We present an update of neutral Higgs boson decays into bottom quark pairs in the minimal supersymmetric extension of the standard model. In particular the resummation of potentially large higher-order corrections due to the soft supersymmetry (SUSY) breaking parameters $A_b$ and $\mu$ is extended. The remaining theoretical uncertainties due to unknown higher-order SUSY-QCD corrections are analyzed quantitatively.

The twist-2 heavy flavor contributions to the polarized structure function $g_2{(x,Q}^2)$ are calculated in the covariant parton. We show that this part of $g_2{(x,Q}^2)$ is related to the heavy flavor contribution to $g_1{(x,Q}^2)$ by the Wandzura-Wilczek relation, neglecting power corrections, to all orders in the strong coupling constant. Numerical results are presented.

We discuss the compactification of type IIB supergravity with fluxes to generate a potential for the moduli. In particular we resolve an apparent conflict with the no-go theorem for de Sitter space. It is shown that a positive potential for certain moduli is possible in situations where the volume modulus has no critical point. We also point out that the derivation of the potential is strictly valid only for a trivial warp factor. To go beyond that seems to require the inclusion of all the Kaluza-Klein excitations. We end with a discussion of the stabilization of the volume modulus.

A class of exactly solvable models of domain walls is worked out in $D=4\mathrm{}\mathcal{N}=1\mathrm{}$ supergravity. We develop a method to embed globally supersymmetric theories with exact BPS domain wall solutions into supergravity, by introducing a gravitationally deformed superpotential. The gravitational deformation is natural in the spirit of maintaining the Kähler invariance. The solutions of the warp factor and the Killing spinor are also obtained. We find that three distinct behaviors of warp factors arise depending on the value of a constant term in the superpotential: exponentially decreasing in both sides of the wall, flat in one side and decreasing in the other, and increasing in one side and decreasing in the other. Only the first possibility gives the localized massless graviton zero mode. Models with multiwalls and models with runaway vacua are also discussed.

In this paper we explore the impact of an era—right after reheating—dominated by mini black holes and radiation on the spectrum of relic gravitational waves. This era may lower the spectrum by several orders of magnitude.

In the standard hot big bang model, the expansion of the early Universe is given by the Friedmann equation with an energy density dominated by relativistic particles. Since in a variety of models this equation is altered, we introduce modifications in the Friedmann equation and show that we can constrain them using big bang nucleosynthesis data. When there is no neutrino-antineutrino asymmetry these modifications are tightly bound but in the presence of an asymmetry the bounds become much looser. As an illustration, we apply our results to a model where the second and third families couple to gravity differently than the first family (nonuniversal gravity).

We investigate five-dimensional Einstein spaces in warped geometries from the point of view of the four-dimensional physically relevant Robertson-Walker-Friedman cosmological metric and the Schwarzschild metric. We show that a four-dimensional cosmology with a closed spacelike section and a cosmological constant can be embedded into five-dimensional flat space-time.

We study the behavior of cosmic string networks in contracting universes, and discuss some of their possible consequences. We note that there is a fundamental time asymmetry between defect network evolution for an expanding universe and a contracting universe. A string network with negligible loop production and small-scale structure will asymptotically behave during the collapse phase as a radiation fluid. In realistic networks these two effects are important, making this solution only approximate. We derive new scaling solutions describing this effect, and test them against high-resolution numerical simulations. A string network in a contracting universe, together with the gravitational radiation background it has generated, can significantly affect the dynamics of the universe both locally and globally. The network can be an important source of radiation, entropy and inhomogeneity. We discuss the possible implications of these findings for bouncing and cyclic cosmological models.

We examine the contributions to rare processes that arise in models where the standard model fermions are localized at distinct points in compact extra dimensions. Tree-level flavor changing neutral current interactions for the Kaluza-Klein gauge field excitations are induced in such models, and hence strong constraints are thought to exist on the size of the additional dimensions. We find a general parametrization of the model which does not depend on any specific fermion geography and show that typical values of the parameters can reproduce the fermion hierarchy pattern. Using this parametrization, we reexamine the contributions to neutral meson mixing, rare meson decays, and single top-quark production in $e^{+}{e}^{-}$ collisions. We find that it is possible to evade the stringent bounds for natural regions of the parameters, while retaining finite separations between the fermion fields and without introducing a new hierarchy. The resulting limits on the size of the compact dimension can be as low as ${\mathrm{TeV}}^{-1}.$

We study gravitational and electromagnetic radiation generated by uniformly accelerated charged black holes in anti–de Sitter spacetime. This is described by the C-metric exact solution of the Einstein-Maxwell equations with a negative cosmological constant Λ. We explicitly find and interpret the pattern of radiation that characterizes the dependence of the fields on a null direction from which the (timelike) conformal infinity is approached. This directional pattern exhibits specific properties which are more complicated if compared with recent analogous results obtained for asymptotic behavior of fields near a de Sitter–like infinity. In particular, for large acceleration the anti–de Sitter–like infinity is divided by Killing horizons into several distinct domains with a different structure of principal null directions, in which the patterns of radiation differ.

We generalize the pull approach to define the ${\chi }^2$ function to the analysis of the data with correlated statistical errors. We apply this method to the analysis of the Sudbury Neutrino Collaboration data obtained in the salt phase. In the global analysis of all the solar neutrino and KamLAND data we find the best fit (minimum ${\chi }^2)$ values of neutrino parameters to be ${\tan }^2{\theta }_{12}\sim 0.42$ and $\delta m_{12}^2\sim 7.1\times {10}^{-5}{\mathrm{eV}}^2.$ We confirm that the maximal mixing is strongly disfavored while the bounds on $\delta m_{12}^2$ are significantly strengthened.

