Using the domain-wall formulation of lattice fermions, we have computed the one-loop renormalization factors of one-link operators which measure the first nontrivial moment of the unpolarized, polarized, and transversity structure functions, in the flavor nonsinglet sector. The knowledge of these factors is necessary in order to extract physical numbers from domain-wall Monte Carlo simulations of parton distributions. We have automated the perturbative calculations by developing suitable FORM codes. The results show that in many instances the total renormalization factors are almost equal to one, and that hence the corresponding operators are, for the appropriate values of the Dirac mass $M$ and the coupling $g_0$, practically unrenormalized.

The irreducible representations (IRs) of the double cover of the Euclidean group with parity in three dimensions are subduced to the corresponding cubic space group. The reduction of these representations gives the mapping of continuum angular momentum states to the lattice in the case of nonzero linear momentum. The continuous states correspond to lattice states with the same momentum and continuum rotational quantum numbers decompose into those of the IRs of the little group of the momentum vector on the lattice. The inverse mapping indicates degeneracies that will appear between levels of different lattice IRs in the continuum limit, recovering the continuum angular momentum multiplets. An example of this inverse mapping is given for the case of the “moving” isotropic harmonic oscillator.

We study the proposal that mass-varying neutrinos could provide an explanation for the LSND signal for ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$ oscillations. We first point out that all positive oscillation signals occur in matter and that three active mass-varying neutrinos are insufficient to describe all existing neutrino data including LSND. We then examine the possibility that a model with four mass-varying neutrinos (three active and one sterile) can explain the LSND effect and remain consistent with all other neutrino data. We find that such models with a $3+1$ mass structure in the neutrino sector may explain the LSND data and a null MiniBooNE result for $0.10\lesssim {sin}^{2}2{\theta }_x\lesssim 0.30$. Predictions of the model include a null result at Double-CHOOZ, but positive signals for underground reactor experiments and for ${\nu }_{\mu }\to {\nu }_e$ oscillations in long-baseline experiments.

We discuss the local Lorentz invariance in the context of $N=1$ supergravity and show that a previous attempt to find explicit solutions to the Lorentz constraint in terms of $\gamma$-matrices is not correct. We improve that solution by using a different representation of the Lorentz operators in terms of the generators of the rotation group, and show its compatibility with the matrix representation of the fermionic field. We find the most general wave functional that satisfies the Lorentz constraint in this representation.

In string-inspired effective actions, representing the low-energy bulk dynamics of brane/string theories, the higher-curvature ghost-free Gauss-Bonnet combination is obtained by local field redefinitions which leave the (perturbative) string amplitudes invariant. We show that such redefinitions lead to surface terms which induce curvature on the brane world boundary of the bulk spacetime.

Magnetic plasma instabilities appear to play an important role in the early stages of quark-gluon plasma equilibration in the high-energy (weak coupling) limit. Numerical studies of the growth of such instabilities from small seed fluctuations have found initial exponential growth in their energy, followed by linear growth once the associated color magnetic fields become so large that their non-Abelian interactions are nonperturbative. In this paper, we use simulations to determine the nature of this linear energy growth. We find that the long-wavelength modes associated with the instability have ceased to grow, but that they cascade energy towards the ultraviolet in the form of plasmon excitations of ever increasing energy. We find a quasi-steady-state power-law distribution $f_k\propto k^{-\nu }$ for this cascade, with spectral index $\nu \simeq 2$.

We consider the perturbations of the massive vector field around Schwarzschild, Schwarzschild-de Sitter, and Schwarzschild-anti-de Sitter black holes. Equations for a spherically symmetric massive vector perturbation can be reduced to a single wavelike equation. We have proved the stability against these perturbations and investigated the quasinormal spectrum. The quasinormal behavior for Schwarzschild black hole is quite unexpected: the fundamental mode and higher overtones show totally different dependence on the mass of the field $m$: as $m$ is increasing, the damping rate of the fundamental mode is decreasing, what results in appearing of the infinitely long living modes, while, on the contrary, damping rate of all higher overtones are increasing, and their real oscillation frequencies gradually go to tiny values. Thereby, for all higher overtones, almost nonoscillatory, damping modes can exist. In the limit of asymptotically high damping, $\mathrm{Re}\omega$ goes to $ln3/(8\pi M)$, while imaginary part shows equidistant behavior with spacing $\mathrm{Im}{\omega }_{n+1}-\mathrm{Im}{\omega }_n=1/4M$. In addition, we have found quasinormal spectrum of massive vector field for Schwarzschild-anti-de Sitter black hole.

