Showing papers in "Physical Review D in 1988"
TL;DR: It is argued that a number of models in which the energy density of the scalar field red-shifts in a specific manner are studied could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
Abstract: The cosmological consequences of a pervasive, rolling, self-interacting, homogeneous scalar field are investigated. A number of models in which the energy density of the scalar field red-shifts in a specific manner are studied. In these models the current epoch is chosen to be scalar-field dominated to agree with dynamical estimates of the density parameter, ${\ensuremath{\Omega}}_{\mathrm{dyn}\mathrm{\ensuremath{\sim}}0.2}$, and zero spatial curvature. The required scalar-field potential is ``nonlinear'' and decreases in magnitude as the value of the scalar field increases. A special solution of the field equations which is an attractive, time-dependent, fixed point is presented. These models are consistent with the classical tests of gravitation theory. The E\"otv\"os-Dicke measurements strongly constrain the coupling of the scalar field to light (nongravitational) fields. Nucleosynthesis proceeds as in the standard hot big-bang model. In linear perturbation theory the behavior of baryonic perturbations, in the baryon-dominated epoch, do not differ significantly from the canonical scenario, while the presence of a substantial amount of homogeneous scalar-field energy density at low red-shifts inhibits the growth of perturbations in the baryonic fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, either in the radiation-dominated, matter-dominated, or scalar-field-dominated epochs. On the basis of this effect, we argue that these models could reconcile the low dynamical estimates of the mean mass density with the negligibly small spatial curvature preferred by inflation.
3,948 citations
TL;DR: This work has considered four models in which the conformal invariance of electromagnetism is broken and the primeval magnetic fields which result can have astrophysically interesting strengths, but are very model-dependent.
Abstract: We study the production of large-scale (∼ Mpc) magnetic fields in inflationary Universe models. In the usual electromagnetic gauge theory, the photon field is conformally invariant and the magnetic fields that are produced during an inflationary epoch are uninterestingly small. We have considered four models in which the conformal invariance of electromagnetism is broken. The primeval magnetic fields which result can have astrophysically interesting strengths, but are very model-dependent.
925 citations
TL;DR: A formalism which is adapted to study the evolution of a photon (axion, graviton) beam in the presence of external fields is developed, and the possibility of detecting axions by a measurement of the magnetically induced birefringence of the vacuum is discussed.
Abstract: Photons can mix with low-mass bosons in the presence of external electromagnetic fields if these particles---not necessarily of spin 1---couple by a two-photon vertex. Important examples are the hypothetical axion (spin 0) and graviton (spin 2). We develop a formalism which is adapted to study the evolution of a photon (axion, graviton) beam in the presence of external fields. We apply our results to discuss the possibility of detecting axions by a measurement of the magnetically induced birefringence of the vacuum. We also discuss photon-axion (graviton) transitions in pulsar magnetic fields. The QED-induced nonlinearity of Maxwell's equations causes magnetic birefringence effects which are much stronger than the axion-induced effects in the range of axion parameters allowed by astrophysical constraints. Also, this QED effect induces an index of refraction for photons in vacuum which is so large near pulsars that photon-axion (graviton) transitions are strongly suppressed. However, this QED effect can be canceled by plasma refractive effects, leading to degeneracy between photons and axions so that resonant transitions can occur in analogy with the Mikheyev-Smirnov-Wolfenstein effect. The adiabatic condition can be met only in spatially extended systems, possibly in the magnetosphere of magnetic white dwarfs. Our conclusions differ substantially from several recent discussions of various aspects of these mixing phenomena.
772 citations
Journal Article•
TL;DR: A new parameter-free unification of micro- and macrodynamics is constructed and gravitational measures for reducing macroscopic quantum fluctuations of the mass density are applied to lead to classical trajectories in the Macroscopic limit of translational motion.
Abstract: This paper adopts the hypothesis that the absence of macroscopic quantum fluctuations is due to a certain universal mechanism. Such a mechanism has recently been proposed by Ghirardi et al. [Phys. Rev. D 34, 470 (1986)], and here we recapitulate a compact version of it. K\'arolyh\'azy [Nuovo Cimento 52, 390 (1966)] showed earlier the possible role of gravity and, along this line, we construct here a new parameter-free unification of micro- and macrodynamics. We apply gravitational measures for reducing macroscopic quantum fluctuations of the mass density. This model leads to classical trajectories in the macroscopic limit of translational motion. For massive objects, unwanted macroscopic superpositions of quantum states become destroyed in very short times. The relation between state-vector and density-operator formalisms has also been discussed. We only anticipate the need for elaborating characteristic predictions of the model in the region separating micro- and macroscopic properties.
