It has recently been realized that brane-antibrane annihilation (a possible explanation for ending inflation) may result in defect formation, due to the dynamics of the tachyon field. Studies of this possibility have generally ignored the interaction of the brane fields with fields in the bulk; recently it has been argued [G. Dvali and A. Vilenkin, J. Cosmol. Astropart. Phys. 03 (2004) 010.] that interactions with bulk fields suppress or even eliminate defect formation. To investigate the impact of bulk fields on brane defect formation, we construct a toy model that captures the essential features of the tachyon condensation with bulk fields. We study the structure of defects in this toy model, and simulate their formation and evolution on the lattice. We find that, while the energetics and interactions of defects are influenced by the size of the extra dimension and the bulk-brane coupling, the bulk-brane coupling does not prevent the formation of a defect network.

We study the scattering of massive spin-half waves by a Schwarzschild black hole using analytical and numerical methods. We begin by extending a recent perturbation-theory calculation to next order to obtain Born series for the differential cross section and Mott polarization, valid at small couplings. We continue by deriving an approximation for glory scattering of massive spinor particles by considering classical timelike geodesics and spin precession. Next, we formulate the Dirac equation on a black hole background, and outline a simple numerical method for finding partial wave series solutions. Finally, we present our numerical calculations of absorption and scattering cross sections and polarization, and compare with theoretical expectations.

The low energy effective action of gravity in any even dimension generally acquires nonlocal terms associated with the trace anomaly, generated by the quantum fluctuations of massless fields. The local auxiliary field description of this effective action in four dimensions requires two additional scalar fields, not contained in classical general relativity, which remain relevant at macroscopic distance scales. The auxiliary scalar fields depend upon boundary conditions for their complete specification, and therefore carry global information about the geometry and macroscopic quantum state of the gravitational field. The scalar potentials also provide coordinate invariant order parameters describing the conformal behavior and divergences of the stress tensor on event horizons. We compute the stress tensor due to the anomaly in terms of its auxiliary scalar potentials in a number of concrete examples, including the Rindler wedge, the Schwarzschild geometry, and de Sitter spacetime. In all of these cases, a small number of classical order parameters completely determine the divergent behaviors allowed on the horizon, and yield qualitatively correct global approximations to the renormalized expectation value of the quantum stress tensor.

We study the Affleck-Dine mechanism with various types of the Kähler potential and investigate whether or not the Affleck-Dine field could acquire a large vacuum expectation value as an initial condition for successful baryogenesis. In addition to a negative Hubble-induced mass term, we find that large enough Hubble-induced $A$ terms also could develop the minimum at large amplitude of the field. Therefore, the Affleck-Dine mechanism works for broader classes of the theories.

We investigate the large scale anomalies in the angular distribution of the cosmic microwave background radiation as measured by WMAP using several tests. These tests, based on the multipole vector expansion, measure correlations between the phases of the multipoles as expressed by the directions of the multipole vectors and their associated normal planes. We have computed the probability distribution functions for 46 such tests, for the multipoles $\ell =2-5$. We confirm earlier findings that point to a high level of alignment between $\ell =2$ (quadrupole) and $\ell =3$ (octopole), but with our tests we do not find significant planarity in the octopole. In addition, we have found other possible anomalies in the alignment between the octopole and the $\ell =4$ (hexadecupole) components, as well as in the planarity of $\ell =4$ and $\ell =5$. We introduce the notion of a global anomaly statistic to estimate the relevance of the low-multipoles tests of non-Gaussianity. We show that, as a result of these tests, the CMB maps which are most widely used for cosmological analysis lie within the $\sim 10\%$ of randomly generated maps with lowest global anomaly statistics.

We explore the impact of Lorentz violation on the inflationary scenario. More precisely, we study the inflationary scenario in the scalar-vector-tensor theory where the Lorentz violating vector is constrained to be unit and timelike. It turns out that the Lorentz violating vector affects the dynamics of the chaotic inflationary model and divides the inflationary stage into two parts: the Lorentz violating stage and the standard slow roll stage. We show that the universe is expanding as a de Sitter space-time in the Lorentz violating stage although the inflaton field is rolling down the potential. More interestingly, we find the exact Lorentz violating inflationary solutions in the absence of the inflaton potential. In this case, the inflation is completely associated with the Lorentz violation.

