the best ever survey of the Earth's magnetic field and its temporal evolution. This will be achieved by a constellation of three identical satellites, launched together on the 22nd of November 2013. In order to observe the magnetic field thoroughly, each satellite carries two magnetometers: a Vector Field Magnetometer (VFM) coupled with a star tracker camera, to measure the direction of the magnetic field in space, and an Absolute Scalar Magnetometer (ASM), to measure its intensity. The ASM is the French contribution to the Swarm mission. This new generation instrument was designed by CEA-Leti and developed in close partnership with CNES, with scientific support from IPGP. Its operating principle is based on the atomic spectroscopy of the helium 4 metastable state. It makes use of the Zeeman's effect to transduce the magnetic field into a frequency, the signal being amplified by optical pumping. The primary role of the ASM is to provide absolute measurements of the magnetic field's strength at 1 Hz, for the in-flight calibration of the VFM. As the Swarm magnetic reference, the ASM scalar performance is crucial for the mission's success. Thanks to its innovative design, the ASM offers the best precision, resolution and absolute accuracy ever attained in space, with similar performance all along the orbit. In addition, thanks to an original architecture, the ASM implements on an experimental basis a capacity for providing simultaneously vector measurements at 1 Hz. This new feature makes it the first instrument capable of delivering both scalar and vector measurements simultaneously at the same point. Swarm offers a unique opportunity to validate the ASM vector data in orbit by comparison with the VFM's. Furthermore, the ASM can provide scalar data at a much higher sampling rate, when run in "burst" mode at 250 Hz, with a 100 Hz measurement bandwidth. An analysis of the spectral content of the magnetic field above 1 Hz becomes thus
A minimal sub-Planckian axion inflation model with large tensor-to-scalar ratio
McDonald, John
2015-01-01
We present a minimal axion inflation model which can generate a large tensor-to-scalar ratio while remaining sub-Planckian. The modulus of a complex scalar field Φ with a λ|Φ|{sup 4} potential couples directly to the gauge field of a strongly-coupled sector via a term of the form (|Φ|/M{sub Pl}){sup m}F F-tilde . This generates a minimum of the potential which is aperiodic in the phase. The resulting inflation model is equivalent to a φ{sup 4/(m+1)} chaotic inflation model. For the natural case of a leading-order portal-like interaction of the form Φ{sup †}ΦF F-tilde , the model is equivalent to a φ{sup 4/3} chaotic inflation model and predicts a tensor-to-scalar ratio r = 16/3N = 0.097 and a scalar spectral index n{sub s} = 1 - 5/3N = 0.970. The value of |Φ| remains sub-Planckian throughout the observable era of inflation, with |Φ| ∼< 0.01M{sub Pl} for N ∼< 60 when λ ∼ 1.
Song, Ning; Kim, Nameun; Xiao, Rui; Choi, Hojun; Chun, Hyo-Im; Kang, Min-Hee; Kim, Jin-Hoi; Seo, Kunho; Soundrarajan, Nagasundarapandian; Do, Jeong-Tae; Song, Hyuk; Ge, Zhao-Jia; Park, Chankyu
2015-01-01
Females homozygous for the Purkinje cell degeneration mutation (pcd) are fertile, although the success rate is much lower than in the wild type. We performed detailed analysis of reproductive abnormalities of pcd females. The number of oocytes produced following exogenous gonadotropin treatment was much lower in pcd3J-/- females than in pcd3J+/+ females. Furthermore, the estrous cyclicity of pcd3J-/- females according to the appearance of the vagina was almost undetectable comparing to that of the wild type. Histological analyses and follicle counting of 4- and 8-week-old pcd3J-/- ovaries showed an increase in the number of secondary follicles and a decrease in the number of antral follicles, indicating that AGTPBP1/ CCP1 plays an important role in the development of secondary follicles into antral follicles. Consistent with a previous analysis of the pcd cerebellum, pcd3J-/- ovaries also showed a clear increase in the level of polyglutamylation. Gene expression analysis showed that both oocytes and cumulus cells express CCP1. However, Ccp4 and CCP6, which can compensate the function of CCP1, were not expressed in mouse ovaries. Failure of microtubule deglutamylation did not affect the structure and function of the meiotic spindle in properly aligning chromosomes in the center of the nucleus during meiosis in pcd3J-/- females. We also showed that the pituitary-derived growth and reproduction-related endocrine system functions normally in pcd3J-/- mice. The results of this study provide insight into additional functions of CCP1, which cannot be fully explained by the side chain deglutamylation of microtubules alone. PMID:26452267
Scalar field theory on fuzzy S 4
NASA Astrophysics Data System (ADS)
Medina, Julieta; O'Connor, Denjoe
2003-11-01
Scalar fields are studied on fuzzy S 4 and a solution is found for the elimination of the unwanted degrees of freedom that occur in the model. The resulting theory can be interpreted as a Kaluza-Klein reduction of Bbb CP3 to S 4 in the fuzzy context.
Minkowski, Peter; Ochs, Wolfgang
2006-02-11
We summarize some persistent problems in scalar spectroscopy and discuss what could be learned here from charmless B-decays. Recent experimental results are discussed in comparison with theoretical expectations: a simple model based on penguin dominance leads to various symmetry relations in good agreement with recent data; a factorisation approach yields absolute predictions of rates.
Scalar field radiation from dilatonic black holes
NASA Astrophysics Data System (ADS)
Gohar, H.; Saifullah, K.
2012-12-01
We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well.
Black holes in scalar-tensor gravity.
Sotiriou, Thomas P; Faraoni, Valerio
2012-02-24
Hawking has proven that black holes which are stationary as the end point of gravitational collapse in Brans-Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any symmetries apart from stationarity.
Challenging the presence of scalar charge and dipolar radiation in binary pulsars
NASA Astrophysics Data System (ADS)
Yagi, Kent; Stein, Leo C.; Yunes, Nicolás
2016-01-01
Corrections to general relativity that introduce long-ranged scalar fields which are nonminimally coupled to curvature typically predict that neutron stars possess a nontrivial scalar field profile anchored to the star. An observer far from a star is most sensitive to the spherically symmetric piece of this profile that decays linearly with the inverse of the distance to the source, the so-called scalar monopole charge, which is related to the emission of dipolar radiation from compact binary systems. The presence of dipolar radiation has the potential to rule out or very strongly constrain extended theories of gravity. These facts may lead people to believe that gravitational theories that introduce long-ranged scalar fields have already been constrained strongly from binary pulsar observations. Here we challenge this "lore" by investigating the decoupling limit of Gauss-Bonnet gravity as an example, in which the scalar field couples linearly to the Gauss-Bonnet density in the action. We prove a theorem that neutron stars in this theory cannot possess a scalar charge, due to the topological nature of the Gauss-Bonnet density. Thus Gauss-Bonnet gravity evades the strong binary pulsar constraints on dipole radiation. We discuss the astrophysical systems which will yield the best constraints on Gauss-Bonnet gravity and related quadratic gravity theories. To achieve this we compute the scalar charge in quadratic gravity theories by performing explicit analytic and numerical matching calculations for slowly rotating neutron stars. In generic quadratic gravity theories, either neutron star-binary or neutron star-black hole systems can be used to constrain the theory, but because of the vanishing charge, Gauss-Bonnet gravity evades the neutron star-binary constraints. However, in contrast to neutron stars, black holes in Gauss-Bonnet gravity do anchor scalar charge, because of the difference in topology. The best constraints on Gauss-Bonnet gravity will thus come from
A two conserved scalar model for HCCI and PPCI engine applications
NASA Astrophysics Data System (ADS)
Hamosfakidis, Vasileios
There is a strong demand for a versatile computational model in the design of modern engines such as homogeneous charge compression ignition (HCCI) and partially premixed compression ignition (PPCI) engines. A robust model is required to describe accurately both the chemistry and turbulent mixing processes in the reacting flow. Although the existing computational fluid dynamics (CFD) codes coupled with detailed kinetics models may reproduce some realistic results, the excessive computational cost prevents them to be applicable as engineering tools. The present study aims at developing a new modeling approach that can describe the combustion process with high fidelity and computational efficiency. In this study, a two-conserved scalar approach is proposed to model HCCI and PPCI combustion. The first conserved scalar, the mixture fraction Z, is introduced to capture the inhomogeneities in the fuel-air mixture, and the second conserved scalar, the initial EGR fraction J, is introduced to capture the inhomogeneities in the fresh mixture-EGR charge. The main benefits of this approach are the reduction of dimensionality and the compactness of the domain in the conserved scalar plane, and the capability to use different resolutions for the chemistry and the fluid mechanics calculation. To solve the flow in the conserved scalar plane, two algorithms are proposed. First, the flamelet (zone) creation strategy is introduced to discretize the conserved scalar space based on its mass distribution and reactivity. The second part is the regeneration procedure which accounts for the nonlinear effect of EGR on reaction rates. Test results from the two-conserved scalar approach are compared to those obtained by direct calculation, and it is demonstrated that the regeneration process in the present approach can properly account for the nonlinear effects arising from chemical reactions, as an improvement over the representative interactive flamelet (RIF) approach. The two conserved
Scalar sector of two-Higgs-doublet models: A minireview
NASA Astrophysics Data System (ADS)
Bhattacharyya, Gautam; Das, Dipankar
2016-09-01
A vast literature on the theory and phenomenology of Two-Higgs-Doublet models (2HDM) exists since long. However, the present situation demands a revisit of some 2HDM properties. Now that a 125 GeV scalar resonance has been discovered at the LHC, with its couplings to other particles showing increasing affinity to the Standard Model Higgs-like behavior, the 2HDM parameter space is more squeezed than ever. We briefly review the different parametrizations of the 2HDM potential and discuss the constraints on the parameter space arising from the unitarity and stability of the potential together with constraints from the oblique electroweak $T$-parameter. We also differentiate the consequences of imposing a global continuous U(1) symmetry on the potential from a discrete $Z_2$ symmetry.
Revisiting the quantum scalar field in spherically symmetric quantum gravity
NASA Astrophysics Data System (ADS)
Borja, Enrique F.; Garay, Iñaki; Strobel, Eckhard
2012-07-01
We extend previous results in spherically symmetric gravitational systems coupled with a massless scalar field within the loop quantum gravity framework. As a starting point, we take the Schwarzschild spacetime. The results presented here rely on the uniform discretization method. We are able to minimize the associated discrete master constraint using a variational method. The trial state for the vacuum consists of a direct product of a Fock vacuum for the matter part and a Gaussian centered around the classical Schwarzschild solution. This paper follows the line of research presented by Gambini et al (2009 Class. Quantum Grav. 26 215011 (arXiv:0906.1774v1)) and a comparison between their result and the one given in this work is made.
Cosmological backreaction of a quantized massless scalar field
Kaya, Ali; Tarman, Merve E-mail: merve.tarman@boun.edu.tr
2012-01-01
We consider the backreaction problem of a quantized minimally coupled massless scalar field in cosmology. The adiabatically regularized stress-energy tensor in a general Friedmann-Robertson-Walker background is approximately evaluated by using the fact that subhorizon modes evolve adiabatically and superhorizon modes are frozen. The vacuum energy density is verified to obey a new first order differential equation depending on a dimensionless parameter of order unity, which calibrates subhorizon/superhorizon division. We check the validity of the approximation by calculating the corresponding vacuum energy densities in fixed backgrounds, which are shown to agree with the known results in de Sitter space and space-times undergoing power law expansions. We then apply our findings to slow-roll inflationary models. Although backreaction effects are found to be negligible during the near exponential expansion, the vacuum energy density generated during this period might be important at later stages since it decreases slower than radiation or dust.
Inflationary predictions in scalar-tensor DBI inflation
Weller, Joel M.; Bruck, Carsten van de; Mota, David F. E-mail: c.vandebruck@sheffield.ac.uk
2012-06-01
The scalar-tensor Dirac-Born-Infeld (DBI) inflation scenario provides a simple mechanism to reduce the large values of the boost factor associated with single field models with DBI action, whilst still being able to drive 60 efolds of inflation. Using a slow-roll approach, we obtain an analytical expression for the spectral index of the perturbations and, moreover, determine numerically the regions of the parameter space of the model capable of giving rise to a power spectrum with amplitude and spectral index within the observed bounds. We find that regions that exhibit significant DBI effects throughout the inflationary period can be discarded by virtue of a blue-tilted spectral index, however, there are a number of viable cases — associated with a more red-tilted spectral index — for which the boost factor is initially suppressed by the effect of the coupling between the fields, but increases later to moderate values.
Self-gravitating scalar breathers with a negative cosmological constant
NASA Astrophysics Data System (ADS)
Fodor, Gyula; Forgács, Péter; Grandclément, Philippe
2015-07-01
Breather-type (time-periodic and spatially localized) solutions with spherical symmetry are investigated in a massless scalar field theory coupled to Einstein's gravity with cosmological constant in d spatial dimensions imposing anti-de Sitter (AdS) asymptotics on space-time. Using a code constructed with the Kadath library that enables the use of spectral methods, the phase space of breather solutions is explored in detail for d =3 and d =4 . It is found that there are discrete families of solutions indexed by an integer and by their frequency. Using a time evolution code these AdS breathers are found to be stable for up to a critical central density, in analogy to boson stars. Using an analytical perturbative expansion small amplitude breathers are worked out for arbitrary dimensions d .
Amino acid and carbohydrate preferences in C57BL/6ByJ and 129P3/J mice
Bachmanov, Alexander A.; Beauchamp, Gary K.
2008-01-01
Compared with mice from the 129P3/J (129) inbred strain, mice from the C57BL/6ByJ (B6) inbred strain have higher consumption of several sweet-tasting amino acids and carbohydrates. To examine the relative contribution of taste and nutritive properties in these strain differences, we measured responses of B6 and 129 mice to eight sweet and non-sweet amino acids and carbohydrates in two-bottle preference tests with water. Mice from the two strains did not differ in consumption of non-sweet L-valine and L-histidine. Compared with 129 mice, B6 mice had higher consumption and lower preference thresholds for sweet amino acids L-glutamine, L-alanine and L-threonine, monosaccharides glucose and fructose, and maltooligosaccharide. These data suggest that differences in gustatory responsiveness are an important factor underlying higher consumption of some amino acids and carbohydrates by B6 mice compared with 129 mice. It is likely that in B6 mice, higher sweet taste responsiveness results in increased consumption of sweet-tasting amino acids and sugars, and higher taste responsiveness to complex carbohydrates results in increased consumption of maltooligosaccharide. However, postingestive processes also influence nutrient consumption and may be responsible for higher intake of carbohydrates compared with sweet-tasting amino acids. Results of this study set the stage for genetic analysis of differences between B6 and 129 mice in taste responsiveness and macronutrient consumption. PMID:17764708
NASA Astrophysics Data System (ADS)
Hartanto, A.; Zen, F. P.; Kosasih, J. S.
2014-03-01
Special condition of Scherk-Schwarz and Orbifold S1/Z2 breakings brings about both the weakly-coupled SU(6) Baby Higgs and the strongly-coupled will-be-SimplestLittleHiggs scalar in the near-brane of SU(3)×SU(3)×U(1). The later produces SU(3) VEVs and Simplest Little-like Higgs after triplet-triplet splitting and, under Uncertainty Principles with Coleman-Weinberg potential, the second yields finally exotic Higgses, the scalar-pair and 3-scalar Higgses in the so-called non-asymptotic and asymptotic states produced successively via one-by-one and collective (just-one) one-time breakings.
Dynamical scalarization of neutron stars in scalar-tensor gravity theories
NASA Astrophysics Data System (ADS)
Palenzuela, Carlos; Barausse, Enrico; Ponce, Marcelo; Lehner, Luis
2014-02-01
We present a framework to study generic neutron-star binaries in scalar-tensor theories of gravity. Our formalism achieves this goal by suitably interfacing a post-Newtonian orbital evolution (described by a set of ordinary differential equations) with a set of nonlinear algebraic equations, which provide a description of the scalar charge of each binary's component along the evolution in terms of isolated-star data. We validate this semianalytical procedure by comparing its results to those of fully general-relativistic simulations, and use it to investigate the behavior of binary systems in large portions of the parameter space of scalar-tensor theories. This allows us to shed further light on the phenomena of "dynamical scalarization," which we uncovered in [E. Barausse et al., Phys. Rev. D 87, 081506(R) (2013)] and which takes place in tight binaries, even for stars that have exactly zero scalar charge in isolation. We also employ our formalism to study representative binary systems, obtain their gravitational-wave signals and discuss the extent to which deviations from general relativity can be detected. The insights gained by this framework allow us to additionally show that eccentric binaries can undergo scalarization/descalarization phenomena.
Disformal coupling, CMB spectral distortion and distance duality relation.
NASA Astrophysics Data System (ADS)
Gubitosi, G.
Light scalar fields can naturally couple disformally to Standard Model fields without giving rise to the unacceptably large fifth forces usually associated with light scalars. We show that these scalar fields can be studied and constrained through their interaction with photons, and focus particularly on changes to the Cosmic Microwave Background spectral distortions and violations of the distance duality relation. We then specialise our constraints to scalars which could play the role of axionic quintessence. The work here presented was done in collaboration with P. Brax, C. Burrage and A. C. Davis.
Black holes with surrounding matter in scalar-tensor theories.
Cardoso, Vitor; Carucci, Isabella P; Pani, Paolo; Sotiriou, Thomas P
2013-09-13
We uncover two mechanisms that can render Kerr black holes unstable in scalar-tensor gravity, both associated with the presence of matter in the vicinity of the black hole and the fact that this introduces an effective mass for the scalar. Our results highlight the importance of understanding the structure of spacetime in realistic, astrophysical black holes in scalar-tensor theories.
Stealth dark matter: Dark scalar baryons through the Higgs portal
NASA Astrophysics Data System (ADS)
Appelquist, T.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X.-Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Rinaldi, E.; Schaich, D.; Schroeder, C.; Syritsyn, S.; Vranas, P.; Weinberg, E.; Witzel, O.; Lattice Strong Dynamics LSD Collaboration
2015-10-01
We present a new model of stealth dark matter: a composite baryonic scalar of an S U (ND) strongly coupled theory with even ND≥4 . All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vectorlike representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to S U (4 ), and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass mB≳300 GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. We briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.
Floating and sinking: the imprint of massive scalars around rotating black holes.
Cardoso, Vitor; Chakrabarti, Sayan; Pani, Paolo; Berti, Emanuele; Gualtieri, Leonardo
2011-12-01
We study the coupling of massive scalar fields to matter in orbit around rotating black holes. It is generally expected that orbiting bodies will lose energy in gravitational waves, slowly inspiraling into the black hole. Instead, we show that the coupling of the field to matter leads to a surprising effect: because of superradiance, matter can hover into "floating orbits" for which the net gravitational energy loss at infinity is entirely provided by the black hole's rotational energy. Orbiting bodies remain floating until they extract sufficient angular momentum from the black hole, or until perturbations or nonlinear effects disrupt the orbit. For slowly rotating and nonrotating black holes floating orbits are unlikely to exist, but resonances at orbital frequencies corresponding to quasibound states of the scalar field can speed up the inspiral, so that the orbiting body sinks. These effects could be a smoking gun of deviations from general relativity.