587 citations
TL;DR: A simple explanation of the Swendsen-Wang algorithm for Potts models in terms of a joint model of Potts spin variables interacting with bond occupation variables is given and how to generalize this representation to arbitrary models is shown.
Abstract: We give a simple explanation of the Swendsen-Wang algorithm for Potts models in terms of a joint model of Potts spin variables interacting with bond occupation variables. We then show how to generalize this representation, as well as the corresponding Monte Carlo algorithm, to arbitrary models. We give initial results of tests of the new algorithm on the two-dimensional XY model.
556 citations
TL;DR: A search was made for neutral objects which might be produced by 20-GeV electrons incident on the SLAC beam dump, penetrate the downstream natural shielding, and decay upstream of an electromagnetic shower calorimeter.
Abstract: A search was made for neutral objects which might be produced by 20-GeV electrons incident on the SLAC beam dump, penetrate the downstream natural shielding, and decay upstream of an electromagnetic shower calorimeter. With about 30 C of electrons dumped, no candidate events were found above an energy of \ensuremath{\sim}2 GeV. The 95%-confidence-level limit on the product of mass and lifetime of light axionlike bosons decaying primarily into two photons is determined to be greater than 1.4 keV sec. Limits on photino parameters are also given.
482 citations
TL;DR: The seasonal modulation of the signal can be used to detect WIMP's even at low-signal-to-background levels and thus without the necessity of going to very-low-energy thresholds, suggesting the prospects for detecting a variety of cold-dark-matter candidates may be closer at hand than previously thought.
Abstract: If weakly interacting massive particles (WIMP's) are the dark matter in the galactic halo, they may be detected in low-background ionization detectors now operating or with low-temperature devices under development. In detecting WIMP's of low mass or WIMP's with spin-dependent nuclear interactions (e.g., photinos), a principal technical difficulty appears to be achieving very low thresholds (\ensuremath{\lesssim} keV) in large (\ensuremath{\sim} kg) detectors with low background noise. We present an analytic treatment of WIMP detection and show that the seasonal modulation of the signal can be used to detect WIMP's even at low-signal-to-background levels and thus without the necessity of going to very-low-energy thresholds. As a result, the prospects for detecting a variety of cold-dark-matter candidates may be closer at hand than previously thought. We discuss in detail the detector characteristics required for a number of WIMP candidates, and carefully work out expected event rates for several present and proposed detectors.
481 citations
TL;DR: This paper treats a system of self-interacting bosons described by λφ4 scalar fields in flat space and adopts the closed-time-path (CTP) functional formalism and uses a two-particle irreducible (2PI) representation for the effective action.
Abstract: This is the first of a series of papers which describe the functional-integral approach to the study of the statistical and kinetic properties of nonequilibrium quantum fields in flat and curved spacetimes. In this paper we treat a system of self-interacting bosons described by \ensuremath{\lambda}${\ensuremath{\varphi}}^{4}$ scalar fields in flat space. We adopt the closed-time-path (CTP or ``in-in'') functional formalism and use a two-particle irreducible (2PI) representation for the effective action. These formalisms allow for a full account of the dynamics of quantum fields, and put the correlation functions on an equal footing with the mean fields. By assuming a thermal distribution we recover the real-time finite-temperature theory as a special case. By requiring the CTP effective action to be stationary with respect to variations of the correlation functions we obtain an infinite set of coupled equations which is the quantum-field-theoretical generalization of the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. Truncation of this series leads to dissipative characteristics in the subsystem. In this context we discuss the nature of dissipation in interacting quantum fields.To one-loop order in a perturbative expansion of the CTP effective action, the 2PI formalism yields results equivalent to the leading 1/N expansion for an O(N)-symmetric scalar field. To higher-loop order we introduce a two-time approximation to separate the quantum-field effects of radiative correction and renormalization from the statistical-kinetic effects of collisions and relaxation. In the weak-coupling quasiuniform limit, the system of nonequilibrium quantum fields can subscribe to a kinetic theory description wherein the propagators are represented in terms of relativistic Wigner distribution functions. From a two-loop calculation we derive the Boltzmann equation for the distribution function and the gap equation for the effective mass of the quasiparticles. One can define an entropy function for the quantum gas of quasiparticles which satisfies the H theorem. We also calculate the limits to the validity of the binary collision approximation from a three-loop analysis. The theoretical framework established here can be generalized to nonconstant background fields and for curved spacetimes.
