We consider bouncing cosmologies in which an ekpyrotic contraction phase with $w\gg 1$ is followed by a bouncing phase with $w<-1$ that violates the null energy condition. The bouncing phase, induced by ghost condensation, is designed to produce a classically nonsingular bounce at a finite value of the scale factor. We show that the initial curvature and anisotropy, though diluted during the ekpyrotic phase, grow back exponentially during the bouncing phase. Moreover, curvature perturbations and anisotropy are generated by quantum fluctuations during the ekpyrotic phase. In the bouncing phase, however, an adiabatic curvature perturbation grows to dominate and contributes a blue spectrum that spoils the scale invariance. Meanwhile, a scalar shear perturbation grows nonlinear and creates an overwhelming anisotropy that disrupts the nonsingular bounce altogether.

We study the muon anomalous magnetic moment (muon $g-2$) and the Higgs boson mass in a simple extension of the minimal supersymmetric (SUSY) standard model with extra vectorlike matters, in the frameworks of gauge-mediated SUSY breaking (GMSB) models and gravity mediation (mSUGRA) models. It is shown that the deviation of the muon $g-2$ and a relatively heavy Higgs boson can be simultaneously explained in large $\tan \beta$ region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where the muon $g-2$ is consistent with the experimental value at the $2\sigma$ ($1\sigma$) level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when the muon $g-2$ is consistent with the experimental value at the $2\sigma$ level. In both cases, the Higgs mass can be above 140 GeV if the $g-2$ constraint is not imposed.

In quantum chromodynamics (QCD) the eigenmodes of the Dirac operator with small absolute eigenvalues have a close relationship to the dynamical breaking of the chiral symmetry. In a simulation with two dynamical quarks, we study the behavior of meson propagators when removing increasingly more of those modes in the valence sector, thus partially removing effects of chiral symmetry breaking. We find that some of the symmetry aspects are restored (e.g., the masses of $\rho$ and $a_1$ approach each other) while confining properties persist.

We discuss the nonrelativistic limit of quantum field theory in an inertial frame, in the Rindler frame and in the presence of a weak gravitational field, and attempt to highlight and clarify several subtleties. In particular, we study the following issues: (a) While the action for a relativistic free particle is invariant under the Lorentz transformation, the corresponding action for a nonrelativistic free particle is not invariant under the Galilean transformation, but picks up extra contributions at the end points. This leads to an extra phase in the nonrelativistic wave function under a Galilean transformation, which can be related to the rest energy of the particle even in the nonrelativistic limit. We show that this is closely related to the peculiar fact that the relativistic action for a free particle remains invariant even if we restrict ourselves to $\mathcal{O}(1/c^2)$ in implementing the Lorentz transformation. (b) We provide a brief critique of the principle of equivalence in the quantum mechanical context. In particular, we show how solutions to the generally covariant Klein-Gordon equation in a noninertial frame, which has a time-dependent acceleration, reduce to the nonrelativistic wave function in the presence of an appropriate (time-dependent) gravitational field in the $c\to \infty$ limit, and relate this fact to the validity of the principle of equivalence in a quantum mechanical context. We also show that the extra phase acquired by the nonrelativistic wave function in an accelerated frame, actually arises from the gravitational time dilation and survives in the nonrelativistic limit. (c) While the solution of the Schrödinger equation can be given an interpretation as being the probability amplitude for a single particle, such an interpretation fails in quantum field theory. We show how, in spite of this, one can explicitly evaluate the path integral using the (nonquadratic) action for a relativistic particle (involving a square root) and obtain the Feynman propagator. Further, we describe how this propagator reduces to the standard path integral kernel in the nonrelativistic limit. (d) We show that the limiting procedures for the propagators mentioned above work correctly even in the presence of a weak gravitational field, or in the Rindler frame, and discuss the implications for the principle of equivalence.

We investigate the large baryon number sector of the Einstein-Skyrme model as a possible model for baryon stars and construct low energy configurations that resemble neutron stars. Previous studies have shown that gravitating Skyrmions produced by using rational maps can achieve spherically symmetric, multibaryon-bound states at large baryon numbers, but these configurations were hollow shells. In this paper, we improve on the previous work by constructing configurations corresponding to solid spheres with a radius-dependent baryon density.

