We discuss the scalar cosmological perturbations in a 3-brane world with a 5D bulk. We first show explicitly how the effective perturbed Einstein equations on the brane (involving the Weyl fluid) are encoded into Mukohyama’s master equation. We give the relation between Mukohyama’s master variable and the perturbations of the Weyl fluid; we also discuss the relation between the former and the perturbations of matter and induced metric. The boundary condition for the master variable on the brane is then given in the case of a perfect fluid with adiabatic perturbations on a Randall-Sundrum or Dvali-Gabadadze-Porrati brane. This provides an easy way to solve numerically for the evolution of the perturbations and also should shed light on the various approximations done in the literature to deal with the Weyl degrees of freedom.

We make a comparison between results from numerically generated, quasiequilibrium configurations of compact binary systems of black holes in close orbits, and results from the post-Newtonian (PN) approximation. The post-Newtonian results are accurate through third PN order $[{O(v/c)\mathrm{}}^6$ beyond Newtonian gravity], and include rotational and spin-orbit effects, but are generalized to permit orbits of nonzero eccentricity. Both treatments ignore gravitational radiation reaction. The energy E and angular momentum J of a given configuration are compared between the two methods as a function of the orbital angular frequency $\Omega .$ For small $\Omega ,$ corresponding to orbital separations a factor of two larger than that of the innermost stable orbit, we find that, if the orbit is permitted to be slightly eccentric, with e ranging from $\approx 0.03$ to $\approx 0.05,$ and with the two objects initially located at the orbital apocenter (maximum separation), our PN formulas give much better fits to the numerically generated data than do any circular-orbit PN methods, including various “effective one-body” resummation techniques. We speculate that the approximations made in solving the initial value equations of general relativity numerically may introduce a spurious eccentricity into the orbits.

The high density effective theory formalism is used to calculate the low energy properties of the phonons and gluons in the Larkin-Ovchinnikov-Fulde-Ferrell phase of two-flavor QCD. The effective phonon Lagrangian for the cubic crystal structure, which is favored according to a recent study, depends, at the second order in the derivatives, on three parameters which we calculate in this paper. We also compute for soft momenta the effective Lagrangian for the gluons of the unbroken $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_c$ group, both for a single plane wave structure and for the cube. In both cases the Meissner gluon mass vanishes as in the case of complete isotropy; on the other hand, there is a partial Debye screening due to the existence of blocking regions on the Fermi spheres. For the single plane wave structure the gluon dielectric tensor is nonisotropic, while it is isotropic for the cubic crystal, in spite of the intrinsic anisotropy of the structure.

We explore the consequences for diffractive production, ${\gamma }^{*}\overrightarrow{p}Xp,$ in deep inelastic scattering at low values of $x\cong Q^2{/W}^2\ll 1$ that follow from our recent representation of the total photoabsorption cross section, ${\sigma }_{{\gamma }^{*}p},$ in the generalized vector dominance or color dipole picture that is based on the generic structure of the two-gluon exchange from QCD. Sum rules are derived that relate the transverse and the longitudinal (virtual) photoabsorption cross section to diffractive forward production of $q\overline{q}$ states that carry photon quantum numbers (“elastic diffraction”). Agreement with experiment in the $W^2$ and $Q^2$ dependence is found for $M_X^2{/Q}^2\ll 1,$ where $M_X$ is the mass of the produced system X. An additional component (“inelastic diffraction”), not actively contributing to the forward Compton amplitude, is needed for diffractive production at high values of $M_X.$ Our previous theoretical representation of the total photoabsorption cross section, ${\sigma }_{{\gamma }^{*}p}={\sigma }_{{\gamma }^{*}p}\left(\eta \right),$ in terms of the scaling variable $\eta \equiv {(Q}^2{+m}_0^2)/{\Lambda }^2{(W}^2)$ is extended to include the entire kinematic domain, $x<~0.1$ and all $Q^2$ with $Q^2>~0,$ where scaling in $\eta$ holds experimentally.

The flavor changing decay $\overrightarrow{Z}{d}_I{d}_J$ is investigated with special emphasis on the $b\overline{s}$ final state. Various models for flavor violation are considered: two Higgs doublet models (2HDM’s), supersymmetry (SUSY) with flavor violation in the up- and down-type squark mass matrices and SUSY with flavor violation mediated by R-parity-violating interaction. We find that, within the SUSY scenarios for flavor violation, the branching ratio for the decay $\overrightarrow{Z}b\overline{s}$ can reach ${10}^{-6}$ for large $\tan \beta$ values, while the typical size for this branching ratio in the 2HDM’s considered is about two orders of magnitude smaller at best. Thus, flavor changing SUSY signatures in radiative Z decays such as $\overrightarrow{Z}b\overline{s}$ may be accessible to future “$Z$ factories” such as a giga-$Z$ version of the DESY TESLA design.