444 citations
TL;DR: It is shown that the tunneling wave function predicts initial states that lead to inflation, while the Hartle-Hawking wave function does not.
Abstract: Cosmological wave functions are found in a minisuperspace model (1) with ``tunneling'' and (2) with Hartle-Hawking boundary conditions. The probability distributions for the initial states of the Universe corresponding to the two wave functions are calculated and compared. It is shown that the tunneling wave function predicts initial states that lead to inflation, while the Hartle-Hawking wave function does not. Small perturbations about the minisuperspace model are considered and it is argued that both wave functions predict that the Universe nucleates with quantum fields in de Sitter-invariant vacuum states.
376 citations
TL;DR: The thermodynamic properties of black holes in Lovelock gravity are examined and it is found that the specific heat of a black hole becomes positive at small mass, allowing the black hole to achieve stable equilibrium with its environment and giving it an infinite lifetime.
Abstract: The thermodynamic properties of black holes in Lovelock gravity are examined. In particular, the case of the Einstein Lagrangian plus the four-dimensional Euler density is discussed in detail. In five dimensions, one finds that the specific heat of a black hole becomes positive at small mass, allowing the black hole to achieve stable equilibrium with its environment and giving it an infinite lifetime. This behavior is not universal, however, but it always occurs in 2k+1 dimensions for a Lovelock theory including the 2k-dimensional Euler density. For theories including six-derivative or higher-order interactions, black holes with degenerate zero-temperature horizons are also possible.
368 citations
TL;DR: The angular dependence and the amplitude of the seasonal modulation for an isothermal halo model is calculated and it is shown that Earth's motion relative to the galactic halo produces a seasonal modulation in the expected event rate.
Abstract: If the galactic halo is composed of weakly interacting massive particles (WIMP's), then cryogenic experiments may be capable of detecting the recoil of nuclei struck by the WIMP's. Earth's motion relative to the galactic halo produces a seasonal modulation in the expected event rate. The direction of nuclear recoil has a strong angular dependence that also can be used to confirm the detection of WIMP's. I calculate the angular dependence and the amplitude of the seasonal modulation for an isothermal halo model.
TL;DR: It is shown that it may be made to further enhance the sensitivity within a narrow bandwidth, becoming tuned recycling, and the various sensitivity-bandwidth combinations, together with the tuning properties, are discussed.
Abstract: Laser interferometers may detect gravitational waves by sensing the strain in space produced by their passage. The resultant change in intensity of an interference fringe must be observable against a background noise due to the statistical fluctuations in the number of detected photons. Optimization of the detector sensitivity thus involves devising an optical system which both maximizes the signal and minimizes the noise. This is attempted in the various arrangements known collectively as light recycling. Here, the performance of these systems is quantitatively assessed. Standard or broadband recycling functions essentially by making efficient use of the available light, but it is shown that it may also be made to further enhance the sensitivity within a narrow bandwidth, becoming tuned recycling. This works, as do all the narrow-band variants, by arranging for both the laser light and a gravitational-wave-induced sideband to be resonant in the optical system. The original narrow-band system, resonant recycling, can also be made broadband; the various sensitivity-bandwidth combinations, together with the tuning properties of such a system, are discussed.
TL;DR: A potential new kind of resonant solar-neutrino conversion is found, which could help account for the lower than expected solar- NEUTrino ..nu../sub e/ flux and/or indications of an anticorrelation between fluctuations in the ..nu-bar/sub ..mu ..mu../ flux and sunspot activity.
