Lorentzian wormholes generalize thermodynamics still further

This paper deals with some thermodynamical aspects of Lorentzian wormholes, including the formulation of the three main laws and the consideration of a possible thermal emission made up of some sort of phantom radiation coming out from the wormhole at a negative temperature. In order for these topics to be consistently developed we have used a 2+2 formalism first advanced by Hayward for spherically symmetric spacetimes, where a generalized surface gravity is defined on the trapping horizon. Our results generalize still further those of the already generalized gravitational thermodynamics. © 2009 IOP Publishing Ltd.This work was supported by a Spanish MEC Research Project No. FIS2008-06332/FIS.Peer Reviewe

Stability in quadratic torsion theories

We revisit the definition and some of the characteristics of quadratic theories of gravity with torsion. We start from the most general Lagrangian density quadratic in the curvature and torsion tensors. By assuming that General Relativity should be recovered when torsion vanishes and investigating the behaviour of the vector and pseudovector torsion fields in the weak-gravity regime, we present a set of necessary conditions for the stability of these theories. Moreover, we explicitly obtain the gravitational field equations using the Palatini variational principle with the metricity condition implemented via a Lagrange multiplier

Cosmología no estándar: presente y futuro del Universo

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 19-07-201

Isotropic extensions of the vacuum solutions in general relativity

In this work, we obtain isotropic extensions of the usual spherically symmetric vacuum geometries in general relativity. Exact and perturbative solutions are derived. The classes of geometries obtained include black holes in compact and noncompact universes, wormholes in the interior region of cosmological horizons, and anti-de Sitter geometries with excess/deficit solid angle. The tools developed here are applicable in more general contexts.Comment: 12 pages, 6 figures. Version to be published in Physical Review