The event horizon of black holes is capable of reflection: there is a finite probability for any particle that approaches the horizon to bounce back. The albedo of the horizon depends on the black hole temperature and the energy of the incoming particle. The reflection shares its physical origins with the Hawking process of radiation; both of them arise as consequences of the mixing of the incoming and outgoing waves that takes place due to quantum processes on the event horizon.

We prepare a general framework for analyzing the dynamics of a cylindrical shell in a spacetime with cylindrical symmetry. Based on this framework, we investigate a particular model of a cylindrical shell collapse with rotational pressure, accompanying the radiation of gravitational waves and massless particles. The model has been introduced previously but has been awaiting a proper analysis. Here the analysis is put forward: It is proved that, as far as the weak energy condition is satisfied outside the shell, the collapsing shell bounces back at some point irrespective of the initial conditions and escapes from the singularity formation. The behavior after the bounce depends on the sign of $p_z,$ the shell pressure in the z direction. When $p_z>~0,$ the shell continues to expand without recontraction. On the other hand, when $p_z<0\mathrm{}$ (i.e., it has a tension), the behavior after the bounce can be more complicated depending on the details of the model. However, even in this case, the shell never reaches the zero-radius configuration.

An approximate analytical and nonlinear solution of the Einstein field equations is derived for a system of multiple nonrotating black holes. The associated space-time has the same asymptotic structure as the Brill-Lindquist initial data solution for multiple black holes. The system admits an Arnowitt-Deser-Misner (ADM) Hamiltonian that can particularly evolve the Brill-Lindquist solution over finite time intervals. The gravitational field of this model may properly be referred to as a skeleton approximate solution of the Einstein field equations. The approximation is based on a conformally flat truncation, which excludes gravitational radiation, as well as a removal of some additional gravitational field energy. After these two simplifications, only source terms proportional to Dirac delta distributions remain in the constraint equations. The skeleton Hamiltonian is exact in the test-body limit, it leads to the Einsteinian dynamics up to the first post-Newtonian approximation, and in the time-symmetric limit it gives the energy of the Brill-Lindquist solution exactly. The skeleton model for binary systems may be regarded as a kind of analytical counterpart to the numerical treatment of orbiting Misner-Lindquist binary black holes proposed by Gourgoulhon, Grandclément, and Bonazzola, even if they actually treat the corotating case. Along circular orbits, the two-black-hole skeleton solution is quasistationary and it satisfies the important property of the equality of Komar and ADM masses. Explicit calculations for the determination of the last stable circular orbit of the binary system are performed up to the tenth post-Newtonian order within the skeleton model.

We study cosmological perturbations in generalized Einstein scenarios and show the equivalence of inflationary observables both in the Jordan frame and the Einstein frame. In particular the consistency relation relating the tensor-to-scalar ratio with the spectral index of tensor perturbations coincides with the one in Einstein gravity, which leads to the same likelihood results in terms of inflationary observables. We apply this formalism to nonminimally coupled chaotic inflationary scenarios with the potential $V=c{\phi }^p$ and place constraints on the strength of the nonminimal couplings using a compilation of the latest observational data. In the case of the quadratic potential $\mathrm{}(p=2\mathrm{}),$ the nonminimal coupling is constrained to be $\xi >-7.0\times {10}^{-3}$ for negative $\xi$ from the $1\sigma$ observational contour bound. Although the quartic potential $\mathrm{}(p=4\mathrm{})\mathrm{}$ is under strong observational pressure for $\xi =0,$ this property is relaxed by taking into account negative nonminimal couplings. We find that inflationary observables are within the $1\sigma$ contour bound as long as $\xi <-1.7\times {10}^{-3}.$ We also show that the $p>~6$ cases are disfavored even in the presence of nonminimal couplings.

