The time evolution of a set of $22M_{\odot }$ unstable charged stars that collapse is computed integrating the Einstein-Maxwell equations. The model simulates the collapse of a spherical star that had exhausted its nuclear fuel and has or acquires a net electric charge in its core while collapsing. When the charge-to-mass ratio is $Q/\sqrt{G}M\ge 1$, the star does not collapse but spreads. On the other hand, a different physical behavior is observed with a charge-to-mass ratio of $1>Q/\sqrt{G}M>0.1$. In this case, the collapsing matter forms a bubble enclosing a lower density core. We discuss an immediate astrophysical consequence of these results that is a more efficient neutrino trapping during the stellar collapse and an alternative mechanism for powerful supernova explosions. The outer space-time of the star is the Reissner-Nordström solution that matches smoothly with our interior numerical solution; thus the collapsing models form Reissner-Nordström black holes.

We study the numerical implementation of a set of boundary conditions derived from the isolated horizon formalism, and which characterize a black hole whose horizon is in quasiequilibrium. More precisely, we enforce these geometrical prescriptions as inner boundary conditions on an excised sphere, in the numerical resolution of the conformal thin sandwich equations. As main results, we first establish the consistency of including in the set of boundary conditions a constant surface gravity prescription, interpretable as a lapse boundary condition, and second we assess how the prescriptions presented recently by Dain et al. for guaranteeing the well-posedness of the conformal transverse traceless equations with quasiequilibrium horizon conditions extend to the conformal thin sandwich elliptic system. As a consequence of the latter analysis, we discuss the freedom of prescribing the expansion associated with the ingoing null normal at the horizon.

We study the case of brane world models with an additional Gauss-Bonnet term in the presence of a bulk scalar field which interacts nonminimally with gravity, via a possible interaction term of the form $-\frac{1}{2}\xi R{\varphi }^2$. The Einstein equations and the junction conditions on the brane are formulated, in the case of the bulk scalar field. Static solutions of this model are obtained by solving numerically the Einstein equations with the appropriate boundary conditions on the brane. Finally, we present graphically and comment these solutions for several values of the free parameters of the model.

Perturbed stationary axisymmetric isolated bodies, e.g. stars, represented by a matter-filled interior and an asymptotically flat vacuum exterior joined at a surface where the Darmois matching conditions are satisfied, are considered. The initial state is assumed to be static. The perturbations of the matching conditions are derived and used as boundary conditions for the perturbed Ernst equations in the exterior region. The perturbations are calculated to second order. The boundary conditions are overdetermined: necessary and sufficient conditions for their compatibility are derived. The special case of perturbations of spherical bodies is given in detail.

We present an approach to cosmological perturbations based on a covariant perturbative expansion between two worldlines in the real inhomogeneous universe. As an application, at an arbitrary order we define an exact scalar quantity which describes the inhomogeneities in the number of e-folds on uniform density hypersurfaces and which is conserved on all scales for a barotropic ideal fluid. We derive a compact form for its conservation equation at all orders and assign it a simple physical interpretation. To make a comparison with the standard perturbation theory, we develop a method to construct gauge-invariant quantities in a coordinate system at arbitrary order, which we apply to derive the form of the $n$th order perturbation in the number of e-folds on uniform density hypersurfaces and its exact evolution equation. On large scales, this provides the gauge-invariant expression for the curvature perturbation on uniform density hypersurfaces and its evolution equation at any order.

The future of direct terrestrial WIMP detection lies on two fronts: new, much larger low background detectors sensitive to energy deposition, and detectors with directional sensitivity. The former can explore a large range of WIMP parameter space using well-tested technology while the latter may be necessary if one is to disentangle particle physics parameters from astrophysical halo parameters. Because directional detectors will be quite difficult to construct it is worthwhile exploring in advance generally which experimental features will yield the greatest benefits at the lowest costs. We examine the sensitivity of directional detectors with varying angular tracking resolution with and without the ability to distinguish forward versus backward recoils, and compare these to the sensitivity of a detector where the track is projected onto a two-dimensional plane. The latter detector regardless of where it is placed on the Earth, can be oriented to produce a significantly better discrimination signal than a 3D detector without this capability, and with sensitivity within a factor of 2 of a full 3D tracking detector. Required event rates to distinguish signals from backgrounds for a simple isothermal halo range from the low teens in the best case to many thousands in the worst.