Abstract: The combined effect of matter and magnetic fields on neutrino spin and flavor precession is examined. We find a potential new kind of resonant solar-neutrino conversion ..nu../sub e//sub >//sub L//sub =/..--> nu../sub ..mu..//sub =/ or ..nu../sub tau//sub >//sub R//sub =/ (for Dirac neutrinos) or ..nu../sub e/..-->..nu-bar/sub ..mu../ or nu-bar/sub tau/ (for Majorana neutrinos). Such a resonance could help account for the lower than expected solar-neutrino ..nu../sub e/ flux and/or indications of an anticorrelation between fluctuations in the ..nu../sub e/ flux and sunspot activity. Consequences of spin-flavor precession for supernova neutrinos are also briefly discussed.
TL;DR: The possible quantum states of these closed universes, which correspond to wormholes which connect two asymptotically Euclidean regions, are described.
Abstract: Any reasonable theory of quantum gravity will allow closed universes to branch off from our nearly flat region of spacetime. I describe the possible quantum states of these closed universes. They correspond to wormholes which connect two asymptotically Euclidean regions, or two parts of the same asymptotically Euclidean region. I calculate the influence of these wormholes on ordinary quantum fields at low energies in the asymptotic region. This can be represented by adding effective interactions in flat spacetime which create or annihilate closed universes containing certain numbers of particles. The effective interactions are small except for closed universes containing scalar particles in the spatially homogeneous mode. If these scalar interactions are not reduced by sypersymmetry, it may be that any scalar particles we observe would have to be bound states of particles of higher spin, such as the pion. An observer in the asymptotically flat region would not be able to measure the quantum state of closed universes that branched off. He would therefore have to sum over all possibilities for the closed universes. This would mean that the final state would appear to be a mixed quantum state, rather than a pure quantum state.
TL;DR: The nature of the single, observed neutrino burst coincides remarkably well with the elements of the current model of type-II supernovae and neutron-star formation.
Abstract: The properties of the Kamiokande-II detector and the method of measurement are described in detail. The data on the neutrino burst from the supernova SN1987A on 23 February 1987 at 7:35:35 UT\ifmmode\pm\else\textpm\fi{}1 min are presented, with records of earlier and later observation periods in which other neutrino events possibly associated with SN1987A might have occurred. There is no evidence in the data for any excess of neutrino-induced events, either in a burst of a few seconds duration or over a longer time interval, relative to the usual count rate, excepting only the neutrino burst at 7:35:35 UT. The nature of the single, observed neutrino burst coincides remarkably well with the elements of the current model of type-II supernovae and neutron-star formation. This is the first direct observation in neutrino astronomy.
TL;DR: It is shown that a charmed quark created when the plasma is hot will be stopped before propagating 1 fm and subsequent diffusion will be fast, which should serve to increase the yield of J/\ensuremath{\psi} mesons in relativistic heavy-ion collisions.
Abstract: We calculate the classical drag and diffusion coefficients for a charmed quark propagating in the quark-gluon plasma. Both coefficients turn out rather large, so that (1) a charmed quark created when the plasma is hot will be stopped before propagating 1 fm and (2) subsequent diffusion will be fast. The first effect should serve to increase the yield of J/\ensuremath{\psi} mesons in relativistic heavy-ion collisions, while the second should work in the opposite direction. In any case, the two effects should dominate the dynamics of a cc\ifmmode\bar\else\textasciimacron\fi{} pair.
TL;DR: In this article, all spherically symmetric solutions of d-dimensional Einstein gravity coupled to the Gauss-Bonnet and Born-Infeld terms are derived, classified, and compared with the previous solutions.
Abstract: Spherically symmetric solutions of d-dimensional Einstein-Maxwell theory with a Gauss-Bonnet term are classified. All spherically symmetric solutions of d-dimensional Einstein gravity coupled to the Gauss-Bonnet and Born-Infeld terms are derived, classified, and compared with the previous solutions. Thermodynamic properties of the black holes are discussed and the black-hole temperatures derived. Unlike the solutions of Einstein-Maxwell theory the solutions with a Born-Infeld term do not appear to have a stable end point with regard to thermal evaporation.
TL;DR: The relationship between path-integral and Dirac quantization for a simple class of reparametrization-invariant theories and the results are applied to two simple examples: the nonrelativistic point particle in parametrized form and the relativity point particle.
