Localization of Vector Field on Pure Geometrical Thick Brane

We investigate the localization of a five-dimensional vector field on a pure geometrical thick brane. By introducing two types of interactions between the vector field and the background scalar field, we obtain a typical volcano potential for the first type of coupling and a Poschl-Teller potential for the second one. These two types of couplings guarantee that the vector zero mode can be localized on the pure geometrical thick brane under certain conditions.     

A new relativistic viscous hydrodynamics code and its application to the Kelvin–Helmholtz instability in high-energy heavy-ion collisions

The European Physical Journal C - It has been shown that the thin brane model in a five-dimensional Weyl gravity can deal with the wrong-signed Friedmann-like equation in the...     

Configurational Entropy and Newton's Law in Double Sine‐Gordon Braneworlds

The Shannon‐like entropic measure of spatially localized functions for a 5D braneworld generated by a double sine‐Gordon (DSG) potential is evaluated. The differential configurational entropy (DCE) has been shown in several recent works to be a configurational informational measure (CIM) that selects critical points and brings out phase transitions in confined energy models with arbitrary parameters. The DSG scenario is selected because it presents an energy‐degenerate spatially localized profile where the solutions to the scalar field demonstrate critical behavior that is only a result of geometrical effects. As is shown, the DCE evaluation provides a method for predicting the existence of a transition between the phases of the domain wall solutions. Moreover, the entropic measure reveals information about the model that is capable of describing the phase sector where resonance modes on the massive spectra of the graviton is obtained. The graviton resonance lifetimes are related to the existence of scales on which 4D gravity is recovered. Thus, the critical points defined by the CIMs with the existence of resonances and their lifetimes are correlated. To extend the research regarding this system, the corrections to Newton's law coming from the graviton modes are calculated.     

Letter: String Cosmology in Brane World Scenarios

We present exact solutions of the gravitational field equations in the generalized Randall-Sundrum model for an anisotropic brane with Bianchi I & V geometry and string dust as the matter source. We assume the Weyl tensor in the bulk has vanishing projection on the brane and examine the different equations of state, for the string dust system. Exact analytic solutions are possible only in few cases.     

Cosmic microwave background radiation anisotropies in brane worlds

We propose a new formulation to calculate the cosmic microwave background (CMB) spectrum in the Randall-Sundrum two-brane model based on recent progress in solving the bulk geometry using a low energy approximation. The evolution of the anisotropic stress imprinted on the brane by the 5D Weyl tensor is calculated. An impact of the dark radiation perturbation on the CMB spectrum is investigated in a simple model assuming an initially scale-invariant adiabatic perturbation. The dark radiation perturbation induces isocurvature perturbations, but the resultant spectrum can be quite different from the prediction of simple mixtures of adiabatic and isocurvature perturbations due to Weyl anisotropic stress.     

Nonlinear realization of <Emphasis Type="Italic">N</Emphasis>=2 superconformal symmetry and brane effective actions

Since there is an incompatibility of simultaneously nonlinear breaking the superconformal symmetry and the dilatation symmetry with the dilaton taken as the compensator field, in the present paper is shown an alternative mechanism of spontaneous breaking the N=2 superconformal symmetry to the N=0 case. By using the approach of nonlinear transformations one finds that it leads to a space-filling brane theory with Weyl scale W(1,3) symmetry. The dynamics of the resulting Weyl scale invariant brane, along with that of other Nambu–Goldstone fields, is derived in terms of the building blocks of the vierbein and the covariant derivative from the Maurer–Cartan one-forms. A general coupling of the matter fields localized on the brane world volume to these NG fields is also constructed.     

Modified gravitational equations on braneworld with Lorentz invariant violation

The modified gravitational equations to describe a four-dimensional braneworld in the case with the Lorentz invariant violation in a bulk spacetime is presented. It contains a trace part of the brane energy-momentum tensor and the coefficients of all terms describe the Lorentz violation effects from the bulk spacetime. As an application, we apply this formalism to study cosmology. In respect to standard effective Friedmann equations on the brane, Lorentz invariance violation in the bulk causes a modification of this equations that can lead to significant physical consequences. In particular, the effective Friedmann equation on the brane explicitly depends on the equation of state of the brane matter and the Lorentz violating parameters. We show that the components of five-dimensional Weyl curvature are related to the matter on brane even at low energies. We also find that the constraints on the theory parameters are depend on the equation of state of the energy components of the brane matter. Finally, the stability of the model depend on the specific choices of initial conditions and the parameters β _i .     

