We study the static, spherically symmetric black hole solutions for a nonminimally coupled multiscalar theory. We find numerical solutions for values of the scalar fields when a certain constraint on the maximal charge is satisfied. Beyond this constraint no black hole solutions exist. This constraint therefore corresponds to extremal solutions; however, this does not match the $\kappa =0$ constraint which typically indicates extremal solutions in other models. This implies that the limiting extremal solutions have nonzero, finite and varying surface gravity. These solutions also violate the no-hair theorems for $N>1$ scalar fields and have previously been proven to be linearly stable.

Recent investigations have established an analogy between the entropy of four-dimensional supersymmetric black holes in string theory and entanglement in quantum information theory. Examples include: (1) $N=2$ STU black holes and the tripartite entanglement of three qubits (2-state systems), where the common symmetry is $[SL(2){]}^3$ and (2) $N=8$ black holes and the tripartite entanglement of seven qubits where the common symmetry is $E_7\supset [SL(2){]}^7$. Here we present another example: $N=8$ black holes (or black strings) in five dimensions and the bipartite entanglement of three qutrits (3-state systems), where the common symmetry is $E_6\supset [SL(3){]}^3$. Both the black hole (or black string) entropy and the entanglement measure are provided by the Cartan cubic $E_6$ invariant. Similar analogies exist for magic $N=2$ supergravity black holes in both four and five dimensions.

Inspired by the warped Randall-Sundrum scenario proposed to solve the mass scale hierarchy problem with a compactified fifth extra dimension, a similar model with no metric singularities has been elaborated. In this framework, the Kaluza-Klein reduction equations for a real massless scalar field propagating in the bulk have been studied carefully from the point of view of Hermiticity so as to formulate in a mathematically rigorous way all the possible boundary conditions and corresponding mass eigenvalue towers and tachyon states. The physical masses as observable in our four-dimensional brane are deduced from these mass eigenvalues depending on the location of the brane on the extra dimension axis. Examples of mass towers and tachyons and related field probability densities are presented from numerical computations performed for some arbitrary choices of the parameters of the model.

A new revision of the gamma flux that we expect to detect in imaging atmospheric Cherenkov telescopes from neutralino annihilation in the Draco dwarf spheroidal galaxy is presented in the context of the minimal supersymmetric standard models compatible with the present phenomenological and cosmological constraints, and using the dark matter density profiles compatible with the latest observations. This revision also takes into account the important effect of the point spread function of the telescope, and is valid not only for Draco but also for any other dark matter target. We show that this effect is crucial in the way we will observe and interpret a possible signal detection. Finally, we discuss the prospects to detect a possible gamma signal from Draco for current or planned gamma-ray experiments, i.e., MAGIC, GLAST, and GAW. Even with the large astrophysical and particle physics uncertainties we find that the chances to detect a neutralino annihilation signal in Draco seem to be very scarce for current experiments. However, the prospects for future imaging atmospheric Cherenkov telescopes with upgraded performances, (especially lower threshold energies and higher sensitivities) such as those offered by the Cherenkov Telescope Array project, might be substantially better.

Taking into account that the Sandage-Loeb test is unique in its coverage of the redshift desert and available in the near future, we explore the cosmic time evolution behavior of the source redshift for the holographic dark energy model, an important competing cosmological model. As a result, we find that the Sandage-Loeb test can provide an extremely strong bound on ${\Omega }_m^0$, while its constraint on another dimensionless parameter $\lambda$ is weak. In addition, it is proposed here for the first time that we can also constrain various cosmological models by measuring the value of $z_{\max }$ at which the peak of redshift velocity occurs. Combining this new proposed method with the traditional Sandage-Loeb test, we should be able to provide a better constraint on $\lambda$, at least from the theoretical perspective.

The coupling between Ricci scalar curvature and the baryon number current dynamically breaks $CPT$ in an expanding universe and leads to baryon asymmetry. We study the effect of time dependence of the equation of state parameter of the Friedmann-Robertson-Walker universe on this asymmetry.

Spectra, triple, and quartic gauge couplings of the Higgsless model with gauge group $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ defined in warped space are explored with a numerical method. We extend the equation of motions, boundary conditions, and formalism of multi-gauge-boson vertices to the Hirn-Sanz scenario. By assuming the ideally delocalized fermion profile, we study the spectra of vector bosons as well as the triple and quartic gauge couplings among vector bosons. It is found that mass spectra can be greatly modified by the parameters of QCD power corrections. Meanwhile, the triple and quartic gauge couplings can deviate from the values of the standard model to at least $\pm 10\%$ and can saturate the LEP2 bounds. We find the triple gauge couplings of $Z\overline{W}W$ can be 50% smaller than the unitarity bounds. The triple gauge couplings of $\overline{Z}WW$ is 20% smaller than the unitarity bounds, which might challenge the detection of $\overline{Z}$ via $s$ channel at LHC if $m_{\overline{Z}}>500\mathrm{GeV}$.