Using the $O\left(N\right)\mathrm{}$ model as an example, we investigate the self-interaction effects of inflaton on the dynamics of the primordial perturbations. When taking interactions into account, it is essential to employ a self-consistent off-equilibrium formalism to study the evolution of the inflationary background field and its fluctuations with back-reaction effects. Within the Hartree factorization scheme, we show that the $O\left(N\right)\mathrm{}$ model has at least two observable remains left behind by the off-equilibrium processes: the running spectral index of primordial density perturbations and the correlations between perturbation modes in phase space. We find that the running of the spectral index is fully determined by the rate of the energy transfer from the inflationary background field to its fluctuations via particle creation processes as well as the dynamics of the background field itself. Furthermore, the amplitude of the field fluctuations turns out to be scale dependent due to the off-equilibrium evolution. As a consequence, the scale dependence of fluctuations yields a correlation between the phase-space modes of energy density perturbations, while the one-point function of the fluctuations in each Hartree mode is still Gaussian. More importantly, the mode-mode correlation of the primordial perturbations depends upon the dynamics of the self-interaction as well as the initial conditions of the inflation. Hence, we propose that the running spectral index and the correlation between phase-space modes would be two observable fossils to probe the epoch of inflation, even beyond.

Quintessence is a possible candidate for dark energy. In this paper we study the phenomenologies of the fermionic partner of quintessence, the quintessino. Our results show that, for suitable choices of the model parameters, the quintessino is a good candidate for cold or warm dark matter. In our scenario, the dark energy and dark matter of the Universe are connected in one chiral superfield.

Neutron stars that are cold enough should have two or more superfluids or supercondutors in their inner crusts and cores. The implication of superfluidity or superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An important consequence of the quasiparticle nature of each condensate is the so-called entrainment effect; i.e., the momentum of a condensate is a linear combination of its own current and those of the other condensates. We present here the first fully relativistic modeling of slowly rotating superfluid neutron stars with entrainment that is accurate to the second-order in the rotation rates. The stars consist of superfluid neutrons, superconducting protons, and a highly degenerate, relativistic gas of electrons. We use a relativistic $\sigma -\omega$ mean field model for the equation of state of the matter and the entrainment. We determine the effect of a relative rotation between the neutrons and protons on a star’s total mass, shape, and Kepler, mass-shedding limit.

We describe a fast and accurate method to perform the convolution of a sky map with a general asymmetric main beam along any given scanning strategy. The method is based on the decomposition of the beam as a sum of circular functions, here Gaussians. It can be easily implemented and is much faster than pixel-by-pixel convolution. In addition, ASYMFAST can be used to estimate the effective circularized beam transfer functions of cosmic microwave background instruments with nonsymmetric main beam. This is shown using realistic simulations and by comparison to analytical approximations which are available for Gaussian elliptical beams. Finally, the application of this technique to ARCHEOPS data is also described. Although developed within the framework of cosmic microwave background observations, our method can be applied to other areas of astrophysics.

We reexamine the problem of strong coupling in a regularized version of Dvali-Gabadadze-Porrati (DGP) (or “brane-induced”) gravity. We find that the regularization of Kolanovic, Porrati, and Rombouts [Phys. Rev. D 68, 064018 (2003)] differs from DGP in that it does not exhibit strong coupling or ghosts up to cubic order in the interactions. We suggest that the nonlocal nature of the theory, when written in terms of the 4D metric, is a plausible reason for this phenomenon. Finally, we briefly discuss the possible behavior of the model at higher order in perturbation theory.

Good tracking requires that the quintessence energy fraction slowly increase while the roll $\lambda \equiv -d\ln V/\varkappa d\phi$ slowly decreases, but is not yet truly slow-rolling. The supernova bound on the present quintessence equation of state requires either (1) a cosmological constant or other fine-tuned “crawling quintessence” or (2) “roll-over quintessence” that tracked until recently, but now became slow rolling, because of a sharp increase in potential curvature. Thus, fine-tuning is required by constant equation of state and inverse power potentials, but can be avoided by the supergravity and Skordis-Albrecht potentials and other good trackers, provided quintessence energy domination and slow roll both began only recently. This makes the time in which we live special in two respects.