Abstract: We explore the relationship between path-integral and Dirac quantization for a simple class of reparametrization-invariant theories. The main object is to study minisuperspace models in quantum cosmology---models for quantum gravity in which one restricts attention to a finite number of degrees of freedom. Our starting point for the construction of the (Lorentzian) path integral is the very general and powerful method introduced by Batalin, Fradkin, and Vilkovisky. Particular attention is paid to the measure in the large, i.e., to the range of integration of the Lagrange multiplier. We show how to derive the Wheeler-DeWitt equation from our path-integral expression. The relationship between the choice of measure in the path integral and the operator ordering in the Wheeler-DeWitt equation is thus determined. The operator-ordering ambiguity in the Wheeler-DeWitt equation is completely fixed by demanding invariance under field redefinitions of both the three-metric and the lapse function. Our results are applied to two simple examples: the nonrelativistic point particle in parametrized form and the relativistic point particle. We also consider a simple minisuperspace example and discuss a difficulty that arises: namely, the problem of incorporating the fact that det${h}_{\mathrm{ij}}$g0 into the quantization procedure.
TL;DR: It is shown that a variety of constraints, including the relation between the W and Z masses and the Fermi constant, charged-current universality, limits on induced right-handed charged currents, and flavor-diagonal neutral currents suffice to limit all directions in parameter space that are not excluded by the absence of flavor-changing neutral currents.
Abstract: The results of a comprehensive analysis of the limits on mixings between ordinary fermions and possible heavy fermions with exotic SU(2) x U(1) assignments (e.g., left-handed singlets and/or right-handed doublets) are presented. A general formalism for describing such mixings is given. It is shown that a variety of constraints, including the relation between the W and Z masses and the Fermi constant, charged-current universality, limits on induced right-handed charged currents, and flavor-diagonal neutral currents suffice to limit all directions in parameter space that are not excluded by the absence of flavor-changing neutral currents. Limits on s/sup 2/, the square of the mixing between ordinary and exotic fermions, are quite stringent for the ..nu../sub ..mu..//sub L/, ..mu../sub L//sup -/, u/sub L/, and d/sub L/ (s/sup 2/less than or equal to0.002--0.005) if only one particle is allowed to mix at a time, but are weaker by an order of magnitude if fine-tuned cancellations between different mixings are allowed. Similar statements apply to quark mixings with heavy sequential doublets. Limits on s/sup 2/ for the other light fermions (..nu../sub e//sub L/, e/sub L//sup -/,e/sub R//sup -/,..mu../sub R//sup -/, u/sub R/,d/sub R/) are in the range 0.02--0.06, while those for the s, c, b,more » ..nu../sub tau/, and tau/sup -/ are considerably weaker. Slightly stronger limits are found in specific models (e.g., E/sub 6/). Implications for the masses of the heavy exotic fermions are discussed.« less
TL;DR: An interesting consequence of the low-frequency behavior of P(\ensuremath{\omega}) is that gravitational radiation contributes a constant fraction of the energy density of the Universe, even after the time of matter domination.
Abstract: The gravitational-wave-noise power spectrum P(\ensuremath{\omega}) is found for a simple cosmological model with an ``inflationary'' early stage of expansion. The source of the gravitational-wave noise is quantum fluctuations during the inflationary de Sitter stage, which are amplified by the subsequent expansion of the Universe. The resulting spectrum P(\ensuremath{\omega}) is compared to a naive estimate: a thermal spectrum at the (appropriately red-shifted) Gibbons-Hawking temperature. The two spectra are remarkably different. Unlike the thermal spectrum, P(\ensuremath{\omega}) increases at low frequencies. We show that the source of the corresponding long-wavelength perturbations is a global gravitational instability during the inflationary de Sitter stage of expansion. An interesting consequence of the low-frequency behavior of P(\ensuremath{\omega}) is that gravitational radiation contributes a constant fraction of the energy density of the Universe, even after the time of matter domination.
TL;DR: The existence of retarded correlations over arbitrarily large time spans in the dynamics of a gravitating system, namely, the influence of the past evolution of a material system on its present gravitational internal dynamics, is investigated and this term is found to modify the Burke-Thorne gravitational radiation quadrupole damping force.