We study the approach, initiated by Marinari et al., to the static interquark potential based on Polyakov lines of finite temporal extent, evaluated in Coulomb gauge. We show that, at small spatial separations, the potential can be understood as being between two separately gauge invariant color charges. At larger separations Gribov copies obstruct the nonperturbative identification of individually gauge invariant color states. We demonstrate, for the first time, how gauge invariance can be maintained quite generally by averaging over Gribov copies. This allows us to extend the analysis of the Polyakov lines and the corresponding, gauge invariant quark-antiquark state to all distance scales. Using large scale lattice simulations, we show that this interpolating state possesses a good overlap with the ground state in the quark-antiquark sector and yields the full static interquark potential at all distances. A visual representation of the Gribov copies on the lattice is also presented.

We explore the highly nonperturbative hot region of the QCD phase diagram close to $T_c$ by use of an imaginary chemical potential $\mu$ which avoids the sign problem. The simulations use four flavors of staggered fermions and are carried out on a ${16}^3\times 4$ lattice. The number density and the quark number susceptibility are consistent with a critical behavior associated with the transition line in the negative ${\mu }^2$ half-plane. We compare the analytic continuation of these results with various phenomenological models, none of which provides a satisfactory description of data, a failure on which we make some comments. These results complement and extend the information obtained via the analysis of the susceptibilities evaluated at zero $\mu$, yielding a simple description of the candidate strongly interacting quark-gluon plasma phase. As a byproduct of our analysis we investigate the Polyakov loop and its hermitian conjugate. Our data offer vivid evidence of the importance of the complex nature of the functional integral measure, which results in $L(\mu )\ne \overline{L}(\mu )$ for a real chemical potential $\mu$.

We systematically construct realistic mass matrices for the type-I seesaw mechanism out of more than $20\times {10}^{12}$ possibilities. We use only very generic assumptions from extended quark-lepton complementarity, i.e., the leptonic mixing angles between flavor and mass eigenstates are either maximal or parametrized by a single small quantity $ϵ$ that is of the order of the Cabibbo angle $ϵ\simeq {\theta }_{\mathrm{C}}$. The small quantity $ϵ$ also describes all fermion mass hierarchies. We show that special cases often considered in the literature, such as having a symmetric Dirac mass matrix or small mixing among charged leptons, constitute only a tiny fraction of our possibilities. Moreover, we find that in most cases the spectrum of right-handed neutrino masses is only mildly hierarchical. As a result, we provide for the charged leptons and neutrinos a selected list of 1981 qualitatively different Yukawa coupling matrices (or textures) that are parametrized by the Cabibbo angle and allow for a perfect fit to current data. In addition, we also briefly show how the textures could be generated in explicit models from flavor symmetries.

We develop the canonical theory of gravitational collapse in $2+1$ dimensions with a negative cosmological constant and obtain exact solutions of the Wheeler-DeWitt equation regularized on a lattice. We employ these solutions to derive the Hawking radiation from black holes formed in all models of dust collapse. We obtain an (approximate) Planck spectrum near the horizon characterized by the Hawking temperature $T_{\mathrm{H}}=\hslash \sqrt{G\Lambda M}/2\pi$, where $M$ is the mass of a black hole that is presumed to form at the center of the collapsing matter cloud and $-\Lambda$ is the cosmological constant. Our solutions to the Wheeler-DeWitt equation are exact, so we are able to reliably compute the gray-body factors that result from going beyond the near-horizon region.

A higher order theory of dilaton gravity is constructed as a generalization of the Einstein-Lovelock theory of pure gravity. Its Lagrangian contains terms with higher powers of the Riemann tensor and of the first two derivatives of the dilaton. Nevertheless, the resulting equations of motion are quasilinear in the second derivatives of the metric and of the dilaton. This property is crucial for the existence of brane solutions in the thin wall limit. At each order in the derivatives the contribution to the Lagrangian is unique up to an overall normalization. Relations between symmetries of this theory and the $O(d,d)$ symmetry of the string-inspired models are discussed.

We construct an exact stationary solution of black-hole–bubble sequence in the five-dimensional Kaluza-Klein theory by using solitonic solution-generating techniques. The solution describes two stationary black holes with topology $S^3$ on a Kaluza-Klein bubble and has a linear momentum component in the compactified direction. We call the solution boosted black holes on Kaluza-Klein bubble because it has the linear momentum. The Arnowitt-Deser-Misner mass and the linear momentum depend on the two boosted velocity parameters of black holes. In the effective four-dimensional theory, the solution has an electric charge which is proportional to the linear momentum. The solution includes the static solution found by Elvang and Horowitz. The small and the big black holes limits are investigated. The relation between the solution and the single boosted black string are considered.

