A numerical simulation is presented here of the evolution of initial data of the kind that was conjectured by Hertog, Horowitz, and Maeda to be a violation of cosmic censorship. Those initial data are essentially a thick domain wall connecting two regions of anti–de Sitter space. The initial data have a free parameter that is the initial size of the wall. The simulation shows no violation of cosmic censorship, but rather the formation of a small black hole. The simulation described here is for a moderate wall size and leaves open the possibility that cosmic censorship might be violated for larger walls.

Iterative solutions to fourth-order gravity describing static and electrically charged black holes are constructed. The obtained solutions are parametrized by two integration constants which are related to the electric charge and the exact location of the event horizon. Special emphasis is put on the extremal black holes. It is explicitly demonstrated that in the extremal limit the exact location of the (degenerate) event horizon is given by $r_{+}=|e|.$ Similarly to the classical Reissner-Nordström solution, the near-horizon geometry of the charged black holes in quadratic gravity, when expanded into the whole manifold, is simply that of Bertotti and Robinson. Similar considerations have been carried out for boundary conditions of the second type which employ the electric charge and the mass of the system as seen by a distant observer. The relations between results obtained within the framework of each method are briefly discussed.

We consider a model of topological solitons where charged particles have finite mass and the electric charge is already quantized at the classical level. In the electrodynamic limit, which physically corresponds to electrodynamics of solitons of zero size, the Lagrangian of this model has two degrees of freedom only and reduces to the Lagrangian of the Maxwell field in the dual representation. We derive the equations of motion and discuss their relations with Maxwell’s equations. It is shown that Coulomb and Lorentz forces are a consequence of topology. Further, we relate the U(1) gauge invariance of electrodynamics to the geometry of the soliton field, give a general relation for the derivation of the soliton field from the field strength tensor in electrodynamics, and use this relation to express homogeneous electric fields in terms of the soliton field.

In a scalar-tensor theory of gravity we consider a global monopole field as a candidate for galactic dark matter. Within the weak gravity approximation we solve the equations of a metric tensor and a scalar field coupled to the monopole and determine the asymptotic structure of a galactic spacetime for large r. In the case of a massless scalar field, we derive a formula for the rotation velocity of stars, which contains an extra constant value in addition to the other known terms, and we discuss its relation to flat rotation curves in the galaxy.

The nature of the fuel that drives today’s cosmic acceleration is an open and tantalizing mystery. The brane-world theory of Dvali, Gabadadze, and Porrati (DGP) provides a context where late-time acceleration is driven not by some energy-momentum component (dark energy), but rather is the manifestation of the excruciatingly slow leakage of gravity off our four-dimensional world into an extra dimension. At the same time, DGP gravity alters the gravitational force law in a specific and dramatic way at cosmologically accessible scales. We derive the DGP gravitational force law in a cosmological setting for spherical perturbations at subhorizon scales and compute the growth of large-scale structures. We find that a residual repulsive force at large distances gives rise to a suppression of the growth of density and velocity perturbations. Explaining the cosmic acceleration in this framework leads to a present day fluctuation power spectrum normalization ${\sigma }_8<~0.8$ at about the two-sigma level, in contrast with observations. We discuss further theoretical work necessary to go beyond our approximations to confirm these results.

The existence of a natural ultraviolet cutoff at the Planck scale is widely expected. In a previous Letter, it has been proposed to model this cutoff as an information density bound by utilizing suitably generalized methods from the mathematical theory of communication. Here, we prove the mathematical conjectures that were made in this Letter.

One often-used approximation in the study of binary compact objects (i.e., black holes and neutron stars) in general relativity is the instantaneously circular orbit assumption. This approximation has been used extensively, from the calculation of innermost circular orbits to the construction of initial data for numerical relativity calculations. While this assumption is inconsistent with generic general relativistic astrophysical inspiral phenomena where the dissipative effects of gravitational radiation cause the separation of the compact objects to decrease in time, it is usually argued that the time scale of this dissipation is much longer than the orbital time scale so that the approximation of circular orbits is valid. Here, we quantitatively analyze this approximation using a post-Newtonian approach that includes terms up to order $\left[{Gm/(rc}^2\right){]}^{9/2}$ for nonspinning particles. By calculating the evolution of equal mass black-hole–black-hole binary systems starting with circular orbit configurations and comparing them to the more astrophysically relevant quasicircular solutions, we show that a minimum initial separation corresponding to at least 6 (3.5) orbits before merger is required in order to bound the detection event loss rate in gravitational wave detectors to below 5% (20%). In addition, we show that the detection event loss rate is greater than 95% for a range of initial separations that includes all modern calculations of the innermost stable circular orbit.