We systematically study black holes in the Horava-Lifshitz theory by following the kinematic approach, in which a horizon is defined as the surface at which massless test particles are infinitely redshifted. Because of the nonrelativistic dispersion relations, the speed of light is unlimited, and test particles do not follow geodesics. As a result, there are significant differences in causal structures and black holes between general relativity (GR) and the Horava-Lifshitz theory. In particular, the horizon radii generically depend on the energies of test particles. Applying them to the spherical static vacuum solutions found recently in the nonrelativistic general covariant theory of gravity, we find that, for test particles with sufficiently high energy, the radius of the horizon can be made as small as desired, although the singularities can be seen, in principle, only by observers with infinitely high energy. In these studies, we pay particular attention to the global structure of the solutions, and find that, because of the foliation-preserving-diffeomorphism symmetry, $\mathrm{Diff}(M,\mathcal{F})$, they are quite different from the corresponding ones given in GR, even though the solutions are the same. In particular, the $\mathrm{Diff}(M,\mathcal{F})$ does not allow Penrose diagrams. Among the vacuum solutions, some give rise to the structure of the Einstein-Rosen bridge, in which two asymptotically flat regions are connected by a throat with a finite nonzero radius. We also study slowly rotating solutions in such a setup, and obtain all the solutions characterized by an arbitrary function $A_0(r)$. The case $A_0=0$ reduces to the slowly rotating Kerr solution obtained in GR.

We calculate puncture initial data, corresponding to single and binary black holes with linear momenta, which solve the constraint equations of $D$-dimensional vacuum gravity. The data are generated by a modification of the pseudospectral code presented in [M. Ansorg, B. Bruegmann, and W. Tichy, Phys. Rev. D 70, 064011 (2004).] and made available as the TwoPunctures thorn inside the Cactus computational toolkit. As examples, we exhibit convergence plots, the violation of the Hamiltonian constraint as well as the initial data for $D=4,5,6,7$. These initial data are the starting point to perform high-energy collisions of black holes in $D$ dimensions.

Numerical relativity has seen incredible progress in the last years, and is being applied with success to a variety of physical phenomena, from gravitational wave research and relativistic astrophysics to cosmology and high-energy physics. Here we probe the limits of current numerical setups, by studying collisions of unequal mass, nonrotating black holes of mass ratios up to $1:100$ and making contact with a classical calculation in general relativity: the infall of a pointlike particle into a massive black hole. Our results agree well with the predictions coming from linearized calculations of the infall of pointlike particles into nonrotating black holes. In particular, in the limit that one hole is much smaller than the other, and the infall starts from an infinite initial separation, we recover the point-particle limit. Thus, numerical relativity is able to bridge the gap between fully nonlinear dynamics and linearized approximations, which may have important applications. Finally, we also comment on the “spurious” radiation content in the initial data and the linearized predictions.

Recent work by the authors led to the development of a mathematical theory dealing with “second-order hyperbolic Fuchsian systems,” as we call them. In the present paper, we adopt a physical standpoint and discuss the implications of this theory which provides one with a new tool to tackle the Einstein equations of general relativity (under certain symmetry assumptions). Specifically, we formulate the “Fuchsian singular initial value problem” and apply our general analysis to the broad class of vacuum Gowdy spacetimes with spatial toroidal topology. Our main focus is on providing a detailed description of the asymptotic geometry near the initial singularity of these inhomogeneous cosmological spacetimes and, especially, analyzing the asymptotic behavior of timelike geodesics—which represent the trajectories of freely falling observers—and null geodesics. In particular, we numerically construct Gowdy spacetimes which contain a black hole–like region together with a flat Minkowski-like region. By using the Fuchsian technique, we investigate the effect of the gravitational interaction between these two regions and we study the unexpected behavior of geodesic trajectories within the intermediate part of the spacetime limited by these two regions.