Collider constraints and prospects of a scalar singlet extension to Higgs portal dark matter
NASA Astrophysics Data System (ADS)
Dupuis, Grace
2016-07-01
This work considers an extension of the Standard Model (SM) Higgs sector by a real, scalar singlet field, including applicability to a dark matter (DM) model with the addition of a Yukawa coupling to a fermionic dark matter candidate. The collider signatures and constraints on the mixed two-Higgs scenario are determined, including limits from Higgs production signals and exclusion searches, as well as constraints arising from the Higgs total and invisible widths. As there is overwhelming Higgs data which is consistent with a SM scenario, the case in which an additional scalar has evaded detection is further explored in the context of Higgs precision measurement. The discovery reach and prospective signatures of the model at a proposed linear collider are investigated, with particular focus on the Higgs triple coupling, and di-Higgs production processes.
Scattering and bound states of fermions in a mixed vector–scalar smooth step potential
Castilho, W.M. Castro, A.S. de
2014-07-15
The scattering of a fermion in the background of a smooth step potential is considered with a general mixing of vector and scalar Lorentz structures with the scalar coupling stronger than or equal to the vector coupling. Charge-conjugation and chiral-conjugation transformations are discussed and it is shown that a finite set of intrinsically relativistic bound-state solutions appears as poles of the transmission amplitude. It is also shown that those bound solutions disappear asymptotically as one approaches the conditions for the realization of the so-called spin and pseudospin symmetries in a four-dimensional space–time. - Highlights: • Scattering and bound states of fermions in a kink-like potential. • No pair production despite the high localization. • No bounded solution under exact spin and pseudospin symmetries.
Connection dynamics of higher-dimensional scalar-tensor theories of gravity
NASA Astrophysics Data System (ADS)
Han, Yu; Ma, Yongge; Zhang, Xiangdong
2014-09-01
The scalar-tensor theories (STTs) of gravity in spacetime dimensions (D+1)>2 are studied. By performing Hamiltonian analysis, we obtain the geometrical dynamics of the theories from their Lagrangian. The Hamiltonian formalism indicates that the theories are naturally divided into two sectors by the coupling parameter ω. The Hamiltonian structures in both sectors are similar to the corresponding structures of four-dimensional cases. It turns out that, similar to the case of general relativity (GR), there is also a symplectic reduction from the canonical structure of so(D+1) Yang-Mills theories coupled to the scalar field to the canonical structure of the geometrical STTs. Therefore, the non-perturbative loop quantum (LQG) gravity techniques can also be applied to the STTs in D+1 dimensions based on their connection-dynamical formalism.
Floating and sinking: the imprint of massive scalars around rotating black holes.
Cardoso, Vitor; Chakrabarti, Sayan; Pani, Paolo; Berti, Emanuele; Gualtieri, Leonardo
2011-12-01
We study the coupling of massive scalar fields to matter in orbit around rotating black holes. It is generally expected that orbiting bodies will lose energy in gravitational waves, slowly inspiraling into the black hole. Instead, we show that the coupling of the field to matter leads to a surprising effect: because of superradiance, matter can hover into "floating orbits" for which the net gravitational energy loss at infinity is entirely provided by the black hole's rotational energy. Orbiting bodies remain floating until they extract sufficient angular momentum from the black hole, or until perturbations or nonlinear effects disrupt the orbit. For slowly rotating and nonrotating black holes floating orbits are unlikely to exist, but resonances at orbital frequencies corresponding to quasibound states of the scalar field can speed up the inspiral, so that the orbiting body sinks. These effects could be a smoking gun of deviations from general relativity. PMID:22242985
750 GeV diphoton resonance as a singlet scalar in an extra dimensional model
NASA Astrophysics Data System (ADS)
Cai, Chengfeng; Yu, Zhao-Huan; Zhang, Hong-Hao
2016-04-01
We interpret the 750 GeV diphoton excess recently found in the 13 TeV LHC data as a singlet scalar in an extra dimensional model, where one extra dimension is introduced. In the model, the scalar couples to multiple vectorlike fermions, which are just the Kaluza-Klein modes of SM fermions. Mediated by the loops of these vectorlike fermions, the ϕ effective couplings to gluons and photons can be significantly large. Therefore, it is quite easy to obtain an observed cross section for the diphoton excess. We also calculate the cross sections for other decay channels of ϕ , and find that this interpretation can evade the bounds from the 8 TeV LHC data.
Black hole temperature: Minimal coupling vs conformal coupling
Fazel, Mohamadreza; Mirza, Behrouz; Mansoori, Seyed Ali Hosseini
2014-05-15
In this article, we discuss the propagation of scalar fields in conformally transformed spacetimes with either minimal or conformal coupling. The conformally coupled equation of motion is transformed into a one-dimensional Schrödinger-like equation with an invariant potential under conformal transformation. In a second stage, we argue that calculations based on conformal coupling yield the same Hawking temperature as those based on minimal coupling. Finally, it is conjectured that the quasi normal modes of black holes are invariant under conformal transformation.
Vacuum stress-energy tensor of a massive scalar field in a wormhole spacetime
Bezerra, V. B.; Bezerra de Mello, E. R.; Khusnutdinov, N. R.; Sushkov, S. V.
2010-04-15
The vacuum average value of the stress-energy tensor of a massive scalar field with nonminimal coupling {xi} to the curvature on the short-throat flat-space wormhole background is calculated. The final analysis is made numerically. It was shown that the energy-momentum tensor does not violate the null energy condition near the throat. Therefore, the vacuum polarization cannot self-consistently support the wormhole.
Quick re-introduction of selective scalar interactions in a pure-shift NMR spectrum.
Lokesh, N; Chaudhari, Sachin Rama; Suryaprakash, N
2014-12-21
A new 1D NMR experiment cited as 'Quick G-SERF', which re-introduces selective proton-proton scalar interactions in a pure shift spectrum during real time data acquisition, is reported. The method provides information on multiple proton-proton couplings from a single experiment, analogous to the 2D G-SERF technique, while significantly shortening the experimental time by 1-2 orders of magnitude due to reduced dimension and enhanced sensitivity.
Static spacetimes with Einstein surfaces in 4d Einstein-Maxwell-Higgs theory with general couplings
NASA Astrophysics Data System (ADS)
Gunara, Bobby Eka
2015-04-01
Static spacetimes of four dimensional Einstein-Maxwell-Higgs theory with general couplings can be thought of as static black holes and static domain walls. In this paper, we study a static spacetime where the two-surface is in general to be Einstein. In particular, if the scalars are frozen everywhere in the spacetime which can be viewed as the critical points of the black hole and the scalar potentials, then the geometries are of a constant scalar curvature which in general are not Einstein describing charged black holes. Whereas, in the case of charged domain walls the scalars are frozen in the asymptotic region describing spaces of constant scalar curvature.
Stationary charged scalar clouds around black holes in string theory
NASA Astrophysics Data System (ADS)
Bernard, Canisius
2016-10-01
It was reported that Kerr-Newman black holes can support linear charged scalar fields in their exterior regions. These stationary massive charged scalar fields can form bound states, which are called stationary scalar clouds. In this paper, we show that Kerr-Sen black holes can also support stationary massive charged scalar clouds by matching the near- and far-region solutions of the radial part of the Klein-Gordon wave equation. We also review stationary scalar clouds within the background of static electrically charged black hole solutions in the low-energy limit of heterotic string field theory, namely, the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black holes.
Continuity of scalar fields with logarithmic correlations
NASA Astrophysics Data System (ADS)
Rajeev, S. G.; Ranken, Evan
2015-08-01
We apply select ideas from the modern theory of stochastic processes in order to study the continuity/roughness of scalar quantum fields. A scalar field with logarithmic correlations (such as a massless field in 1 +1 spacetime dimensions) has the mildest of singularities, making it a logical starting point. Instead of the usual inner product of the field with a smooth function, we introduce a moving average on an interval which allows us to obtain explicit results and has a simple physical interpretation. Using the mathematical work of Dudley, we prove that the averaged random process is in fact continuous, and give a precise modulus of continuity bounding the short-distance variation.
Scalar waves in a wormhole geometry
Kar, S.; Sahdev, D. ); Bhawal, B. )
1994-01-15
The reflection and transmission of massless scalar waves in the curved background geometry of a typical Lorentzian wormhole (in 2+1 and 3+1 dimensions) are discussed. Using the exact solutions which involve modified Mathieu (in 2+1 dimensions) and radial oblate spheroidal (in 3+1 dimensions) functions, explicit analytic expressions are obtained for the reflection and transmission coefficients at specific values of the quantity [omega][ital b][sub 0] ([omega] being the energy of the scalar wave and [ital b][sub 0] the throat radius of the wormhole). It is found that both near-perfect reflection as well as transmission are possible for specific choices of certain parameters.
Scalar field cosmologies with inverted potentials
Boisseau, B.; Giacomini, H.
2015-10-01
Regular bouncing solutions in the framework of a scalar-tensor gravity model were found in a recent work. We reconsider the problem in the Einstein frame (EF) in the present work. Singularities arising at the limit of physical viability of the model in the Jordan frame (JF) are either of the Big Bang or of the Big Crunch type in the EF. As a result we obtain integrable scalar field cosmological models in general relativity (GR) with inverted double-well potentials unbounded from below which possess solutions regular in the future, tending to a de Sitter space, and starting with a Big Bang. The existence of the two fixed points for the field dynamics at late times found earlier in the JF becomes transparent in the EF.
Swarm's Absolute Scalar Magnetometer metrological performances
NASA Astrophysics Data System (ADS)
Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.
2012-12-01
The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.
Constraints on scalar-tensor models of dark energy from observational and local gravity tests
Tsujikawa, Shinji; Uddin, Kotub; Tavakol, Reza; Mizuno, Shuntaro; Yokoyama, Jun'ichi
2008-05-15
We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling Q between the scalar field and the nonrelativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of f(R) gravity theories corresponding to the coupling Q=-1/{radical}(6). We find that these models can be made compatible with local gravity constraints even when |Q| is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occurs at smaller redshifts as the deviation from the {lambda}CDM model becomes more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling |Q| as well as model parameters of the field potential from observations of the matter power spectrum and the cosmic microwave background (CMB) anisotropies. We find that, as long as |Q| is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.
Noncommutative scalar fields from symplectic deformation
Daoud, M.; Hamama, A.
2008-02-15
This paper is concerned with the quantum theory of noncommutative scalar fields in two dimensional space-time. It is shown that the noncommutativity originates from the the deformation of symplectic structures. The quantization is performed and the modes expansions of the fields, in the presence of an electromagnetic background, are derived. The Hamiltonian of the theory is given and the degeneracies lifting, induced by the deformation, is also discussed.
FESDIF -- Finite Element Scalar Diffraction theory code
Kraus, H.G.
1992-09-01
This document describes the theory and use of a powerful scalar diffraction theory based computer code for calculation of intensity fields due to diffraction of optical waves by two-dimensional planar apertures and lenses. This code is called FESDIF (Finite Element Scalar Diffraction). It is based upon both Fraunhofer and Kirchhoff scalar diffraction theories. Simplified routines for circular apertures are included. However, the real power of the code comes from its basis in finite element methods. These methods allow the diffracting aperture to be virtually any geometric shape, including the various secondary aperture obstructions present in telescope systems. Aperture functions, with virtually any phase and amplitude variations, are allowed in the aperture openings. Step change aperture functions are accommodated. The incident waves are considered to be monochromatic. Plane waves, spherical waves, or Gaussian laser beams may be incident upon the apertures. Both area and line integral transformations were developed for the finite element based diffraction transformations. There is some loss of aperture function generality in the line integral transformations which are typically many times more computationally efficient than the area integral transformations when applicable to a particular problem.
Age Crises, Scalar Fields, and the Apocalypse
NASA Astrophysics Data System (ADS)
Jackson, J. C.
Recent observations suggest that Hubble's constant is large, to the extent that the oldest stars appear to have ages which are greater than the Hubble time, and that the Hubble expansion is slowing down, so that according to conventional cosmology the age of the Universe is less than the Hubble time. The concepts of weak and strong age crises (respectively t0<1/H0 but longer than the age inferred from some lower limit on q0, and t0>1/H0 and q0>0) are introduced. These observations are reconciled in models which are dynamically dominated by a homogeneous scalar field, corresponding to an ultra-light boson whose Compton wavelength is of the same order as the Hubble radius. Two such models are considered, an open one with vacuum energy comprising a conventional cosmological term and a scalar field component, and a flat one with a scalar component only, aimed respectively at weak and strong age crises. Both models suggest that anti-gravity plays a significant role in the evolution of the Universe.
Cosmological scalar field perturbations can grow
NASA Astrophysics Data System (ADS)
Alcubierre, Miguel; de la Macorra, Axel; Diez-Tejedor, Alberto; Torres, José M.
2015-09-01
It has been argued that the small perturbations to the homogeneous and isotropic configurations of a canonical scalar field in an expanding universe do not grow. We show that this is not true in general, and clarify the root of the misunderstanding. We revisit a simple model in which the zero mode of a free scalar field oscillates with high frequency around the minimum of the potential. Under this assumption the linear perturbations grow like those in the standard cold dark matter scenario, but with a Jeans length at the scale of the Compton wavelength of the scalar particle. Contrary to previous analyses in the literature our results do not rely on time averages and/or fluid identifications, and instead we solve both analytically (in terms of a well-defined series expansion) and numerically the linearized Einstein-Klein-Gordon system. Also, we use gauge-invariant fields, which makes the physical analysis more transparent and simplifies the comparison with previous works carried out in different gauges. As a byproduct of this study we identify a time-dependent modulation of the different physical quantities associated to the background as well as the perturbations with potential observational consequences in dark matter models.
Scalar-vector quantization of medical images.
Mohsenian, N; Shahri, H; Nasrabadi, N M
1996-01-01
A new coding scheme based on the scalar-vector quantizer (SVQ) is developed for compression of medical images. The SVQ is a fixed rate encoder and its rate-distortion performance is close to that of optimal entropy-constrained scalar quantizers (ECSQs) for memoryless sources. The use of a fixed-rate quantizer is expected to eliminate some of the complexity of using variable-length scalar quantizers. When transmission of images over noisy channels is considered, our coding scheme does not suffer from error propagation that is typical of coding schemes using variable-length codes. For a set of magnetic resonance (MR) images, coding results obtained from SVQ and ECSQ at low bit rates are indistinguishable. Furthermore, our encoded images are perceptually indistinguishable from the original when displayed on a monitor. This makes our SVQ-based coder an attractive compression scheme for picture archiving and communication systems (PACS). PACS are currently under study for use in an all-digital radiology environment in hospitals, where reliable transmission, storage, and high fidelity reconstruction of images are desired. PMID:18285124
A note on viability of nonminimally coupled f( R) theory
NASA Astrophysics Data System (ADS)
Koivisto, Tomi S.; Tamanini, Nicola
2016-07-01
Consistency conditions for nonminimally coupled f( R) theories have been derived by requiring the absence of tachyons and instabilities in the scalar fluctuations. This note confirms these results and clarifies a subtlety regarding different definitions of sound speeds.
Conformal inflation coupled to matter
Brax, Philippe
2014-05-01
We formulate new conformal models of inflation and dark energy which generalise the Higgs-Dilaton scenario. We embed these models in unimodular gravity whose effect is to break scale invariance in the late time Universe. In the early Universe, inflation occurs close to a maximum of both the scalar potential and the scalar coupling to the Ricci scalar in the Jordan frame. At late times, the dilaton, which decouples from the dynamics during inflation, receives a potential term from unimodular gravity and leads to the acceleration of the Universe. We address two central issues in this scenario. First we show that the Damour-Polyalov mechanism, when non-relativistic matter is present prior to the start of inflation, sets the initial conditions for inflation at the maximum of the scalar potential. We then show that conformal invariance implies that matter particles are not coupled to the dilaton in the late Universe at the classical level. When fermions acquire masses at low energy, scale invariance is broken and quantum corrections induce a coupling between the dilaton and matter which is still small enough to evade the gravitational constraints in the solar system.
Screening Modifications of Gravity Through Disformally Coupled Fields
NASA Astrophysics Data System (ADS)
Koivisto, Tomi S.; Mota, David F.; Zumalacárregui, Miguel
2012-12-01
It is shown that extensions to general relativity, which introduce a strongly coupled scalar field, can be viable if the interaction has a nonconformal form. Such disformal coupling depends upon the gradients of the scalar field. Thus, if the field is locally static and smooth, the coupling becomes invisible in the Solar System: this is the disformal screening mechanism. A cosmological model is considered where the disformal coupling triggers the onset of accelerated expansion after a scaling matter era, giving a good fit to a wide range of background observational data. Moreover, the interaction leaves signatures in the formation of large-scale structure that can be used to probe such couplings.
Consistency of nonminimally coupled f(R) gravity
NASA Astrophysics Data System (ADS)
Tamanini, Nicola; Koivisto, Tomi S.
2013-09-01
Theories with a nonminimal coupling between the space-time curvature and matter fields introduce an extra force due to the nonconservation of the matter energy momentum. In the present work the theoretical consistency of such couplings is studied using a scalar field Lagrangian to model the matter content. The conditions that the coupling does not introduce ghosts, classical instabilities or superluminal propagation of perturbations are derived. These consistency conditions are then employed to rule out or severely restrict the forms of the nonminimal coupling functions considered in the previous literature. For example, a power-law coupling is viable only for sublinear positive power of the curvature scalar.
Factorization and resummation for single color-octet scalar production at the LHC
Idilbi, Ahmad; Kim, Chul; Mehen, Thomas
2009-06-01
Heavy colored scalar particles appear in a variety of new physics (NP) models and could be produced at the Large Hadron Collider. Knowing the total production cross section is important for searching for these states and establishing bounds on their masses and couplings. Using soft-collinear effective theory, we derive a factorization theorem for the process pp{yields}SX, where S is a color-octet scalar, that is applicable to any NP model provided the dominant production mechanism is gluon-gluon fusion. The factorized result for the inclusive cross section is similar to that for the standard model Higgs production; however, differences arise due to color exchange between initial and final states. We provide formulas for the total cross section with large (partonic) threshold logarithms resummed to next-to-leading logarithm accuracy. The resulting K factors are similar to those found in Higgs production. We apply our formalism to the Manohar-Wise model and find that the next-to-leading logarithm cross section is roughly 2 times (3 times) as large as the leading order cross section for a color-octet scalar of mass of 500 GeV (3 TeV). A similar enhancement should appear in any NP model with color-octet scalars.
