261 research outputs found
Supergravity at the boundary of AdS supergravity
We give a general analysis of AdS boundary conditions for spin-3/2
Rarita-Schwinger fields and investigate boundary conditions preserving
supersymmetry for a graviton multiplet in AdS_4. Linear Rarita-Schwinger fields
in AdS_d are shown to admit mixed Dirichlet-Neumann boundary conditions when
their mass is in the range . We also demonstrate that
mixed boundary conditions are allowed for larger masses when the inner product
is "renormalized" accordingly with the action. We then use the results obtained
for |m| = 1/l_{AdS} to explore supersymmetric boundary conditions for N = 1
AdS_4 supergravity in which the metric and Rarita-Schwinger fields are
fluctuating at the boundary. We classify boundary conditions that preserve
boundary supersymmetry or superconformal symmetry. Under the AdS/CFT
dictionary, Neumann boundary conditions in d=4 supergravity correspond to
gauging the superconformal group of the 3-dimensional CFT describing M2-branes,
while N = 1 supersymmetric mixed boundary conditions couple the CFT to N = 1
superconformal topologically massive gravity.Comment: 23 pages, RevTe
Three dimensional origin of Godel spacetimes and black holes
We construct Godel-type black hole and particle solutions to Einstein-Maxwell
theory in 2+1 dimensions with a negative cosmological constant and a
Chern-Simons term. On-shell, the electromagnetic stress-energy tensor
effectively replaces the cosmological constant by minus the square of the
topological mass and produces the stress-energy of a pressure-free perfect
fluid. We show how a particular solution is related to the original Godel
universe and analyze the solutions from the point of view of identifications.
Finally, we compute the conserved charges and work out the thermodynamics.Comment: 11 pages, 5 figures, twocolumn revtex style, reference added,
acknowledgments correcte
Boundary conditions for spacelike and timelike warped AdS_3 spaces in topologically massive gravity
We propose a set of consistent boundary conditions containing the spacelike
warped black holes solutions of Topologically Massive Gravity. We prove that
the corresponding asymptotic charges whose algebra consists in a Virasoro
algebra and a current algebra are finite, integrable and conserved. A similar
analysis is performed for the timelike warped AdS_3 spaces which contain a
family of regular solitons. The energy of the boundary Virasoro excitations is
positive while the current algebra leads to negative (for the spacelike warped
case) and positive (for the timelike warped case) energy boundary excitations.
We discuss the relationship with the Brown-Henneaux boundary conditions.Comment: 16 pages, ESI proceedings, v2: typos corrected, published versio
Supersymmetric G\"odel and warped black holes in string theory
It is observed that three-dimensional G\"odel black holes can be promoted to
exact string theory backgrounds through an orbifold of an hyperbolic asymmetric
marginal deformation of the SL(2,R) WZW model. Tachyons are found in the
spectrum of long strings. Uplifting these solutions in type IIB supergravity,
extremal black holes are shown to preserve one supersymmetry in accordance with
the BTZ limit. We also make connections with some recently discussed warped
black hole solutions of topologically massive gravity, showing that they
actually correspond to quotients of spacelike squashed AdS_3.Comment: 15 page
Solitons in Five Dimensional Minimal Supergravity: Local Charge, Exotic Ergoregions, and Violations of the BPS Bound
We describe a number of striking features of a class of smooth solitons in
gauged and ungauged minimal supergravity in five dimensions. The solitons are
globally asymptotically flat or asymptotically AdS without any Kaluza-Klein
directions but contain a minimal sphere formed when a cycle pinches off in the
interior of the spacetime. The solutions carry a local magnetic charge and many
have rather unusual ergosurfaces. Perhaps most strikingly, many of the solitons
have more electric charge or, in the asymptotically AdS case, more electric
charge and angular momentum than is allowed by the usual BPS bound. We comment
on, but do not resolve, the new puzzle this raises for AdS/CFT.Comment: 60 pages, 12 figures, 3 table
The holographic fluid dual to vacuum Einstein gravity
We present an algorithm for systematically reconstructing a solution of the
(d+2)-dimensional vacuum Einstein equations from a (d+1)-dimensional fluid,
extending the non-relativistic hydrodynamic expansion of Bredberg et al in
