QCD sum rules are used to estimate the flavor SU(3)-symmetry violation in two-body B decays to pions and kaons. In the factorizable amplitudes the SU(3) violation manifests itself in the ratio of the decay constants ${(f}_K{/f}_{\pi })$ and in the differences between the $\overrightarrow{B}K,$ $B_s\to K$ and $\overrightarrow{B}\pi$ form factors. These effects are calculated from the QCD two-point and light-cone sum rules, respectively, in terms of the strange quark mass and the ratio of the strange and nonstrange quark-condensate densities. Importantly, QCD sum rules predict that SU(3) breaking in the heavy-to-light form factors can be substantial and does not vanish in the heavy-quark mass limit. Furthermore, we investigate the strange-quark mass dependence of nonfactorizable effects in the $\overrightarrow{B}K\pi$ decay amplitudes. Taking into account these effects we estimate the accuracy of several SU(3)-symmetry relations between charmless B-decay amplitudes.

Lifetime differences of heavy hadrons can be consistently computed in heavy-quark expansion. The leading effects appear through spectator interactions at order ${1/m}_b^3.$ We compute a well-defined subset of ${1/m}_b^4$ corrections to the lifetime ratio of a ${\Lambda }_b$ baryon and $B_d$ meson. We find that these corrections are large and should be taken into account in the systematic analysis of heavy hadron lifetimes. We claim that they could shift the ratio ${\tau }_{{\Lambda }_b}/{\tau }_{B_d}$ by as much as $-4.5\%,$ significantly reducing the discrepancy between the theoretical predictions and experimental observations.

We develop a dipole model for DESY HERA deep inelastic scattering data which incorporates the impact parameter distribution of the proton. The model describes the inclusive total ${\gamma }^{*}p$ cross sections as well as the diffractive $J/\psi$ differential cross sections. We compare the model with previous approaches and show that the t distributions are sensitive to saturation phenomena. We estimate the boundary of the saturation region and show that it dominates the data in the low-$Q^2$ region where the total ${\gamma }^{*}p$ cross section exhibits the same universal rise as hadronic cross sections. The model is then extended to nuclei and shows good agreement with the nuclear shadowing data at small x. Finally, we estimate the saturation scale in nuclei.

We study the electromagnetic vertex function of a neutrino that propagates in an electron background in the presence of a static magnetic field. The structure of the vertex function under the stated conditions is determined and it is written down in terms of a minimal and complete set of tensors. The one-loop expressions for all the form factors are given, up to terms that are linear in the magnetic field, and the approximate integral formulas that hold in the long wavelength limit are obtained. We discuss the physical interpretation of some of the form factors and their relation with the concept of the neutrino induced charge. The neutrino acquires a longitudinal and a transverse charge, due to the fact that the form factors depend on the transverse and longitudinal components of the photon momentum independently. We compute those form factors explicitly in various limiting cases and find that the longitudinal and transverse charges are the same for the case of a nonrelativistic electron gas, but not otherwise.

An estimate of the next-to-next-to-leading order (NNLO) supersymmetric QCD effects for Higgs production at hadron colliders is given. Assuming an effective gluon-Higgs interaction, these corrections enter only in terms of process-independent, factorizable terms. We argue that the current knowledge of these terms up to NLO is sufficient to derive the NNLO hadronic cross section within the limitations of the standard theoretical uncertainties arising mainly from renormalization and factorization scale variations. The supersymmetric contributions are small with respect to the QCD effects, which means that the NNLO corrections to Higgs production are very similar in the standard model and its minimal supersymmetric extension.

We review the physics of the Grishchuk-Zel’dovich effect which describes the impact of large amplitude, superhorizon gravitational field fluctuations on the cosmic microwave background anisotropy power spectrum. Using the latest determination of the spectrum by the Wilkinson Microwave Anisotropy Probe satellite, we infer a lower limit on the present length scale of such fluctuations of $3.9\times {10}^3$ times the cosmological particle horizon (at the 95% confidence level).