We discuss the consistency of fermion mass generation by boundary conditions and brane localized terms in higher dimensional models of gauge symmetry breaking without a Higgs boson. The sum rules imposed by tree-level unitarity and Ward identities are applied to check the consistency of mass generation by orbifold projections and more general boundary conditions consistent with the variational principle. We find that the sum rules are satisfied for boundary conditions corresponding to brane localized mass and kinetic terms consistent with the reduced gauge symmetry on the brane.

We report a calculation of the shear viscosity in a relativistic multicomponent meson gas as a function of temperature and chemical potentials. We approximately solve the Uehling-Uhlenbeck transport equation of kinetic theory, appropriate for a boson gas, with relativistic kinematics. Since at low temperatures the gas can be taken as mostly composed of pions, with a fraction of kaons and etas, we explore the region where binary elastic collisions with at least one pion are the dominant scattering processes. Our input meson scattering phase shifts are fits to the experimental data obtained from chiral perturbation theory and the inverse amplitude method. Our results take the correct nonrelativistic limit (viscosity proportional to the square root of the temperature), show a viscosity of the order of the cube of the pion mass up to temperatures somewhat below that mass, and then a large increase due to kaons and etas. Our approximation may break down at even higher temperatures, where the viscosity follows a temperature power law with an exponent near 3.

A minimal supersymmetric SO(10) model with one 10 and one 126 Higgs superfield has recently been shown to predict all neutrino mixings as well as the solar mass difference squared in agreement with observations. Two assumptions critical to the predictivity and success of the model are that (i) the superpotential includes only renormalizable terms, thereby limiting the number of free parameters, and (ii) the triplet term in the type II seesaw formula for neutrino mass dominates, leading to the sum rule $M_{\nu }{=c(M}_d-M_e),$ which is responsible for large mixings. However, the CKM CP phase is constrained to be in the second or third quadrant, requiring a significant non-CKM component to CP violation to explain observations. We reexamine this issue using a type I seesaw formula for neutrino masses and obtain the following results. (i) We show that the above sum rule responsible for large mixing angles can also emerge in type I seesaw models; the detailed predictions are, however, not compatible with present data for any choice of CP phases. (ii) We then show that addition of a nonrenormalizable term restores compatibility with neutrino data and CKM CP violation both in type I and type II cases. We further find (iii) the MSSM parameter $\tan \beta >~30$ in the type I model and (iv) lepton flavor violation and lepton electric dipole moments that are accessible to proposed experiments in both type I and type II models. We also discuss the unification of the gauge couplings in the type I model, which requires an intermediate scale.

The magnetic dipole, the electric quadrupole, and the Coulomb quadrupole amplitudes for the transition $\gamma \overrightarrow{N}\Delta$ are evaluated both in quenched lattice QCD at $\beta =6.0\mathrm{}$ and using two dynamical Wilson fermions simulated at $\beta =\mathrm{5.6.}\mathrm{}$ The dipole transition form factor is accurately determined at several values of momentum transfer. On the lattices studied in this work, the electric quadrupole amplitude is found to be nonzero, yielding a negative value for the ratio $R_{\mathrm{EM}}$ of electric quadrupole to magnetic dipole amplitudes at three values of momentum transfer.

We study the standard model prediction for the mass difference between the two neutral D meson mass eigenstates, $\Delta m.\mathrm{}$ We derive a dispersion relation based on heavy quark effective theory that relates $\Delta m$ to an integral of the width difference of heavy mesons, $\Delta \Gamma ,$ over varying values of the heavy meson mass. Modeling the $m_D$ dependence of certain D decay partial widths, we investigate the effects of SU(3) breaking from phase space on the mass difference. We find that $\Delta m$ may be comparable in magnitude to $\Delta \Gamma$ in the standard model.