The emission spectrum from a simple accretion disk model around a compact object is compared for the cases of a black hole (BH) and a boson star (BS) playing the role of the central object. It was found in the past that such a spectrum presents a hardening at high frequencies; however, here it is shown that the self-interaction and compactness of the BS have the effect of softening the spectrum; the less compact the star is, the softer the emission spectrum at high frequencies. Because the mass of the boson fixes the mass of the star and the self-interaction the compactness of the star, we find that, for certain values of the BS parameters, it is possible to produce similar spectra to those generated when the central object is a BH. This result presents two important implications: (i) Using this simple accretion model, a BS can supplant a BH in the role of compact object accreting matter, and (ii) within the assumptions of the present accretion disk model, we do not find a prediction that could help distinguish a BH from a BS with appropriate parameters of mass and self-interaction.

In the context of topcolor-assisted technicolor (TC2) models, we study the production of the top-pions ${\pi }_t^{0,\pm }$ with single top quark via the processes $p\overline{p}\to t{\pi }_t^0+X$ and $p\overline{p}\to t{\pi }_t^{\pm }+X$, and discuss the possibility of detecting these new particles at Tevatron and LHC. We find that it is very difficult to observe the signals of these particles via these processes at Tevatron, while the neutral and charged top-pions ${\pi }_t^0$ and ${\pi }_t^{\pm }$ can be detecting via considering the same sign top pair $tt\overline{c}$ event and the $tt\overline{b}$ (or $t\overline{t}b$) event at LHC, respectively.

In a previous analysis presented in Phys. Rev. D 71, 075009 (2005), electroweak constraints were given on arbitrary linear combinations of a set of dimension-6 operators. Flavor universality and thus $U(3{)}^5$ flavor symmetry were assumed for the operators. In this article, we expand the analysis to account for the flavor-dependent theories that distinguish the third generation of fermions from the light two generations. We still assume flavor universality for the light two generations to avoid large FCNCs. Consequently, the $U(3{)}^5$ flavor symmetry is relaxed to $[U(2)\times U(1){]}^5$, and therefore more operators are added. We calculate the corrections to electroweak precision observables, assuming arbitrary coefficients for the operators. The corrections are combined with the standard model predictions and the experimental data to obtain the ${\chi }^2$ distribution as a function of the operator coefficients. We apply our result to constrain two flavor-dependent extensions of the standard model: the simplest little Higgs model and a model with an $SU(2)\times SU(2)\times U(1)$ gauge group.

We apply the topology conserving gauge action proposed by Lüscher to the four-dimensional lattice QCD simulation in the quenched approximation. With this gauge action the topological charge is stabilized along the hybrid Monte Carlo updates compared to the standard Wilson gauge action. The quark potential and renormalized coupling constant are in good agreement with the results obtained with the Wilson gauge action. We also investigate the low-lying eigenvalue distribution of the Hermitian Wilson-Dirac operator, which is relevant for the construction of the overlap-Dirac operator.

We study inclusive heavy quarkonium production with definite polarizations in polarized proton-proton collisions using the nonrelativistic QCD color-octet mechanism. We present results for rapidity distributions of cross sections and spin asymmetries for the production of $J/\psi$ and ${\psi }^{\prime }$ with specific polarizations in polarized p-p collisions at $\sqrt{s}=200$ GeV and 500 GeV at the RHIC within the PHENIX detector acceptance range.

We consider various forms of the mass term that can be used in the Skyrme model and their implications on the properties of baryonic states. It is shown that modifications of the mass term, without changing the asymptotic behavior of the profile function at large $r$, can considerably alter the mass term contribution to the classical mass of the soliton. We find that, for some choices of this mass term, multibaryon configurations can be classically bound at large baryon numbers. It is pointed out that some restrictions on the possible form of the mass term can follow from studies of multimeson interactions.