Configurational entropy of systems with non-additive lateral interactions

The configurational entropy per site of a lattice gas model with non-additive interactions between adsorbed particles for square, triangular and honeycomb lattices is discussed in the present study. The model used here assumes that the energy which links a certain atom with any of its nearest-neighbors strongly depends on the state of occupancy in the first coordination sphere of that adatom. By means of Monte Carlo simulations in the canonical ensemble by following the algorithm of parallel tempering and the thermodynamic integration method the configurational entropy per site has been calculated. By analyzing the behavior of the configurational entropy per site, the different low-temperature-ordered phases are described. The dependency of the critical temperature of the system as a function of characteristic parameters of the model is established.     

Abelian and non‐abelian D‐brane effective actions

In this Ph.D. thesis, accepted at the Vrije Universiteit Brussel, we review and elaborate on a method to find the D‐brane effective action, based on BPS equations. Firstly, both for the Yang‐Mills action and the Born‐Infeld action it is shown that these configurations are indeed BPS, i.e. solutions to these equations saturate a Bogomolny bound and leave some supersymmetry unbroken. Next, we use the BPS equations as a tool to construct the D‐brane effective action and require that (a deformation of) these equations should still imply the equations of motion in more general cases. In the abelian case we managed to calculate all order in α′ four‐derivative corrections to the effective action and the BPS equations while in the non‐abelian case we obtained the effective action up to order α′⁴. Furthermore, we discuss a check based on the spectrum of strings stretching between intersecting branes. Finally, this Ph.D. thesis also discusses the construction of a boundary superspace which would be the first step to use the method of Weyl invariance in N = 2 superspace in order to again construct the D‐brane effective action. A more detailed summary of each section can be found in the introduction.     

Black hole acoustics in the minimal geometric deformation of a de Laval nozzle

The correspondence between sound waves, in a de Laval propelling nozzle, and quasinormal modes emitted by brane-world black holes deformed by a 5D bulk Weyl fluid are here explored and scrutinized. The analysis of sound waves patterns in a de Laval nozzle in the laboratory, reciprocally, is here shown to provide relevant data about the 5D bulk Weyl fluid and its on-brane projection, comprised by the minimal geometrically deformed compact stellar distribution on the brane. Acoustic perturbations of the gas fluid flow in the de Laval nozzle are proved to coincide with the quasinormal modes of black holes solutions deformed by the 5D Weyl fluid, in the geometric deformation procedure. Hence, in a phenomenological Eötvös–Friedmann fluid brane-world model, the realistic shape of a de Laval nozzle is derived and its consequences studied.     

The Friedmann equation in brane-world scenarios

The Friedmann law on the brane generically depends quadratically on the brane energy density and involves a "dark radiation" term due to the bulk Weyl tensor. Despite its unfamiliar form, we show how it can be derived from a standard four-dimensional Brans-Dicke theory at low energy. In particular, the dark radiation term is found to depend linearly on the brane energy densities. For any equation of state on the branes, the radion evolves such as to generate radiation-dominated cosmology. The radiation-dominated era is conventional and consistent with nucleosynthesis.     

Spherically Symmetric Solutions and Dark Matter on the Brane

It has recently been suggested that our universe is a three-brane embedded in a higher dimensional spacetime. In this paper I examine static, spherically symmetric solutions that satisfy the effective Einstein field equations on a brane embedded in a five dimensional spacetime. The field equations involve a term depending on the five dimensional Weyl tensor, so that the solutions will not be Schwarzschild in general. This Weyl term is traceless so that any solution of ⁽⁴⁾ R = 0 is a possible four dimensional spacetime. Different solutions correspond to different five dimensional spacetimes and to different induced energy-momentum tensors on the brane. One interesting possibility is that the Weyl term could be responsible for the observed dark matter in the universe. It is shown that there are solutions of the equation ⁽⁴⁾ R = 0 that can account for the observed rotation curves of spiral galaxies.     