Time evolution of tunneling phenomena proceeding in a thermal medium is studied using a standard model of environmental interaction. A semiclassical probability formula for the particle motion in a metastable state of a one-dimensional system put in a thermal medium is combined with the formula of the quantum penetration factor through a potential barrier to derive the tunneling rate in the medium. The effect of environment, its influence on time evolution in particular, is clarified in our real-time formalism. A nonlinear resonance effect is shown to enhance the tunneling rate at finite times of order $2/\eta ,$ with $\eta$ the friction coefficient unless $\eta$ is too small. In the linear approximation this effect has relevance to the parametric resonance. This effect enhances the possibility of early termination of the cosmological phase transition much prior to the typical Hubble time.

The processes ${\nu }_e+n\rightleftharpoons {p+e}^{-}$ and ${\overline{\nu }}_e+p\rightleftharpoons {n+e}^{+}$ provide the dominant mechanisms for heating and cooling the material between the protoneutron star and the stalled shock in a core-collapse supernova. Observations suggest that some neutron stars are born with magnetic fields of at least $\sim {10}^{15}\mathrm{G}$ while theoretical considerations give an upper limit of $\sim {10}^{18}\mathrm{G}$ for the protoneutron star magnetic fields. We calculate the rates for the above neutrino processes in strong magnetic fields of $\sim {10}^{16}\mathrm{G}.$ We find that the main effect of such magnetic fields is to change the equations of state through the phase space of $e^{-}$ and $e^{+},$ which differs from the classical case due to quantization of the motion of $e^{-}$ and $e^{+}$ perpendicular to the magnetic field. As a result, the cooling rate can be greatly reduced by magnetic fields of $\sim {10}^{16}\mathrm{G}$ for typical conditions below the stalled shock and a nonuniform protoneutron star magnetic field (e.g., a dipole field) can introduce a large angular dependence of the cooling rate. In addition, strong magnetic fields always lead to an angle-dependent heating rate by polarizing the spin of n and p. The implications of our results for the neutrino-driven supernova mechanism are discussed.

The large scale anisotropies of Wilkinson Microwave Anisotropy Probe (WMAP) data have attracted a lot of attention and have been a source of controversy, with many favorite cosmological models being apparently disfavored by the power spectrum estimates at low $\mathcal{l}.$ All the existing analyses of theoretical models are based on approximations for the likelihood function, which are likely to be inaccurate on large scales. Here we present exact evaluations of the likelihood of the low multipoles by direct inversion of the theoretical covariance matrix for low resolution WMAP maps. We project out the unwanted galactic contaminants using the WMAP derived maps of these foregrounds. This improves over the template based foreground subtraction used in the original analysis, which can remove some of the cosmological signal and may lead to a suppression of power. As a result we find an increase in power at low multipoles. For the quadrupole the maximum likelihood values are rather uncertain and vary between 140 and $220\mu {\mathrm{K}}^2.$ On the other hand, the probability distribution away from the peak is robust and, assuming a uniform prior between 0 and $2000\mu {\mathrm{K}}^2,$ the probability of having the true value above $1200\mu {\mathrm{K}}^2$ (as predicted by the simplest cold dark matter model with a cosmological constant) is 10%, a factor of 2.5 higher than predicted by the WMAP likelihood code. We do not find the correlation function to be unusual beyond the low quadrupole value. We develop a fast likelihood evaluation routine that can be used instead of WMAP routines for low $\mathcal{l}$ values. We apply it to the Markov chain Monte Carlo analysis to compare the cosmological parameters between the two cases. The new analysis of WMAP either alone or jointly with the Sloan Digital Sky Survey (SDSS) and the Very Small Array (VSA) data reduces the evidence for running to less than $1\sigma ,$ giving ${\alpha }_s=-0.022\pm 0.033$ for the combined case. The new analysis prefers about a $1\sigma$ lower value of ${\Omega }_m,$ a consequence of an increased integrated Sachs-Wolfe (ISW) effect contribution required by the increase in the spectrum at low $\mathcal{l}.$ These results suggest that the details of foreground removal and full likelihood analysis are important for parameter estimation from the WMAP data. They are robust in the sense that they do not change significantly with frequency, mask, or details of foreground template marginalization. The marginalization approach presented here is the most conservative method to remove the foregrounds and should be particularly useful in the analysis of polarization, where foreground contamination may be much more severe.

Several recent experiments have reported evidence for a narrow feature in the $K^{+}$-neutron system, an apparent resonant state $\sim 100\mathrm{MeV}$ above threshold and with a width $<~25\mathrm{MeV}.$ This state has been labeled as ${\Theta }^{+}$ (previously as $Z^{*}),$ and because of the implied inclusion of a strange antiquark is referred to as a pentaquark, that is, five quarks within a single bag. We present an alternative explanation for such a structure, as a higher angular momentum resonance in the isospin zero $K^{+}N$ system. One might call this an exit channel or molecular resonance. In a nonrelativistic potential model we find a possible candidate for the kaon-nucleon system with a relative angular momentum $L=3,$ while $L=1\mathrm{}$ states possess centripetal barriers much too low to confine the kaon and nucleon at an energy so high above threshold. Under some circumstances, however, an $L=2\mathrm{}$ state can exist.