We discuss resummation strategies for free energy in quantum field theories at nonzero temperatures T. We point out that resummations should be performed for the short- and long-distance parts separately in order to avoid spurious interference effects and double counting. We then discuss and perform Padé resummations of these two parts for QCD at high T. The resummed results are almost invariant under variation of the renormalization and factorization scales. We perform the analysis also in the case of the massless scalar ${\phi }^4$ theory.

We devote effort to studying some nonlinear actions, characteristic of $\mathcal{W}$ theories, in the framework of the soldering formalism. We disclose interesting new results concerning the embedding of the original chiral $\mathcal{W}$ particles in different metrical spaces in the final soldered action; i.e., the metric is modified by the soldering interference process. The results are presented in a weak field approximation for the ${\mathcal{W}}_N$ case when $N>~3$ and also in an exact way for ${\mathcal{W}}_2.$ We promote a generalization of the interference phenomenon to ${\mathcal{W}}_N$ theories of different chiralities and show that the geometrical features introduced can yield a new understanding of the interference formalism in quantum field theories.

In order to investigate the effect of inhomogeneities on the volume expansion of the universe, we study a modified Swiss-cheese universe model. Since this model is an exact solution of Einstein’s equations, we can get insight into the nonlinear dynamics of an inhomogeneous universe from it. We find that inhomogeneities make the volume expansion slower than that of the background Einstein–de Sitter universe when they can be regarded as small fluctuations in the background universe. This result is consistent with the previous studies based on the second order perturbation analysis. On the other hand, if the inhomogeneities cannot be treated as small perturbations, the volume expansion of the universe depends on the type of fluctuations. Although the volume expansion rate approaches the background value asymptotically, the volume itself can be finally arbitrarily smaller than the background one and can be larger than that of the background, but there is an upper bound on it.

We study the scattering of fermions off a finite width kink wall during the electroweak phase transition in the presence of a background hypermagnetic field. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when the fermions move from the symmetric to the broken symmetry phase. We show that the chiral nature of the fermion coupling with the background field in the symmetric phase generates an axial asymmetry in the scattering processes. We discuss the possible implications of such axial charge segregation for baryon number generation.

Data obtained during five months of 2001 with the gravitational wave (GW) detectors EXPLORER and NAUTILUS, operating with a bandwidth of a few Hz at frequencies near 900 Hz, were studied in correlation with the gamma ray burst data (GRB) obtained with the BeppoSAX satellite. During this period BeppoSAX was the only GRB satellite in operation, while EXPLORER and NAUTILUS were the only GW detectors in operation. No correlation between the GW data and the GRB bursts was found. The analysis, performed over 47 GRB’s, excludes the presence of signals of amplitude $h>~6.5\times {10}^{-19},$ with 95% probability, if we allow a time delay between GW bursts and GRB within $\pm 5\mathrm{s},$ and $h>~1.2\times {10}^{-18},$ if the time delay is within $\pm 400\mathrm{s}.$ The result is also provided in the form of scaled likelihood for unbiased interpretation and easier use for further analysis.

The aim of this work is to study lepton flavor violation in a newly proposed seesaw model of neutrino mass and to see whether it could explain the Liquid Scintillation Neutrino Detector excess. The motivation of this seesaw model is that there is no new physics beyond the TeV scale. By studying $\overrightarrow{\mu }3e$ in this model, it is shown that the upper bound on the branching ratio requires a Higgs boson mass $m_h$ of a new scalar doublet with the lepton number $L=-1$ needed in this model to be about 9 TeV. The predicted branching ratio for $\overrightarrow{\mu }e{\nu }_l{\overline{\nu }}_l$ is too small to explain the LSND.

We performed dynamical simulations with HYP smeared staggered fermions using the recently proposed partial-global stochastic Metropolis algorithm with fermion matrix reduction and determinant breakup improvements. In this paper we discuss our choice of the action parameters and study the autocorrelation time both with four and two fermionic flavors at different quark mass values on approximately $10{\mathrm{fm}}^4$ lattices. We find that the update is especially efficient with two flavors making simulations on larger volumes feasible.

In this paper, we investigate the global monopole in asymptotically dS or AdS spacetime and find that the mass of the monopole in the asymptotically dS spacetime can be positive if the cosmological constant is greater than a critical value. This shows that the gravitational field of the global monopole can be attractive or repulsive depending on the value of the cosmological constant.

We investigate the ABJ anomaly in the framework of an effective field theory for a 3-brane scenario and show that the contribution from induced gravity on the brane depends on both the topological structure of the bulk space-time and the embedding of the brane in the bulk. This fact implies the existence of a nontrivial vacuum structure of bulk quantum gravity. Furthermore, we argue that this axial gravitational anomaly may not necessarily be canceled by choosing the matter content on the brane since it could be considered as a possible effect from bulk quantum gravity.