Myers-Perry black holes with scalar hair and a mass gap: Unequal spins
NASA Astrophysics Data System (ADS)
Herdeiro, Carlos; Kunz, Jutta; Radu, Eugen; Subagyo, Bintoro
2015-09-01
We construct rotating boson stars and Myers-Perry black holes with scalar hair (MPBHsSH) as fully non-linear solutions of five dimensional Einstein gravity minimally coupled to a complex, massive scalar field. The MPBHsSH are, in general, regular on and outside the horizon, asymptotically flat, and possess angular momentum in a single rotation plane. They are supported by rotation and have no static limit. Such hairy BHs may be thought of as bound states of boson stars and singly spinning, vacuum MPBHs and inherit properties of both these building blocks. When the horizon area shrinks to zero, the solutions reduce to (in a single plane) rotating boson stars; but the extremal limit also yields a zero area horizon, as for singly spinning MPBHs. Similarly to the case of equal angular momenta, and in contrast to Kerr black holes with scalar hair, singly spinning MPBHsSH are disconnected from the vacuum black holes, due to a mass gap. We observe that for the general case, with two unequal angular momenta, the equilibrium condition for the existence of MPBHsSH is w =m1Ω1 +m2Ω2, where Ωi are the horizon angular velocities in the two independent rotation planes and w ,mi, i = 1 , 2, are the scalar field's frequency and azimuthal harmonic indices.
A symplectic rearrangement of the four dimensional non-geometric scalar potential
NASA Astrophysics Data System (ADS)
Shukla, Pramod
2015-11-01
We present a symplectic rearrangement of the effective four-dimensional non-geometric scalar potential resulting from type IIB superstring compactification on Calabi Yau orientifolds. The strategy has two main steps. In the first step, we rewrite the four dimensional scalar potential utilizing some interesting flux combinations which we call new generalized flux orbits. After invoking a couple of non-trivial symplectic relations, in the second step, we further rearrange all the pieces of scalar potential into a completely `symplectic-formulation' which involves only the symplectic ingredients (such as period matrix etc.) without the need of knowing Calabi Yau metric. Moreover, the scalar potential under consideration is induced by a generic tree level Kähler potential and (non-geometric) flux superpotential for arbitrary numbers of complex structure moduli, Kähler moduli and odd-axions. Finally, we exemplify our symplectic formulation for the two well known toroidal examples based on type IIB superstring compactification on {T}^6/({Z}_2× {Z}_2) -orientifold and {T}^6/{Z}_4 -orientifold.
Freeze-in production of fermionic dark matter with pseudo-scalar and phenomenological aspects
NASA Astrophysics Data System (ADS)
Yaser Ayazi, Seyed; Mahdi Firouzabadi, S.; Peyman Zakeri, S.
2016-09-01
In this paper, we study the freeze-in production of fermionic dark matter with a pseudo scalar as the mediator between the dark sector and standard model (SM). While the fermionic DM is non-thermal, we will explain two scenarios in which the production of pseudo-scalar particles are either thermal or non thermal. We will present an elaborate discussion to derive yield quantity and relic density and illustrate these values for the different range of model parameters. We will investigate constraints on parameter space coming from invisible Higgs decay at LHC. For the case of extremely small couplings and zero mixing between the SM Higgs field with the pseudo scalar field, where the pseudo scalar boson can play the role of DM, we will justify recent observations of merging galaxies with a case of self-interacting DM. We will show that the influence of DM annihilation in this case would provide a better fit to the AMS-02 data of positron flux.
Code of Federal Regulations, 2010 CFR
2010-04-01
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Standard Model with a real singlet scalar and inflation
Enqvist, Kari; Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo E-mail: sami.nurmi@helsinki.fi E-mail: kimmo.i.tuominen@helsinki.fi
2014-08-01
We study the post-inflationary dynamics of the Standard Model Higgs and a real singlet scalar s, coupled together through a renormalizable coupling λ{sub sh}h{sup 2}s{sup 2}, in a Z{sub 2} symmetric model that may explain the observed dark matter abundance and/or the origin of baryon asymmetry. The initial values for the Higgs and s condensates are given by inflationary fluctuations, and we follow their dissipation and relaxation to the low energy vacua. We find that both the lowest order perturbative and the non-perturbative decays are blocked by thermal effects and large background fields and that the condensates decay by two-loop thermal effects. Assuming instant reheating at T=10{sup 16} GeV, the characteristic temperature for the Higgs condensate thermalization is found to be T{sub h} ∼ 10{sup 14} GeV, whereas s thermalizes typically around T{sub s} ∼ 10{sup 6} GeV. By that time, the amplitude of the singlet is driven very close to the vacuum value by the expansion of the universe, unless the portal coupling takes a value λ{sub sh}∼< 10{sup -7} and the singlet s never thermalizes. With these values of the coupling, it is possible to slowly produce a sizeable fraction of the observed dark matter abundance via singlet condensate fragmentation and thermal Higgs scattering. Physics also below the electroweak scale can therefore be affected by the non-vacuum initial conditions generated by inflation.
Quantum field theories on manifolds with curved boundaries: Scalar fields
NASA Astrophysics Data System (ADS)
McAvity, D. M.; Osborn, H.
1993-04-01
A framework allowing for perturbative calculations to be carried out for quantum field theories with arbitrary smoothly curved boundaries is described. It is based on an expansion of the Green function for second-order differential operators valid in the neighbourhood of the boundary and which is obtained from a corresponding expansion of the associated heat kernel derived earlier for arbitrary mixed Dirichlet and Neumann boundary conditions. The first few leading terms in the expansion are sufficient to calculate all additional divergences present in a perturbative loop expansion as a consequence of the presence of the boundary. The method is applied to a general renormalisable scalar field theory in four dimensions using dimensional regularisation to two loops and expanding about arbitrary background fields. Detailed results are also specialised to an O( n) symmetric model with a single coupling constant. Extra boundary terms are introduced into the action which give rise to either Dirichlet orgeneralized Neumann boundary conditions for the quantum fields. For plane boundaries the resulting renormalisation group functions are in accord with earlier results but here the additional terms depending on the extrinsic curvature of the boundary are found. Various consistency relations are also checked and the implications of conformal invariance at the critical point where the β-function vanishes are also derived. For a general scalar field theory, where the fieldsø attain specified values ϕ in the boundary, the local Schrödinger equation for the wave functional defined by the functional integral under deformations of the boundary is also verified to two loops. The perturbative expansion for the wave functional is defined by expansion around the solution of the classical field equations satisfying the required boundary values and the counterterms necessary to derive a finite hamiltonian operator, which includes a functional Laplace operator on the fields ϕ, are
(An)Isotropic models in scalar and scalar-tensor cosmologies
NASA Astrophysics Data System (ADS)
Belinchón, José Antonio
2012-04-01
We study how the constants G and Λ may vary in different theoretical models (general relativity with a perfect fluid, scalar cosmological models ("quintessence") with and without interacting scalar and matter fields and a scalar-tensor model with a dynamical Λ) in order to explain some observational results. We apply the program outlined in section II to study three different geometries which generalize the FRW ones, which are Bianchi V, VII0 and IX, under the self-similarity hypothesis. We put special emphasis on calculating exact power-law solutions which allow us to compare the different models. In all the studied cases we arrive at the conclusion that the solutions are isotropic and noninflationary while the cosmological constant behaves as a positive decreasing time function (in agreement with the current observations) and the gravitational constant behaves as a growing time function.
Some advance on the comprehension of SR analysis for estimating the flux of a scalar
NASA Astrophysics Data System (ADS)
Castellví, Dr
2009-04-01
the scalar time trace to estimate scalar surface fluxes (Paw U et al., 1995). The analysis consists on determination of the mean ramp-pattern dimensions observed in the trace measured at one height. SR analysis is a simple transilient theory that is Lagrangian in nature and based on the scalar conservation equation. Here, it is shown (indirectly) that for a steady, incompressible and horizontally homogeneous flow, the production term in the budget equation of the mean turbulent variance of a scalar can be expressed in terms of the mean ramp dimensions observed in the trace. Therefore, the budget equation provides a link between the contrasting DM and SR analysis methods for estimating scalar surface fluxes. The dissipation method is based on the finest turbulence scales, whereas the SR analysis is based on canopy-scale coherent structures. By normalizing the budget equation, and invoking similarity, it is shown that DM and SR analysis are closely related (details were given in Castellvi and Snyder, 2008). However, SR analysis avoids the disadvantages of DM and it also overcomes potential problems related with the EC method (such as perfect alignment, rotation of the wind field, sensor separation, shadowing, etc.) because the velocity field (i.e., the sonic anemometer) is not required in SR analysis. The relation between SR analysis and DM allows to better interpret a crucial parameter (originally, denoted as ) involved in SR analysis. The parameter was implemented to account for three assumptions made to solve the scalar flux conservation equation coupled with the Lagrangian scalar mass conservation equation. Considering an air parcel that suddenly moves down to the surface which volume covers all the vertical extend of the surface sources (sinks), the assumptions made are the following; (1) The air parcel remains in contact with the sources (sinks) for a period during which it has been enriched (depleted) of scalar, (2) During the enrichment phase there is not
Local approximations for effective scalar field equations of motion
Berera, Arjun; Moss, Ian G.; Ramos, Rudnei O.
2007-10-15
Fluctuation and dissipation dynamics is examined at all temperature ranges for the general case of a background time evolving scalar field coupled to heavy intermediate quantum fields which in turn are coupled to light quantum fields. The evolution of the background field induces particle production from the light fields through the action of the intermediate catalyzing heavy fields. Such field configurations are generically present in most particle physics models, including grand unified and supersymmetry theories, with application of this mechanism possible in inflation, heavy ion collision, and phase transition dynamics. The effective evolution equation for the background field is obtained and a fluctuation-dissipation theorem is derived for this system. The effective evolution, in general, is nonlocal in time. Appropriate conditions are found for when these time nonlocal effects can be approximated by local terms. Here careful distinction is made between a local expansion and the special case of a derivative expansion to all orders, which requires analytic behavior of the evolution equation in Fourier space.
PYESSENCE: Generalized Coupled Quintessence Linear Perturbation Python Code
NASA Astrophysics Data System (ADS)
Leithes, Alexander
2016-09-01
PYESSENCE evolves linearly perturbed coupled quintessence models with multiple (cold dark matter) CDM fluid species and multiple DE (dark energy) scalar fields, and can be used to generate quantities such as the growth factor of large scale structure for any coupled quintessence model with an arbitrary number of fields and fluids and arbitrary couplings.
Non-minimal coupling in Higgs–Yukawa model with asymptotically safe gravity
NASA Astrophysics Data System (ADS)
Oda, Kin-ya; Yamada, Masatoshi
2016-06-01
We study the fixed-point structure of the Higgs–Yukawa model, with its scalar being non-minimally coupled to the asymptotically safe gravity, using the functional renormalization group. We have obtained the renormalization group equations for the cosmological and Newton constants, the scalar mass squared and quartic coupling constant, and the Yukawa and non-minimal coupling constants, taking into account all the scalar, fermion, and graviton loops. We find that switching on the fermionic quantum fluctuations makes the non-minimal coupling constant irrelevant around the Gaussian-matter fixed point with asymptotically safe gravity.
New production mechanism for keV sterile neutrino Dark Matter by decays of frozen-in scalars
Merle, Alexander; Niro, Viviana; Schmidt, Daniel E-mail: niro@ecm.ub.edu
2014-03-01
We propose a new production mechanism for keV sterile neutrino Dark Matter. In our setting, we assume the existence of a scalar singlet particle which never entered thermal equilibrium in the early Universe, since it only couples to the Standard Model fields by a really small Higgs portal interaction. For suitable values of this coupling, the scalar can undergo the so-called freeze-in process, and in this way be efficiently produced in the early Universe. These scalars can then decay into keV sterile neutrinos and produce the correct Dark Matter abundance. While similar settings in which the scalar does enter thermal equilibrium and then freezes out have been studied previously, the mechanism proposed here is new and represents a versatile extension of the known case. We perform a detailed numerical calculation of the DM production using a set of coupled Boltzmann equations, and we illustrate the successful regions in the parameter space. Our production mechanism notably can even work in models where active-sterile mixing is completely absent.
Non-canonical scalar fields and their applications in cosmology and astrophysics
NASA Astrophysics Data System (ADS)
Gauthier, Christopher S.
In this thesis we will discuss several issues concerning cosmological applications of non-canonical scalar fields, which are generically referred to as k-essence. First, we consider two examples of k-essence. These are the rolling tachyon and static spherically symmetric solutions of non-canonical scalar fields in flat space. We find constraints on the form of the allowed interactions in the first case and on the choice of boundary conditions in the latter. For the rolling tachyon we find that at late times the tachyon matter behaves like a non-relativistic dust, thus making it a dark matter candidate. For the static spherically symmetric solutions we show that solutions which are finite at the origin must have negative energy density there. Next, we consider static spherically symmetric solutions of non-canonical scalar fields coupled to gravity as a way to explain dark matter halos as a coherent state of the scalar field. Consistent solutions are found with a smooth scalar profile which can describe observed rotation curves. The non-trivial solutions have negative energy density near the origin, though the total energy is positive. We also reconsider the no scalar hair theorems for black holes with emphasis on asymptotic boundary conditions and superluminal propagation. After this we show that, for general scalar fields, stationary configurations are possible for shift symmetric theories only. This symmetry with respect to constant translations in field space should either be manifest in the original field variables or reveal itself after an appropriate field redefinition. In particular this result implies that neither k-essence nor quintessence can have exact steady state/Bondi accretion onto black holes. Finally, we find that stationary field configurations are necessarily linear in Killing time, provided that shift symmetry is realized in terms of these field variables. The next discussion outlines a general program for reconstructing the action of non
Scalar mesons and polarizability of the nucleon
Schumacher, Martin
2008-08-31
It is shown that the scalar mesons {sigma}, f{sub 0}(980) and a{sub 0}(980) as t-channel exchanges quantitatively solve the problem of diamagnetism and give an explanation of the large missing part of the electric polarizability {alpha} showing up when only the pion cloud is taken into account. The electric polarizability of the proton {alpha}{sub p} confirms a two-photon width of the {sigma} meson of {gamma}{sub {sigma}}{sub {gamma}}{sub {gamma}} = (2.58{+-}0.26) keV.
Scalar wave diffraction from a circular aperture
Cerjan, C.
1995-01-25
The scalar wave theory is used to evaluate the expected diffraction patterns from a circular aperture. The standard far-field Kirchhoff approximation is compared to the exact result expressed in terms of oblate spheroidal harmonics. Deviations from an expanding spherical wave are calculated for circular aperture radius and the incident beam wavelength using suggested values for a recently proposed point diffractin interferometer. The Kirchhoff approximation is increasingly reliable in the far-field limit as the aperture radius is increased, although significant errors in amplitude and phase persist.
Universal Attractor for Inflation at Strong Coupling
NASA Astrophysics Data System (ADS)
Kallosh, Renata; Linde, Andrei; Roest, Diederik
2014-01-01
We introduce a novel nonminimal coupling between gravity and the inflaton sector. Remarkably, for large values of this coupling all models asymptote to a universal attractor. This behavior is independent of the original scalar potential and generalizes the attractor in the φ4 theory with nonminimal coupling to gravity. The attractor is located in the "sweet spot" of parameter values that are preferred by Planck's recent results.
Modeling dynamical scalarization with a resummed post-Newtonian expansion
NASA Astrophysics Data System (ADS)
Sennett, Noah; Buonanno, Alessandra
2016-06-01
Despite stringent constraints set by astrophysical observations, there remain viable scalar-tensor theories that could be distinguished from general relativity with gravitational-wave detectors. A promising signal predicted in these alternative theories is dynamical scalarization, which can dramatically affect the evolution of neutron-star binaries near merger. Motivated by the successful treatment of spontaneous scalarization, we develop a formalism that partially resums the post-Newtonian expansion to capture dynamical scalarization in a mathematically consistent manner. We calculate the post-Newtonian order corrections to the equations of motion and scalar mass of a binary system. Through comparison with quasiequilibrium configuration calculations, we verify that this new approximation scheme can accurately predict the onset and magnitude of dynamical scalarization.
Study of Several Potentials as Scalar Field Dark Matter Candidates
Matos, Tonatiuh; Vazquez-Gonzalez, Alberto; Magan a, Juan
2008-12-04
In this work we study several scalar field potentials as a plausible candidate to be the dark matter in the universe. The main idea is the following; if the scalar field is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations which oscillate in space-time (oscillatons). The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the free parameters of the scalar field potentials. We are able to reproduce very well the cosmological predictions of the standard {lambda}CDM model with some scalar field potentials. Therefore, scalar field dark matter seems to be a good alternative to be the nature of the dark matter of the universe.
Passive scalar transport in peripheral regions of random flows
Chernykh, A.; Lebedev, V.
2011-08-15
We investigate statistical properties of the passive scalar mixing in random (turbulent) flows assuming its diffusion to be weak. Then at advanced stages of the passive scalar decay, its unmixed residue is primarily concentrated in a narrow diffusive layer near the wall and its transport to the bulk goes through the peripheral region (laminar sublayer of the flow). We conducted Lagrangian numerical simulations of the process for different space dimensions d and revealed structures responsible for the transport, which are passive scalar tongues pulled from the diffusive boundary layer to the bulk. We investigated statistical properties of the passive scalar and of the passive scalar integrated along the wall. Moments of both objects demonstrate scaling behavior outside the diffusive boundary layer. We propose an analytic scheme for the passive scalar statistics, explaining the features observed numerically.
Coupling Electromagnetism to Global Charge
NASA Astrophysics Data System (ADS)
Guendelman, E. I.
2013-12-01
It is shown that an alternative to the standard scalar quantum electrodynamics (QED) is possible. In this new version, there is only global gauge invariance as far as the charged scalar fields are concerned, although local gauge invariance is kept for the electromagnetic field. The electromagnetic coupling has the form jμ(Aμ +∂μB) where B is an auxiliary field and the current jμ is Aμ independent, so that no "sea gull terms" are introduced. As a consequence of the absence of sea gulls, it is seen that no Klein paradox appears in the presence of a strong square well potential. In a model of this kind, spontaneous breaking of symmetry does not lead to photon mass generation, instead the Goldstone boson becomes a massless source for the electromagnetic field. When spontaneous symmetry breaking takes place infrared questions concerning the theory and generalizations to global vector QED are discussed. In this framework, Q-Balls and other nontopological solitons that owe their existence to a global U(1) symmetry can be coupled to electromagnetism and could represent multiply charged particles now in search in the large hadron collider (LHC). Furthermore, we give an example where an "Emergent" Global Scalar QED can appear from an axion-photon system in an external magnetic field. Finally, formulations of Global Scalar QED that allow perturbative expansions without sea gulls are developed.
Scalar dissipation rate statistics in turbulent swirling jets
NASA Astrophysics Data System (ADS)
Stetsyuk, V.; Soulopoulos, N.; Hardalupas, Y.; Taylor, A. M. K. P.