Abstract: The existence of retarded correlations over arbitrarily large time spans in the dynamics of a gravitating system, namely, the influence of the past evolution of a material system on its present gravitational internal dynamics, is investigated. This ''hereditary'' influence can be thought of as transported by the gravitational waves emitted by the system in the past and subsequently scattered off the curvature of spacetime back onto the system (''backscattered waves'' or ''tails''). The method used here applies to weakly self-gravitating slowly varying sources. It is a combination of a multipolar post-Minkowskian expansion for the metric in the weak-field region outside the system, and of a post-Newtonian-type expansion for the metric in the near zone. The two expansions are then ''matched'' in the weak-field-near-zone overlap region. The lowest-order nonlinear piece in the near-zone metric which depends on the full past history of the source (''hereditary'' term) is determined. This term arises at the fourth post-Newtonian (PN) level. The arising of this ''hereditary'' term signifies the breakdown of one of the fundamental tenets of the post-Newtonian approximation schemes. Indeed, at the 4PN level it becomes impossible to express the near-zone metric as a functional of the instantaneous state of the material source.more » This means also that there is a fundamental breakdown of the concept of near zone versus the concept of wave zone. The direct dynamical influence of the above-determined hereditary, or tail, term on the evolution of the material system is then studied. This term is found to modify the Burke-Thorne gravitational radiation quadrupole damping force.« less
TL;DR: Neutralino annihilation and elastic scattering cross sections are derived which differ in important ways from previous work and are applied to relic abundance calculations and to direct detection of neutralino dark matter from the galactic halo.
Abstract: Neutralino annihilation and elastic scattering cross sections are derived which differ in important ways from previous work. These are applied to relic abundance calculations and to direct detection of neutralino dark matter from the galactic halo. Assuming the neutralino to be the lightest supersymmetric particle and that it is less massive than the Z sup 0, we find relic densities of neutralinos greater than 4 percent of critical density for almost all values of the supersymmetric parameters. We constrain the parameter space by using results from PETRA (chargino mass less than 23 GeV) and ASP, and then assuming a critical density of neutralinos, display event rates in a cryogenic detector for a variety of models. A new term implies spin independent elastic scattering even for those majorana particles and inclusion of propagator momenta increases detection rates by 10 to 300 percent for pure photinos. Z sup 0-squark interference leads to very low detection rates for some values of the parameters. The new term in the elastic cross section dominates for heavy, mostly spinless materials and mitigates the negative interference cancellations in light materials; except for the pure photino or pure higgsinos cases where it does not contribute. In general, the rates can be substantially different from the pure photino and pure higgsino special cases usually considered.
TL;DR: Using the equivalence between the curvature-squared gravity theory and the Einstein theory with a scalar field, it is shown that the potential in the latter system has a very flat plateau.
Abstract: Using the equivalence between the curvature-squared gravity theory and the Einstein theory with a scalar field, we show that the potential in the latter system has a very flat plateau. It turns out that inflation is quite natural but transient in the ${R}^{2}$ cosmology. All anisotropic Bianchi types of space-time except IX approach the de Sitter solution as an attractor, followed by the Friedmann universe after sufficient inflation. We find a similar behavior in higher- (4lDl10) dimensional theories, in which inflation is not exponential-type but power-law-type. The dilaton coupling to the ${R}^{2}$ term is also investigated. The coupling destroys the inflationary solution.
TL;DR: A new semiclassical theory is constructed in which the quantum and classical fluctuations do affect each other; the Wigner probability function turns out to be a special case.
Abstract: We investigate theories in which classical and quantum-mechanical degrees of freedom interact dynamically. In commonly used semiclassical theories, such as those used to study inflationary-universe models, quantum fluctuations do not affect the dynamics of the classical variables. We construct a new semiclassical theory in which the quantum and classical fluctuations do affect each other; the Wigner probability function turns out to be a special case. Relevance to calculations of perturbations from inflation are discussed.
TL;DR: In this article, the issue of sphaleron-induced baryon decay and various paradoxes related to the instanton method of computation are addressed, and it is shown that there is no contradiction between instanton estimates and sphaleon estimates.
Abstract: The issue of sphaleron-induced baryon decay and various paradoxes related to the instanton method of computation are addressed. By various examples we argue that there is no contradiction between the instanton estimates and sphaleron estimates, and argue that for electroweak theory these estimates correspond to different approximations for distinct phenomena. We also investigate numerically the nature of the classical decay of a sphaleron in the (1+1)-dimensional Abelian Higgs model.
