We find the general solution of the Einstein equation for spherically symmetric collapse of type II fluid (null strange quark fluid) in higher dimensions. It turns out that the nakedness and curvature strength of the shell focusing singularities carry over to higher dimensions. However, there is shrinkage of the initial data space for a naked singularity of the Vaidya collapse due to the presence of strange quark matter.

In two-dimensional conformal field theory the generating functional for correlators of the stress-energy tensor is given by the nonlocal Polyakov action associated with the background geometry. We study this functional holographically by calculating the regularized on-shell action of asymptotically AdS gravity in three dimensions, associated with a specified (but arbitrary) boundary metric. This procedure is simplified by making use of the Chern-Simons formulation, and a corresponding first-order expansion of the bulk dreibein, rather than the metric expansion of Fefferman and Graham. The dependence of the resulting functional on local moduli of the boundary metric agrees precisely with the Polyakov action, in accord with the AdS/conformal field theory correspondence. We also verify the consistency of this result with regard to the nontrivial transformation properties of bulk solutions under Brown-Henneaux diffeomorphisms.

Based on the (in part verified) ideas of a dynamical “Abelianization” and subsequent “centerization” of pure $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ gauge theory an effective potential for relevant field variables is constructed in the limit of large N. To do this the theory is assumed to be thermalized and to be gravitationally deformed. BPS saturation in the dynamics of the monopole field is shown to lead to a suppression of the back reaction due to classical gravity. The classical, effective description of the gauge theory can be justified for both the regime of maximal Abelian gauge symmetry and the center symmetric phase.

We examine orbifolds of the type IIB string via gauged supergravity. For the gravity duals of the $A_{n-1}$ quiver gauge theories, we extract the massless degrees of freedom and assemble them into multiplets of $\mathcal{N}=4\mathrm{}$ gauged supergravity in five dimensions. We examine the embedding of the gauge group into the isometry group of the scalar manifold, as well as the symmetries of the scalar potential. From this we find that there is a large $\mathrm{SU}(1,n)\mathrm{}$ symmetry group which relates different RG flows in the dual quiver gauge theory. We find that this symmetry implies an extension of the usual duality between ten-dimensional type IIB solutions which involves exchanging geometric moduli with background fluxes.

We compare a momentum space implicit regularization (IR) framework with other renormalization methods which may be applied to dimension specific theories, namely differential renormalization (DfR) and the Bogolubov-Parasiuk-Hepp-Zimmermann (BPHZ) formalism. In particular, we define what is meant by minimal subtraction in IR in connection with DfR and dimensional renormalization. We illustrate with the calculation of the gluon self-energy a procedure by which a constrained version of IR automatically ensures gauge invariance at the one-loop level and handles infrared divergences in a straightforward fashion. Moreover, using the ${\phi }_4^4$ theory setting sun diagram as an example and comparing explicitly with the BPHZ framework, we show that IR directly displays the finite part of the amplitudes. We then construct a parametrization for the ambiguity in separating the infinite and finite parts whose parameter serves as a renormalization group scale for the Callan-Symanzik equation. Finally we argue that constrained IR, constrained DfR, and dimensional reduction are equivalent within one-loop order.

Four dimensional gravity in the low energy limit of a higher dimensional theory has been expected to be a (generalized) Brans-Dicke theory. A subtle point in brane world scenarios is that the system of four dimensional effective gravitational equations is not closed due to bulk gravitational waves and bulk scalars. Nonetheless, weak gravity on the brane can be analyzed completely. We reexamine the theory of weak brane gravity using gauge-invariant gravitational and scalar perturbations around a background warped geometry with a bulk scalar between two flat branes. We obtain a simple condition for the radion stabilization in terms of the scalar field potentials. We show that for general potentials of the scalar field which provides radion stabilization and a general conformal transformation to a frame in which matter on the branes are minimally coupled to the metric, 4-dimensional Einstein gravity, not BD gravity, is restored at low energies on either brane. In contrast, in RS brane world scenario without a bulk scalar, low energy gravity is a BD one. We conjecture that in general brane world scenarios with more than one scalar field one will again encounter the situation that low energy gravity is not described by the Einstein theory. Equipped with the weak gravity results, we discuss the properties of 4D brane gravitational equations, in particular, the value and sign of 4D Newton gravitational coupling.

We find the general solution for the spacetimes describing the interior of static black holes with an equation of state of the type $T_0^0{=T}_1^1$ $(T$ being the stress-energy tensor). This form is the one expected from taking into account different quantum effects associated with strong gravitational fields. We recover all the particular examples found in the literature. We remark that all the solutions found follow the natural scheme of an interior core linked smoothly with the exterior solution by a transient region. We also discuss their local energy properties and give the main ideas involved in a possible generalization of the scheme in order to include other realistic types of sources.