2016-07-01
The scalar dissipation rate statistics were measured in an isothermal flow formed by discharging a central jet in an annular stream of swirling air flow. This is a typical geometry used in swirl-stabilised burners, where the central jet is the fuel. The flow Reynolds number was 29 000, based on the area-averaged velocity of 8.46 m/s at the exit and the diameter of 50.8 mm. The scalar dissipation rate and its statistics were computed from two-dimensional imaging of the mixture fraction fields obtained with planar laser induced fluorescence of acetone. Three swirl numbers, S, of 0.3, 0.58, and 1.07 of the annular swirling stream were considered. The influence of the swirl number on scalar mixing, unconditional, and conditional scalar dissipation rate statistics were quantified. A procedure, based on a Wiener filter approach, was used to de-noise the raw mixture fraction images. The filtering errors on the scalar dissipation rate measurements were up to 15%, depending on downstream positions from the burner exit. The maximum of instantaneous scalar dissipation rate was found to be up to 35 s-1, while the mean dissipation rate was 10 times smaller. The probability density functions of the logarithm of the scalar dissipation rate fluctuations were found to be slightly negatively skewed at low swirl numbers and almost symmetrical when the swirl number increased. The assumption of statistical independence between the scalar and its dissipation rate was valid for higher swirl numbers at locations with low scalar fluctuations and less valid for low swirl numbers. The deviations from the assumption of statistical independence were quantified. The conditional mean of the scalar dissipation rate, the standard deviation of the scalar dissipation rate fluctuations, the weighted probability of occurrence of the mean conditional scalar dissipation rate, and the conditional probability are reported.
Quantum tunneling from scalar fields in rotating black strings
NASA Astrophysics Data System (ADS)
Gohar, H.; Saifullah, K.
2013-08-01
Using the Hamilton-Jacobi method of quantum tunneling and complex path integration, we study Hawking radiation of scalar particles from rotating black strings. We discuss tunneling of both charged and uncharged scalar particles from the event horizons. For this purpose, we use the Klein-Gordon equation and find the tunneling probability of outgoing scalar particles. The procedure gives Hawking temperature for rotating charged black strings as well.
Black hole accretion discs and screened scalar hair
NASA Astrophysics Data System (ADS)
Davis, Anne-Christine; Gregory, Ruth; Jha, Rahul
2016-10-01
We present a novel way to investigate scalar field profiles around black holes with an accretion disc for a range of models where the Compton wavelength of the scalar is large compared to other length scales. By analysing the problem in ``Weyl" coordinates, we are able to calculate the scalar profiles for accretion discs in the static Schwarzschild, as well as rotating Kerr, black holes. We comment on observational effects.
Massive basketball diagram for a thermal scalar field theory
NASA Astrophysics Data System (ADS)
Andersen, Jens O.; Braaten, Eric; Strickland, Michael
2000-08-01
The ``basketball diagram'' is a three-loop vacuum diagram for a scalar field theory that cannot be expressed in terms of one-loop diagrams. We calculate this diagram for a massive scalar field at nonzero temperature, reducing it to expressions involving three-dimensional integrals that can be easily evaluated numerically. We use this result to calculate the free energy for a massive scalar field with a φ4 interaction to three-loop order.
Stealth Dark Matter: Dark scalar baryons through the Higgs portal
Appelquist, T.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X. -Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; et al
2015-10-23
We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an SU(ND) strongly coupled theory with even ND ≥ 4. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vectorlike representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to SU(4), and investigate the constraints on the model from dark meson decay, electroweak precision measurements,more » basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass mB ≳ 300 GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. Furthermore, we briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.« less
Stealth Dark Matter: Dark scalar baryons through the Higgs portal
Appelquist, T.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X. -Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Rinaldi, E.; Schaich, D.; Schroeder, C.; Syritsyn, S.; Vranas, P.; Weinberg, E.; Witzel, O.
2015-10-23
We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an SU(N_{D}) strongly coupled theory with even N_{D} ≥ 4. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vectorlike representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to SU(4), and investigate the constraints on the model from dark meson decay, electroweak precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass m_{B} ≳ 300 GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. Furthermore, we briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.
Relativistic Two and Three-Particle Bound States in Scalar Quantum Field Theory.
NASA Astrophysics Data System (ADS)
di Leo, Leo
This thesis is concerned with the application of the variational method, within the Hamiltonian formalism of quantum field theory (QFT), to describe relativistic two and three particle states in scalar field theories. Two models are considered: scalar particles interacting through the exchange of scalar quanta, and the Higgs sector of the Minimal Standard Model. We derive relativistic particle-antiparticle wave equations for scalar particles, phi and |phi, interacting via a massive or massless scalar field, chi (the Wick-Cutkosky model), using simple Fock space ansatze. The variational method, within the Hamiltonian formalism of QFT, is used to derive equations with and without coupling of this quasi-bound phi|phi system to the chichi decay channel. The equations are then approximately decoupled to yield a relativistic momentum-space (Schrodinger-like) wave equation from which we determine bound-state energies numerically, perturbatively or variationally for various strengths of the coupling. Bound-state energies in the massless case are compared to the known ladder Bethe-Salpeter and light-cone solutions of this model. In the case of coupling to the decay channel, which is easily accomplished in the present formalism by expanding our Fock-space ansatz, the quasi-bound phi|phi states are seen to arise as resonances in the chichi scattering cross section. Numerical results are presented for the massive and massless chi case for various coupling strengths. The same variational method can be easily extended to derive relativistic three-particle wave equations for scalar particles phi,phi and |phi, interacting via a massive or massless scalar field, chi. In this case, the equations are obtained using a simple |phiphi|phi > +| phiphi|{phi}chi > ansatz. Approximate variational solutions (using product-type hydrogenic wave functions) of these equations are presented for various strengths of the coupling. The magnitude of the relativistic effects in the three
Ruiz Arriola, Enrique; Broniowski, Wojciech
2011-05-23
Scalar-isoscalar states (J{sup PC} = 0{sup ++}) are analyzed within the large-N{sub c} Regge approach. We find that the lightest f{sub 0}(600) scalar-isoscalar state fits very well into the pattern of the radial Regge trajectory. We confirm the obtained mass values from an analysis of the pion and nucleon spin-0 gravitational form factors, recently measured on the lattice. We find that a simple two-state model suggests a meson nature of f{sub 0}(600), and a glueball nature of f{sub 0}(980), which naturally explains the ratios of various coupling constants. Finally, matching to the OPE requires a fine-tuned mass condition of the vanishing dimension-2 condensate in the Regge approach with infinitely many scalar-isoscalar states.
Wightman function and scalar Casimir densities for a wedge with two cylindrical boundaries
Saharian, A.A. Tarloyan, A.S.
2008-07-15
Wightman function, the vacuum expectation values of the field square and the energy-momentum tensor are investigated for a massive scalar field with general curvature coupling parameter inside a wedge with two coaxial cylindrical boundaries. It is assumed that the field obeys Dirichlet boundary condition on bounding surfaces. The application of a variant of the generalized Abel-Plana formula enables to extract from the expectation values the contribution corresponding to the geometry of a wedge with a single shell and to present the interference part in terms of exponentially convergent integrals. The local properties of the vacuum are investigated in various asymptotic regions of the parameters. The vacuum forces acting on the boundaries are presented as the sum of self-action and interaction terms. It is shown that the interaction forces between the separate parts of the boundary are always attractive. The generalization to the case of a scalar field with Neumann boundary condition is discussed.
A composite light scalar, electro-weak symmetry breaking and the recent LHC searches
NASA Astrophysics Data System (ADS)
Elander, Daniel; Piai, Maurizio
2012-11-01
We construct a model in which electro-weak symmetry breaking is induced by a strongly coupled sector, which is described in terms of a five-dimensional model in the spirit of the bottom-up approach to holography. We compute the precision electro-weak parameters, and identify regions of parameter space allowed by indirect tests. We compute the spectrum of scalar and vector resonances, which contains a set of parametrically light states that can be identified with the electro-weak gauge bosons and a light dilaton. There is then a little desert, up to 2-3 TeV, where towers of resonances of the vector, axial-vector and scalar particles appear.
Kerr-Newman black holes with scalar hair
NASA Astrophysics Data System (ADS)
Delgado, Jorge F. M.; Herdeiro, Carlos A. R.; Radu, Eugen; Rúnarsson, Helgi
2016-10-01
We construct electrically charged Kerr black holes (BHs) with scalar hair. Firstly, we take an uncharged scalar field, interacting with the electromagnetic field only indirectly, via the background metric. The corresponding family of solutions, dubbed Kerr-Newman BHs with ungauged scalar hair, reduces to (a sub-family of) Kerr-Newman BHs in the limit of vanishing scalar hair and to uncharged rotating boson stars in the limit of vanishing horizon. It adds one extra parameter to the uncharged solutions: the total electric charge. This leading electromagnetic multipole moment is unaffected by the scalar hair and can be computed by using Gauss's law on any closed 2-surface surrounding (a spatial section of) the event horizon. By contrast, the first sub-leading electromagnetic multipole - the magnetic dipole moment -, gets suppressed by the scalar hair, such that the gyromagnetic ratio is always smaller than the Kerr-Newman value (g = 2). Secondly, we consider a gauged scalar field and obtain a family of Kerr-Newman BHs with gauged scalar hair. The electrically charged scalar field now stores a part of the total electric charge, which can only be computed by applying Gauss' law at spatial infinity and introduces a new solitonic limit - electrically charged rotating boson stars. In both cases, we analyze some physical properties of the solutions.
Invariant slow-roll parameters in scalar-tensor theories
NASA Astrophysics Data System (ADS)
Kuusk, Piret; Rünkla, Mihkel; Saal, Margus; Vilson, Ott
2016-10-01
A general scalar-tensor theory can be formulated in different parametrizations that are related by a conformal rescaling of the metric and a scalar field redefinition. We compare formulations of slow-roll regimes in the Einstein and Jordan frames using quantities that are invariant under the conformal rescaling of the metric and transform as scalar functions under the reparametrization of the scalar field. By comparing spectral indices, calculated up to second order, we find that the frames are equivalent up to this order, due to the underlying assumptions.
Isocurvature constraints on portal couplings
NASA Astrophysics Data System (ADS)
Kainulainen, Kimmo; Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo; Vaskonen, Ville
2016-06-01
We consider portal models which are ultraweakly coupled with the Standard Model, and confront them with observational constraints on dark matter abundance and isocurvature perturbations. We assume the hidden sector to contain a real singlet scalar s and a sterile neutrino ψ coupled to s via a pseudoscalar Yukawa term. During inflation, a primordial condensate consisting of the singlet scalar s is generated, and its contribution to the isocurvature perturbations is imprinted onto the dark matter abundance. We compute the total dark matter abundance including the contributions from condensate decay and nonthermal production from the Standard Model sector. We then use the Planck limit on isocurvature perturbations to derive a novel constraint connecting dark matter mass and the singlet self coupling with the scale of inflation: mDM/GeV lesssim 0.2λs3/8 (H*/1011 GeV)‑3/2. This constraint is relevant in most portal models ultraweakly coupled with the Standard Model and containing light singlet scalar fields.
Emergence of Lorentzian signature and scalar gravity
Girelli, F.; Liberati, S.; Sindoni, L.
2009-02-15
In recent years, a growing momentum has been gained by the emergent gravity framework. Within the latter, the very concepts of geometry and gravitational interaction are not seen as elementary aspects of nature but rather as collective phenomena associated to the dynamics of more fundamental objects. In this paper we want to further explore this possibility by proposing a model of emergent Lorentzian signature and scalar gravity. Assuming that the dynamics of the fundamental objects can give rise in first place to a Riemannian manifold and a set of scalar fields we show how time (in the sense of hyperbolic equations) can emerge as a property of perturbations dynamics around some specific class of solutions of the field equations. Moreover, we show that these perturbations can give rise to a spin-0 gravity via a suitable redefinition of the fields that identifies the relevant degrees of freedom. In particular, we find that our model gives rise to Nordstroem gravity. Since this theory is invariant under general coordinate transformations, this also shows how diffeomorphism invariance (albeit of a weaker form than the one of general relativity) can emerge from much simpler systems.
Dynamical analysis in scalar field cosmology
NASA Astrophysics Data System (ADS)
Paliathanasis, Andronikos; Tsamparlis, Michael; Basilakos, Spyros; Barrow, John D.
2015-06-01
We give a general method to find exact cosmological solutions for scalar-field dark energy in the presence of perfect fluids. We use the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We show that the existence of a point transformation under which the WdW equation is invariant is equivalent to the existence of conservation laws for the field equations, which indicates the existence of analytical solutions. We extend previous work by providing exact solutions for the Hubble parameter and the effective dark-energy equation of state parameter for cosmologies containing a combination of perfect fluid and a scalar field whose self-interaction potential is a power of hyperbolic functions. We find solutions explicitly when the perfect fluid is radiation or cold dark matter and determine the effects of nonzero spatial curvature. Using the Planck 2015 data, we determine the evolution of the effective equation of state of the dark energy. Finally, we study the global dynamics using dimensionless variables. We find that if the current cosmological model is Liouville integrable (admits conservation laws) then there is a unique stable point which describes the de-Sitter phase of the universe.
Scalar field theory on noncommutative Snyder spacetime
Battisti, Marco Valerio; Meljanac, Stjepan
2010-07-15
We construct a scalar field theory on the Snyder noncommutative space-time. The symmetry underlying the Snyder geometry is deformed at the co-algebraic level only, while its Poincare algebra is undeformed. The Lorentz sector is undeformed at both the algebraic and co-algebraic level, but the coproduct for momenta (defining the star product) is non-coassociative. The Snyder-deformed Poincare group is described by a non-coassociative Hopf algebra. The definition of the interacting theory in terms of a nonassociative star product is thus questionable. We avoid the nonassociativity by the use of a space-time picture based on the concept of the realization of a noncommutative geometry. The two main results we obtain are (i) the generic (namely, for any realization) construction of the co-algebraic sector underlying the Snyder geometry and (ii) the definition of a nonambiguous self-interacting scalar field theory on this space-time. The first-order correction terms of the corresponding Lagrangian are explicitly computed. The possibility to derive Noether charges for the Snyder space-time is also discussed.
Searching for Chameleon-Like Scalar Fields
NASA Astrophysics Data System (ADS)
Levshakov, S. A.; Molaro, P.; Kozlov, M. G.; Lapinov, A. V.; Henkel, Ch.; Reimersi, D.; Sakai, T.; Agafonova, I. I.
Using the 32-m Medicina, 45-m Nobeyama, and 100-m Effelsberg telescopes we found a statistically significant velocity offset ΔV ≈ 27 ± 3 m s - 1 (1σ) between the inversion transition in NH3(1,1) and low-J rotational transitions in N2H + (1-0) and HC3N(2-1) arising in cold and dense molecular cores in the Milky Way. Systematic shifts of the line centers caused by turbulent motions and velocity gradients, possible non-thermal hyperfine structure populations, pressure and optical depth effects are shown to be lower than or about 1 m s - 1 and thus can be neglected in the total error budget. The reproducibility of ΔV at the same facility (Effelsberg telescope) on a year-to-year basis is found to be very good. Since the frequencies of the inversion and rotational transitions have different sensitivities to variations in μ ≡ m e / m p, the revealed non-zero ΔV may imply that μ changes when measured at high (terrestrial) and low (interstellar) matter densities as predicted by chameleon-like scalar field models - candidates to the dark energy carrier. Thus we are testing whether scalar field models have chameleon-type interactions with ordinary matter. The measured velocity offset corresponds to the ratio Δμ / μ ≡ (μspace - μlab) / μlab of (26 ± 3) ×10 - 9 (1σ).
Bagchi, Arjun; Rama, S. Kalyana
2004-11-15
We consider scalar-tensor theories in D-dimensional spacetime, D{>=}4. They consist of a metric and a nonminimally coupled scalar field, with its nonminimal coupling characterized by a function. The probes couple minimally to the metric only. We obtain vacuum solutions--both cosmological and static spherically symmetric ones--and study their properties. We find that, as seen by the probes, there is no singularity in the cosmological solutions for a class of functions which obey certain constraints. It turns out that for the same class of functions, there are static spherically symmetric solutions which exhibit novel properties: e.g., near the 'horizon', the gravitational force as seen by the probe becomes repulsive.
NASA Astrophysics Data System (ADS)
Baldocchi, Dennis
1992-10-01
An integrated canopy micrometeorological model is described for calculating CO2, water vapor and sensible heat exchange rates and scalar concentration profiles over and within a crop canopy. The integrated model employs a Lagrangian random walk algorithm to calculate turbulent diffusion. The integrated model extends previous Lagrangian modelling efforts by employing biochemical, physiological and micrometeorological principles to evaluate vegetative sources and sinks. Model simulations of water vapor, CO2 and sensible heat flux densities are tested against measurements made over a soybean canopy, while calculations of scalar profiles are tested against measurements made above and within the canopy. The model simulates energy and mass fluxes and scalar profiles above the canopy successfully. On the other hand, model calculations of scalar profiles inside the canopy do not match measurements. The tested Lagrangian model is also used to evaluate simpler modelling schemes, as needed for regional and global applications. Simple, half-order closure modelling schemes (which assume a constant scalar profile in the canopy) do not yield large errors in the computation of latent heat (LE) and CO2 (F c ) flux densities. Small errors occur because the source-sink formulation of LE and F c are relatively insensitive to changes in scalar concentrations and the scalar gradients are small. On the other hand, complicated modelling frames may be needed to calculate sensible heat flux densities; the source-sink formulation of sensible heat is closely coupled to the within-canopy air temperature profile.
Some advance on the comprehension of SR analysis for estimating the flux of a scalar
NASA Astrophysics Data System (ADS)
Castellví, Dr
2009-04-01
the scalar time trace to estimate scalar surface fluxes (Paw U et al., 1995). The analysis consists on determination of the mean ramp-pattern dimensions observed in the trace measured at one height. SR analysis is a simple transilient theory that is Lagrangian in nature and based on the scalar conservation equation. Here, it is shown (indirectly) that for a steady, incompressible and horizontally homogeneous flow, the production term in the budget equation of the mean turbulent variance of a scalar can be expressed in terms of the mean ramp dimensions observed in the trace. Therefore, the budget equation provides a link between the contrasting DM and SR analysis methods for estimating scalar surface fluxes. The dissipation method is based on the finest turbulence scales, whereas the SR analysis is based on canopy-scale coherent structures. By normalizing the budget equation, and invoking similarity, it is shown that DM and SR analysis are closely related (details were given in Castellvi and Snyder, 2008). However, SR analysis avoids the disadvantages of DM and it also overcomes potential problems related with the EC method (such as perfect alignment, rotation of the wind field, sensor separation, shadowing, etc.) because the velocity field (i.e., the sonic anemometer) is not required in SR analysis. The relation between SR analysis and DM allows to better interpret a crucial parameter (originally, denoted as α) involved in SR analysis. The parameter α was implemented to account for three assumptions made to solve the scalar flux conservation equation coupled with the Lagrangian scalar mass conservation equation. Considering an air parcel that suddenly moves down to the surface which volume covers all the vertical extend of the surface sources (sinks), the assumptions made are the following; (1) The air parcel remains in contact with the sources (sinks) for a period during which it has been enriched (depleted) of scalar, (2) During the enrichment phase there is not
Scalar self-energy for a charged particle in global monopole spacetime with a spherical boundary
NASA Astrophysics Data System (ADS)
Bezerra de Mello, E. R.; Saharian, A. A.