We show the evolution of nonspherically symmetric balls of a self-gravitating scalar field in the Newtonian regime or equivalently an ideal self-gravitating condensed Bose gas. In order to do so, we use a finite differencing approximation of the Schrödinger-Poisson (SP) system of equations with axial symmetry in cylindrical coordinates. Our results indicate: (i) that spherically symmetric ground state equilibrium configurations are stable against nonspherical perturbations and (ii) that such configurations of the SP system are late-time attractors for nonspherically symmetric initial profiles of the scalar field, which is a generalization of such behavior for spherically symmetric initial profiles. Our system and the boundary conditions used, work as a model of scalar field dark matter collapse after the turnaround point. In such case, we have found that the scalar field overdensities tolerate nonspherical contributions to the profile of the initial fluctuation.

We present constraints on the presence of isocurvature modes from the temperature and polarization cosmic microwave background (CMB) spectrum data from the WMAP satellite alone, and in combination with other data sets including SDSS galaxy survey and SNLS supernovae. We find that the inclusion of polarization data allows the WMAP data alone, as well as in combination with complementary observations, to place improved limits on the contribution of CDM and neutrino density isocurvature components individually. With general correlations, the upper limits on these subdominant isocurvature components are reduced to $\sim 60\%$ of the first year WMAP results, with specific limits depending on the type of fluctuations. If multiple isocurvature components are allowed, however, we find that the data still allow a majority of the initial power to come from isocurvature modes. As well as providing general constraints we also consider their interpretation in light of specific theoretical models like the curvaton and double inflation.

We study QCD effects in single graviton production at the CERN Large Hadron Collider (LHC) in the Randall-Sundrum (RS) model. We present in detail the complete next-to-leading order (NLO) QCD corrections to the inclusive total cross sections. The NLO QCD corrections enhance significantly the total cross sections and decrease efficiently the dependence of the total cross sections on the factorization and renormalization scales. We also examine the uncertainty of the total cross sections due to the parton distribution function (PDF) uncertainties. For the differential cross sections on the transverse momentum ($q_T$) of the graviton, within the CSS resummation formalism, we resum the logarithmically-enhanced terms at small $q_T$ to all orders up to NLO logatithmic accuracy. Combined with the fixed-order calculations, we give consistent predictions for both small $q_T$ and large $q_T$.

Reduced large $N$ gauge theories have a phase with unbroken center symmetry and phases in which that symmetry is broken for Polyakov loops in one or more lattice directions. The phase with unbroken symmetry is associated with the zero temperature, infinite volume, infinite $N$ theory while the phase in which the symmetry is broken in just one lattice direction has been conjectured to be the spatial reduction of the high temperature, infinite volume, infinite $N$ theory. Measurements of the scaling properties of the latent heat of the transition between these phases test that hypothesis. The results indicate a nonzero latent heat in the continuum limit. Substantial finite spacing effects remain, and finer lattices will be needed to confirm physical scaling.

On the basis of the perturbative QCD and the relativistic quark model we investigate the relativistic and bound state effects in the production processes of a pair of $S$-wave doubly heavy mesons consisting of $b$ and $c$ quarks. Relativistic factors in the production amplitude connected with the relative motion of heavy quarks and the transformation law of the bound state wave function to the reference frame of the moving pseudoscalar $\mathcal{P}$- and vector $\mathcal{V}$-mesons are taken into account. Relativistic corrections of the second order in the heavy quark relative momentum and bound state corrections proportional to the quark binding energies in the doubly heavy mesons are calculated in the production rates. We obtain an increase of the cross section for the reaction $e^{+}+e^{-}\to J/\Psi +{\eta }_c$ due to the considered effects by a factor $2÷2.5$ in the range of the center-of-mass energy $\sqrt{s}=6÷12\mathrm{GeV}$.

The main part of coherent pion production by neutrinos on nuclei is essentially determined by partial conservation of the axial current (PCAC), provided that the leptonic momentum transferred square $Q^2$ remains sufficiently small. We give the formulas for the charged and neutral current cross sections, including also the small non-PCAC transverse current contributions and taking into account the effect of the ${\mu }^{-}$-mass. Our results are compared with the experimental ones and other theoretical treatments.