We calculate the complete one-loop effective potential for $\mathrm{SU}\left(2\right)\mathrm{}$ gauge bosons at temperature T as a function of two variables: $\phi ,$ the angle associated with a nontrivial Polyakov loop, and H, a constant background chromomagnetic field. These two variables are indicators for confinement and scale symmetry breaking, respectively. Using techniques broadly applicable to finite temperature field theories, we develop both low and high temperature expansions. At low temperatures, the real part of the effective potential $V_R$ indicates a rich phase structure, with a discontinuous alternation between confined $(\phi =\pi )$ and deconfined phases $(\phi =0).\mathrm{}$ The background field H moves slowly upward from its zero temperature value as T increases, in such a way that $\sqrt{\mathrm{gH}}/\pi T$ is approximately an integer. This behavior stops at $T_c=0.722\mathrm{}\left(1\right)\mathrm{}{\mu }_0,$ where ${\mu }_0$ is a zero-temperature renormalization group invariant scale; beyond this temperature, the deconfined phase is always preferred. At high temperatures, where perturbation theory should be reliable as a consequence of asymptotic freedom, the deconfined phase $(\phi =0)$ is always preferred, and $\sqrt{\mathrm{gH}}$ is of order $g^2\mathrm{}\left(T\right)T.\mathrm{}$ The imaginary part of the effective potential $V_I,$ which originates in a tachyonic mode associated with the lowest Landau level, is nonzero at the global minimum of $V_R$ for all temperatures. A nonperturbative magnetic screening mass of the form $M_m{=cg}^2\mathrm{}\left(T\right)T$ with a sufficiently large coefficient c removes this instability at high temperature, leading to a stable high-temperature phase with $\phi =0\mathrm{}$ and $H=0,$ characteristic of a weakly interacting gas of gauge particles. The value of $M_m$ obtained is comparable with lattice estimates.

We generalize a result of Vollick constraining the possible behavior of the renormalized expected stress-energy tensor of a free massless scalar field in two dimensional spacetimes that are globally conformal to Minkowski spacetime. Vollick derived a lower bound for the energy density measured by a static observer in a static spacetime, averaged with respect to the observers proper time by integrating against a smearing function. Here we extend the result to arbitrary curves in non-static spacetimes. The proof, like Vollick’s proof, is based on conformal transformations and the use of our earlier optimal bound in flat Minkowski spacetime. The existence of such a quantum inequality was previously established by Fewster.

The generic crease set of an event horizon possesses anisotropic structure although most black holes are dynamically stable. This fact suggests that a generic almost spherical black hole has a very crumpled crease set on a microscopic scale although the crease set is similar to a pointwise crease set on a macroscopic scale. In the present article, we count the number of such microstates of an almost spherical black hole by analogy with an elastic chain polymer. This estimation of black hole entropy reproduces the well-known Bekenstein-Hawking entropy of a Schwarzschild black hole.

Recent studies of homogeneous anisotropic universe models in the brane world scenario show that the cosmological singularity in this context is isotropic. It has therefore been suggested that this may be a generic feature of singularities on the brane, even in the inhomogeneous case. Using a perturbative approach, we show that this is not the case. As in the GR case, the presence of decaying modes in the perturbations signal the instability (in the past) of the isotropic singularity. The brane universe is therefore not born with isotropy built in: as in standard cosmology, the observed large-scale isotropy and homogeneity remains to be explained.

The result of Burnett and Kroll (BK) states that for radiative decays, the interference of $O\left({\omega }^{-1}\right)$ in the photon energy $\omega$ vanishes after the sum over polarizations of the involved particles. Using radiative decays of vector mesons, we show that if the vector meson is polarized, the $O\left({\omega }^{-1}\right)$ terms are null only for the canonical value of the magnetic dipole moment of the vector meson, namely, $\mathbf{g}=2\mathrm{}$ in Bohr magneton units. A subtle cancellation of all $O\left({\omega }^{-1}\right)$ terms happens when summing over all polarizations to recover the Burnett-Kroll result. We also show the source of these terms and the corresponding cancellation for the unpolarized case and exhibit a global structure that can make them individually vanish in a particular kinematical region.

We calculate the one-loop effective action of the $\mathrm{SU}\left(2\right)\mathrm{}$ Yang-Mills theory for center-vortex configurations, both in 3D and 4D. We find that in both cases there are minima of the effective action, corresponding to vortices of the transverse size approximately ${4/g}_3^2$ and $1.7/{\Lambda }_{\mathrm{MS}¯},$ respectively. The values of the effective actions at the minima are negative, suggesting that the Euclidian vacuum may be unstable with respect to the creation of vortices.