2012-07-01
We analyze combined effects of the geometry produced by a global monopole and a concentric spherical boundary on the self-energy of a point-like scalar charged test particle at rest. We assume that the boundary is outside the monopole’s core with a general spherically symmetric inner structure. An important quantity to this analysis is the three-dimensional Green function associated with this system. For both Dirichlet and Neumann boundary conditions obeyed by the scalar field on the sphere, the Green function presents a structure that contains contributions due to the background geometry of the spacetime and the boundary. Consequently, the corresponding induced scalar self-energy also presents a similar structure. For points near the sphere, the boundary-induced part dominates and the self-force is repulsive/attractive with respect to the boundary for Dirichlet/Neumann boundary condition. In the region outside the sphere at large distances from it, the boundary-free part in the self-energy dominates and the corresponding self-force can be either attractive or repulsive with dependence of the curvature coupling parameter for scalar field. In particular, for the minimal coupling we show the presence of a stable equilibrium point for the Dirichlet boundary condition. In the region inside the sphere, the nature of the self-force depends on the specific model for the monopole’s core. As illustrations of the general procedure adopted, we shall consider two distinct models, namely the flower-pot and the ballpoint-pen ones.
Spin-independent interferences and spin-dependent interactions with scalar dark matter
NASA Astrophysics Data System (ADS)
Martinez, R.; Ochoa, F.
2016-05-01
We explore mechanisms of interferences under which the spin-independent interaction in the scattering of scalar dark matter with nucleus is suppressed in relation to the spin-dependent one. We offer a detailed derivation of the nuclear amplitudes based on the interactions with quarks in the framework of a nonuniversal U(1)' extension of the standard model. By assuming a range of parameters compatible with collider searches, electroweak observables and dark matter abundance, we find scenarios for destructive interferences with and without isospin symmetry. The model reveals solutions with mutually interfering scalar particles, canceling the effective spin-independent coupling with only scalar interactions, which requires an extra Higgs boson with mass M H > 125 GeV. The model also possesses scenarios with only vector interactions through two neutral gauge bosons, Z and Z', which do not exhibit interference effects. Due to the nonuniversality of the U(1)' symmetry, we distinguish two family structures of the quark sector with different numerical predictions. In one case, we obtain cross sections that pass all the Xenon-based detector experiments. In the other case, limits from LUX experiment enclose an exclusion region for dark matter between 9 and 800 GeV. We examine a third scenario with isospin-violating couplings where interferences between scalar and vector boson exchanges cancel the scattering. We provide solutions where interactions with Xenon-based detectors is suppressed for light dark matter, below 6 GeV, while interactions with Germanium- and Silicon-based detectors exhibit solutions up to the regions of interest for positive signals reported by CoGeNT and CDMS-Si experiments, and compatible with the observed DM relic density for DM mass in the range 8 .3-10 GeV. Spin-dependent interactions become the dominant source of scattering around the interference regions, where Maxwellian speed distribution is considered.
A line source in Minkowski for the de Sitter spacetime scalar Green’s function: massive case
NASA Astrophysics Data System (ADS)
Chu, Yi-Zen
2015-07-01
For certain classes of space(time)s embeddable in a higher dimensional flat space(time), it appears possible to compute the minimally coupled massless scalar Green’s function in the former by convolving its cousin in the latter with an appropriate scalar charge density. The physical interpretation is that beings residing in the higher dimensional flat space(time) may set up sources to fool the observer confined on the lower dimensional curved submanifold that she is detecting the field generated by a space(time) point source in her own world. In this paper we extend the general formula to include a non-zero mass. We then employ it to derive the Green’s function of the massive wave operator in (d≥slant 2)-dimensional de Sitter spacetime and that of the Helmholtz differential operator—the Laplacian plus a ‘mass term’—on the (d≥slant 2)-sphere. For both cases, the trajectories of the scalar sources are the same as that of the massless case, while the required scalar charge densities are determined by solving an eigenvalue equation. To source these massive Green’s functions, we show that the (d+1)-dimensional Minkowski/Euclidean experimentalists may choose to use either massive or massless scalar line charges. In de Sitter spacetime, the embedding method employed here leads directly to a manifest separation between the null cone versus tail terms of the Green’s functions.
Static weak dipole moments of the τ lepton via renormalizable scalar leptoquark interactions
NASA Astrophysics Data System (ADS)
Bolaños, A.; Moyotl, A.; Tavares-Velasco, G.
2014-03-01
The weak dipole moments of elementary fermions are calculated at the one-loop level in the framework of a renormalizable scalar leptoquark model that forbids baryon number violating processes and so is free from the strong constraints arising from experimental data. In this model there are two scalar leptoquarks accommodated in a SUL(2)×UY(1) doublet: One of these leptoquarks is nonchiral and has electric charge of 5/3e, whereas the other one is chiral and has electric charge 2/3e. In particular, a nonchiral leptoquark contributes to the weak properties of an up fermion via a chirality-flipping term proportional to the mass of the virtual fermion, and can also induce a nonzero weak electric dipole moment provided that the leptoquark couplings are complex. The numerical analysis is focused on the weak properties of the τ lepton since they offer good prospects for experimental study. The constraints on leptoquark couplings are briefly discussed for a nonchiral leptoquark with nondiagonal couplings to the second and third fermion generations, a third-generation nonchiral leptoquark, and a third-generation chiral leptoquark. It is found that although the chirality-flipping term can enhance the weak properties of the τ lepton via the top quark contribution, such an enhancement would be offset by the strong constraints on the leptoquark couplings. So, the contribution of scalar leptoquarks to the weak magnetic dipole moment of the τ lepton are smaller than the standard model (SM) contributions but can be of similar size to those arising in some SM extensions. A nonchiral leptoquark can also give contributions to the weak electric dipole moment larger than the SM one but well below the experimental limit. We also discuss the case of the off-shell weak dipole moments and, for completeness, analyze the behavior of the τ electromagnetic properties.
Higgs boson self-coupling from two-loop analysis
Alhendi, H. A.; Barakat, T.; Loqman, I. Gh.
2010-09-01
The scale invariant of the effective potential of the standard model at two loop is used as a boundary condition under the assumption that the two-loop effective potential approximates the full effective potential. This condition leads with the help of the renormalization-group functions of the model at two loop to an algebraic equation of the scalar self-coupling with coefficients that depend on the gauge and the top quark couplings. It admits only two real positive solutions. One of them, in the absence of the gauge and top quark couplings, corresponds to the nonperturbative ultraviolet fixed point of the scalar renormalization-group function and the other corresponds to the perturbative infrared fixed point. The dependence of the scalar coupling on the top quark and the strong couplings at two-loop radiative corrections is analyzed.
Limits on dark energy scalars using atom interferometry
NASA Astrophysics Data System (ADS)
Hamilton, Paul; Jaffe, Matt; Haslinger, Philipp; Simmons, Ethan; Khoury, Justin; Müller, Holger
2015-05-01
Dark energy makes up 70% of the mass-energy of the universe yet its identity remains unknown. Using atom interferometry we tightly constrain dark energy models based on scalar fields which become heavily screened in the presence of macroscopic matter. These ``chameleon'' fields were proposed as a form of quintessence which would be undetectable to macroscopic experiments searching for fifth forces. Combined with an ultra-high vacuum environment, the small mass of individual atoms prevents screening and makes them ideal test masses for detecting small forces from chameleons. We use our recently developed optical cavity atom interferometer to limit anomalous accelerations below 10-6g at millimeter-scale distances from a spherical source mass. This rules out a large range of chameleon theories consistent with the cosmological dark-energy density. With feasible improvements in sensitivity, we could detect chameleon fields with couplings up to the expected limit of the Planck mass scale. Adding a second source mass would also allow the measurement of the gravitational Aharonov-Bohm effect.
Symmetric scalar constraint for loop quantum gravity
NASA Astrophysics Data System (ADS)
Lewandowski, Jerzy; Sahlmann, Hanno
2015-02-01
In the framework of loop quantum gravity, we define a new Hilbert space of states which are solutions of a large number of components of the diffeomorphism constraint. On this Hilbert space, using the methods of Thiemann, we obtain a family of gravitational scalar constraints. They preserve the Hilbert space for every choice of lapse function. Thus adjointness and commutator properties of the constraint can be investigated in a straightforward manner. We show how the space of solutions of the symmetrized constraint can be defined by spectral decomposition, and the Hilbert space of physical states by subsequently fully implementing the diffeomorphism constraint. The relationship of the solutions to those resulting from a proposal for a symmetric constraint operator by Thiemann remains to be elucidated.
Visualization of Scalar Adaptive Mesh Refinement Data
VACET; Weber, Gunther; Weber, Gunther H.; Beckner, Vince E.; Childs, Hank; Ligocki, Terry J.; Miller, Mark C.; Van Straalen, Brian; Bethel, E. Wes
2007-12-06
Adaptive Mesh Refinement (AMR) is a highly effective computation method for simulations that span a large range of spatiotemporal scales, such as astrophysical simulations, which must accommodate ranges from interstellar to sub-planetary. Most mainstream visualization tools still lack support for AMR grids as a first class data type and AMR code teams use custom built applications for AMR visualization. The Department of Energy's (DOE's) Science Discovery through Advanced Computing (SciDAC) Visualization and Analytics Center for Enabling Technologies (VACET) is currently working on extending VisIt, which is an open source visualization tool that accommodates AMR as a first-class data type. These efforts will bridge the gap between general-purpose visualization applications and highly specialized AMR visual analysis applications. Here, we give an overview of the state of the art in AMR scalar data visualization research.
A broad-band scalar vortex coronagraph
NASA Astrophysics Data System (ADS)
Errmann, R.; Minardi, S.; Pertsch, T.
2013-10-01
Broad-band coronagraphy with deep nulling and small inner working angle has the potential of delivering images and spectra of exoplanets and other faint objects. In recent years, many coronagraphic schemes have been proposed, the most promising being the optical vortex phase mask coronagraphs. In this paper, a new scheme of broad-band optical scalar vortex coronagraph is proposed and characterized experimentally in the laboratory. Our setup employs a pair of computer-generated phase gratings (one of them containing a singularity) to control the chromatic dispersion of phase plates and achieves a constant peak-to-peak attenuation below 1 × 10-3 over a bandwidth of 120 nm centred at 700 nm. An inner working angle of ˜λ/D is demonstrated along with a raw contrast of 11.5 mag at 2λ/D.
A broadband scalar optical vortex coronagraph
NASA Astrophysics Data System (ADS)
Errmann, Ronnie; Minardi, Stefano; Pertsch, Thomas
2014-07-01
In recent years, new coronagraphic schemes have been proposed, the most promising being the optical vortex phase mask coronagraphs. In our work, a new scheme of broadband optical scalar vortex coronagraph is proposed and characterized experimentally in the laboratory. Our setup employs a pair of computer generated phase gratings (one of them containing a singularity) to control the chromatic dispersion of phase plates and achieves a constant peak-to-peak attenuation below 1:1000 over a bandwidth of 120 nm centered at 700 nm. An inner working angle of λ/D is demonstrated along with a raw contrast of 11.5magnitudes at 2λ/D. A more compact setup achieves a peak-to-peak attenuation below 1:1000 over a bandwidth of 60 nm with the other results remaining the same.
Light scalar susceptibilities and isospin breaking
Andres, R. Torres; Nicola, A. Gomez
2010-12-28
Making a thermal analysis in the context of NLO SU(3) Chiral Perturbation Theory we see that isospin breaking (IB) corrections (both electromagnetic and QCD ones) to quark condensates are of order O(e{sup 2}) and O({epsilon}), with {epsilon} the {pi}{sup 0}-{eta} mixing angle. However the combination {chi}{sub uu}-{chi}{sub ud} of flavour breaking susceptibilities, which vanishes in the isospin limit and can be identified essentially with the connected susceptibility, has an order O(1) contribution enhanced with T because of the {pi}{sup 0}-{eta}) mixing. Finally we present a thermal sum rule that relates quark condensate ratios and the light scalar susceptibility without IB, {chi}(T)-{chi}(0).
Gauge Fields, Scalars, Warped Geometry, and Strings
Silverstein, Eva M
2000-12-07
We review results on several interesting phenomena in warped compactifications of M theory, as presented at Strings 2000. The behavior of gauge fields in dimensional reduction from d + 1 to d dimensions in various backgrounds is explained from the point of view of the holographic duals (and a point raised in the question session at the conference is addressed). We summarize the role of additional fields (in particular scalar fields) in 5d warped geometries in making it possible for Poincare-invariant domain wall solutions to exist to a nontrivial order in a controlled approximation scheme without fine-tuning of parameters in the 5d action (and comment on the status of the singularities arising in the general relativistic description of these solutions). Finally, we discuss briefly the emergence of excitations of wrapped branes in warped geometries whose effective thickness, as measured along the Poincare slices in the geometry, grows as the energy increases.
Gastric cryptosporidiosis in freshwater angelfish (Pterophyllum scalare)
Murphy, B.G.; Bradway, D.; Walsh, T.; Sanders, G.E.; Snekvik, K.
2009-01-01
A freshwater angelfish (Pterophyllum scalare) hatchery experienced variable levels of emaciation, poor growth rates, swollen coelomic cavities, anorexia, listlessness, and increased mortality within their fish. Multiple chemotherapeutic trials had been attempted without success. In affected fish, large numbers of protozoa were identified both histologically and ultrastructurally associated with the gastric mucosa. The youngest cohort of parasitized fish was the most severely affected and demonstrated the greatest morbidity and mortality. The protozoa were morphologically most consistent with Cryptosporidium. All of the protozoan life stages were identified ultrastructurally and protozoal genomic DNA was isolated from parasitized tissue viscera and sequenced. Histological, ultrastructural, genetic, and phylogenetic analyses confirmed this protozoal organism to be a novel species of Cryptosporidium.
Renormalization group analysis in nonrelativistic QCD for colored scalars
Hoang, Andre H.; Ruiz-Femenia, Pedro
2006-01-01
The velocity nonrelativistic QCD Lagrangian for colored heavy scalar fields in the fundamental representation of QCD and the renormalization group analysis of the corresponding operators are presented. The results are an important ingredient for renormalization group improved computations of scalar-antiscalar bound state energies and production rates at next-to-next-to-leading-logarithmic (NNLL) order.
On relation between scalar interfaces and vorticity in inviscid flows
NASA Astrophysics Data System (ADS)
Ramesh, O. N.; Patwardhan, Saurabh
2013-11-01
A great variety of applications like pollutant mixing in the atmosphere, mixing of reactants in combustion highlight the importance of passive scalar dynamics in fluid flows. The other dynamically important variable in the study of fluid flow is the vorticity. Vorticity though, unlike a passive scalar, does affect the fluid motion. The dynamics of scalar (linear) and vorticity (non-linear) are governed by the equations which inherently have different characteristics. This paper addresses the question of the faithfulness of representation of vorticity by scalar marker and the motivation for this comes from the experiment of Head and Bandyopadhyay (1981) which showed the existence of coherent vortices by using smoke flow visualization in a turbulent boundary layer. We will show analytically in regions where the molecular diffusion effects are negligible, the vorticity and scalar gradients are orthogonal to each other. The iso- surface of scalar follows the vorticity in an inviscid situation. Also, we will demonstrate that in the case of unsteady burgers vortex and vortex shedding behind a finite circular cylinder, the scalar gradient is orthogonal to vorticity and inner product of vorticity and scalar gradients is zero in regions away from the wall.
Scalar field theory in {kappa}-Minkowski spacetime from twist
Kim, Hyeong-Chan; Lee, Youngone; Rim, Chaiho; Yee, Jae Hyung
2009-10-15
Using the twist deformation of U(igl(4,R)), the linear part of the diffeomorphism, we define a scalar function and construct a free scalar field theory in four-dimensional {kappa}-Minkowski spacetime. The action in momentum space turns out to differ only in the integration measure from the commutative theory.
Search for scalar top and bottom quarks at the Tevatron
Calfayan, Philippe
2008-11-23
This document reviews recent results on the search for scalar top and scalar bottom quarks in pp-bar collisions at {radical}(s) = 1.96 TeV. The analyses presented are based on data samples with integrated luminosities from 1.0 to 1.9 fb{sup -1} recorded at the Tevatron with the D0 and CDF detectors.
Emission of scalar particles from cylindrical black holes
NASA Astrophysics Data System (ADS)
Gohar, H.; Saifullah, K.
2013-01-01
We study quantum tunneling of scalar particles from black strings. For this purpose we apply WKB approximation and Hamilton-Jacobi method to solve the Klein-Gordon equation for outgoing trajectories. We find the tunneling probability of outgoing charged and uncharged scalars from the event horizon of black strings, and hence the Hawking temperature for these black configurations.
Simultaneous timing of multiple intervals: implications of the scalar property.
Leak, T M; Gibbon, J
1995-01-01
Three experiments with pigeons are reported in which the scalar property in simultaneous timing tasks was studied. According to scalar expectancy theory, the scalar property should be maintained in simultaneous timing, but the behavioral theory of timing predicts that the scalar property should be evident only in independent timing. Experiment 1 showed that the appearance of distinct peaks at reinforcement times required about a 4:1 ratio between intervals. Experiment 2 (2-interval timing task) and Experiment 3 (3-interval timing task) used an individual trial analysis technique to examine high-rate responding segments bracketing the times of reinforcement. The standard deviations of the starting and stopping times of high-rate segments were linearly related to their means and to reinforcement time, supporting the scalar property in simultaneous timing.