This paper delineates the first steps in a systematic quantitative study of the spacetime fluctuations induced by quantum fields in an evaporating black hole under the stochastic gravity program. The central object of interest is the noise kernel, which is the symmetrized two-point quantum correlation function of the stress tensor operator. As a concrete example we apply it to the study of the spherically symmetric sector of metric perturbations around an evaporating black hole background geometry. For macroscopic black holes we find that those fluctuations grow and eventually become important when considering sufficiently long periods of time (of the order of the evaporation time), but well before the Planckian regime is reached. In addition, the assumption of a simple correlation between the fluctuations of the energy flux crossing the horizon and far from it, which was made in earlier work on spherically symmetric induced fluctuations, is carefully scrutinized and found to be invalid. Our analysis suggests the existence of an infinite amplitude for the fluctuations when trying to localize the horizon as a three-dimensional hypersurface, as in the classical case, and, as a consequence, a more accurate picture of the horizon as possessing a finite effective width due to quantum fluctuations. This is supported by a systematic analysis of the noise kernel in curved spacetime smeared with different functions under different conditions; the details are collected in the appendixes. This case study shows a pathway for probing quantum metric fluctuations near the horizon and understanding their physical meaning.

Suitable shaping (in particular, flattening and broadening) of the laser beam has recently been proposed as an effective device to reduce internal (mirror) thermal noise in advanced gravitational-wave interferometric detectors. Based on some recently published analytic approximations (valid in the infinite-test-mass limit) for the Brownian and thermoelastic mirror noises in the presence of arbitrary-shaped beams, this paper addresses certain preliminary issues related to the optimal beam-shaping problem. In particular, with specific reference to the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, absolute and realistic lower bounds for the various thermal-noise constituents are obtained and compared with the current status (Gaussian beams) and trends (mesa beams), indicating fairly ample margins for further reduction. In this framework, the effective dimension of the related optimization problem, and its relationship to the critical design parameters are identified, physical-feasibility and model-consistency issues are considered, and possible additional requirements and/or prior information exploitable to drive the subsequent optimization process are highlighted.

The existence of an unparticle sector, weakly coupled to the standard model, would have a profound impact on supernova (SN) physics. Emission of energy into the unparticle sector from the core of SN 1987A would have significantly shortened the observed neutrino burst. The unparticle interaction with nucleons, neutrinos, electrons and muons is constrained to be so weak that it is unlikely to provide any missing-energy signature at colliders. One important exception are models where scale invariance in the hidden sector is broken by the Higgs vacuum expectation value. In this case the SN emission is suppressed by threshold effects.

The ${}^6\mathrm{Li}$ abundance observed in metal-poor halo stars exhibits a plateau similar to that for ${}^7\mathrm{Li}$ suggesting a primordial origin. However, the observed abundance of ${}^6\mathrm{Li}$ is a factor of ${10}^3$ larger and that of ${}^7\mathrm{Li}$ is a factor of 3 lower than the abundances predicted in the standard big bang when the baryon-to-photon ratio is fixed by Wilkinson microwave anisotropy probe. Here we show that both of these abundance anomalies can be explained by the existence of a long-lived massive, negatively charged leptonic particle during nucleosynthesis. Such particles would capture onto the synthesized nuclei thereby reducing the reaction Coulomb barriers and opening new transfer reaction possibilities, and catalyzing a second round of big bang nucleosynthesis. This novel solution to both of the Li problems can be achieved with or without the additional effects of stellar destruction.

Recent findings by imaging atmospheric Cherenkov telescopes indicate a large transparency of the Universe to gamma rays, which can be hardly explained within the current models of extragalactic background light. We show that the observed transparency is naturally produced by an oscillation mechanism—which can occur inside intergalactic magnetic fields—whereby a photon can become a new spin-zero boson with mass $m\ll {10}^{-10}\mathrm{eV}$. Because the latter particle travels unimpeded throughout the Universe, photons can reach the observer even if the distance from the source considerably exceeds their mean free path. We compute the expected flux of gamma rays from blazar 3C279 at different energies. Our predictions can be tested in the near future by the gamma-ray telescopes H.E.S.S., MAGIC, CANGAROO, and VERITAS. Moreover, our result provides an important observational test for models of dark energy wherein quintessence is coupled to the photon through an effective dimension-five operator.

A previous work establishing a connection between a quark model, with relativistic kinematics and a $Y$-confinement plus one gluon exchange, and the $1/N_c$ expansion mass formula is extended to strange baryons. Both methods predict values for the SU(3)-breaking mass terms which are in good agreement with each other. Strange and nonstrange baryons are shown to exhibit Regge trajectories with an equal slope, but with an intercept depending on the strangeness. Both approaches agree on the value of the slope and of the intercept, and on the existence of a single good quantum number labeling the baryons within a given Regge trajectory.