For improved actions composed of plaquette and rectangular six-link loops, $\eta ,$ the ratio of renormalized to bare anisotropies, is calculated for $\xi =2,$ 3, 4, and 6 in the $\beta$ region where numerical simulations such as hadron spectroscopy are currently carried out. The $\beta$ dependence of $\eta$ for the renormalization-group-improved actions is quite different from those of the standard and Symanzik actions. In the Iwasaki and DBW2 (doubly blocked from Wilson action in two-coupling space) actions, $\eta$ remains almost constant in a wide range of $\beta ,$ which is also different from the one-loop perturbative results, while in the case of the Symanzik action, $\eta$ increases as $\beta$ decreases, which is qualitatively similar to the perturbative result, but the slope is steeper. In the calculation of $\eta$ close to and in the confined phase, we have applied a link integration method to suppress the fluctuation of the gauge field. Some technical details of the integration method are summarized.

We consider the flavor-changing operators associated with the strong axial and trace anomalies. Their short-distance generation through penguinlike diagrams is obtained within the QCD external field formalism. Standard-model operator evolution exhibits a suppression of anomalous effects in K and B hadronic weak decays. A genuine set of dimension-eight $\Delta S=1\mathrm{}$ operators is also displayed.

We present a new exact perfect fluid interior solution for a particular scalar-tensor theory. The solution is regular everywhere and has a well defined boundary where the fluid pressure vanishes. The metric and the dilaton field match the external solution continuously.

We consider a Lorentz-violating modification to the fermionic Lagrangian of QED that is known to produce a finite Chern-Simons term at leading order. We compute the second order correction to the one-loop photon self-energy in the massless case using an exact propagator and a nonperturbative formulation of the theory. This nonperturbative theory assigns a definite value to the coefficient of the induced Chern-Simons term; however, we find that the theory fails to preserve gauge invariance at higher orders. We conclude that the specific nonperturbative value of the Chern-Simons coefficient has no special significance.

We study Q stars with global and local $U\left(1\right)\mathrm{}$ symmetry in extra dimensions in asymptotically anti–de Sitter or flat spacetime. The behavior of the mass, radius, and particle number of the star is quite different in three dimensions, but in five, six, eight, and eleven dimensions is similar to the behavior in four.

Modifications to the Friedmann equation in brane cosmology can have important implications for early Universe phenomena such as inflation and the generation of the baryon asymmetry. We study a simple scenario of chaotic brane inflation where, in a minimal supersymmetric seesaw model, the scalar superpartner of a heavy singlet Majorana neutrino drives inflation and, simultaneously, generates the required lepton asymmetry through its direct out-of-equilibrium decays after the inflationary era. For a gravitino mass in the range $m_{3/2}\simeq 100\mathrm{GeV}–1\mathrm{TeV},$ we find that successful nucleosynthesis and leptogenesis in this framework require that the 5D Planck mass is in the range $M_5\simeq {10}^{10}–{10}^{13}\mathrm{GeV}$ and the reheating temperature $T_{\mathrm{rh}}\simeq {10}^6–{10}^8\mathrm{GeV}.$

We reanalyze the mass matrix model of quarks and leptons that gives a unified description of quark and lepton mass matrices with the same texture form. By investigating possible types of assignment for the texture components of the lepton mass matrix, we find that a different assignment for neutrinos than for charged leptons can also lead to consistent values of the Maki-Nakagawa-Sakata-Pontecorv (MNSP) lepton mixing matrix. We also find that the predicted value for the lepton mixing matrix element $U_{13}$ of the model depends on the assignment. A proper assignment will be discriminated by future experimental data for $U_{13}.$

Additional broader $I=0\mathrm{}$ states in the KN channel near ${\Theta }^{+}\mathrm{}\left(1540\right)\mathrm{}$ are expected in many models, making the absence of any signature in the ${\mathrm{K}}^{+}$-deuteron scattering data even more puzzling. In an ideal “three-body” picture the $\Theta$ is viewed as two compact $\mathrm{ud}\left(1\right)\mathrm{ud}\left(2\right)\mathrm{}$ $3¯$ color diquarks and an $\overline{s}$ quark. A “QCD-type” inequality involving $m\left({\Theta }^{+}\right),$ $m\left(\Lambda \right),$ the mass of the $\Lambda {(1/2\mathrm{}}^{-})$ $L=1\mathrm{}$ excitation, and that of a new $I=0\mathrm{}$ tetraquark vector meson then follows. The inequality suggests a very light new vector meson, and is violated. We note that “associated production” of the pentaquark with another quadriquark or antipentaquark may be favored. This along with some estimates of the actual production cross sections suggest that the $\Theta$ can be found in BaBar or Belle $e^{+}{-e}^{-}$ colliders.