In the presence of a minimal uncertainty in length, there exists a critical temperature above which the thermodynamics of a gas of radiation changes drastically. We find that the equilibrium temperature of a system composed of a Schwarzschild black hole surrounded by radiation is unaffected by these modifications. This is in agreement with works related to the robustness of the Hawking evaporation. The only change the deformation introduces concerns the critical volume at which the system ceases to be stable. On the contrary, the evolution of the very early universe is sensitive to the new behavior. We readdress the shortcomings of the standard big bang model (flatness, entropy, and horizon problems) in this context, assuming a minimal coupling to general relativity. Although they are not solved, some qualitative differences set in.

We rederive the thermodynamical properties of a noninteracting gas in the presence of a minimal uncertainty in length. Apart from the phase space measure which is modified due to a change of the Heisenberg uncertainty relations, the presence of an ultraviolet cutoff plays a tremendous role. The theory admits an intrinsic temperature above which the fermion contribution to energy density, pressure and entropy is negligible.

We present a new non-Abelian generalization of the Born-Infeld Lagrangian. It is based on the observation that the basic quantity defining it is the generalized volume element, computed as the determinant of a linear combination of metric and Maxwell tensors. We propose to extend the notion of the determinant to the tensor product of space-time and a matrix representation of the gauge group. We compute such a Lagrangian explicitly in the case of the $\mathrm{SU}\left(2\right)\mathrm{}$ gauge group and then explore the properties of static, spherically symmetric solutions in this model. We have found a one-parameter family of finite energy solutions. In the last section, the main properties of these solutions are displayed and discussed.

We address solutions of a brane-world with a cosmological constant $\lambda$ by introducing the dilaton in 5D bulk, and we examine the localization of the graviton, gauge bosons, and dilaton. For those solutions, we find that both the graviton and gauge bosons can be trapped for either sign, positive or negative, and a wide range of $\lambda$ due to the nontrivial dilaton, while the dilaton cannot be trapped on the brane.

We study the nature of boundary dynamics in teleparallel 3D gravity. The asymptotic field equations with anti–de Sitter boundary conditions yield only two nontrivial boundary modes, associated with a conformal field theory with a classical central charge. After showing that the teleparallel gravity can be formulated as a Chern-Simons theory, we identify the dynamical structure at the boundary as the Liouville theory.

We study the gravitational radiation reaction in compact binary systems composed of neutron stars with spin and huge magnetic dipole moments (magnetars). The magnetic dipole moments undergo a precessional motion about the respective spins. At sufficiently high values of the magnetic dipole moments, their interaction generates second post-Newtonian order contributions both to the equations of motion and to the gravitational radiation escaping the system. We parametrize the radial motion and average over a radial period in order to find the secular contributions to the energy and magnitude of the orbital angular momentum losses, in the generic case of eccentric orbits. Similarly as for the spin-orbit, spin-spin, quadrupole-monopole interactions, here too we deduce the secular evolution of the relative orientations of the orbital angular momentum and spins. These equations, supplemented by the evolution equations for the angles characterizing the orientation of the dipole moments form a first order differential system, which is closed. The circular orbit limit of the energy loss agrees with the earlier result of Ioka and Taniguchi.

Spacetime-varying coupling constants can be associated with violations of local Lorentz invariance and CPT symmetry. An analytical supergravity cosmology with a time-varying fine-structure constant provides an explicit example. Estimates are made for some experimental constraints.

We study analytically and numerically the core structure of global vortices forming on topologically deformed brane worlds with a single toroidally compact extra dimension. It is shown that for an extra dimension size larger than the scale of symmetry breaking, the magnitude of the complex scalar field at the vortex center can dynamically remain nonzero. Single valuedness and regularity are not violated. Instead, the winding escapes to the extra dimension at the vortex center. As the extra dimension size decreases the field magnitude at the core dynamically also decreases, and in the limit of zero extra dimension size we reobtain the familiar global vortex solution. Extensions to other types of defects and gauged symmetries are also discussed.