arXiv:1101.2451 to arbitrary order. The fluid satisfies equations of motion
which are the incompressible Navier-Stokes equations, corrected by specific
higher derivative terms. The uniqueness and regularity of this solution is
established to all orders and explicit results are given for the bulk metric
and the stress tensor of the dual fluid through fifth order in the hydrodynamic
expansion. We establish the validity of a relativistic hydrodynamic description
for the dual fluid, which has the unusual property of having a vanishing
equilibrium energy density. The gravitational results are used to identify
transport coefficients of the dual fluid, which also obeys an interesting and
exact constraint on its stress tensor. We propose novel Lagrangian models which
realise key properties of the holographic fluid.Comment: 31 pages; v2: references added and minor improvements, published
versio
Non-Einstein geometries in Chiral Gravity
We analyze the asymptotic solutions of Chiral Gravity (Topologically Massive
Gravity at \mu l = 1 with Brown-Henneaux boundary conditions) focusing on
non-Einstein metrics. A class of such solutions admits curvature singularities
in the interior which are reflected as singularities or infinite bulk energy of
the corresponding linear solutions. A non-linear solution is found exactly. The
back-reaction induces a repulsion of geodesics and a shielding of the
singularity by an event horizon but also introduces closed timelike curves.Comment: 11 pages, 3 figures. v2: references and comments on linear stability
(Sect.2) adde
Classical central extension for asymptotic symmetries at null infinity in three spacetime dimensions
The symmetry algebra of asymptotically flat spacetimes at null infinity in
three dimensions is the semi-direct sum of the infinitesimal diffeomorphisms on
the circle with an abelian ideal of supertranslations. The associated charge
algebra is shown to admit a non trivial classical central extension of Virasoro
type closely related to that of the anti-de Sitter case.Comment: 4 sign mistakes due to a change of conventions are corrected in
section 2, none of the conclusions are affected, takes precedence over
published version, including corrigendu
Relaxing the Parity Conditions of Asymptotically Flat Gravity
Four-dimensional asymptotically flat spacetimes at spatial infinity are
defined from first principles without imposing parity conditions or
restrictions on the Weyl tensor. The Einstein-Hilbert action is shown to be a
correct variational principle when it is supplemented by an anomalous
counter-term which breaks asymptotic translation, supertranslation and
logarithmic translation invariance. Poincar\'e transformations as well as
supertranslations and logarithmic translations are associated with finite and
conserved charges which represent the asymptotic symmetry group. Lorentz
charges as well as logarithmic translations transform anomalously under a
change of regulator. Lorentz charges are generally non-linear functionals of
the asymptotic fields but reduce to well-known linear expressions when parity
conditions hold. We also define a covariant phase space of asymptotically flat
spacetimes with parity conditions but without restrictions on the Weyl tensor.
In this phase space, the anomaly plays classically no dynamical role.
Supertranslations are pure gauge and the asymptotic symmetry group is the
expected Poincar\'e group.Comment: Four equations corrected. Two references adde
G2 Dualities in D=5 Supergravity and Black Strings
Five dimensional minimal supergravity dimensionally reduced on two commuting
Killing directions gives rise to a G2 coset model. The symmetry group of the
coset model can be used to generate new solutions by applying group
transformations on a seed solution. We show that on a general solution the
generators belonging to the Cartan and nilpotent subalgebras of G2 act as
scaling and gauge transformations, respectively. The remaining generators of G2
form a sl(2,R)+sl(2,R) subalgebra that can be used to generate non-trivial
charges. We use these generators to generalize the five dimensional Kerr string
in a number of ways. In particular, we construct the spinning electric and
spinning magnetic black strings of five dimensional minimal supergravity. We
analyze physical properties of these black strings and study their
thermodynamics. We also explore their relation to black rings.Comment: typos corrected (26 pages + appendices, 2 figures
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