Involvement of prefrontal cortex in scalar implicatures: evidence from magnetoencephalography
Politzer-Ahles, Stephen; Gwilliams, Laura
2015-01-01
The present study investigated the neural correlates of the realisation of scalar inferences, i.e., the interpretation of some as meaning some but not all. We used magnetoencephalography, which has high temporal resolution, to measure neural activity while participants heard stories that included the scalar inference trigger some in contexts that either provide strong cues for a scalar inference or provide weaker cues. The middle portion of the lateral prefrontal cortex (Brodmann area 46) showed an increased response to some in contexts with fewer cues to the inference, suggesting that this condition elicited greater effort. While the results are not predicted by traditional all-or-nothing accounts of scalar inferencing that assume the process is always automatic or always effortful, they are consistent with more recent gradient accounts which predict that the speed and effort of scalar inferences is strongly modulated by numerous contextual factors. PMID:26247054
Screening of heavy scalars beyond the standard model
Einhorn, M.B. Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 ); Wudka, J. )
1993-06-01
Spontaneously broken gauge models generically present large radiative corrections when the masses of the scalars are larger than the symmetry-breaking scale(s). This is not necessary, however, and we determine, based on the symmetry and renormalization properties of the theory, the most general conditions under which scalar radiative effects are screened. Barring fine tuning, the properties of the Goldstone sector determine whether this type of screening is present or not, and this can be decided in most cases by inspection (given the pattern of symmetry breaking). We consider several examples. In particular we show that in left-right symmetric models the two requirements that all scalars be significantly heavier than the gauge bosons is inconsistent with screening; this implies either the presence of large radiative corrections produced by the heavy scalars, or the presence of scalars with masses similar to that of the (heaviest) gauge bosons in these models.
Limits of scalar diffraction theory for conducting gratings.
Gremaux, D A; Gallagher, N C
1993-04-10
Scalar diffraction theory and electromagnetic vector theory are compared by analyzing plane-wave scattering by a perfectly conducting, rectangular-grooved grating. General field solutions for arbitrary angles of incidence are derived by using scalar and vector theories. Diffraction efficiencies for the scalar and the vector cases as functions of wavelength, grating period, and angles of incidence are determined numerically and plotted. When the wavelength of the incident field is much shorter than the grating period, the diffraction efficiencies match. But when the wavelength is of the order of the grating period, large differences between the scalar and the vector solutions emerge. One general conclusion is that, depending on polarization, scalar theory should not be used when the grating period becomes smaller than ten wavelengths.
A non-perturbative approach to non-commutative scalar field theory
NASA Astrophysics Data System (ADS)
Steinacker, Harold
2005-03-01
Non-commutative euclidean scalar field theory is shown to have an eigenvalue sector which is dominated by a well-defined eigenvalue density, and can be described by a matrix model. This is established using regularizations of Bbb R2nθ via fuzzy spaces for the free and weakly coupled case, and extends naturally to the non-perturbative domain. It allows to study the renormalization of the effective potential using matrix model techniques, and is closely related to UV/IR mixing. In particular we find a phase transition for the phi4 model at strong coupling, to a phase which is identified with the striped or matrix phase. The method is expected to be applicable in 4 dimensions, where a critical line is found which terminates at a non-trivial point, with nonzero critical coupling. This provides evidence for a non-trivial fixed-point for the 4-dimensional NC phi4 model.
Light colored scalar as messenger of up-quark flavor dynamics in grand unified theories
Dorsner, Ilja; Fajfer, Svjetlana; Kamenik, Jernej F.; Kosnik, Nejc
2010-11-01
The measured forward-backward asymmetry in the tt production at the Tevatron might be explained by the additional exchange of a colored weak singlet scalar. Such state appears in some of the grand unified theories, and its interactions with the up-quarks are purely antisymmetric in flavor space. We systematically investigate the resulting impact on charm and top quark physics. The constraints on the relevant Yukawa couplings come from the experimentally measured observables related to D{sup 0}-D{sup 0} oscillations, as well as dijet and single-top production measurements at the Tevatron. After fully constraining the relevant Yukawa couplings, we predict possible signatures of this model in rare top quark decays. In a class of grand unified models we demonstrate how the obtained information enables to constrain the Yukawa couplings of the up-quarks at very high energy scale.
Scalar-fluid theories: cosmological perturbations and large-scale structure
Koivisto, Tomi S.; Saridakis, Emmanuel N.; Tamanini, Nicola E-mail: Emmanuel_Saridakis@baylor.edu
2015-09-01
Recently a new Lagrangian framework was introduced to describe interactions between scalar fields and relativistic perfect fluids. This allows two consistent generalizations of coupled quintessence models: non-vanishing pressures and a new type of derivative interaction. The implications of these to the formation of cosmological large-scale structure are uncovered here at the linear order. The full perturbation equations in the two cases are derived in a unified formalism and their Newtonian, quasi-static limit is studied analytically. Requiring the absence of an effective sound speed term in the coupled dark matter fluid restricts the Lagrangian to be a linear function of the matter number density. This leaves new potentially viable classes of both algebraically and derivatively interacting models wherein the coupling may impact the background expansion dynamics and imprint new signatures into the large-scale structure.
The scalar bi-spectrum in the Starobinsky model: the equilateral case
Martin, Jérôme; Sriramkumar, L. E-mail: sriram@physics.iitm.ac.in
2012-01-01
While a featureless, nearly scale invariant, primordial scalar power spectrum fits the most recent Cosmic Microwave Background (CMB) data rather well, certain features in the spectrum are known to lead to a better fit to the data (although, the statistical significance of such results remains an open issue). In the inflationary scenario, one or more periods of deviations from slow roll are necessary in order to generate features in the scalar perturbation spectrum. Over the last couple of years, it has been recognized that such deviations from slow roll inflation can also result in reasonably large non-Gaussianities. The Starobinsky model involves the canonical scalar field and consists of a linear inflaton potential with a sudden change in the slope. The change in the slope causes a brief period of departure from slow roll which, in turn, results in a sharp rise in power, along with a burst of oscillations in the scalar spectrum for modes that leave the Hubble radius just before and during the period of fast roll. The hallmark of the Starobinsky model is that it allows the scalar power spectrum to be evaluated analytically in terms of the three parameters that describe the model, viz. the two slopes that describe the potential on either side of the discontinuity and the Hubble scale at the time when the field crosses the discontinuity. In this work, we evaluate the bi-spectrum of the scalar perturbations in the Starobinsky model in the equilateral limit. Remarkably, we find that, just as the power spectrum, all the different contributions to the the bi-spectrum too can be evaluated completely analytically and expressed in terms of the three paramaters that describe the model. We show that the quantity f{sub NL}, which characterizes the extent of non-Gaussianity, can be expressed purely in terms of the ratio of the two slopes on either side of the discontinuity in the potential. Further, we find that, for certain values of the parameters, f{sub NL} in the
Localization and mass spectra of various matter fields on scalar-tensor brane
Xie, Qun-Ying; Zhao, Zhen-Hua; Zhong, Yi; Yang, Jie; Zhou, Xiang-Nan
2015-03-10
Recently, a new scalar-tensor braneworld model was presented in [http://dx.doi.org/10.1103/PhysRevD.86.127502]. It not only solves the gauge hierarchy problem but also reproduces a correct Friedmann-like equation on the brane. In this new model, there are two different brane solutions, for which the mass spectra of gravity on the brane are the same. In this paper, we investigate localization and mass spectra of various bulk matter fields (i.e., scalar, vector, Kalb-Ramond, and fermion fields) on the brane. It is shown that the zero modes of all the matter fields can be localized on the positive tension brane under some conditions, and the mass spectra of each kind of bulk matter field for the two brane solutions are different except for some special cases, which implies that the two brane solutions are not physically equivalent. When the coupling constants between the dilaton and bulk matter fields take special values, the mass spectra for both solutions are the same, and the scalar and vector zero modes are localized on the negative tension brane, while the KR zero mode is still localized on the positive tension brane.
Scalar and vector leptoquark pair production at hadron colliders: Signal and backgrounds
NASA Astrophysics Data System (ADS)
Dion, B.; Marleau, L.; Simon, G.
1999-01-01
We perform a systematic analysis of scalar and vector leptoquark pair production at the Fermilab Tevatron and at the CERN LHC. We evaluate signal expectations and background levels for the processes pp(pp¯)-->2 jets+e+e- and 2 jets+e+pT. The Monte Carlo event generator ISAJET is used to simulate the experimental conditions at the current (s=1.8 TeV, L=100 pb-1) and upgraded (L=2 fb-1) Tevatron as well as the LHC (s=14 TeV, L=10 fb-1). Depending on the luminosity, and assuming a branching ratio B(LQ-->eq)=0.5, we find a discovery reach up to 170 (255) GeV for scalar leptoquarks at the current (upgraded) Tevatron. Similarly, we find vector leptoquarks to be detectable at masses below 300 (400) GeV depending on the coupling. At the LHC, the discovery reach is enhanced to 1 TeV for scalar leptoquarks and to 1.5 TeV for vectors.
Frame-covariant formulation of inflation in scalar-curvature theories
NASA Astrophysics Data System (ADS)
Burns, Daniel; Karamitsos, Sotirios; Pilaftsis, Apostolos
2016-06-01
We develop a frame-covariant formulation of inflation in the slow-roll approximation by generalizing the inflationary attractor solution for scalar-curvature theories. Our formulation gives rise to new generalized forms for the potential slow-roll parameters, which enable us to examine the effect of conformal transformations and inflaton reparameterizations in scalar-curvature theories. We find that cosmological observables, such as the power spectrum, the spectral indices and their runnings, can be expressed in a concise manner in terms of the generalized potential slow-roll parameters which depend on the scalar-curvature coupling function, the inflaton wavefunction, and the inflaton potential. We show how the cosmological observables of inflation are frame-invariant in this generalized potential slow-roll formalism, as long as the end-of-inflation condition is appropriately extended to become frame-invariant as well. We then apply our formalism to specific scenarios, such as the induced gravity inflation, Higgs inflation and F (R) models of inflation, and obtain more accurate results, without making additional approximations to the potential. Our results are shown to be consistent to lowest order with those presented in the literature. Finally, we outline how our frame-covariant formalism can be naturally extended beyond the tree-level approximation, within the framework of the Vilkovisky-DeWitt effective action.
Resonant signatures of heavy scalar fields in the cosmic microwave background
Saito, Ryo; Takamizu, Yu-ichi; Nakashima, Masahiro; Yokoyama, Jun'ichi E-mail: nakashima@resceu.s.u-tokyo.ac.jp E-mail: yokoyama@resceu.s.u-tokyo.ac.jp
2012-11-01
We investigate the possibility that a heavy scalar field, whose mass exceeds the Hubble scale during inflation, could leave non-negligible signatures in the Cosmic Microwave Background (CMB) temperature anisotropy power spectrum through the parametric resonance between its background oscillations and the inflaton fluctuations. By assuming the heavy scalar field couples with the inflaton derivatively, we show that the resonance can be efficient without spoiling the slow-roll inflation. The primordial power spectrum modulated by the resonance has a sharp peak at a specific scale and could be an origin of the anomalies observed in the angular power spectrum of the CMB. In some values of parameters, the modulated spectrum can fit the observed data better than the simple power-law power spectrum, though the resultant improvement of the fit is not large enough and hence other observations such as non-Gaussianity are necessary to confirm that the CMB anomalies are originated from the resonant effect of the heavy scalar field. The resonant signatures can provide an opportunity to observe heavy degrees of freedom during inflation and improve our understanding of physics behind inflation.
Metric-affine formalism of higher derivative scalar fields in cosmology
Li, Mingzhe; Wang, Xiulian E-mail: wangxiulian2000@yahoo.com.cn
2012-07-01
Higher derivative scalar field theories have received considerable attention for the potentially explanations of the initial state of the universe or the current cosmic acceleration which they might offer. They have also attracted many interests in the phenomenological studies of infrared modifications of gravity. These theories are mostly studied by the metric variational approach in which only the metric is the fundamental field to account for the gravitation. In this paper we study the higher derivative scalar fields with the metric-affine formalism where the affine connection is treated arbitrarily at the beginning. Because the higher derivative scalar fields couple to the connection directly in a covariant theory these two formalisms will lead to different results. These differences are suppressed by the powers of the Planck mass and are usually expected to have small effects. But in some cases they may cause non-negligible deviations. We show by a higher derivative dark energy model that the two formalisms lead to significantly different pictures of the future universe.
NASA Technical Reports Server (NTRS)
Selle, L. C.; Bellan, Josette
2006-01-01
Transitional databases from Direct Numerical Simulation (DNS) of three-dimensional mixing layers for single-phase flows and two-phase flows with evaporation are analyzed and used to examine the typical hypothesis that the scalar dissipation Probability Distribution Function (PDF) may be modeled as a Gaussian. The databases encompass a single-component fuel and four multicomponent fuels, two initial Reynolds numbers (Re), two mass loadings for two-phase flows and two free-stream gas temperatures. Using the DNS calculated moments of the scalar-dissipation PDF, it is shown, consistent with existing experimental information on single-phase flows, that the Gaussian is a modest approximation of the DNS-extracted PDF, particularly poor in the range of the high scalar-dissipation values, which are significant for turbulent reaction rate modeling in non-premixed flows using flamelet models. With the same DNS calculated moments of the scalar-dissipation PDF and making a change of variables, a model of this PDF is proposed in the form of the (beta)-PDF which is shown to approximate much better the DNS-extracted PDF, particularly in the regime of the high scalar-dissipation values. Several types of statistical measures are calculated over the ensemble of the fourteen databases. For each statistical measure, the proposed (beta)-PDF model is shown to be much superior to the Gaussian in approximating the DNS-extracted PDF. Additionally, the agreement between the DNS-extracted PDF and the (beta)-PDF even improves when the comparison is performed for higher initial Re layers, whereas the comparison with the Gaussian is independent of the initial Re values. For two-phase flows, the comparison between the DNS-extracted PDF and the (beta)-PDF also improves with increasing free-stream gas temperature and mass loading. The higher fidelity approximation of the DNS-extracted PDF by the (beta)-PDF with increasing Re, gas temperature and mass loading bodes well for turbulent reaction rate
NASA Astrophysics Data System (ADS)
Libanov, M.; Rubakov, V.
2010-11-01
We consider a scenario in which primordial scalar perturbations are generated when complex conformal scalar field rolls down its negative quartic potential. Initially, these are the perturbations of the phase of this field; they are converted into the adiabatic perturbations at a later stage. A potentially dangerous feature of this scenario is the existence of perturbations in the radial field direction, which have red power spectrum. We show, however, that to the linear order in the small parameter — the quartic self-coupling — the infrared effects are completely harmless, as they can be absorbed into field redefinition. We then evaluate the statistical anisotropy inherent in the model due to the existence of the long-ranged radial perturbations. To the linear order in the quartic self-coupling the statistical anisotropy is free of the infrared effects. The latter show up at the quadratic order in the self-coupling and result in the mild (logarithmic) enhancement of the corresponding contribution to the statistical anisotropy. The resulting statistical anisotropy is a combination of a larger term which, however, decays as momentum increases, and a smaller term which is independent of momentum.
Creation of quantized particles, gravitons, and scalar perturbations by the expanding universe
NASA Astrophysics Data System (ADS)
Parker, Leonard
2015-04-01
Quantum creation processes during the very rapid early expansion of the universe are believed to give rise to temperature anisotropies and polarization patterns in the CMB radiation. These have been observed by satellites such as COBE, WMAP, and PLANCK, and by bolometric instruments placed near the South Pole by the BICEP collaborations. The expected temperature anisotropies are well-confirmed. The B-mode polarization patterns in the CMB are currently under measurement jointly by the PLANCK and BICEP groups to determine the extent to which the B-modes can be attributed to gravitational waves from the creation of gravitons in the earliest universe. As the original discoverer of the quantum phenomenon of particle creation from vacuum by the expansion of the universe, I will explain how the discovery came about and how it relates to the current observations. The first system that I considered when I started my Ph.D. thesis in 1962 was the quantized minimally-coupled scalar field in an expanding FLRW (Friedmann, Lemaitré, Robertson, Walker) universe having a general continuous scale factor a(t) with continuous time derivatives. I also considered quantized fermion fields of spin-1/2 and the spin-1 massless photon field, as well as the quantized conformally-invariant field equations of arbitrary integer and half-integer spins that had been written down in the classical context for general gravitational metrics by Penrose. It was during 1962 that I proved that quanta of the minimally-coupled scalar field were created by the general expanding FLRW universe. This was relevant also to the creation of quantized perturbations of the gravitational field, since these perturbations satisfied linear field equations that could be quantized in the same way as the minimally-coupled scalar field equation. In fact, in 1946, E.M. Lifshitz had considered the classical Einstein gravitational field in FLRW expanding universes and had shown that the classical linearized Einstein field
Nuclear relativistic Hartree-Fock calculations including pions interacting with a scalar field
Marcos, S.; Lopez-Quelle, M.; Niembro, R.; Savushkin, L. N.
2012-10-20
The effect of pions on the nuclear shell structure is analyzed in a relativistic Hartree-Fock approximation (RHFA). The Lagrangian includes, in particular, a mixture of {pi}N pseudoscalar (PS) and pseudovector (PV) couplings, self-interactions of the scalar field {sigma} and a {sigma} - {pi} interaction that dresses pions with an effective mass (m*{sub {pi}}). It is found that an increase of m*{sub {pi}} strongly reduces the unrealistic effect of pions, keeping roughly unchanged their contribution to the total binding energy.
Confinement Driven by Scalar Field in 4d Non Abelian Gauge Theories
Chabab, Mohamed
2007-01-12
We review some of the most recent work on confinement in 4d gauge theories with a massive scalar field (dilaton). Emphasis is put on the derivation of confining analytical solutions to the Coulomb problem versus dilaton effective couplings to gauge terms. It is shown that these effective theories can be relevant to model quark confinement and may shed some light on confinement mechanism. Moreover, the study of interquark potential, derived from Dick Model, in the heavy meson sector proves that phenomenological investigation of tmechanism is more than justified and deserves more efforts.
Constraints on general second-order scalar-tensor models from gravitational Cherenkov radiation
Kimura, Rampei; Yamamoto, Kazuhiro E-mail: kazuhiro@hiroshima-u.ac.jp
2012-07-01
We demonstrate that the general second-order scalar-tensor theories, which have attracted attention as possible modified gravity models to explain the late time cosmic acceleration, could be strongly constrained from the argument of the gravitational Cherenkov radiation. To this end, we consider the purely kinetic coupled gravity and the extended galileon model on a cosmological background. In these models, the propagation speed of tensor mode could be less than the speed of light, which puts very strong constraints from the gravitational Cherenkov radiation.