We investigate the recently proposed class of chaotic inflation models in supergravity with an arbitrary inflaton potential $V(\varphi )$. These models are extended to include matter fields in the visible sector and we employ a mechanism of supersymmetry breaking based on a particular phenomenological version of the KKLT mechanism (the KL model). We describe specific features of reheating in this class of models and show how one can solve the cosmological moduli and gravitino problems in this context.

We present the results of a systematic leading-order calculation of hyperon Compton scattering and extract the forward spin polarizability—${\gamma }_0$—of hyperons within the framework of SU(3) heavy baryon chiral perturbation theory (HBChPT). The results obtained for ${\gamma }_0$ in the case of nucleons agree with that of the known results of SU(2) HBChPT when kaon loops are not considered.

A recent $D$-brane model designed to accommodate a phenomenologically acceptable fourth generation of chiral fermions was noted to produce an unexpected additional unbroken nonanomalous U(1) gauge group at the string scale. We show that the corresponding charges acting on minimal supersymmetric standard model fields count baryon and lepton numbers. If broken spontaneously at lower scales, these $\mathrm{U}(1{)}_B$ and $\mathrm{U}(1{)}_L$ symmetries provide potential avenues for preserving baryogenesis while nonetheless explaining the suppression of proton decay (without the need for $R$ parity), as well as the smallness of right-handed neutrino Majorana masses compared to the string scale.

We consider no-scale supergravity inspired scenarios, where the gravitino mass and related soft supersymmetry-breaking parameters are determined dynamically by radiative corrections to an essentially flat tree-level potential in the supersymmetry-breaking hidden sector. We examine the theoretical and phenomenological viability of such a mechanism, when including up-to-date calculations of the low-energy sparticle spectrum and taking into account the latest LHC results and other experimental constraints. We (re)emphasize the role of the scale-dependent vacuum energy contribution to the effective potential, in obtaining realistic no-scale electroweak minima, examining carefully the impact of boundary conditions and of variants of the minimization procedure. We also discuss and implement the $B_0$ (soft breaking Higgs mixing parameter) input boundary condition at high scale, therefore fixing $\tan \beta (B_0)$ at low scales. For general high-scale boundary conditions with $B_0,m_0,\cdots \ne 0$, our analysis provides theoretical correlations among the supersymmetric, soft, and vacuum energy parameters and related phenomenological consequences at the LHC. For instance, a zero vacuum energy at the grand unified theory scale would lead to a decoupled supersymmetric spectrum, together with a light standard-model-like Higgs boson at the electroweak scale. Given the experimental exclusion limits, a substantial class of the boundary conditions, and, in particular, the strict no-scale with $m_0=A_0=B_0=0$, are only compatible with a stau being the lightest Minimal Supersymmetric Standard Model particle. Then, an enlarged allowed parameter space emerges when assuming a gravitino lightest supersymmetric particle to account for the observed dark matter relic density.

We consider two classes of $t$-$b$-$\tau$ quasi-Yukawa unification scenarios which can arise from realistic supersymmetric SO(10) and $SU(4{)}_C\times SU(2{)}_L\times SU(2{)}_R$ models. We show that these scenarios can be successfully implemented in the nonuniversal Higgs model with $m_{H_u}=m_{H_d}\ne m_0$ and the constrained minimal sumersymmetric model frameworks, and they yield a variety of sparticle spectra with Wilkinson Microwave Anisotropy Probe compatible neutralino dark matter. In the nonuniversal Higgs model with $m_{H_u}=m_{H_d}\ne m_0$, we find bino-Higgsino dark matter as well as the stau coannihilation and $A$-funnel solutions. The constrained minimal sumersymmetric model case yields the stau coannihilation and $A$-funnel solutions. The gluino and squark masses are found to lie in the TeV range.