Properties of the proton and neutron are studied in partially quenched chiral perturbation theory at finite lattice spacing. Masses, magnetic moments, the matrix elements of isovector twist-2 operators and axial-vector currents are examined at the one-loop level in a double expansion in the light-quark masses and the lattice spacing. This work will be useful in extrapolating the results of simulations using Wilson valence and sea quarks, as well as simulations using Wilson sea quarks and Ginsparg-Wilson valence quarks, to the continuum.

We investigate the basic features of the gluon density predicted by a renormalization group improved small-$x$ equation which incorporates both the gluon splitting function at the leading collinear level and the exact Balitskii-Fadin-Kuraev-Lipatov (BFKL) kernel at the next-to-leading level. We provide resummed results for Green’s function and its hard Pomeron exponent ${\omega }_s\left({\alpha }_s\right),$ and for the splitting function and its critical exponent ${\omega }_c\left({\alpha }_s\right).\mathrm{}$ We find that nonlinear resummation effects considerably extend the validity of the hard Pomeron regime by decreasing diffusion corrections to Green’s function exponent and by slowing down the drift towards the nonperturbative Pomeron regime. As in previous analyses, the resummed exponents are reduced to phenomenologically interesting values. Furthermore, significant preasymptotic effects are observed. In particular, the resummed splitting function departs from the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) result in the moderate small-$x$ region, showing a shallow dip followed by the expected power increase in the very small-$x$ region. Finally, we outline the extension of the resummation procedure to include the photon impact factors.

We discuss the gravitational self-force on a particle in a black hole space-time. For a point particle, the full (bare) self-force diverges. It is known that the metric perturbation induced by a particle can be divided into two parts, the direct part (or the S part) and the tail part (or the R part), in the harmonic gauge, and the regularized self-force is derived from the R part which is regular and satisfies the source-free perturbed Einstein equations. In this paper, we consider a gauge transformation from the harmonic gauge to the Regge-Wheeler gauge in which the full metric perturbation can be calculated, and present a method to derive the regularized self-force for a particle in circular orbit around a Schwarzschild black hole in the Regge-Wheeler gauge. As a first application of this method, we then calculate the self-force to first post-Newtonian order. We find the correction to the total mass of the system due to the presence of the particle is correctly reproduced in the force at the Newtonian order.

We present a dark energy model with a double exponential potential for a minimally coupled scalar field, which allows general exact integration of the cosmological equations. The solution can perfectly emulate a Λ-term model at low-medium redshift, exhibits tracking behavior, and does not show eternal acceleration.

Chiral perturbation theory predicts that in quantum chromodynamics light dynamical quarks suppress the topological (instanton) susceptibility. We investigate this suppression through direct numerical simulation using the Asqtad improved lattice fermion action. This action holds promise for carrying out nonperturbative simulations over a range of quark masses for which chiral perturbation theory is expected to converge. To test the effectiveness of the action in capturing instanton physics, we measure the topological susceptibility as a function of quark masses with $2+1$ dynamical flavors. Our results, when extrapolated to zero lattice spacing, are consistent with predictions of leading order chiral perturbation theory. Included in our study is a comparison of three methods for analyzing the topological susceptibility: (1) the Boulder hypercubic blocking technique with the Boulder topological charge operator, (2) the more traditional Wilson cooling method with the twisted plaquette topological charge operator and (3) the improved cooling method of de Forcrand, Perez, and Stamatescu and their improved topological charge operator. We show in one comparison at nonzero lattice spacing that the largest difference between methods (1) and (2) can be attributed to the operator, rather than the smoothing method.

We consider the hadroproduction of ${\chi }_{c1\mathrm{}}$ and ${\chi }_{c2\mathrm{}}$ mesons and their subsequent radiative decays to $J/\psi$ mesons and photons in the factorization formalism of nonrelativistic quantum chromodynamics, and study the decay angular distributions, by means of helicity density matrices, in view of their sensitivity to color-octet processes. We present numerical results appropriate for the Fermilab Tevatron.

We evaluate the decays $\overrightarrow{B}{K}^{*}\pi ,K(\rho ,\omega ,\phi )$ adding the long distance charming penguin contributions to the short distance: tree+penguin amplitudes. We estimate the imaginary part of the charming penguin contribution by an effective field theory inspired by heavy quark effective theory and parametrize its real part. The final results for branching ratios depend on only two real parameters and show a significant role of the charming penguin contributions. The overall agreement with the available experimental data is satisfactory.

The one-loop effective potential calculated for a generic model that originates from 5-dimensional theory reduced down to 4 dimensions is considered. The cutoff and dimensional regularization schemes are discussed and compared. It is demonstrated that the prescriptions are consistent with each other and lead to the same physical consequences. The stability of the ground state is discussed for a U(1) model that is supposed to mimic the standard model extended to 5 dimensions. It has been shown that fermionic Kaluza-Klein modes can dramatically influence the shape of the effective potential shifting the instability scale even by several orders of magnitude.

We analyze further the possibility of obtaining localized black hole solutions in the framework of Randall-Sundrum-type brane-world models. We consider black hole line elements analytic at the horizon, namely, generalizations of the Painlevé and Vaidya metrics, which are taken to have a decaying dependence of the horizon on the extra dimension. These backgrounds have no other singularities apart from the standard black hole singularity which is localized in the direction of the fifth dimension. Both line elements can be sustained by a regular, shell-like distribution of bulk matter of a non-standard form. Of the two, the Vaidya line element is shown to provide the most attractive, natural choice: despite the scaling of the horizon, the five-dimensional spacetime has the same topological structure as the one of a Randall-Sundrum–Schwarzschild spacetime and demands a minimal bulk energy-momentum tensor.