With a special intention of clarifying the underlying spin contents of the nucleon, we investigate the generalized form factors of the nucleon, which are defined as the $n$th $x$ moments of the generalized parton distribution functions, within the framework of the chiral quark soliton model. A particular emphasis is put on the pion mass dependence of final predictions, which we shall compare with the predictions of lattice QCD simulations carried out in the so-called heavy pion region around $m_{\pi }\simeq (700–900)\mathrm{MeV}$. We find that some observables are very sensitive to the variation of the pion mass. It will be argued that the negligible importance of the quark orbital angular momentum indicated by the LHPC and QCDSF lattice collaborations might be true in the unrealistic heavy pion world, but it is not necessarily the case in our real world close to the chiral limit.

We investigate the electric form factors and charge radii of the pentaquark baryons within the framework of the chiral quark-soliton model. We consider the rotational $1/N_c$ and linear $m_s$ corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. The flavor-decomposed charge densities of the ${\Theta }^{+}$ are presented. The electric form factors and charge radii of the charged pentaquark baryons turn out to be very similar to those of the corresponding octet baryons. The charge radii of the neutral pentaquark baryons are obtained to be very tiny and positive. The strange electric form factor of the pentaquark proton is shown to be larger than the corresponding one of the proton by around 20%. We also present the charge radii of the baryon decuplet for comparison.

After dimensional reduction to three dimensions, the lowest order effective actions for pure gravity, M theory, and the bosonic string admit an enhanced symmetry group. In this paper we initiate study of how this enhancement is affected by the inclusion of higher derivative terms. In particular we show that the coefficients of the scalar fields associated to the Cartan subalgebra are given by weights of the enhanced symmetry group.

We study the numerical propagation of waves through future null infinity in a conformally compactified spacetime. We introduce an artificial cosmological constant, which allows us some control over the causal structure near null infinity. We exploit this freedom to ensure that all light cones are tilted outward in a region near null infinity, which allows us to impose excision-style boundary conditions in our finite-difference code. In this preliminary study we consider electromagnetic waves propagating in a static, conformally compactified spacetime.

We examine nonthermal dark matter production from a late-decaying scalar field, with a particular attention on nonrenormalizable operators of $D=5$ through which the scalar field decays into the standard model particles and their superpartners. We show that almost the same number of superparticles as that of particles are generally produced from the decay. To avoid the gravitino overproduction problem, the decay is favored to proceed via interactions with an intermediate cutoff scale $M\ll M_P$. This should be contrasted to the conventional scenario using the modulus decay. The saxion, a scalar partner of the axion, is proposed as a natural candidate for such late-decaying scalar fields. We find that a right amount of the W-ino/Higgsino dark matter with a mass of $O(100)\mathrm{GeV}$ is obtained for the saxion mass around the weak scale and axion decay constant, $F_{\mathcal{A}}=O({10}^{9-12})\mathrm{GeV}$.

We argue that string theory has ingredients to provide us with candidates for cold dark matter and explain the current acceleration of our universe. In any generic string compactification the dilaton plays an important role, as it couples to the standard model and other heavy nonrelativistic degrees of freedom such as string winding modes and wrapped branes, which we collectively call stringy cold dark matter. These couplings are nonuniversal, which results in an interesting dynamics for a rolling dilaton. Initially, it can track radiation and matter while beginning to dominate the dynamics recently, triggering a phase of acceleration. This scenario can be realized as long as the dilaton also couples strongly to some heavy modes. We furnish examples of such modes. We provide analytical and numerical results and compare them with the current supernovae result. We also mention some of the challenges for the success of our model favoring certain stringy candidates.

We generalize our previous work on gravitational lensing by a Kerr black hole in the strong deflection limit, removing the restriction to observers on the equatorial plane. Starting from the Schwarzschild solution and adding corrections up to the second order in the black hole spin, we perform a complete analytical study of the lens equation for relativistic images created by photons passing very close to a Kerr black hole. We find out that, to the lowest order, all observables (including shape and shift of the black hole shadow, caustic drift and size, images position and magnification) depend on the projection of the spin on a plane orthogonal to the line of sight. In order to break the degeneracy between the black hole spin and its inclination relative to the observer, it is necessary to push the expansion to higher orders. In terms of future very-long base line interferometry observations, this implies that very accurate measures are needed to determine these two parameters separately.