This paper presents a post-Newtonian (PN) template family of gravitational waveforms from inspiralling compact binaries with nonprecessing spins, where the spin effects are described by a single “reduced-spin” parameter. This template family, which reparametrizes all the spin-dependent PN terms in terms of the leading-order (1.5PN) spin-orbit coupling term in an approximate way, has very high overlaps (fitting factor $>0.99$) with nonprecessing binaries with arbitrary mass ratios and spins. We also show that this template family is “effectual” for the detection of a significant fraction of generic spinning binaries in the comparable-mass regime ($m_2/m_1\lesssim 10$), providing an attractive and feasible way of searching for gravitational waves from spinning low-mass binaries. We also show that the secular (nonoscillatory) spin-dependent effects in the phase evolution (which are taken into account by the nonprecessing templates) are more important than the oscillatory effects of precession in the comparable-mass ($m_1\simeq m_2$) regime. Hence the effectualness of nonspinning templates is particularly poor in this case, as compared to non-precessing-spin templates. For the case of binary neutron stars observable by Advanced LIGO, even moderate spins (${\widehat{\mathbf{L}}}_N·\mathbf{S}/m^2\simeq 0.015–0.1$) will cause considerable mismatches ($\sim 3\%–25\%$) with nonspinning templates. This is contrary to the expectation that neutron-star spins may not be relevant for gravitational wave detection.

We reexamine some aspects of scattering by a Schwarzschild black hole in the framework of complex angular momentum techniques. More precisely, we consider, for massive scalar perturbations, the high-energy behavior of the resonance spectrum and of the absorption cross section by emphasizing analytically the role of the mass. This is achieved (i) by deriving asymptotic expansions for the Regge poles of the $S$-matrix and then for the associated weakly damped quasinormal frequencies and (ii) by taking into account the analytic structure of the greybody factors which allows us to extract by resummation the physical information encoded in the absorption cross section.

The $5–20M_{\odot }$ dark objects in x-ray binary systems and the ${10}^5–{10}^9{M}_{\odot }$ dark objects in galactic nuclei are currently thought to be the Kerr black holes predicted by general relativity. However, direct observational evidence for this identification is still elusive, and the only viable approach to confirm the Kerr black hole hypothesis is to explore and rule out any other possibility. Here we investigate the final stages of the accretion process onto generic compact objects. While for Kerr black holes and for more oblate bodies the accreting gas reaches the innermost stable circular orbit (ISCO) and plunges into the compact object, we find that for more prolate bodies several scenarios are possible, depending on the spacetime geometry. In particular, we find examples in which the gas reaches the ISCO but then gets trapped between the ISCO and the compact object. In this situation, accretion onto the compact object is possible only if the gas loses additional angular momentum, forming toruslike structures inside the ISCO.

We model the chameleon effect on cosmological statistics for the modified gravity $f(R)$ model of cosmic acceleration. The chameleon effect, required to make the model compatible with local tests of gravity, reduces force enhancement as a function of the depth of the gravitational potential wells of collapsed structure and so is readily incorporated into a halo model by including parameters for the chameleon mass threshold and rapidity of transition. We show that the abundance of halos around the chameleon mass threshold is enhanced by both the merging from below and the lack of merging to larger masses. This property also controls the power spectrum in the nonlinear regime and we provide a description of the transition to the linear regime that is valid for a wide range of $f(R)$ models.

Recent numerical work on the gravitational collapse of a five-dimemsional (5D) [$4+1$] Yang-Mills instanton has provided numerical evidence that the free energy $F=E-TS=E/3$ of a 5D Schwarzschild black hole of mass $E$ can be obtained classically via the Lagrangian. Although there is no Hawking radiation, these numerical results suggest that the quantity $TS$ has a classical meaning. We investigate this association for the physically relevant case of $3+1$ dimensional collapse. We track numerically the negative of the total Lagrangian $-L$ during the gravitational collapse of a massless scalar field to a Schwarzschild black hole in isotropic coordinates. We show that $-L$ approaches the free energy $F=E-TS=E/2$ of a four-dimensional Schwarzschild black hole to within 5%. We also show that the matter contribution to the free energy tends towards zero so that the entropy at late stages of the collapse is gravitational in origin. The entropy $S$ makes a negative contribution to the free energy and this feature is observed in our numerical simulation. There is a pronounced dip (negative contribution) in a thin slice just inside the event horizon precisely where the metric field is nonstationary. This is in accord with recent work suggesting black hole entropy is connected with the nonstationary phase space hidden behind the event horizon. We also obtain thermodynamic results for the 5D collapse of a massless scalar field which confirms that previous 5D results are universal and independent of the type of matter undergoing the collapse.