We study the dynamical localization of a massless gauge field on a lower-dimensional surface (2-brane). In flat space, the necessary and sufficient condition for this phenomenon is the existence of confinement in the bulk. The resulting configuration is equivalent to a dual Josephson junction. This duality leads to an interesting puzzle, as it implies that a localized massless theory, even in the Abelian case, must become confining at exponentially large distances. Through the use of topological arguments we clarify the physics behind this large-distance confinement and identify the instantons of the brane world-volume theory that are responsible for its appearance. We show that they correspond to the (condensed) bulk magnetic charges (monopoles), that occasionally tunnel through the brane and induce weak confinement of the brane theory. We consider the possible generalization of this effect to higher dimensions and discuss phenomenological bounds on the confinement of electric charges at exponentially large distances within our Universe.

We consider vector and axial-vector mesons in the framework of a gauged linear sigma model with chiral $U(N_f{)}_R\times U(N_f{)}_L$ symmetry. For $N_f=2$, we investigate the behavior of the chiral condensate and the meson masses as a function of temperature by solving a system of coupled Dyson-Schwinger equations derived via the 2PI formalism in double-bubble approximation. We find that the inclusion of vector and axial-vector mesons tends to sharpen the chiral transition. Within our approximation scheme, the mass of the $\rho$ meson increases by about 100 MeV towards the chiral transition.

Bonazzola, Gourgoulhon, Grandclément, and Novak [Phys. Rev. D 70, 104007 (2004)] proposed a new formulation for $3+1$ numerical relativity. Einstein equations result, according to that formalism, in a coupled elliptic-hyperbolic system. We have carried out a preliminary analysis of the mathematical structure of that system, in particular, focusing on the equations governing the evolution for the deviation of a conformal metric from a flat fiducial one. The choice of a Dirac gauge for the spatial coordinates guarantees the mathematical characterization of that system as a (strongly) hyperbolic system of conservation laws. In the presence of boundaries, this characterization also depends on the boundary conditions for the shift vector in the elliptic subsystem. This interplay between the hyperbolic and elliptic parts of the complete evolution system is used to assess the prescription of inner boundary conditions for the hyperbolic part when using an excision approach to black hole space-time evolutions.

We explore models of intersecting brane worlds with induced gravity terms on codimension-one branes and on their intersection. Maximally symmetric solutions for the branes and the intersection are found. We find new self-accelerating solutions. In a 6D spacetime, the solutions realize the seesaw modification of gravity where the UV scale of the modification to 4D gravity is determined by 6D Planck scale given by $M_6\sim {10}^{-3}\mathrm{eV}$ and the IR scale of the modification is determined by $M_6^2/M_4\sim H_0\sim {10}^{-42}\mathrm{GeV}$, where $H_0$ is the present-day Hubble scale. We find that it is increasingly difficult to construct phenomenologically viable models in higher-dimensional spacetime due to the necessity to have the lower value for the fundamental Planck scale to realize the late time acceleration. It is found that the system also admits self-tuning solutions where the tension at the intersection does not change the geometry of the intersection. The induced gravity terms can avoid the necessity to compactify the extra dimensions. Finally, we discuss the possibility to have ordinary matter at the intersection, without introducing any regularization, using the induced gravity terms.

A maximally rotating Kerr black hole is said to be extremal. In this paper we introduce the corresponding restrictions for isolated and dynamical horizons. These reduce to the standard notions for Kerr but in general do not require the horizon to be either stationary or rotationally symmetric. We consider physical implications and applications of these results. In particular we introduce a parameter $e$ which characterizes how close a horizon is to extremality and should be calculable in numerical simulations.

In the space of thermodynamic equilibrium states we introduce a Legendre invariant metric which contains all the information about the thermodynamics of black holes. The curvature of this thermodynamic metric becomes singular at those points where, according to the analysis of the heat capacities, phase transitions occur. This result is valid for the Kerr-Newman black hole and all its special cases and, therefore, provides a unified description of black hole phase transitions in terms of curvature singularities.

