We calculate the Debye and Meissner masses of photons and gluons for a spin-one color superconductor in the polar and color-spin-locked phases as well as for a spin-zero color superconductor in the 2SC and color-flavor-locked phases. A general derivation for photon-gluon mixing is provided in terms of the QCD partition function. We show qualitatively and quantitatively which of the gauge bosons attain a mass via the Anderson-Higgs mechanism. Contrary to the spin-zero phases, both spin-one phases exhibit an electromagnetic Meissner effect.

We compute radiative corrections in five- and six-dimensional field theories, using winding modes in mixed momentum-coordinate space. This method provides a simple way of finding UV divergencies, finite corrections and localized terms when the space is compactified on orbifolds. As an application we compute the finite piece of scalar masses, the logarithmic contributions to the couplings and the effect of localized parallel and perpendicular kinetic terms. We apply it to get a two loop effective potential that can stabilize large extra dimensions.

We construct a supermatrix model whose classical background gives a two-dimensional noncommutative supersphere. Quantum fluctuations around it give the supersymmetric gauge theories on the fuzzy supersphere constructed by Klimčík. This model has a parameter $\beta$ that can tune the masses of the particles in the model and interpolate various supersymmetric gauge theories on the sphere.

Sequences of initial-data sets representing binary black holes in quasi-circular orbits have been used to calculate what may be interpreted as the innermost stable circular orbit. These sequences have been computed with two approaches. One method is based on the traditional conformal-transverse-traceless decomposition and locates quasi-circular orbits from the turning points in an effective potential. The second method uses a conformal-thin-sandwich decomposition and determines quasi-circular orbits by requiring the existence of an approximate helical Killing vector. Although the parameters defining the innermost stable circular orbit obtained from these two methods differ significantly, both approaches yield approximately the same initial data, as the separation of the binary system increases. To help understand this agreement between data sets, we consider the case of initial data representing a single boosted or spinning black hole puncture of the Bowen-York type and show that the conformal-transverse-traceless and conformal-thin-sandwich methods yield identical data at the perturbative level, both satisfying the conditions for the existence of an approximate Killing vector.

To test the strong-gravity regime in Randall-Sundrum braneworlds, we consider black holes bound to a brane. In a previous paper, we studied numerical solutions of localized black holes whose horizon radii are smaller than the AdS curvature radius. In this paper, we improve the numerical method and discuss properties of the six-dimensional (6D) localized black holes whose horizon radii are larger than the AdS curvature radius. At a horizon temperature $\mathcal{T}\approx 1/2\pi \mathcal{l},$ the thermodynamics of the localized black hole undergo a transition with its character changing from a 6D Schwarzschild black hole type to a 6D black string type. The specific heat of the localized black holes is negative, and the entropy is greater than or nearly equal to that of the 6D black strings with the same thermodynamic mass. The large localized black holes show flattened horizon geometries, and the intrinsic curvature of the horizon four-geometry becomes negative near the brane. Our results indicate that the recovery mechanism of lower-dimensional Einstein gravity on the brane works even in the presence of the black holes.

A procedure is considered that upgrades the Lagrangian description of quantum relativistic particles to the Lagrangian of a proper field theory in the case that the Klein-Gordon wave equation is classically interpreted in terms of a relativistic subquantum potential. We apply the resulting field theory to cosmology and show that the relativistic version of Bohm’s subquantum potential which can be associated with a homogeneous and isotropic distribution of particles behaves as though it was a cosmological constant responsible for the current accelerating expansion of the Universe, at least in the limit where the field potential vanishes.

We present a study of charmonia in hot gluonic plasma, for temperatures up to three times the deconfinement transition temperature $T_c.$ $q\overline{q}$ systems with quark masses close to the charm mass and different spin-parity quantum numbers were studied on very fine isotropic lattices. The analysis of temporal correlators, and spectral functions constructed from them, shows that the $J/\psi$ and ${\eta }_c$ survive up to quite high temperatures, with little observable change up to ${1.5T}_c,$ and then gradually weaken and disappear by ${3T}_c.$ For the scalar and axial vector channels, serious modifications are induced by the hot medium already close to $T_c,$ possibly dissociating the mesons by ${1.1T}_c.$

A detailed study of the heavy quark $h=c,b,\dots$ contributions to deeply virtual Compton scattering is performed at both the amplitude and the cross section level, and their phenomenological relevance is discussed. For this purpose I calculate the lowest order off-forward photon-gluon scattering amplitude with a massive quark loop and the corresponding hard scattering coefficients. In a first numerical analysis these fixed order perturbation theory results are compared with the conventional intrinsic “massless” parton approach considering generalized parton distributions for the heavy quarks. The differences between these two prescriptions can be quite significant, especially at small skewedness where the massless approach largely overestimates the deeply virtual Compton scattering cross section.

We analyze polarization effects in the associative photoproduction of pseudoscalar $\left(D_c\right)$ charmed mesons in exclusive processes $\gamma +\overrightarrow{N}{Y}_c+D_c,$ $Y_c={\Lambda }_c^{+},$ ${\Sigma }_c.$ Circularly polarized photons induce nonzero polarization of the $Y_c$ hyperon with x and z components (in the reaction plane) and nonvanishing asymmetries ${\mathcal{A}}_x$ and ${\mathcal{A}}_z$ for polarized nucleon targets. These polarization observables can be predicted in a model-independent way for the exclusive $D_c$-production processes in collinear kinematics. The T-even components of the $Y_c$-polarization and asymmetries for noncollinear kinematics can be calculated in the framework of an effective Lagrangian approach. The depolarization coefficients $D_{\mathrm{ab}},$ characterizing the dependence of the $Y_c$ polarization on the nucleon polarization, are also calculated.