A cosmological scenario is proposed in which the dark matter (DM) and dark energy (DE) of the Universe are two simultaneous manifestations of an inhomogeneous dilaton. The equation of state of the field is scale dependent and pressureless at galactic and larger scales and it has a negative pressure as DE at very large scales. The dilaton drives an initial inflationary phase followed by a kinetic-energy-dominated one, as in the “quintessential inflation” model introduced by Peebles and Vilenkin, and soon after the end of inflation particle production seeds the first inhomogeneities that lead to galaxy formation. The dilaton is trapped near the minimum of the potential where it oscillates like a massive field, and the excess of kinetic energy is dissipated via the mechanism of “gravitational cooling” first introduced by Seidel and Suen. The inhomogeneities therefore behave like solitonic oscillations around the minimum of the potential, known as “oscillatons,” which we propose account for most of the DM in galaxies. Those regions where the dilaton does not transform enough kinetic energy into reheating, or carry an excess of it from regions that have cooled, evolve to the tail of the potential as DE, driving the acceleration of the Universe.

We constrain slow-roll inflationary models using the recent Wilkinson Microwave Anisotropy Probe data combined with data from the VSA, CBI, ACBAR and 2dF experiments. We find the slow-roll parameters to be $0<\mathrm{}{\epsilon }_1<0.032\mathrm{}$ and ${\epsilon }_2+5.0\mathrm{}{\epsilon }_1=0.036\mathrm{}\pm \mathrm{0.025.}$ For inflation models $V\propto {\phi }^{\alpha }$ we find that $\alpha <3.9,4.3\mathrm{}$ at the $2\sigma$ and $3\sigma$ levels, indicating that the $\lambda {\phi }^4$ model is under very strong pressure from observations. We define a convergence criterion to judge the necessity of introducing further power spectrum parameters such as the spectral index and running of the spectral index. This criterion is typically violated by models with large negative running that fit the data, indicating that the running cannot be reliably measured with present data.

The Universe is modeled as a binary mixture whose constituents are described by a van der Waals fluid and by a dark energy density. The dark energy density is considered either as quintessence or as the Chaplygin gas. The irreversible processes concerning the energy transfer between the van der Waals fluid and the gravitational field are taken into account. This model can simulate (a) an inflationary period where the acceleration grows exponentially and the van der Waals fluid behaves like an inflaton, (b) an accelerated period where the acceleration is positive but it decreases and tends to zero whereas the energy density of the van der Waals fluid decays, (c) a decelerated period which corresponds to a matter dominated period with a non-negative pressure, and (d) a present accelerated period where the dark energy density outweighs the energy density of the van der Waals fluid.

It is argued why, contrary to expectations, steep brane-inflation cannot really help in overcoming the $\eta$ problem of quintessential inflation model building. In contrast it is shown that the problem is substantially ameliorated under the curvaton hypothesis. This is quantified by considering possible modular quintessential inflationary models in the context of both standard and brane cosmology.

We point out that inflaton decay products acquire plasma masses during the reheating phase following inflation. The plasma masses may render inflaton decay kinematically forbidden, causing the temperature to remain frozen for a period at a plateau value. We show that the final reheating temperature may be uniquely determined by the inflaton mass, and may not depend on its coupling. Our findings have important implications for the thermal production of dangerous relics during reheating (e.g., gravitinos), for extracting bounds on particle physics models of inflation from cosmic microwave background anisotropy data, for the production of massive dark matter candidates during reheating, and for models of baryogenesis or leptogenesis where massive particles are produced during reheating.

We report new constraints on extra-dimensional models and other physics beyond the standard model based on measurements of the Casimir force between two dissimilar metals for separations in the range $0.2–1.2\mu \mathrm{m}.$ The Casimir force between a Au-coated sphere and a Cu-coated plate of a microelectromechanical torsional oscillator was measured statically with an absolute error of 0.3 pN. In addition, the Casimir pressure between two parallel plates was determined dynamically with an absolute error of $\approx 0.6\mathrm{mPa}.$ Within the limits of experimental and theoretical errors, the results are in agreement with a theory that takes into account the finite conductivity and roughness of the two metals. The level of agreement between experiment and theory was then used to set limits on the predictions of extra-dimensional physics and thermal quantum field theory. It is shown that two theoretical approaches to the thermal Casimir force which predict effects linear in temperature are ruled out by these experiments. Finally, constraints on Yukawa corrections to Newton’s law of gravity are strengthened by more than an order of magnitude in the range 56–330 nm.