We study bound object formation in a background universe accelerated by a cosmological constant and by quintessence. If the acceleration lasts forever, due to the existence of an event horizon, one would have naively expected the universe to approach a state of cold death. However, we find that many local regions in the universe can in fact be protected by their own gravity to form miniuniverses, provided that their present matter densities exceed some critical value. In the case with a cosmological constant $(\Lambda$ cold dark matter cosmology), the condition for forming a miniuniverse is that the ratio of the present density parameters ${\Omega }_i^0/{\Omega }_{\Lambda }$ should be larger than a critical value $\mathrm{3.63.}$ Such miniuniverses typically weigh less than $2\times {10}^{14}$ solar masses, with the lighter ones having tight and compact configurations. In the case with quintessence, the final ratio ${\Omega }_i/{\Omega }_q$ of a miniuniverse is found to be always larger than $w_q^2-w_q,$ where $w_q$ is the equation-of-state parameter.

We show that the linear dynamics of cosmological perturbations can be described by coupled wave equations, allowing their efficient numerical and, in certain limits, analytical integration directly in position space. The linear evolution of any perturbation can then be analyzed with the Green’s function method. Prior to hydrogen recombination, assuming tight coupling between photons and baryons, neglecting neutrino perturbations, and taking isentropic (adiabatic) initial conditions, the obtained Green’s functions for all metric, density, and velocity perturbations vanish beyond the acoustic horizon. A localized primordial cosmological perturbation expands as an acoustic wave of photon-baryon density perturbation with narrow spikes at its acoustic wave fronts. These spikes provide one of the main contributions to the cosmic microwave background radiation anisotropy on all experimentally accessible scales. The gravitational interaction between cold dark matter and baryons causes a dip in the observed temperature of the radiation at the center of the initial perturbation. We first model the radiation by a perfect fluid and then extend our analysis to account for finite photon mean free path. The resulting diffusive corrections smear the sharp features in the photon and baryon density Green’s functions over the scale of Silk damping.

In family unification models, all three families of quarks and leptons are grouped together into an irreducible representation of a simple gauge group, thus unifying the standard model gauge symmetries and a gauged family symmetry. Large orthogonal groups, and the exceptional groups $E_7$ and $E_8,$ have been much studied for family unification. The main theoretical difficulty of family unification is the existence of mirror families at the weak scale. It is shown here that family unification without mirror families can be realized in simple five-dimensional and six-dimensional orbifold models similar to those recently proposed for $\mathrm{SU}\left(5\right)\mathrm{}$ and $\mathrm{SO}\left(10\right)\mathrm{}$ grand unification. It is noted that a family unification group that survived to near the weak scale and whose coupling extrapolated to high scales unified with those of the standard model would be evidence, accessible in principle at low energy, of the existence of small (Planckian or GUT-scale) extra dimensions.

We show that any generally covariant coupling of matter fields to gravity gives rise to a conserved, on-shell symmetric energy-momentum tensor equivalent to the canonical energy-momentum tensor of the flat-space theory. For matter fields minimally coupled to gravity our algorithm gives the conventional Belinfante tensor. We establish that different matter-gravity couplings give metric energy-momentum tensors differing by identically conserved tensors. We prove that the metric energy-momentum tensor obtained from an arbitrary gravity theory is on-shell equivalent to the canonical energy-momentum tensor of the flat-space theory.

For spinor fields, the entropies from the spin-${\frac{1}{2}}^{-}$ and spin-${\frac{1}{2}}^{+}$ components, $S_{\mathrm{ext}}^{q-}$ and $S_{\mathrm{ext}}^{q+},$ are quite different, though the former is $\frac{7}{8}$ times the scalar entropy and the latter contains an extra term. The brick wall model is applicable to both NEBH and EBH. For the EDBH with $0\prec a^2\prec 1,$ using the brick wall model with the cutoff $\epsilon$ being given by ${\epsilon }^{\left(1\mathrm{}-a^2{)/(1+a}^2\right)}{=(1+a}^2)\kappa m^{{2/(1+a}^2)}$ and $\kappa$ the surface gravity on the event horizon, at the Hawking temperature $T_H=\kappa /2\mathrm{}\pi ,$ the scalar and spinor entropies are $S_{\mathrm{ext}}^q{=S}_0/(1\mathrm{}-a^2{\left)\right(1+a}^2{)}^2$ with $S_0=\frac{1}{135}$ and $S_{\mathrm{Fext}}^q=\frac{7}{2}{S}_{\mathrm{ext}}^q+[1/6(1-a^2\left)\right],$ respectively. For the EGHSDBH, the spin-${\frac{1}{2}}^{-}$ and spin-${\frac{1}{2}}^{+}$ fields contribute the entropies $S_{\mathrm{ext}}^{q-}=\frac{7}{8}{S}_{\mathrm{ext}}^q,\hspace{0.5em}\hspace{0.5em}{S}_{\mathrm{ext}}^{q+}=\frac{7}{8}{S}_{\mathrm{ext}}^q+(\pi m/6\mathrm{}\beta )\ln (L/\epsilon ),$ respectively; at the Hawking temperature, the spinor entropy is $S_{\mathrm{Fext}}^q=(\frac{7}{2}{+30)S}_{\mathrm{ext}}^q$ with $S_{\mathrm{ext}}^q=\frac{1}{360}\ln (L/\epsilon ).\mathrm{}$