Black string perturbations in RS1 model

Keywords We present a general formalism for black string perturbations in the Randall-Sundrum 1 model (RS1). First, we derive the master equation for the electric part of the Weyl tensor E _μν. Solving the master equation using the gradient expansion method, we give the effective Teukolsky equation on the brane at low energy. It is useful to estimate gravitational waves emitted by perturbed rotating black strings. We also argue on the effect of the Gregory-Laflamme instability on the brane using our formalism.     

Generalization of the Williams--Landel--Ferry equation

Based on the model of Gibbs-Di Marzio we write the logarithmic shift factor without explicit knowledge of the form for the entropy, an expression which enables us to write a generalization of the Williams--Landel--Ferry equation. Comparison with the empirical relation of Williams--Landel--Ferry and use of the fact that the model exhibits the existence of a isoentropic temperature T₀ for which the configurational entropy of the system vanishes, leads to a value of the isoentropic temperature for which the configurational entropy of the system vanishes. The form for the specific heat proposed by Dowell and Di Marzio based on the lattice model of Gibbs-Di Marzio for the glass transition of polymeric substances, has been used by García-Colín et al. to find the molar configurational entropy (MCE) of glass. Knowledge of the form of the MCE, allows us to find an expression for the critical configurational entropy (S^*_c) and a form for the potential energy hindering the cooperative rearrangement per monomer segment (Δμ).     

Configurational Entropy of Confined Yukawa Clusters

Confined strongly coupled systems, such as dust clusters in complex plasmas, are known to support multiple stable configurations corresponding to the same number of particles. In this work, we exploit the recently introduced concept of configurational entropy as a robust measure of the uncertainty arising due to the existence of multiple stable states with different occurrence probabilities. We apply this concept to classical Yukawa clusters of up to 100 particles in two‐ and three‐dimensional parabolic traps and investigate the dependence of the entropy on the system size, dimensionality, interparticle interaction range and anisotropy of the parabolic confinement. A universal behaviour of the configurational entropy close to the dimensional (zigzag) transition is reported (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Entropic measure for localized energy configurations: Kinks,bounces, and bubbles

We construct a configurational entropy measure in functional space. We apply it to several nonlinear scalar field models featuring solutions with spatially-localized energy, including solitons and bounces in one spatial dimension, and critical bubbles in three spatial dimensions, typical of first-order phase transitions. Such field models are of widespread interest in many areas of physics, from high energy and cosmology to condensed matter. Using a variational approach, we show that the higher the energy of a trial function that approximates the actual solution, the higher its relative configurational entropy, defined as the absolute difference between the configurational entropy of the actual solution and of the trial function. Furthermore, we show that when different trial functions have degenerate energies, the configurational entropy can be used to select the best fit to the actual solution. The configurational entropy relates the dynamical and informational content of physical models with localized energy configurations.     

Simulation of spatial correlations of impurity ions in solids using configurational entropy and the hard-sphere model

Based on the hard-sphere model, the spatial correlations are considered in a system of impurities with variable valency. In a zeroth approximation, the configurational entropy of the spatially correlated system of impurity ions is identified with the configurational entropy of a system of hard spheres. The electron mobility limited by scattering on the correlated system of impurity ions at finite temperatures is found. The theory developed explains experimentally observed anomalies of the carrier mobility in an iron-doped HgSe gapless semiconductor.     

Asymptotic Lifshitz-Like Solution in Lovelock Gravityn=3

With R² and R³ corrections to asymptotical Lifshitz space-time,we obtain pure Lovelock gravity solution and solution with non-trivial matter in 7-dimensional space-time. Then we obtain the general solution for any arbitrary dimensional space. In this paper, we also study black brane solutions in 7-dimensional Lifshitz space-time via the method of perturbation. And we popularize the black brane solution to arbitrary higher dimensions and discuss the
ratio of shear viscosity to entropy density ratioη/s. Then we analyze the result ofη/s to find that the correction of n-th (n≥3) order Lovelock term has trivial influence toη/s.