63 research outputs found
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
CosmologĂa no estándar: presente y futuro del Universo
Tesis doctoral inĂ©dita. Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de FĂsica TeĂłrica. 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
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