In a model of a TeV right-handed (RH) neutrino by Krauss, Nasri, and Trodden, the sub-eV scale neutrino masses are generated via a three-loop diagram with the vanishing seesaw mass forbidden by a discrete symmetry, and the TeV mass RH neutrino is simultaneously a novel candidate for cold dark matter. However, we show that with a single RH neutrino it is not possible to generate two mass-square differences as required by the oscillation data. We extend the model by introducing one more TeV RH neutrino and show that it is possible to satisfy the oscillation pattern within the modified model. After studying in detail the constraints coming from the dark matter, lepton flavor violation, the muon anomalous magnetic moment, and the neutrinoless double beta decay, we explore the parameter space and derive predictions of the model. Finally, we study the production and decay signatures of the TeV RH neutrinos at TeV $e^{+}{e}^{-}/{\mu }^{+}{\mu }^{-}$ colliders.

Despite the impressive precision of the $Z-\mathrm{pole}$ measurements made at the $e^{+}{e}^{-}$ colliders at CERN (LEP) and SLAC (SLC), the allowed region for the principal standard model parameters responsible for radiative corrections $[m_{\mathrm{H}},$ $m_{\mathrm{t}},$ and $\alpha {(m}_{\mathrm{Z}}^2\left)\right]$ is still large enough to encompass significant nonlinearities. The nature of the experimental constraints therefore depends in an interesting way on the “accidental” relationships among the various measurements. In particular, the fact that the $Z-\mathrm{pole}$ measurements favor values of $m_{\mathrm{H}}$ excluded by direct searches leads us to examine the effects of external Higgsstrahlung, a process ignored by the usual precision electroweak calculations.

We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a data sample of 52 million ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We determine the branching fraction, first, second, and third moments of the spectrum for lower cutoffs on the electron energy between 0.6 and 1.5 GeV. We measure the partial branching fraction to be $\mathcal{B}(\overrightarrow{B}\mathrm{Xe}\nu {,E}_e>0.6\mathrm{}\mathrm{GeV})=[10.36\pm 0.06(\mathrm{stat}.\mathrm{})\pm 0.23(\mathrm{sys}.\mathrm{}\left)\right]\%.\mathrm{}$

We report a measurement of the first four moments of the hadronic mass distribution in $\overline{B}\to X_c{\mathcal{l}}^{-}\overline{\nu }$ decays. The measurements are based on 89 million ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}\to B\overline{B}$ events where the hadronic decay of one of the B mesons is fully reconstructed and a charged lepton from the decay of the other B meson is identified. The moments are presented for minimum lepton momenta ranging from 0.9 to 1.6 GeV in the B rest frame. It is expected that such measurements will lead to improved determinations of $|V_{\mathrm{cb}}|$ and $|V_{\mathrm{ub}}|.$

We construct the exact solution of one (anti-)instanton in $\mathcal{N}=\frac{1}{2}$ super Yang-Mills theory defined on non(anti-)commutative superspace. We first identify $\mathcal{N}=\frac{1}{2}$ superconformal invariance as maximal spacetime symmetry. For the gauge group U(2), the SU(2) part of the solution is given by the standard (anti-)instanton, but the U(1) field strength also turns out to be nonzero. The solution is SO(4) rotationally symmetric. For the gauge group $\mathrm{U}\mathrm{}\left(N\right),$ in contrast with the U(2) case, we show that the entire $\mathrm{U}\mathrm{}\left(N\right)\mathrm{}$ part of the solution is deformed by non(anti-)commutativity and fermion zero modes. The solution is no longer rotationally symmetric; it is polarized into an axially symmetric configuration because of the underlying non(anti-)commutativity. We compute the “information metric” of one (anti-)instanton. We find that the moduli space geometry is deformed from the hyperbolic space $H_5$ (Euclidean anti–de Sitter space) in a way anticipated from reduced spacetime symmetry. Remarkably, the volume measure of the moduli space turns out to be independent of the non(anti-)commutativity. Implications for D branes in the Ramond-Ramond flux background and the gauge-gravity correspondence are discussed.