810 research outputs found
All the solutions of the form M2(warped)x\Sigma(d-2) for Lovelock gravity in vacuum in the Chern-Simons case
In this note we classify a certain family of solutions of Lovelock gravity in
the Chern-Simons (CS) case, in arbitrary (odd) dimension greater than four. The
spacetime is characterized by admitting a metric that is a warped product of a
two-dimensional spacetime M2 and an (a priori) arbitrary Euclidean base
manifold Sigma(d-2) of dimension d-2. We show that the solutions are naturally
classified in terms of the equations that restrict the base manifold. According
to the strength of such constraints we found the following branches in which
Sigma(d-2) has to fulfill: a Lovelock equation with a single vacuum (Euclidean
Lovelock Chern-Simons in dimension d-2), a single scalar equation that is the
trace of an Euclidean Lovelock CS equation in dimension d-2, or finally a
degenerate case in which the base manifold is not restricted at all. We show
that all the cases have some degeneracy in the sense that the metric functions
are not completely fixed by the field equations. This result extends the static
five-dimensional case previously discussed in Phys.Rev. D76 (2007) 064038, and
it shows that in the CS case, the inclusion of higher powers in the curvature
does not introduce new branches of solutions in Lovelock gravity. Finally we
comment on how the inclusion of a non-vanishing torsion and matter fields may
modify this analysis.Comment: 15 pages, no figure
Topological self-dual vacua of deformed gauge theories
We propose a deformation principle of gauge theories in three dimensions that
can describe topologically stable self-dual gauge fields, i.e., vacua
configurations that in spite of their masses do not deform the background
geometry and are locally undetected by charged particles. We interpret these
systems as describing boundary degrees of freedom of a self-dual Yang-Mills
field in dimensions with mixed boundary conditions. Some of these fields
correspond to Abrikosov-like vortices with an exponential damping in the
direction penetrating into the bulk. We also propose generalizations of these
ideas to higher dimensions and arbitrary p-form gauge connections.Comment: 18 page
Four-dimensional Traversable Wormholes and Bouncing Cosmologies in Vacuum
In this letter we point out the existence of solutions to General Relativity
with a negative cosmological constant in four dimensions, which contain
solitons as well as traversable wormholes. The latter connect two
asymptotically locally AdS spacetimes. At every constant value of the
radial coordinate the spacetime is a spacelike warped AdS. We compute the
dual energy momentum tensor at each boundary showing that it yields different
results. We also show that these vacuum wormholes can have more than one throat
and that they are indeed traversable by computing the time it takes for a light
signal to go from one boundary to the other, as seen by a geodesic observer. We
generalize the wormholes to include rotation and charge. When the cosmological
constant is positive we find a cosmology that is everywhere regular, has either
one or two bounces and that for late and early times matches the
Friedmann-Lema\^{\i}tre-Robertson-Walker metric with spherical topology.Comment: 12 pages, 2 figure
Birkhoff's Theorem in Higher Derivative Theories of Gravity
In this paper we present a class of higher derivative theories of gravity
which admit Birkhoff's theorem. In particular, we explicitly show that in this
class of theories, although generically the field equations are of fourth
order, under spherical (plane or hyperbolic) symmetry, all the field equations
reduce to second order and have exactly the same or similar structure to those
of Lovelock theories, depending on the spacetime dimensions and the order of
the Lagrangian.Comment: 7 pages, no figures. v1: This version received an Honorable Mention
from the Gravity Research Foundation - 2011 Awards for Essays on Gravitation.
v2: Expanded version. To appear in CQ
Hairy Black Hole Stability in AdS, Quantum Mechanics on the Half-Line and Holography
We consider the linear stability of -dimensional hairy black holes with
mixed boundary conditions in Anti-de Sitter spacetime. We focus on the mass of
scalar fields around the maximally supersymmetric vacuum of the gauged
supergravity in four dimensions, . It is shown
that the Schr\"{o}dinger operator on the half-line, governing the ,
or invariant mode around the hairy black hole, allows
for non-trivial self-adjoint extensions and each of them correspons to a class
of mixed boundary conditions in the gravitational theory. Discarding the
self-adjoint extensions with a negative mode impose a restriction on these
boundary conditions. The restriction is given in terms of an integral of the
potential in the Schr\"{o}dinger operator resembling the estimate of Simon for
Schr\"{o}dinger operators on the real line. In the context of AdS/CFT duality,
our result has a natural interpretation in terms of the field theory dual
effective potential.Comment: 13 pages, no figures, references added, matches published versio
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