TL;DR: Constraints on the abundance of quasistable particles with hadronic decay modes are placed using the upper bounds on primordially produced He and D abundances and the sum of D and He abundance.
Abstract: We place constraints on the abundance of quasistable particles with hadronic decay modes using the upper bounds on primordially produced $^{4}\mathrm{He}$ and the sum of D and $^{3}\mathrm{He}$ abundances. The results are presented as a function of particle lifetime (ranging between ${10}^{\mathrm{\ensuremath{-}}1}$ and ${10}^{4}$ sec), particle mass, and hadronic branching ratio. We apply our results to the cases of gravitinos, photinos in R\ifmmode \tilde{}\else \~{}\fi{}-parity-violating theories, and mirror quarks. We also discuss another mechanism for hadron injection: cold-dark-matter annihilation.
TL;DR: Following the method developed by Chandrasekhar, a variational base for determining the eigenfrequencies of the perturbations is found and allows one to find numerically an upper bound for the central density where dynamical instability occurs.
Abstract: Boson stars are gravitationally bound, spherically symmetric equilibrium configurations of cold, free, or interacting complex scalar fields \ensuremath{\varphi}. As these equilibrium configurations naturally present local anisotropy, it is sensible to expect departures from the well-known stability criteria for fluid stars. With this in mind, I investigate the dynamical instability of boson stars against charge-conserving, small radial perturbations. Following the method developed by Chandrasekhar, a variational base for determining the eigenfrequencies of the perturbations is found. This approach allows one to find numerically an upper bound for the central density where dynamical instability occurs. As applications of the formalism, I study the stability of equilibrium configurations obtained both for the free and for the self-interacting [with V(\ensuremath{\varphi})=(\ensuremath{\lambda}/4)\ensuremath{\Vert}\ensuremath{\varphi}${\ensuremath{\Vert}}^{4}$] massive scalar field \ensuremath{\varphi}. Instabilities are found to occur not for the critical central density as in fluid stars but for central densities considerably higher. The departure from the results for fluid stars is sensitive to the coupling \ensuremath{\lambda}; the higher the value of \ensuremath{\lambda}, the more the stability properties of boson stars approach those of a fluid star. These results are linked to the fractional anisotropy at the radius of the configuration.
TL;DR: The laboratory limits on the neutrino oscillation process can be interpreted as tests of the equivalence principle in the quantum-relativistic regime, and put severe constraints on a maximal violation of this Principle in the case of massless neutrinos coupled to the Earth's gravitational field.
Abstract: If the equivalence principle is violated, and gravity is not universally coupled to all leptonic flavors, a gravitational field may contribute to neutrino oscillations. The laboratory limits on the oscillation process can thus be interpreted as tests of the equivalence principle in the quantum-relativistic regime, and put severe constraints on a maximal violation of this principle in the case of massless neutrinos coupled to the Earth's gravitational field.
TL;DR: It is meaningless in minisuperspace of quantum gravity to extend classical paths through this region to a recollapsing phase and higher degrees of freedom are introduced which can produce classical paths by continuous measurement.
Abstract: Wave packets in minisuperspace of quantum gravity are explicitly constructed for a Friedmann model containing either a massless or a massive homogeneous scalar field. Unparametrized tubelike standing waves corresponding to classically returning paths in configuration space can be constructed if a ``final condition'' with respect to the scale factor a is assumed to hold. Sensible wave packets are only obtained for certain discrete values of the mass and only in regions not too close to the classical turning point. Therefore it is meaningless in minisuperspace of quantum gravity to extend classical paths through this region to a recollapsing phase. This suggests that we introduce higher degrees of freedom which can produce classical paths by continuous measurement.
TL;DR: A recent suggestion that the observations of monochromatic photons from annihilation of photinos into quarkonium plus a photon could be a signature of dark-matter photinos is extended to include all S- and P-wave bound quarksonium states for a general interaction Lagrangian and an estimate of the cross sections is given.
Abstract: A recent suggestion that the observations of monochromatic photons from annihilation of photinos into quarkonium plus a photon could be a signature of dark-matter photinos is extended to include all S- and P-wave bound quarkonium states for a general interaction Lagrangian and an estimate of the cross sections is given. We also propose the process \ensuremath{\lambda}\ensuremath{\lambda}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma} as a potentially rich source of monochromatic photons and estimate its strength.