We study the problem of vortex solutions in the background of rotating black holes in both asymptotically flat and asymptotically anti–de Sitter spacetimes. We demonstrate that the Abelian Higgs field equations in the background of four-dimensional Kerr, Kerr-AdS, and Reissner-Nordstrom-AdS black holes have vortex line solutions. These solutions, which have axial symmetry, are a generalization of the Nielsen-Olesen string. By numerically solving the field equations in each case, we find that these black holes can support an Abelian Higgs field as hair. This situation holds even in the extremal case, and no flux expulsion occurs. We also compute the effect of the self-gravity of the Abelian Higgs field and show that the vortex induces a deficit angle in the corresponding black hole metrics.

In this paper we discuss the possible distortions of the ionization history of the universe caused by an injection of nonthermal energy due to decays of hypothetical superheavy dark matter (SHDM) particles. These particles are usually considered as a possible source of ultrahigh energy cosmic rays in the framework of the top-down model. Estimates of the fraction of energy of decays converted to the UV range show that, for suitable parameters of the SHDM particles, significant distortions of the power spectra of the cosmic microwave background anisotropy appear. A comparison with the observed power spectrum allows us to restrict some properties of the SHDM particles. These decays can also increase by about 5–10 times the degree of ionization of hydrogen at redshifts $z\sim 10–50,$ which essentially accelerates the formation of molecules of ${\mathrm{H}}_2$ and the first stars during the “dark ages.”

There has been a great development in our understanding of particle physics at the weak scale in recent years. Precision electroweak observables have played a key role in this process and their values are consistent, within the standard model (SM) interpretation, with a light Higgs boson with a mass lower than about 200 GeV. If new physics were responsible for the mechanism of electroweak symmetry breaking there would, quite generally, be modifications to this prediction induced by the nonstandard contributions to the precision electroweak observables. In this paper, we analyze the experimental signatures of a heavy Higgs boson at linear colliders. We show that a linear collider, with a center of mass energy $\sqrt{s}\lesssim 1\hspace{0.5em}\mathrm{TeV},$ would be very useful to probe the basic ingredients of well motivated heavy Higgs boson models: a relatively heavy SM-like Higgs boson, together with either extra scalar or fermionic degrees of freedom, or with the mixing of the third generation quarks with nonstandard heavy quark modes.

Investigating leptonic decays of ${\pi }^{-}{,K}^{-}{,B}^{-},{\pi }^0{,K}_L^0,$ and $B_s^0$ we present new bounds on some products of two R-parity violating coupling constants. For mesons of a similar structure but with poor experimental data we give the corresponding formulas, to be used in the future.

We have searched a sample of 9.6 million $B\overline{B}$ events for the lepton-flavor-violating decays $\overrightarrow{B}{\mathrm{he}}^{\pm }{\mu }^{\mp },$ $B^{+}\to h^{-}{e}^{+}{e}^{+},$ $B^{+}\to h^{-}{e}^{+}{\mu }^{+},$ and $B^{+}\to h^{-}{\mu }^{+}{\mu }^{+},$ where h is $\pi ,$ K, $\rho ,$ and $K^{*}\mathrm{}\left(892\right),$ a total of sixteen modes. We find no evidence for these decays, and place 90% confidence level upper limits on their branching fractions that range from 1.0 to $8.3\times {10}^{-6}.$

Using an algebraic method previously introduced, we work out the mass spectra, symmetry breaking patterns, and topologies of general vacuum states in $\mathcal{N}=2\mathrm{}$ supersymmetric Chern-Simons-Higgs systems with adjoint matter coupling for arbitrary classical Lie groups. The approach is very general and only makes use of the property that the vacuum states satisfy the SU(2) algebra. Therefore, the results can also be applied to any systems that share the same property. In this kind of analysis, we obtain a natural basis for fields, which is useful for studying the self-dual solutions and quantum corrections in these systems.

We study the physical content of quadratic diff-invariant Lagrangians in arbitrary dimensions by using covariant symplectic techniques. This paper extends previous results in dimension four. We discuss the difference between the even and odd dimensional cases.

We study the consequences of spacetime torsion coexisting with gravity in the bulk in scenarios with large extra dimensions. Having linked torsion with the Kalb-Ramond antisymmetric tensor field arising in string theories, we examine its artifacts on the visible 3-brane when the extra dimensions are compactified. It is found that while torsion would have led to parity violation in a 4-dimensional framework, all parity violating effects disappear on the visible brane when the torsion originates in the bulk. However, such a scenario is found to have characteristics of its own, some of which can be phenomenologically significant.