Gauss-Bonnet Brane Cosmology with Radion Stabilization

We study cosmology in a five-dimensional brane-world with a stabilizing effective potential for the radion and matter localized on the two branes. We consider the corrections induced by the Gauss-Bonnet contribution to the total action performing and expansion around the two possible static solutions up to second order in the ratio between brane matter energy density and brane tensions. The Friedmann and acceleration equations on the visible brane are obtained and discussed.Comment: To be published in Phys.Rev.D, References Adde

Thermodynamics of a collapsing shell in an expanding Universe

We describe the quasi-static collapse of a radiating, spherical shell of matter in de Sitter space-time using a thermodynamical formalism. It is found that the specific heat at constant area and other thermodynamical quantities exhibit singularities related to phase transitions during the collapse.Comment: 9 pages, 2 figures, accepted for publication in Phys. Lett.

Second order brane cosmology with radion stabilization

We study cosmology in the five-dimensional Randall-Sundrum brane-world with a stabilizing effective potential for the radion and matter localized on the branes. The analysis is performed by employing a perturbative expansion in the ratio rho/V between the matter energy density on the branes and the brane tensions around the static Randall-Sundrum solution (which has rho=0 and brane tensions +-V). This approach ensures that the matter evolves adiabatically and allows us to find approximate solutions to second order in \rho/V. Some particular cases are then analyzed in details.Comment: 17 pages, RevTeX4, 4 figures, final version to appear in Phys. Rev.

On boundary terms and conformal transformations in curved space-times

We intend to clarify the interplay between boundary terms and conformal transformations in scalar-tensor theories of gravity. We first consider the action for pure gravity in five dimensions and show that, on compactifing a la Kaluza-Klein to four dimensions, one obtains the correct boundary terms in the Jordan (or String) Frame form of the Brans-Dicke action. Further, we analyze how the boundary terms change under the conformal transformations which lead to the Pauli (or Einstein) frame and to the non-minimally coupled massless scalar field. In particular, we study the behaviour of the total energy in asymptotically flat space-times as it results from surface terms in the Hamiltonian formalism.Comment: LaTeX 2e, 12 pages, no figure