Beyond the Standard Model: Scalar dark matter, and, lepton flavor violation
NASA Astrophysics Data System (ADS)
Gonderinger, Matthew
The Standard Model of particle physics is a highly successful theory of fundamental particle interactions, especially in light of the recent discovery of a Higgs-like boson at the LHC. Nonetheless, the SM is incomplete, and the search for physics beyond the SM has prompted a great amount of experimental and theoretical work. In this thesis, I present theoretical work I have done in two areas of beyond the SM physics: scalar dark matter and lepton flavor violation. Scalar extensions of the SM are simple but nonetheless interesting and well-motivated models for beyond the SM physics that can include a dark matter candidate particle. Using the renormalization group evolution of the model parameters and the Coleman-Weinberg one-loop effective potential, I perform an analysis of the vacuum stability of two of these scalar extensions, the real singlet and the complex singlet. Also included are experimental bounds from dark matter direct detection. The vacuum stability analysis reveals that light dark matter (10 GeV) requires a moderate self-interaction strength and new physics at or below the 109 GeV scale in the case of the real scalar, and a light (order 10 to 100 GeV) Higgs-like particle with reduced couplings and additional new physics below 1000 TeV in the case of the complex scalar. Lepton flavor violation probes the high energy scale of new physics through its effects on low energy processes which are highly suppressed in the SM by small neutrino masses. I utilize the Buchmuller-Ruckl-Wyler parameterization of leptoquarks and limits obtained from the HERA experiments ZEUS and H1 to calculate the cross section for electron-to-tau conversion in DIS at a next generation Electron-Ion Collider (EIC) with high luminosity. The potential for the EIC to search for such events is compared with the ability of future tau → egamma searches to set limits on leptoquark masses and couplings. This analysis demonstrates that a future EIC search would be competitive with or
Reaction enhancement of initially distant scalars by Lagrangian coherent structures
Pratt, Kenneth R. Crimaldi, John P.; Meiss, James D.
2015-03-15
Turbulent fluid flows have long been recognized as a superior means of diluting initial concentrations of scalars due to rapid stirring. Conversely, experiments have shown that the structures responsible for this rapid dilution can also aggregate initially distant reactive scalars and thereby greatly enhance reaction rates. Indeed, chaotic flows not only enhance dilution by shearing and stretching but also organize initially distant scalars along transiently attracting regions in the flow. To show the robustness of this phenomenon, a hierarchical set of three numerical flows is used: the periodic wake downstream of a stationary cylinder, a chaotic double gyre flow, and a chaotic, aperiodic flow consisting of interacting Taylor vortices. We demonstrate that Lagrangian coherent structures (LCS), as identified by ridges in finite time Lyapunov exponents, are directly responsible for this coalescence of reactive scalar filaments. When highly concentrated filaments coalesce, reaction rates can be orders of magnitude greater than would be predicted in a well-mixed system. This is further supported by an idealized, analytical model that was developed to quantify the competing effects of scalar dilution and coalescence. Chaotic flows, known for their ability to efficiently dilute scalars, therefore have the competing effect of organizing initially distant scalars along the LCS at timescales shorter than that required for dilution, resulting in reaction enhancement.
Scalar Decomposition of the Electromagnetic Vector Wave Equation
NASA Astrophysics Data System (ADS)
Franke, Carlos Rodolfo
The accepted definition of separability of the electromagnetic vector wave equation requires that only one scalar field component exists in a scalar partial differential equation of no higher order than the second, for at least one of the scalar field components. The second order constraint so tightly restricts the mathematics that only the rectangular, the three cylindrical, and the spherical and conical coordinates can be separated. The constraint also permits separation of one scalar field component in prolate and oblate spheroidal coordinates, and paraboloidal coordinates, in that absence of azimuthal variations. The definition of separability makes it a particular attribute of a particular coordinate in a particular coordinate system, and not a general property of the coordinate system as a whole. The second order constraint on the scalar partial differential equation is now lifted, permitting the vector wave equation in any orthogonal curvilinear coordinate system to be completely separated into three scalar partial differential equations. The treatment is carried out for the circular-cylindrical and spherical coordinates, and the analysis indicates that the highest order of at least one of the uncoupled scalar partial differential equations in a given orthogonal curvilinear coordinate system is equal to twice the number of curvilinear coordinates.
The Mysterious Transient ROTSE3 J115649.1+542726 is an Extremely Luminous Type II SN at z = 0.21
NASA Astrophysics Data System (ADS)
Chornock, R.; Miller, A. A.; Perley, D. A.; Bloom, J. S.
2008-08-01
We report on further spectroscopic observations of the transient ROTSE3 J115649.1+542726 discovered by Yuan et al. (ATEL #1515) and followed up by several groups (ATEL #1524, ATEL #1576, ATEL #1578, and ATEL #1593). We observed the object for 840 s using the Low-Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) on the Keck I 10-m telescope on 2008 Aug 3.25 UT. Our initial observations of this object (ATEL #1576) showed a blue and largely featureless spectrum, but at later epochs several unidentified weak spectral features appeared (ATEL #1576 and ATEL #1593).
Reheating temperature in non-minimal derivative coupling model
Sadjadi, H. Mohseni; Goodarzi, Parviz E-mail: p_goodarzi@ut.ac.ir
2013-07-01
We consider the inflaton as a scalar field described by a non-minimal derivative coupling model with a power law potential. We study the slow roll inflation, the rapid oscillation phase, the radiation dominated and the recombination eras respectively, and estimate e-folds numbers during these epochs. Using these results and recent astrophysical data we determine the reheating temperature in terms of the spectral index and the amplitude of the power spectrum of scalar perturbations.
Massive basketball diagram for a thermal scalar field theory
Andersen, Jens O.; Braaten, Eric; Strickland, Michael
2000-08-15
The ''basketball diagram'' is a three-loop vacuum diagram for a scalar field theory that cannot be expressed in terms of one-loop diagrams. We calculate this diagram for a massive scalar field at nonzero temperature, reducing it to expressions involving three-dimensional integrals that can be easily evaluated numerically. We use this result to calculate the free energy for a massive scalar field with a {phi}{sup 4} interaction to three-loop order. (c) 2000 The American Physical Society.
Generalized cosmic Chaplygin gas inspired intermediate standard scalar field inflation
NASA Astrophysics Data System (ADS)
Jawad, Abdul; Rani, Shamaila; Mohsaneen, Sidra
2016-08-01
We study the warm intermediate inflationary regime in the presence of generalized cosmic Chaplygin gas and an inflaton decay rate proportional to the temperature. For this purpose, we consider standard scalar field model during weak and strong dissipative regimes. We explore inflationary parameters like spectral index, scalar and tensor power spectra, tensor to scalar ratio and decay rate in order to compare the present model with recent observational data. The physical behavior of inflationary parameters is presented and found that all the results are agreed with recent observational data such as WMAP7, WMAP9 and Planck 2015.
Scalar fluctuations in turbulent combustion - An experimental study
NASA Astrophysics Data System (ADS)
Ballal, D. R.; Chen, T. H.; Yaney, P. P.
1986-01-01
Temperature and velocity fluctuations data were gathered for turbulent premixed combustion to evaluate a model for scalar transport and scalar dissipation. The data were collected using laser Raman spectroscopy and laser Doppler anemometry with a premixed CH4-air flame from a Bunsen burner. Mean temperature profiles were generated and the pdf's temperature fluctuations were calculated. A wrinkled laminar flame structure was noted in the reaction zone, where the scalar field was anisotropic and where the temperature fluctuations exhibited peak values. The Bray, Moss and Libby model (1985) was successful in predicting the temperature fluctuation intensity and the dissipation ratios, the latter reaching peak values in the flame tip region.
Cosmological models in Weyl geometrical scalar-tensor theory
NASA Astrophysics Data System (ADS)
Pucheu, M. L.; Alves Junior, F. A. P.; Barreto, A. B.; Romero, C.
2016-09-01
We investigate cosmological models in a recently proposed geometrical theory of gravity, in which the scalar field appears as part of the spacetime geometry. We extend the previous theory to include a scalar potential in the action. We solve the vacuum field equations for different choices of the scalar potential and give a detailed analysis of the solutions. We show that, in some cases, a cosmological scenario is found that seems to suggest the appearance of a geometric phase transition. We build a toy model, in which the accelerated expansion of the early Universe is driven by pure geometry.
Scalar perturbation in symmetric Lee-Wick bouncing universe
Cho, Inyong; Kwon, O-Kab E-mail: okab@skku.edu
2011-11-01
We investigate the scalar perturbation in the Lee-Wick bouncing universe driven by an ordinary scalar field plus a ghost field. We consider only a symmetric evolution of the universe and the scalar fields about the bouncing point. The gauge invariant Sasaki-Mukhanov variable is numerically solved in the spatially flat gauge. We find a new form of the initial perturbation growing during the contracting phase. After the bouncing, this growing mode stabilizes to a constant mode which is responsible for the late-time power spectrum.
Charged scalar perturbations around Garfinkle-Horowitz-Strominger black holes
NASA Astrophysics Data System (ADS)
Zhang, Cheng-Yong; Zhang, Shao-Jun; Wang, Bin
2015-10-01
We examine the stability of the Garfinkle-Horowitz-Strominger (GHS) black hole under charged scalar perturbations. Employing the appropriate numerical methods, we show that the GHS black hole is always stable against charged scalar perturbations. This is different from the results obtained in the de Sitter and anti-de Sitter black holes. Furthermore, we argue that in the GHS black hole background there is no amplification of the incident charged scalar wave to cause the superradiance, so that the superradiant instability cannot exist in this spacetime.
Noninertial effects on the quantum dynamics of scalar bosons
NASA Astrophysics Data System (ADS)
Castro, Luis B.
2016-02-01
The noninertial effect of rotating frames on the quantum dynamics of scalar bosons embedded in the background of a cosmic string is considered. In this work, scalar bosons are described by the Duffin-Kemmer-Petiau (DKP) formalism. Considering the DKP oscillator in this background the combined effects of a rotating frames and cosmic string on the equation of motion, energy spectrum, and DKP spinor are analyzed and discussed in detail. Additionally, the effect of rotating frames on the scalar bosons' localization is studied.
Scalar dark matter in an extra dimension inspired model
NASA Astrophysics Data System (ADS)
Lineros, Roberto; Pereira dos Santos, Fabio
2016-05-01
In this work we consider a singlet scalar propagating in a flat large extra dimension. The first Kaluza-Klein mode associated to this singlet scalar will be a viable dark matter candidate. The tower of new particles enriches the calculation of the relic density due effect of coannihilation. For large mass splitting, the model converges to the predictions of the singlet dark matter model. For nearly degenerate mass spectrum, coannihilations increase the cross-sections used for direct and indirect dark matter searches. We investigate the impact of the Kaluza-Klein tower associated to singlet scalar for indirect and direct detection of dark matter.
Gaugino and scalar masses in the landscape
NASA Astrophysics Data System (ADS)
Conlon, Joseph P.; Quevedo, Fernando
2006-06-01
In this letter we demonstrate the genericity of suppressed gaugino masses Ma ~ m3/2/ln (MPlanck/m3/2) in the IIB string landscape, by showing that this relation holds for D7-brane gauginos whenever the associated modulus is stabilised by nonperturbative effects. Although m3/2 and Ma take many different values across the landscape, the above small mass hierarchy is maintained. We show that it is valid for models with an arbitrary number of moduli and applies to both the KKLT and exponentially large volume approaches to Kähler moduli stabilisation. In the latter case we explicitly calculate gaugino and moduli masses for compactifications on the two-modulus Calabi-Yau Bbb P4[1,1,1,6,9]. In the large-volume scenario we also show that soft scalar masses are approximately universal with mi2 ~ m3/22(1+epsiloni), with the non-universality parametrised by epsiloni ~ 1/ln (MP/m3/2)2 ~ (1/1000). We briefly discuss possible phenomenological implications of our results.
Scalar Green function of the Kerr spacetime
NASA Astrophysics Data System (ADS)
Yang, Huan; Zhang, Fan; Zimmerman, Aaron; Chen, Yanbei
2014-03-01
In this paper we study the scalar Green function in the Kerr spacetime using Wentzel-Kramers-Brillouin (WKB) methods. The Green function can be expressed by Fourier-transforming to its frequency-domain counterpart, and with the help of complex analysis it can be divided into parts: 1) the "direct part," which propagates on the light cone and dominates at very early times; 2) the "quasinormal-mode part," which represents the waves traveling around the photon sphere and is important at early and intermediate times; and 3) the "tail part," which is due to scattering by the Coulomb-type potential and becomes more important at later times. We focus on the "quasinormal-mode part" of the Green function and derive an approximate analytical formula for it using WKB techniques. This approximate Green function diverges at points that are connected by null geodesics, and it recovers the fourfold singular structure of Green functions that are seen in Schwarzschild and other spacetimes. It also carries unique signatures of the Kerr spacetime such as frame dragging. Along the way, we also derive approximate quasinormal-mode wave functions and expressions for the black hole excitation factors in the Kerr spacetime. We expect this work to benefit the understanding of both wave propagation and the problem of self-force in the Kerr spacetime.
DBI scalar field theory for QGP hydrodynamics
NASA Astrophysics Data System (ADS)
Nastase, Horatiu
2016-07-01
A way to describe the hydrodynamics of the quark-gluon plasma using a Dirac-Born-Infeld (DBI) action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal (η ≃0 ) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well as a bulk viscosity, and regulates the behavior of the energy density at the shock, making it finite. The resulting fluid satisfies the relativistic Navier-Stokes equation with uμ,ρ ,P ,η defined in terms of ϕ and its derivatives. One finds a relation between the parameters of the theory and the quark-gluon plasma thermodynamics, α /β2=η /(s T ), and by fixing α and β from usual (low multiplicity) particle scattering, one finds T ∝mπ.
A search for third generation scalar leptoquarks
Zatserklyaniy, Andriy
2006-08-01
Leptoquarks (LQ) are particles with both color and lepton number predicted in some gauge theories and composite models. Current theory suggests that leptoquarks would come in three different generations. We report on a search for charge 1/3 third generation leptoquarks produced in p$\\bar{p}$ collisions at √s = 1.96 TeV using data collected by the D0 detector at Fermilab. Such leptoquarks would decay into a tau-neutrino plus a b-quark with branching fraction B. We present preliminary results on an analysis where both leptoquarks decay into neutrinos giving a final state with missing energy and two b-jets. Using 425(recorded) pb^{-1} of data, we place limits on σ(p$\\bar{p}$ → LQ$\\bar{LQ}$)B^{2} as a function of the leptoquark mass. Assuming B = 1, we excluded at the 95% confidence level scalar third generation leptoquarks with M_{LQ} < 219 GeV.
Rapid roll inflation with conformal coupling
Kofman, Lev; Mukohyama, Shinji
2008-02-15
Usual inflation is realized with a slow rolling scalar field minimally coupled to gravity. In contrast, we consider dynamics of a scalar with a flat effective potential, conformally coupled to gravity. Surprisingly, it contains an attractor inflationary solution with the rapidly rolling inflaton field. We discuss models with the conformal inflaton with a flat potential (including hybrid inflation). There is no generation of cosmological fluctuations from the conformally coupled inflaton. We consider realizations of modulated (inhomogeneous reheating) or curvaton cosmological fluctuations in these models. We also implement these unusual features for the popular string-theoretic warped inflationary scenario, based on the interacting D3-D3 branes. The original warped brane inflation suffers a large inflaton mass due to conformal coupling to 4-dimensional gravity. Instead of considering this as a problem and trying to cure it with extra engineering, we show that warped inflation with the conformally coupled, rapidly rolling inflaton is yet possible with N=37 efoldings, which requires low-energy scales 1-100 TeV of inflation. Coincidentally, the same warping numerology can be responsible for the hierarchy. It is shown that the scalars associated with angular isometries of the warped geometry of compact manifold (e.g. S{sup 3} of Klebanov-Strassler (KS) geometry) have solutions identical to conformally coupled modes and also cannot be responsible for cosmological fluctuations. We discuss other possibilities.
A global fit of the γ-ray galactic center excess within the scalar singlet Higgs portal model
NASA Astrophysics Data System (ADS)
Cuoco, Alessandro; Eiteneuer, Benedikt; Heisig, Jan; Krämer, Michael
2016-06-01
We analyse the excess in the γ-ray emission from the center of our galaxy observed by Fermi-LAT in terms of dark matter annihilation within the scalar Higgs portal model. In particular, we include the astrophysical uncertainties from the dark matter distribution and allow for unspecified additional dark matter components. We demonstrate through a detailed numerical fit that the strength and shape of the γ-ray spectrum can indeed be described by the model in various regions of dark matter masses and couplings. Constraints from invisible Higgs decays, direct dark matter searches, indirect searches in dwarf galaxies and for γ-ray lines, and constraints from the dark matter relic density reduce the parameter space to dark matter masses near the Higgs resonance. We find two viable regions: one where the Higgs-dark matter coupling is of Script O(10-2), and an additional dark matter component beyond the scalar WIMP of our model is preferred, and one region where the Higgs-dark matter coupling may be significantly smaller, but where the scalar WIMP constitutes a significant fraction or even all of dark matter. Both viable regions are hard to probe in future direct detection and collider experiments.
NASA Astrophysics Data System (ADS)
Pappas, T.; Kanti, P.; Pappas, N.
2016-07-01
In this work, we study the propagation of scalar fields in the gravitational background of a higher-dimensional Schwarzschild-de Sitter black hole as well as on the projected-on-the-brane four-dimensional background. The scalar fields have also a nonminimal coupling to the corresponding, bulk or brane, scalar curvature. We perform a comprehensive study by deriving exact numerical results for the greybody factors, and study their profile in terms of particle and spacetime properties. We then proceed to derive the Hawking radiation spectra for a higher-dimensional Schwarzschild-de Sitter black hole, and we study both bulk and brane channels. We demonstrate that the nonminimal field coupling, which creates an effective mass term for the fields, suppresses the energy emission rates while the cosmological constant assumes a dual role. By computing the relative energy rates and the total emissivity ratio for bulk and brane emission, we demonstrate that the combined effect of a large number of extra dimensions and value of the field coupling gives to the bulk channel the clear domination in the bulk-brane energy balance.
Environmental dependence of masses and coupling constants
Olive, Keith A.; Pospelov, Maxim
2008-02-15
We construct a class of scalar field models coupled to matter that lead to the dependence of masses and coupling constants on the ambient matter density. Such models predict a deviation of couplings measured on the Earth from values determined in low-density astrophysical environments, but do not necessarily require the evolution of coupling constants with the redshift in the recent cosmological past. Additional laboratory and astrophysical tests of {delta}{alpha} and {delta}(m{sub p}/m{sub e}) as functions of the ambient matter density are warranted.
Nonrelativistic approach for cosmological scalar field dark matter
NASA Astrophysics Data System (ADS)
Ureña-López, L. Arturo
2014-07-01
We derive nonrelativistic equations of motion for the formation of cosmological structure in a scalar field dark matter (SFDM) model corresponding to a complex scalar field endowed with a quadratic scalar potential. Starting with the equations of motion written in the Newtonian gauge of scalar perturbations, we separate out the involved fields into relativistic and nonrelativistic parts and find the equations of motion for the latter that can be used to build up the full solution. One important assumption will be that the SFDM field is in the regime of fast oscillations, under which its behavior in the homogeneous regime is exactly that of cold dark matter. The resultant equations are quite similar to the Schrödinger-Poisson system of Newtonian boson stars plus relativistic leftovers, and they can be used to study the formation of cosmological structure in SFDM models, and others alike, to ultimately prove their viability as complete dark matter models.