Big bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of big bang nucleosynthesis, to place bounds on these corrections and especially the patch size of discrete quantum gravity states.

The metric around straight arbitrarily oriented cosmic strings forming a stationary junction is obtained at the linearized level. It is shown that the geometry is flat. The sum rules for lensing by this configuration and the anisotropies of the cosmic microwave background are obtained.

Cosmic microwave background (CMB) polarization provides a unique window into cosmological inflation; the amplitude of the $B$-mode polarization from last scattering is uniquely sensitive to the energetics of inflation. However, numerous systematic effects arising from optical imperfections can contaminate the observed $B$-mode power spectrum. In particular, systematic effects due to the coupling of the underlying temperature and polarization fields with elliptical or otherwise asymmetric beams yield spurious systematic signals. This paper presents a nonperturbative analytic calculation of some of these signals. We show that results previously derived in real space can be generalized, formally, by including infinitely many higher-order corrections to the leading order effects. These corrections can be summed and represented as analytic functions when a fully Fourier-space approach is adopted from the outset. The formalism and results presented in this paper were created to determine the susceptibility of CMB polarization probes of the primary gravitational wave signal but can be easily extended to the analysis of gravitational lensing of the CMB.

Pure hadronic compact stars, above a threshold value of their gravitational mass (central pressure), are metastable to the conversion to quark stars (hybrid or strange stars). In this paper, we present a systematic study of the metastability of pure hadronic compact stars using different relativistic models for the equation of state. In particular, we compare results for the quark-meson coupling model with those for the Glendenning-Moszkowski parametrization of the nonlinear Walecka model. For the quark-meson coupling model, we find large values ($M_{\mathrm{cr}}=1.6–1.9M_{\odot }$) for the critical mass of the hadronic star sequence and we find that the formation of a quark star is only possible with a soft quark matter equation of state. For the Glendenning-Moszkowski parametrization of the nonlinear Walecka model, we explore the effect of different hyperon couplings on the critical mass and on the stellar conversion energy. We find that increasing the value of the hyperon coupling constants shifts the bulk transition point for quark deconfinement to higher densities, increases the stellar metastability threshold mass and the value of the critical mass, and thus makes the formation of quark stars less likely. For the largest values of the hyperon couplings we find a critical mass which may be as high as $1.9–2.1M_{\odot }$. These stellar configurations, which contain a large central hyperon fraction ($f_{Y,\mathrm{cr}}\sim 30\%$), would be able to describe highly massive compact stars, such as the one associated with the millisecond pulsar PSR $\mathrm{B}1516+02\mathrm{B}$ with a mass $M={1.94}_{-0.19}^{+0.17}{M}_{\odot }$.

We have simulated more than ${10}^5$ extensive air showers (EAS) by CORSIKA code, with a proton as the primary particle. The range of energy for primary particles was selected from 50 TeV to 5 PeV, with differential flux given by $dN/dE\propto E^{-2.7}$. Using the secondary charged particles produced of these EASs, we obtained the function $d{N}_{\mathrm{sp}}(\theta ,X)/d\theta$, where $N_{\mathrm{sp}}(\theta ,X)$ is the number of secondary charged particles in EASs as a function of atmosphere depth, $X$, and zenith angle, $\theta$. A $\sin \theta {cos}^{n(X)}\theta$ distribution was obtained for zenith angle distribution of the number of secondary charged particles, where power index, $n(X)$, is a function of atmosphere depth, $X$. We obtained $n(X)=3.02+0.003X\ln X-8.28\times {10}^{-9}{X}^3-1.35\ln X$. We have compared our results with the experimental data of various observatories.

We propose a simple model of gauge mediation where supersymmetry is broken by a strong dynamics at $O(100)\mathrm{TeV}$.