We investigate two points related to existing treatments of isospin-breaking corrections to the conserved vector current relation between $\sigma [e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}]$ and $d\Gamma [{\tau }^{-}\to {\nu }_{\tau }{\pi }^{-}{\pi }^0]/ds$. Implications for the value of the hadronic contribution to $a_{\mu }=(g-2{)}_{\mu }/2$ based on those analyses incorporating hadronic $\tau$ decay data are also considered. We conclude that the uncertainty on the isospin-breaking correction which must be applied to the $\tau$ decay data should be significantly increased, and that the central value of the $\rho \mathrm{\text{−}}\omega$ mixing contribution to this correction may be significantly smaller than indicated by the present standard determination. Such a shift would contribute to reducing the discrepancy between the $\tau$- and electroproduction-based determinations of the leading order hadronic contribution to $a_{\mu }$.

We derive the Boltzmann equation for scalar fields using the Schwinger-Keldysh formalism. The focus lies on the derivation of the collision term. We show that the relevant self-energy diagrams have a factorization property. The collision term assumes the Boltzmann-like form of scattering probability times statistical factors for those self-energy diagrams which correspond to tree level scattering processes. Our proof covers scattering processes with any number of external particles, which come from self-energy diagrams with any number of loops.

The successful prediction of light element abundances from big bang nucleosynthesis (BBN) has been a pillar of the standard model of cosmology. Because many of the relevant reaction rates are sensitive to the values of fundamental constants, such as the fine structure constant and the strong coupling constant, BBN is a useful tool to probe and to put constraints on possible cosmological variations of these constants, which arise naturally from many versions of extra-dimensional theories. In this paper, we study the dependences of fundamental constants on the radion field of the universal extra-dimension model, and calculate the effects of such varying constants on BBN. We also discuss the possibility that the discrepancy between BBN and the Wilkinson Microwave Anisotropy Probe (WMAP) data on the baryon-to-photon ratio can be reduced if the volume of the extra dimensions was slightly larger—by $\mathcal{O}({10}^{-3})$—at the BBN era compared to its present value, which would result in smaller gauge couplings at BBN by the same factor.

We present a numerical model of a collapsing radiating sphere, whose boundary surface undergoes bouncing due to a decreasing of its inertial mass density (and, as expected from the equivalence principle, also of the “gravitational” force term) produced by the “inertial” term of the transport equation. This model exhibits for the first time the consequences of such an effect, and shows that under physically reasonable conditions this decreasing of the gravitational term in the dynamic equation may be large enough as to revert the collapse and produce a bouncing of the boundary surface of the sphere.

The contribution of virtual $s$-channel Kaluza-Klein (KK) gravitons to high energy scattering of the standard model (SM) fields in the Randall-Sundrum (RS) model with two branes is studied. The small curvature option of the RS model is considered in which the KK gravitons are narrow low-mass spin-2 resonances. The analytical tree-level expression for a process-independent gravity part of the scattering amplitude is derived, accounting for nonzero graviton widths. It is shown that one cannot get a correct result, if a series of graviton resonances is replaced by a continuous mass distribution, in spite of the small graviton mass splitting. Such a replacement appeared to be justified only in the trans-Planckian energy region.

We consider globally regular and black holes solutions for the Einstein-Yang-Mills system with negative cosmological constant in $d$-spacetime dimensions. We find that the ADM mass of the spherically symmetric solutions generically diverges for $d>4$. Solutions with finite mass are found by considering corrections to the YM Lagrangian consisting in higher order terms of the Yang–Mills hierarchy. Such systems can occur in the low energy effective action of string theory. A discussion of the main properties of the solutions and the differences with respect to the four dimensional case is presented. The mass of these configurations is computed by using a counterterm method.

The mechanism of thermal leptogenesis is investigated in the high-energy regime of braneworld cosmology. Within the simplest seesaw framework with hierarchical heavy Majorana neutrinos, we study the implications of the modified Friedmann equation on the realization of this mechanism. In contrast with the usual leptogenesis scenario of standard cosmology, where low-energy neutrino data favors a mildly strong washout regime, we find that leptogenesis in the braneworld regime is successfully realized in a weak washout regime. Furthermore, a quasidegenerate light neutrino mass spectrum is found to be compatible with this scenario. For an initially vanishing heavy Majorana neutrino abundance, thermal leptogenesis in the brane requires the decaying heavy Majorana neutrino mass to be $M_1\gtrsim {10}^{10}$ GeV and the fundamental five-dimensional gravity scale ${10}^{12}\lesssim M_5\lesssim {10}^{16}$ GeV, which corresponds to a transition from brane to standard cosmology at temperatures ${10}^8\lesssim T_t\lesssim {10}^{14}$ GeV.