Scalar mesons and the search for the 0{sup ++} Glueball
Ulrike Thoma
2002-10-01
The possibility that gluonic excitations of hadronic matter or of the QCD vacuum may exist is perhaps one of the most fascinating topics in hadron spectroscopy. Glueballs are predicted by many models; in particular present-day lattice gauge calculations require their existence. All these models agree that the lightest glueball should have scalar quantum numbers and a mass around 1.6 GeV, which corresponds to the mass region where the scalar qq[bar]-mesons are expected. Therefore mixing effects can complicate the search for the glueball. Experiments indeed show an overpopulation of states, for which many different interpretations exist. This reflects the complexity of the situation. New data from various experiments on scalar states give hints toward an interpretation of the scalar states. But, still many questions remain.
Wormholes, the weak energy condition, and scalar-tensor gravity
NASA Astrophysics Data System (ADS)
Shaikh, Rajibul; Kar, Sayan
2016-07-01
We obtain a large class of Lorentzian wormhole spacetimes in scalar-tensor gravity, for which the matter stress energy does satisfy the weak energy condition. Our constructions have zero Ricci scalar and an everywhere finite, nonzero scalar field profile. Interpreting the scalar-tensor gravity as an effective on-brane theory resulting from a two-brane Randall-Sundrum model of warped extra dimensions, it is possible to link wormhole existence with that of extra dimensions. We study the geometry, matter content, gravitational redshift and circular orbits in such wormholes and argue that our examples are perhaps among those which may have some observational relevance in astrophysics in the future. We also study traversability and find that our wormholes are indeed traversable for values of the metric parameters satisfying the weak energy condition.
Bianchi type-I models with conformally invariant scalar field
Accioly, A.J.; Vaidya, A.N.; Som, M.M.
1983-05-15
The solutions of the Einstein equations with the trace-free energy-momentum tensor of conformally invariant scalar field as source are obtained in a spatially homogeneous anisotropic space-time. Some interesting features of the solutions are discussed.
Two scalar field cosmology: Conservation laws and exact solutions
NASA Astrophysics Data System (ADS)
Paliathanasis, Andronikos; Tsamparlis, Michael
2014-08-01
We consider the two scalar field cosmology in a Friedmann Robertson Walker spatially flat spacetime where the scalar fields interact both in the kinetic part and the potential. We apply the Noether point symmetries in order to define the interaction of the scalar fields. We use the point symmetries in order to write the field equations in the normal coordinates, and we find that the Lagrangian of the field equations which admits at least three Noether point symmetries describes linear Newtonian systems. Furthermore, by using the corresponding conservation laws we find exact solutions of the field equations. Finally, we generalize our results to the case of N scalar fields interacting both in their potential and their kinematic part in a flat Friedmann Robertson Walker background.
Kasner solutions, climbing scalars and big-bang singularity
Condeescu, Cezar; Dudas, Emilian E-mail: emilian.dudas@cpht.polytechnique.fr
2013-08-01
We elaborate on a recently discovered phenomenon where a scalar field close to big-bang is forced to climb a steep potential by its dynamics. We analyze the phenomenon in more general terms by writing the leading order equations of motion near the singularity. We formulate the conditions for climbing to exist in the case of several scalars and after inclusion of higher-derivative corrections and we apply our results to some models of moduli stabilization. We analyze an example with steep stabilizing potential and notice again a related critical behavior: for a potential steepness above a critical value, going backwards towards big-bang, the scalar undergoes wilder oscillations, with the steep potential pushing it back at every passage and not allowing the scalar to escape to infinity. Whereas it was pointed out earlier that there are possible implications of the climbing phase to CMB, we point out here another potential application, to the issue of initial conditions in inflation.
Modeling scalar flux and the energy and dissipation equations
NASA Technical Reports Server (NTRS)
Yoshizawa, A.
1987-01-01
Closure models derived from the Two-Scale Direct-Interaction Approximation were compared with data from direct simulations of turbulence. Attention was restricted to anisotropic scalar diffusion models, models for the energy dissipation equation, and models for energy diffusion.
Search for scalar glueballs from heavy meson decays
Lue Caidian; Shen Yuelong; Wang Wei
2010-08-05
We investigate the transition form factors of B meson decays into a scalar glueball in the light-cone formalism. Compared with form factors of B to ordinary scalar mesons, the B-to-glueball form factors have the same power in the expansion of 1/m{sub B}. Taking into account the leading twist light-cone distribution amplitude, we find that they are numerically smaller than those form factors of B to ordinary scalar mesons. In the presence of mixing between glueballs and ordinary scalar mesons, the possibility to extract the mixing parameters from semileptonic B decays and nonleptonic B decays are explored. We also point out a clean way to identify a glueball through B{sub c} decays.
Relating spectral indices to tensor and scalar amplitudes in inflation
Kolb, Edward W.; Vadas, Sharon L.
1994-02-01
Within an expansion in slow-roll inflation parameters, we derive the complete second-order expressions relating the ratio of tensor to scalar density perturbations and the spectral index of the scalar spectrum. We find that ``corrections'' to previously derived formulae can dominate if the tensor to scalar ratio is small. For instance, if VV"/(V')^{2}≠1 or if [mPI^{2}/(4π)]||V'"/V'|| ≳ 1, where V(Φ) is the inflaton potential and m_{Pl}is the Planck mass, then the previously used simple relations between the indices and the tensor to scalar ratio fails. This failure occurs in particular for natural inflation, Coleman--Weinberg inflation, and ``chaotic'' inflation.
Janssen, T. M.; Prokopec, T.
2011-04-15
In this paper we consider a massless scalar field, with a possible coupling {xi} to the Ricci scalar in a D dimensional Friedmann-Lemaitre-Robertson-Walker space-time with a constant deceleration parameter q={epsilon}-1, {epsilon}=-H/H{sup 2}. Correlation functions for the Bunch-Davies vacuum of such a theory have long been known to be infrared divergent for a wide range of values of {epsilon}. We resolve these divergences by explicitly matching the space-time under consideration to a space-time without infrared divergencies. Such a procedure ensures that all correlation functions with respect to the vacuum in the space-time of interest are infrared finite. In this newly defined vacuum we construct the coincidence limit of the propagator and as an example calculate the expectation value of the stress-energy tensor. We find that this approach gives both in the ultraviolet and in the infrared satisfactory results. Moreover, we find that, unless the effective mass due to the coupling to the Ricci scalar {xi}R is negative, quantum contributions to the energy density always dilute away faster, or just as fast, as the background energy density. Therefore, quantum backreaction is insignificant at the one-loop order, unless {xi}R is negative. Finally we compare this approach with known results where the infrared is regulated by placing the Universe in a finite box. In an accelerating universe, the results are qualitatively the same, provided one identifies the size of the Universe with the physical Hubble radius at the time of the matching. In a decelerating universe, however, the two schemes give different late time behavior for the quantum stress-energy tensor. This happens because in this case the length scale at which one regulates the infrared becomes sub-Hubble at late times.
Quantum reduced loop gravity: Extension to scalar fields
NASA Astrophysics Data System (ADS)
Bilski, Jakub; Alesci, Emanuele; Cianfrani, Francesco
2015-12-01
The quantization of the Hamiltonian for a scalar field is performed in the framework of quantum reduced loop gravity. We outline how the regularization can be performed by using the analogous tools adopted in full loop quantum gravity, and the matrix elements of the resulting operator between basis states are analytic coefficients. These achievements open the way for a consistent analysis of the quantum gravity corrections to the classical dynamics of gravity in the presence of a scalar field in a cosmological setting.
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).
Wormhole-induced operators for a massless scalar field
Goto, T.; Okada, Y. )
1991-05-15
Bilocal operators induced by an axionic wormhole solution are obtained in the case of a massless scalar field. For this purpose, we first show that the calculation of a Green's function for the scalar field on the wormhole background is reduced to a one-dimensional potential-barrier problem. We then evaluate numerically the asymptotic behavior of the Green's function and identify the effective interaction induced by the wormhole.
Relating neutrino masses to dilepton modes of doubly charged scalars
Chen, Chian-Shu; Geng, C. Q.
2010-11-15
We study a model with Majorana neutrino masses generated through doubly charged scalars at two-loop level. We give explicit relationships between the neutrino masses and the same sign dilepton decays of the doubly charged scalars. In particular, we demonstrate that in the tribimaximal limit of the neutrino mixings, the absolute neutrino masses and Majorana phases can be extracted through the measurements of the dilepton modes at colliders.
FAST TRACK COMMUNICATION: Lorentzian manifolds and scalar curvature invariants
NASA Astrophysics Data System (ADS)
Coley, Alan; Hervik, Sigbjørn; Pelavas, Nicos
2010-05-01
We discuss (arbitrary-dimensional) Lorentzian manifolds and the scalar polynomial curvature invariants constructed from the Riemann tensor and its covariant derivatives. Recently, we have shown that in four dimensions a Lorentzian spacetime metric is either \\mathcal {I}-non-degenerate, and hence locally characterized by its scalar polynomial curvature invariants, or is a degenerate Kundt spacetime. We present a number of results that generalize these results to higher dimensions and discuss their consequences and potential physical applications.
A unified optical theorem for scalar and vectorial wave fields.
Wapenaar, Kees; Douma, Huub
2012-05-01
The generalized optical theorem is an integral relation for the angle-dependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived that encompasses the separate versions for scalar and vectorial waves. Moreover, this unified theorem also holds for scattering by anisotropic elastic and piezoelectric scatterers as well as bianisotropic (non-reciprocal) EM scatterers. PMID:22559339
Search for scalar top and bottom quarks at the Tevatron
Calfayan, Philippe; /Munich U.
2009-01-01
This document reviews recent results on the search for scalar top and scalar bottom quarks in p{bar p} collisions at {radical}s = 1.96 TeV. The analyses presented are based on data samples with integrated luminosities from 1.0 to 1.9 fb{sup -1} recorded at the Tevatron with the D0 and CDF detectors.
Unimodular metagravity vs. general relativity with a scalar field
Pirogov, Yu. F.
2010-01-15
The unimodular metagravity, with the graviscalar as a dark matter, is compared with General Relativity (GR) in the presence of a scalar field. The effect of the graviscalar on the static spherically symmetric metric is studied. An exact limit solution representing a new cosmic object, the (harmonic) graviscalar black hole, is given. The relation with the black hole in the environment of a scalar field in GR is discussed.
A unified optical theorem for scalar and vectorial wave fields.
Wapenaar, Kees; Douma, Huub
2012-05-01
The generalized optical theorem is an integral relation for the angle-dependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived that encompasses the separate versions for scalar and vectorial waves. Moreover, this unified theorem also holds for scattering by anisotropic elastic and piezoelectric scatterers as well as bianisotropic (non-reciprocal) EM scatterers.
Perfect focusing of scalar wave fields in three dimensions.
Benítez, Pablo; Miñano, Juan C; González, Juan C
2010-04-12
A method to design isotropic inhomogeneous refractive index distribution is presented, in which the scalar wave field solutions propagate exactly on an eikonal function (i.e., remaining constant on the Geometrical Optics wavefronts). This method is applied to the design of "dipole lenses", which perfectly focus a scalar wave field emitted from a point source onto a point absorber, in both two and three dimensions. Also, the Maxwell fish-eye lens in two and three dimensions is analysed.
Scalar field equations from quantum gravity during inflation
Kahya, E. O.; Woodard, R. P.
2008-04-15
We exploit a previous computation of the self-mass-squared from quantum gravity to include quantum corrections to the scalar evolution equation. The plane wave mode functions are shown to receive no significant one loop corrections at late times. This result probably applies as well to the inflaton of scalar-driven inflation. If so, there is no significant correction to the {phi}{phi} correlator that plays a crucial role in computations of the power spectrum.
Decay of massive scalar hair on brane black holes
Rogatko, Marek; Szyplowska, Agnieszka
2007-08-15
We study analytically the intermediate and late-time behavior of the massive scalar field in the background of static spherically symmetric brane black hole solutions. The intermediate asymptotic behavior of the scalar field reveals the dependence on the field's parameter mass as well as the multipole moment l, while the late-time behavior has the power-law decay rate independent of those factors.
Analytic treatment of the system of a Kerr-Newman black hole and a charged massive scalar field
NASA Astrophysics Data System (ADS)
Hod, Shahar
2016-08-01
Charged rotating Kerr-Newman black holes are known to be superradiantly unstable to perturbations of charged massive bosonic fields whose proper frequencies lie in the bounded regime 0 <ω
NASA Astrophysics Data System (ADS)
Hafsi, A.; Ma, Y.; Buckley, M.; Tejada-Martinez, A. E.; Veron, F.
2016-05-01
Direct numerical simulations (DNS) of an initially quiescent coupled air-water interface driven by an air flow with free stream speed of 5 m/s have been conducted and scalar transfer from the air side to the water side and subsequent vertical transport in the water column have been analysed. Two simulations are compared: one with a freely deforming interface, giving rise to gravity-capillary waves and aqueous Langmuir turbulence (LT) characterized by small-scale (centimeter-scale) Langmuir cells (LC), and the other with the interface intentionally held flat, i.e., without LC. It is concluded that LT serves to enhance vertical transport of the scalar in the water side and in the process increases scalar transfer efficiency from the air side to the water side relative to the shear-dominated turbulence in the flat interface case. Furthermore, transition to LT was observed to be accompanied by a spike in scalar flux characterized by an order of magnitude increase. These episodic flux increases, if linked to gusts and overall unsteadiness in the wind field, are expected to be an important contributor in determining the long-term average of the air-sea gas fluxes.
Wang, S.-Y.; Boyanovsky, D.; Vega, H. J. de; Lee, D.-S.; Ng, Y. J.
2000-03-15
We study the transport coefficients, damping rates, and mean free paths of soft fermion collective excitations in a hot fermion-gauge-scalar plasma with the goal of understanding the main physical mechanisms that determine transport of chirality in scenarios of nonlocal electroweak baryogenesis. The focus is on identifying the different transport coefficients for the different branches of soft collective excitations of the fermion spectrum. These branches correspond to collective excitations with opposite ratios of chirality to helicity and different dispersion relations. By combining results from the hard thermal loop (HTL) resummation program with a novel mechanism of fermion damping through heavy scalar decay, we obtain a robust description of the different damping rates and mean free paths for the soft collective excitations to leading order in HTL and lowest order in the Yukawa coupling. The space-time evolution of wave packets of collective excitations unambiguously reveals the respective mean free paths. We find that whereas both the gauge and scalar contribution to the damping rates are different for the different branches, the difference of mean free paths for both branches is mainly determined by the decay of the heavy scalar into a hard fermion and a soft collective excitation. We argue that these mechanisms are robust and are therefore relevant for nonlocal scenarios of baryogenesis either in the standard model or extensions thereof. (c) 2000 The American Physical Society.
NASA Astrophysics Data System (ADS)
Lang, Ryan N.
2014-04-01
We derive the tensor gravitational waveform generated by a binary of nonspinning compact objects (black holes or neutron stars) in a general class of scalar-tensor theories of gravity. The waveform is accurate to second post-Newtonian order beyond the leading order quadrupole approximation. We use the direct integration of the relaxed Einstein equations formalism, appropriately adapted to scalar-tensor theories, along with previous results for the equations of motion in these theories. The self-gravity of the compact objects is treated with an approach developed by Eardley. The scalar field causes deviations from the general relativistic waveform that depend only on a small number of parameters. Among the effects of the scalar field are new hereditary terms which depend on the past history of the source. One of these, a dipole-dipole coupling, produces a zero-frequency "gravitational-wave memory" equivalent to the Christodoulou memory of general relativity. In the special case of two black holes, the waveform reduces to the general relativistic waveform. For a mixed (black hole-neutron star) system, the waveform is identical to that of Einstein's theory to first post-Newtonian order, with deviations at higher order depending only on a single parameter. The behavior in these cases matches that found for the equations of motion.
Scalar geometry and masses in Calabi-Yau string models
NASA Astrophysics Data System (ADS)
Farquet, Daniel; Scrucca, Claudio A.
2012-09-01
We study the geometry of the scalar manifolds emerging in the no-scale sector of Kähler moduli and matter fields in generic Calabi-Yau string compactifications, and describe its implications on scalar masses. We consider both heterotic and orientifold models and compare their characteristics. We start from a general formula for the Kähler potential as a function of the topological compactification data and study the structure of the curvature tensor. We then determine the conditions for the space to be symmetric and show that whenever this is the case the heterotic and the orientifold models give the same scalar manifold. We finally study the structure of scalar masses in this type of geometries, assuming that a generic superpotential triggers spontaneous supersymmetry breaking. We show in particular that their behavior crucially depends on the parameters controlling the departure of the geometry from the coset situation. We first investigate the average sGoldstino mass in the hidden sector and its sign, and study the implications on vacuum metastability and the mass of the lightest scalar. We next examine the soft scalar masses in the visible sector and their flavor structure, and study the possibility of realizing a mild form of sequestering relying on a global symmetry.
Screening the fifth force in the Horndeski's most general scalar-tensor theories
Kase, Ryotaro; Tsujikawa, Shinji E-mail: shinji@rs.kagu.tus.ac.jp
2013-08-01
We study how the Vainshtein mechanism operates in the most general scalar-tensor theories with second-order equations of motion. The field equations of motion, which can be also applicable to most of other screening scenarios proposed in literature, are generally derived in a spherically symmetric space-time with a matter source. In the presence of a field coupling to the Ricci scalar, we clarify conditions under which the Vainshtein mechanism is at work in a weak gravitational background. We also obtain the solutions of the field equation inside a spherically symmetric body and show how they can be connected to exterior solutions that accommodate the Vainshtein mechanism. We apply our general results to a number of concrete models such as the covariant/extended Galileons and the DBI Galileons with Gauss-Bonnet and other terms. In these models the fifth force can be suppressed to be compatible with solar-system constraints, provided that non-linear field kinetic terms coupled to the Einstein tensor do not dominate over other non-linear field self-interactions.
Classical and quantum dynamics of a perfect fluid scalar-energy dependent metric cosmology
NASA Astrophysics Data System (ADS)
Khodadi, M.; Nozari, K.; Vakili, B.
2016-05-01
Inspired from the idea of minimally coupling of a real scalar field to geometry, we investigate the classical and quantum models of a flat energy-dependent FRW cosmology coupled to a perfect fluid in the framework of the scalar-rainbow metric gravity. We use the standard Schutz' representation for the perfect fluid and show that under a particular energy-dependent gauge fixing, it may lead to the identification of a time parameter for the corresponding dynamical system. It is shown that, under some circumstances on the minisuperspace prob energy, the classical evolution of the of the universe represents a late time expansion coming from a bounce instead of the big-bang singularity. Then we go forward by showing that this formalism gives rise to a Schrödinger-Wheeler-DeWitt equation for the quantum-mechanical description of the model under consideration, the eigenfunctions of which can be used to construct the wave function of the universe. We use the resulting wave function in order to investigate the possibility of the avoidance of classical singularities due to quantum effects by means of the many-worlds and Bohmian interpretation of quantum cosmology.