The potential of decays of mesons containing heavy quarks [including B mesons and the ${\rm Y}\mathrm{}\left(1S\right)\mathrm{}]$ for producing final states of matter with unusual quark configurations, such as $\mathrm{qq}\overline{q}\overline{q}$ or $\mathrm{qqqq}\overline{q},$ is investigated. The usefulness of antineutron detection in such searches is stressed.

We present a detailed comparison of a variety of predictions for diffractive light vector meson production with the data collected at the DESY HERA collider. All our calculations are performed within a dipole model framework and make use of different models for the meson light-cone wave function. There are no free parameters in any of the scenarios we consider. Generally we find good agreement with the data using rather simple Gaussian motivated wave functions in conjunction with dipole cross sections which have been fitted to other data.

We recently considered $K_{\mathcal{l}4}$ decays in the framework of chiral perturbation theory based on the effective Lagrangian including mesons, photons, and leptons. There, we published analytic one-loop-level expressions for form factors f and g corresponding to the mixed process, $K^0\to {\pi }^0{\pi }^{-}{\mathcal{l}}^{+}{\nu }_{\mathcal{l}}.$ We propose here a possible splitting between strong and electromagnetic parts allowing analytic (and numerical) evaluation of isospin breaking corrections. The latter are sensitive to the infrared divergence subtraction scheme and are sizable near the ππ production threshold. Our results should be used for the extraction of the P-wave isovector ππ phase shift from the outgoing data of the currently running KTeV experiment at Fermilab.

We analyze the consequences of the observation of exotic pentaquark baryons on the location of the nonexotic baryons belonging to the antidecuplet. We suggest that there must be a new nucleon state at 1650–1690 MeV and a new $\Sigma$ baryon at 1760–1810 MeV.

We present the result of a search for the charmless two-body baryonic decay $B^0\to p\overline{p}$ in a sample of 88 million ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}\to B\overline{B}$ decays collected by the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. We use Cherenkov radiation to identify protons cleanly, and determine the signal yield with a maximum-likelihood fit technique using kinematic and topological information. We find no evidence for a signal and place a 90% confidence-level upper limit of $\mathcal{B}{(B}^0\to p\overline{p})<\mathrm{}2.7\mathrm{}\times {10}^{-7}.$

We consider the production of chargino and charged Higgs boson pairs at future linear colliders for c.m. energies in the one TeV range. Working in the MSSM under the assumption of a “moderately” light SUSY scenario, we compute the leading (double) and next-to-leading (linear) supersymmetric logarithmic terms of the so-called “Sudakov expansion” at one loop. We show that a combined analysis of the slopes of the chargino and of the charged Higgs production cross sections would offer a simple possibility for determining $\tan \beta$ for large $\left(\gtrsim 10\right)$ values and an allowed strip in the ${(M}_2,\mu )$ plane. This could provide a strong consistency test of the considered supersymmetric model.

A prescription is developed for matching general relativistic perturbations across singularities of the type encountered in the ekpyrotic and cyclic scenarios, i.e., a collision between orbifold planes. We show that there exists a gauge in which the evolution of perturbations is locally identical to that in a model space-time (compactified Milne mod $Z_2)$ where the matching of modes across the singularity can be treated using a prescription previously introduced by two of us. Using this approach, we show that long wavelength, scale-invariant, growing-mode perturbations in the incoming state pass through the collision and become scale-invariant growing-mode perturbations in the expanding hot big-bang phase.

We study the out-of-equilibrium evolution of an $O\left(2\right)\mathrm{}$-invariant scalar field in which a conserved charge is stored. We apply a loop expansion of the 2-particle irreducible effective action to 3-loop order. Equations of motion are derived which conserve both total charge and total energy yet allow for the effects of scattering whereby charge and energy can transfer between modes. Working in $1+1$ dimensions we solve the equations of motion numerically for a system knocked out of equilibrium by a sudden temperature quench. We examine the initial stages of the charge and energy redistribution. This provides a basis from which we can understand the formation of Bose-Einstein condensates from first principles.

We consider the coupling of fermions to the three-dimensional noncommutative ${\mathrm{CP}}^{N-1}$ model. In the case of minimal coupling, although the infrared behavior of the gauge sector is improved, there are dangerous (quadratic) infrared divergences in the corrections to the two-point vertex function of the scalar field. However, using superfield techniques we prove that the supersymmetric version of this model with “antisymmetrized” coupling of the Lagrange multiplier field is renormalizable up to the first order in $1/N.$ The auxiliary spinor gauge field acquires a nontrivial (nonlocal) dynamics with generation of Maxwell and Chern-Simons noncommutative terms in the effective action. Up to $1/N$ order all divergences are only logarithmic so that the model is free from nonintegrable infrared singularities.

We show that the algebraic aspects of Lie symmetries and generalized symmetries in nonrelativistic and relativistic quantum mechanics can be preserved in linear lattice theories. The mathematical tool for symmetry preserving discretizations on regular lattices is the umbral calculus.

It has been suggested recently that the microcanonical entropy of a system may be accurately reproduced by including a logarithmic correction to the canonical entropy. In this paper we test this claim both analytically and numerically by considering three simple thermodynamic models whose energy spectrum may be defined in terms of one quantum number only, as in a non-rotating black hole. The first two pertain to collections of noninteracting bosons, with logarithmic and power-law spectra. The last is an area ensemble for a black hole with equi-spaced area spectrum. In this case, the many-body degeneracy factor can be obtained analytically in a closed form. We also show that in this model, the leading term in the entropy is proportional to the horizon area A, and the next term is $\ln A$ with a negative coefficient.