Neutrinos from core collapse supernovae can be emitted from a rapidly accreting disk surrounding a black hole, instead of the canonical protoneutron star. For galactic events, detector count rates are considerable and in fact can be in the thousands for Super-Kamiokande. The rate of occurrence of these accreting disks in the Galaxy is predicted to be on the order of $\sim {10}^{-5}{\mathrm{yr}}^{-1}$, yet there is little observational evidence to provide an upper limit on their formation rate. It would therefore be useful to discriminate between neutrinos which have been produced in a protoneutron star and those which have been produced accretion disks. In order to distinguish between the two scenarios, either the time profile of the neutrino luminosity, total energetics, or the relative fluxes of different neutrino flavors may be considered. The flavor content would clearly point to one scenario or the other.

We develop a general formalism for the parameter-space metric of the multidetector $\mathcal{F}$-statistic, which is a matched-filtering detection statistic for continuous gravitational waves. We find that there exists a whole family of $\mathcal{F}$-statistic metrics, parametrized by the (unknown) amplitude parameters of the gravitational wave. The multidetector metric is shown to be expressible in terms of noise-weighted averages of single-detector contributions, which implies that the number of templates required to cover the parameter space does not scale with the number of detectors. Contrary to using a longer observation time, combining detectors of similar sensitivity is therefore the computationally cheapest way to improve the sensitivity of coherent wide-parameter searches for continuous gravitational waves. We explicitly compute the $\mathcal{F}$-statistic metric family for signals from isolated spinning neutron stars, and we numerically evaluate the quality of different metric approximations in a Monte Carlo study. The metric predictions are tested against the measured mismatches and we identify regimes in which the local metric is no longer a good description of the parameter-space structure.

There has been some recent activity in trying to understand the dark matter clustering properties in the quasilinear regime, through resummation of perturbative terms, otherwise known as the renormalized perturbation theory [M. Crocce and R. Scoccimarro, Phys. Rev. D 73, 063519 (2006).], or the renormalization group method [P. McDonald, astro-ph/0606028.]. While it is not always clear why such methods should work so well, there is no reason for them to capture nonperturbative events such as shell-crossing. In order to estimate the magnitude of nonperturbative effects, we introduce a (hypothetical) model of sticky dark matter, which only differs from collisionless dark matter in the shell-crossing regime. This enables us to show that the level of nonperturbative effects in the dark matter power spectrum at $k\sim 0.1{\mathrm{Mpc}}^{-1}$, which is relevant for baryonic acoustic oscillations, is about a percent, but rises to order unity at $k\sim 1{\mathrm{Mpc}}^{-1}$.

We predict the two-photon width of the pseudoscalar bottomonia, ${\Gamma }_{\gamma \gamma }({\eta }_b)$, ${\Gamma }_{\gamma \gamma }({\eta }_b^{\prime })$, and ${\Gamma }_{\gamma \gamma }({\eta }_b^{\prime \prime })$ within a heavy-quark spin-symmetry setting following the same line as our recent work for the corresponding decays for charmonia. Binding-energy effects are included for excited states and are shown to shift up the ${\eta }_b^{\prime }$ and ${\eta }_b^{\prime \prime }$ widths by 10%. We point out that the essentially model independent ratio ${\Gamma }_{\gamma \gamma }({\eta }_b)/{\Gamma }_{\ell \overline{\ell }}({\rm Y})$ and the branching ratio $BR({\eta }_b\to \gamma \gamma )$ obtained could be used to extract the coupling constant ${\alpha }_s$.

An updated and extended analysis of the quark-mass dependence of the nucleon’s axial-vector coupling constant $g_A$ is presented in comparison with state-of-the-art lattice QCD results. Special emphasis is placed on the role of the $\Delta (1232)$ isobar. It is pointed out that standard chiral perturbation theory of the pion-nucleon system at order $p^4$ fails to provide an interpolation between the lattice data and the physical point. In constrast, a version of chiral effective field theory with explicit inclusion of the $\Delta (1232)$ proves to be successful. Detailed error analysis and convergence tests are performed. Integrating out the $\Delta (1232)$ as an explicit degree of freedom introduces uncontrolled errors for pion masses $m_{\pi }\gtrsim 300\mathrm{MeV}$.

In this paper we perform collective quantization of an axially symmetric skyrmion with baryon number two. The rotational and isorotational modes are quantized to obtain the static properties of a deuteron and other dibaryonic objects such as masses, charge densities, and magnetic moments. We discuss how gravity affects those observables.

We report results of a Dalitz plot analysis of the three-body charmless $B^0\to K^0{\pi }^{+}{\pi }^{-}$ decay. The analysis is performed with a data sample that contains $388\times {10}^6$ $B\overline{B}$ pairs collected near the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. Measurements of branching fractions for the quasi-two-body decays $B^0\to \rho (770{)}^0{K}^0$, $B^0\to f_0(980)K^0$, $B^0\to K^{*}(892{)}^{+}{\pi }^{-}$, $B^0\to K^{*}(1430{)}^{+}{\pi }^{-}$, and upper limits on several other quasi-two-body decay modes are reported.

