Article
Exactly solvable model for cosmological perturbations in dilatonic brane worlds
Physical review D: Particles and fields 07/2003; DOI: 10.1103/PhysRevD.68.103512
Source: arXiv

Article: Models for the branebulk interaction: Toward understanding braneworld cosmological perturbations
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ABSTRACT: Using some simple toy models, we explore the nature of the branebulk interaction for cosmological models with a large extra dimension. We are in particular interested in understanding the role of the bulk gravitons, which from the point of view of an observer on the brane will appear to generate dissipation and nonlocality, effects that cannot be incorporated into an effective (3+1)dimensional Lagrangian field theoretic description. We explicitly work out the dynamics of several discrete systems consisting of a finite number of degrees of freedom on the boundary coupled to a (1+1)dimensional field theory subject to a variety of wave equations. Systems both with and without time translation invariance are considered and moving boundaries are discussed as well. The models considered contain all the qualitative features of quantized linearized cosmological perturbations for a RandallSundrum universe having an arbitrary expansion history, with the sole exception of gravitational gauge invariance, which will be treated in a later paper.Physical Review D 01/2004; 70(4). · 4.69 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Abstract The braneworld paradigm provides a tool for including the extra dimensions proposed by string theory into cosmology,in a simple way. With ordinary matter confined to a surface or brane, the extra dimension(s) introduce new degrees of freedom corresponding to the bulk geometry and bulk energy density. After presenting the derivation of the governing equations for braneworlds of codimension 1 (that is, with 1 extra dimension), this thesis will look at examples,of how a nonzero bulk energymomentum,tensor can affect the cosmological evolution on the brane. In such braneworld models, particle interactions at high energies will produce 5 dimensional gravitons that escape into the bulk. Under the assumption,that all these gravitons are emitted radially, this emission can be modelled using a VaidyaAdS5 space time. In Chapter 4 we investigate the dynamics of this model, and find the exact solution of the field equations. We use a dynamical systems approach to analyze global features of the phase space of solutions. In Chapter 5, we generalise the previous radiating braneworld model by allowing for a breaking of Z2 symmetry, via different bulk cosmological constants and different initial black hole masses on either side of the brane. One of the notable features of asymmetry,is a suppression of the asymptotic level of dark radiation, which means that nucleosynthesis constraints are easier to satisfy. There are also models,where the radiation escapes to infinity on one or both sides, rather than falling into a black hole, but these models can have negative energy density on the brane.  [Show abstract] [Hide abstract]
ABSTRACT: We have considered gravity in a fivedimensional warped product spacetime, with a timedependent warp factor and a timedependent extra dimension. The field equations have been solved for a spatially flat FRW brane and the energy conditions and the nature of bulk geometry have been examined. At low energies, the trapping of fields within the brane implies a correlation between the warp factor and the extradimensional scale factor. Generally, the bulk is not conformally flat. At high energies, the bulk is sourced by a dilatonlike minimally coupled scalar field, which depends on the warp factor. Both the bulk and the brane are found to be Anti de Sitter, with some exceptions.07/2012;
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