We study the free energy of static three quark systems in singlet, octet, decuplet, and average color channels in the quenched approximation and in 2-flavor QCD at finite temperature. We show that in the high temperature phase singlet and decuplet free energies of three quark systems are well described by the sum of the free energies of three diquark systems plus self-energy contributions of the three quarks. In the confining low temperature phase we find evidence for a Y-shaped flux tube in SU(3) pure gauge theory, which is less evident in 2-flavor QCD due to the onset of string breaking. We also compare the short distance behavior of octet and decuplet free energies to the free energies of single static quarks in the corresponding color representations.

In order to explain the observed unusually large dipion transition rates of ${\rm Y}(10870)$, the scalar resonance contributions in the rescattering model to the dipion transitions of ${\rm Y}(4S)$ and ${\rm Y}(5S)$ are studied. Since the imaginary part of the rescattering amplitude is expected to be dominant, the large ratios of the transition rates of ${\rm Y}(10870)$, which is identified with ${\rm Y}(5S)$, to that of ${\rm Y}(4S)$ can be understood as mainly coming from the difference between the $p$ values in their decays into open bottom channels, and the ratios are estimated numerically to be about 200–600 with reasonable choices of parameters. The absolute and relative rates of ${\rm Y}(5S)\to {\rm Y}(1S,2S,3S){\pi }^{+}{\pi }^{-}$ and ${\rm Y}(5S)\to {\rm Y}(1S)K^{+}{K}^{-}$ are roughly consistent with data. We emphasize that the dipion transitions observed for some of the newly discovered $Y$ states associated with charmonia may have similar features to the dipion transitions of ${\rm Y}(5S)$. Measurements on the dipion transitions of ${\rm Y}(6S)$ could provide further tests for this mechanism.

Recent measurements for $F_2(x,Q^2)$ have been analyzed in terms of the “dynamical” and “standard” parton model approach at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of perturbative QCD. Having fixed the relevant NLO and NNLO parton distributions, we present the implications and predictions for the longitudinal structure function $F_L(x,Q^2)$. It is shown that the previously noted extreme perturbative NNLO/NLO instability of $F_L(x,Q^2)$ is an artifact of the commonly utilized “standard” gluon distributions. In particular it is demonstrated that using the appropriate—dynamically generated—parton distributions at NLO and NNLO, $F_L(x,Q^2)$ turns out to be perturbatively rather stable already for $Q^2\ge \mathcal{O}(2–3{\mathrm{GeV}}^2)$.

In view of the recent experimental developments in the $\eta \to {\pi }^0\gamma \gamma$ decay, and the fact that the Particle Data Group in the online edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of E. Oset, J. R. Pelaez, and L. Roca [Phys. Rev. D 67, 073013 (2003)], a reevaluation of the decay width of the $\eta$ in this channel has been done, reducing its uncertainty by almost a factor of 2. The new input of the Particle Data Group is used, and invariant mass distributions and total widths are compared with the most recent results from the AGS and MAMI experiments, and preliminary ones of KLOE. The agreement of the theory with the AGS and MAMI data is very good, both for the total rates and for the invariant mass distributions of the two photons.

We consider that the preinflation era is radiation dominated, transiting smoothly to the inflationary era. We work out in detail the dynamics of inflaton fluctuations across the phase transition and the proper choices of initial vacuum states. It is found that this phase transition can suppress long-wavelength quantum fluctuations of inflaton. This may attribute to the large-scale CMB anisotropy a lower power than predicted in the standard $\Lambda \mathrm{CDM}$ model. In constraining this transitional effect by WMAP anisotropy data, we use the WMAP best-fit scale-invariant $\Lambda \mathrm{CDM}$ model with the density power spectrum replaced by the one found in this work. We find that the transition occurs at least about 10 e-folds before the comoving scales comparable to the size of our present horizon cross the Hubble radius during inflation.

Based on recent developments by the authors a next-to-leading order spin(1)-spin(2) Hamiltonian is derived for the first time. The result is obtained within the canonical formalism of Arnowitt, Deser, and Misner (ADM) utilizing their generalized isotropic coordinates. A comparison with other methods is given.