Starting from the Janus solution and its gauge theory dual, we obtain the dual gauge theory description of the cosmological solution by the procedure of double analytic continuation. The coupling is driven either to zero or to infinity at the big-bang and big-crunch singularities, which are shown to be related by the $S$-duality symmetry. In the dual Yang-Mills theory description, these are nonsingular as the coupling goes to zero in the $\mathcal{N}=4$ super Yang-Mills theory. The cosmological singularities simply signal the failure of the supergravity description of the full type IIB superstring theory.

We investigate backgrounds of Type IIB string theory with null singularities and their duals proposed in S. R. Das, J. Michelson, K. Narayan, S. P. Trivedi, hep-th/0602107. The dual theory is a deformed $\mathcal{N}=4$ Yang-Mills theory in $3+1$ dimensions with couplings dependent on a lightlike direction. We concentrate on backgrounds which become ${\mathrm{AdS}}_5\times S^5$ at early and late times and where the string coupling is bounded, vanishing at the singularity. Our main conclusion is that in these cases the dual gauge theory is nonsingular. We show this by arguing that there exists a complete set of gauge invariant observables in the dual gauge theory whose correlation functions are nonsingular at all times. The two-point correlator for some operators calculated in the gauge theory does not agree with the result from the bulk supergravity solution. However, the bulk calculation is invalid near the singularity where corrections to the supergravity approximation become important. We also obtain pp-waves which are suitable Penrose limits of this general class of solutions, and construct the matrix membrane theory which describes these pp-wave backgrounds.

We consider the interaction of a heavy quark-antiquark pair moving in $\mathcal{N}=4$ SYM plasma in the presence of nonvanishing chemical potentials. Of particular importance is the maximal length beyond which the interaction is practically turned off. We propose a simple phenomenological law that takes into account the velocity dependence of this screening length beyond the leading order and in addition its dependence on the $R$-charge. Our proposal is based on studies using rotating D3-branes.

We study prospects of a method to constrain the inclination of a coalescing compact binary by detecting its gravitational waves associated with a three-dimensionally localized (direction and distance) short-hard gamma-ray burst. We take advantage of a synergy of these two observations, and our method can be applied even with a single interferometer. For a nearly face-on binary the inclination angle $I$ can be constrained in the range $1-{\mathrm{SNR}}^{-1}\le \cos I\le 1$ (SNR: the signal-to-noise ratio of gravitational wave detection), provided that the error of the distance estimation is negligible. This method would help us to study properties of the short-hard bursts, including potentially collimated jetlike structures as indicated by recent observation.

We investigate microlensing in the case where the lens is considered as an extended object. We use a multipolar expansion of the lens potential and show that the time-varying nature of the quadrupole contribution allows to separate it from the mass and spin contributions and leads to specific modulations of the amplification signal. As example we study the case of binary system lenses in our galaxy. The modulation is observable if the rotation period of the system is smaller than the time over which the amplification is significant and if the impact parameter of the passing light ray is sufficiently close to the Einstein radius so that the amplification is large. Observations of this modulation can reveal important information on the quadrupole and thus on the gravitational radiation emitted by the binary lens. Even if not observed directly, because of their importance the quadrupole modulation has to be included in the error budget for high magnification ($\mu \le 7$) microlensing events.

In a metric variable based Hamiltonian quantization, we give a prescription for constructing semiclassical matter-geometry states for homogeneous and isotropic cosmological models. These “collective” states arise as infinite linear combinations of fundamental excitations in an unconventional polymer quantization. They satisfy a number of properties characteristic of semiclassicality, such as peaking on classical phase space configurations. We describe how these states can be used to determine quantum corrections to the classical evolution equations, and to compute the initial state of the universe by a backward time evolution.

The second order perturbative field equations for slowly and rigidly rotating perfect fluid balls of Petrov type D are solved numerically. It is found that all the slowly and rigidly rotating perfect fluid balls up to second order, irrespective of Petrov type, may be matched to a possibly nonasymptotically flat stationary axisymmetric vacuum exterior. The Petrov type D interior solutions are characterized by five integration constants, corresponding to density and pressure of the zeroth order configuration, the magnitude of the vorticity, one more second order constant, and an independent spherically symmetric second order small perturbation of the central pressure. A four-dimensional subspace of this five-dimensional parameter space is identified for which the solutions can be matched to an asymptotically flat exterior vacuum region. Hence these solutions are completely determined by the spherical configuration and the magnitude of the vorticity. The physical properties, like equation of state, shape, and speed of sound, are determined for a number of solutions.