77 research outputs found
Diffeomorphisms and Holographic Anomalies
Using the relation between diffeomorphisms in the bulk and Weyl
transformations on the boundary we study the Weyl transformation properties of
the bulk metric on shell and of the boundary action. We obtain a universal
formula for one of the classes of trace anomalies in any even dimension in
terms of the parameters of the gravity action.Comment: 12 pages, harvma
Black Hole Scan
Gravitation theories selected by requiring that they have a unique anti-de
Sitter vacuum with a fixed cosmological constant are studied. For a given
dimension d, the Lagrangians under consideration are labeled by an integer
k=1,2,...,[(d-1)/2]. Black holes for each d and k are found and are used to
rank these theories. A minimum possible size for a localized electrically
charged source is predicted in the whole set of theories, except General
Relativity. It is found that the thermodynamic behavior falls into two classes:
If d-2k=1, these solutions resemble the three dimensional black hole,
otherwise, their behavior is similar to the Schwarzschild-AdS_4 geometry.Comment: Two columns, revtex, 15 pages, 5 figures, minor typos corrected,
final version for Journa
Massive type IIA string theory cannot be strongly coupled
Understanding the strong coupling limit of massive type IIA string theory is
a longstanding problem. We argue that perhaps this problem does not exist;
namely, there may be no strongly coupled solutions of the massive theory. We
show explicitly that massive type IIA string theory can never be strongly
coupled in a weakly curved region of space-time. We illustrate our general
claim with two classes of massive solutions in AdS4xCP3: one, previously known,
with N = 1 supersymmetry, and a new one with N = 2 supersymmetry. Both
solutions are dual to d = 3 Chern-Simons-matter theories. In both these massive
examples, as the rank N of the gauge group is increased, the dilaton initially
increases in the same way as in the corresponding massless case; before it can
reach the M-theory regime, however, it enters a second regime, in which the
dilaton decreases even as N increases. In the N = 2 case, we find
supersymmetry-preserving gauge-invariant monopole operators whose mass is
independent of N. This predicts the existence of branes which stay light even
when the dilaton decreases. We show that, on the gravity side, these states
originate from D2-D0 bound states wrapping the vanishing two-cycle of a
conifold singularity that develops at large N.Comment: 43 pages, 5 figures. v2: added reference
M-Theory as a Holographic Field Theory
We suggest that M-theory could be non-perturbatively equivalent to a local
quantum field theory. More precisely, we present a ``renormalizable'' gauge
theory in eleven dimensions, and show that it exhibits various properties
expected of quantum M-theory, most notably the holographic principle of
't~Hooft and Susskind. The theory also satisfies Mach's principle: A
macroscopically large space-time (and the inertia of low-energy excitations) is
generated by a large number of ``partons'' in the microscopic theory. We argue
that at low energies in large eleven dimensions, the theory should be
effectively described by eleven-dimensional supergravity. This effective
description breaks down at much lower energies than naively expected, precisely
when the system saturates the Bekenstein bound on energy density. We show that
the number of partons scales like the area of the surface surrounding the
system, and discuss how this holographic reduction of degrees of freedom
affects the cosmological constant problem. We propose the holographic field
theory as a candidate for a covariant, non-perturbative formulation of quantum
M-theory.Comment: 27 pp. v2: typos corrected; a small paragraph on naturalness of small
cosmological constant in four dimensions added at end of sect 5.1; final
version to appear in Phys. Rev.
New Gauge Supergravity in Seven and Eleven Dimensions
Locally supersymmetric systems in odd dimensions whose Lagrangians are
Chern-Simons forms for supersymmetric extensions of anti-de Sitter gravity are
discussed. The construction is illustrated for D=7 and 11. In seven dimensions
the theory is an N=2 supergravity whose fields are the vielbein
(), the spin connection (), two gravitini
() and an gauge connection (). These
fields form a connection for . In eleven dimensions the theory is an
N=1 supergravity containing, apart from and ,
one gravitino , and a totally antisymmetric fifth rank Lorentz
tensor one-form, . These fields form a connection for
. The actions are by construction invariant under local
supersymmetry and the algebra closes off shell without requiring auxiliary
fields. The -theory can be shown to have nonnegative energy around
an AdS background, which is a classical solution that saturates the Bogomolnyi
bound obtained from the superalgebra.Comment: 5pages, RevTeX, no figures, two columns, minor typos correcte
Black holes with topologically nontrivial AdS asymptotics
Asymptotically locally AdS black hole geometries of dimension d > 2 are
studied for nontrivial topologies of the transverse section. These geometries
are static solutions of a set of theories labeled by an integer 0 < k <
[(d-1)/2] which possess a unique globally AdS vacuum. The transverse sections
of these solutions are d-2 surfaces of constant curvature, allowing for
different topological configurations. The thermodynamic analysis of these
solutions reveals that the presence of a negative cosmological constant is
essential to ensure the existence of stable equilibrium states. In addition, it
is shown that these theories are holographically related to [(d-1)/2] different
conformal field theories at the boundary.Comment: 13 Pages, 3 figures, two columns, Revtex, last version for PR
Holography and the Polyakov action
In two dimensional conformal field theory the generating functional for
correlators of the stress-energy tensor is given by the non-local Polyakov
action associated with the background geometry. We study this functional
holographically by calculating the regularized on-shell action of
asymptotically AdS gravity in three dimensions, associated with a specified
(but arbitrary) boundary metric. This procedure is simplified by making use of
the Chern-Simons formulation, and a corresponding first-order expansion of the
bulk dreibein, rather than the metric expansion of Fefferman and Graham. The
dependence of the resulting functional on local moduli of the boundary metric
agrees precisely with the Polyakov action, in accord with the AdS/CFT
correspondence. We also verify the consistency of this result with regard to
the nontrivial transformation properties of bulk solutions under Brown-Henneaux
diffeomorphisms.Comment: 20 pages, RevTeX, v2: minor typos corrected and references adde
: Familias populares e institução escolar : entre autonomia e heteronomia
Version française de "Familias populares e institução escolar : entre autonomia e heteronomia", Educação e Pesquisa, 2010, vol. 36, n°espcial, p. 65-76International audienceL'article se propose d'analyser quelques problèmes théoriques dans l'étude des relations entre familles populaires et école, problèmes qui sont ceux que rencontre la sociologie dans l'étude des classes populaires et de leurs relations avec le monde dominant et les institutions. Il explore la possibilité de dépasser l'alternative entre une perspective strictement légitimiste qui tend à réduire les classes populaires et leurs pratiques au rapport de domination qui les aliène (hétéronomie) et la perspective relativiste qui les envisage dans une altérité radicale (autonomie) en occultant les rapports sociaux de domination. Il insiste sur l'ambivalence des logiques et des pratiques des familles populaire
Spacelike Singularities and Hidden Symmetries of Gravity
We review the intimate connection between (super-)gravity close to a
spacelike singularity (the "BKL-limit") and the theory of Lorentzian Kac-Moody
algebras. We show that in this limit the gravitational theory can be
reformulated in terms of billiard motion in a region of hyperbolic space,
revealing that the dynamics is completely determined by a (possibly infinite)
sequence of reflections, which are elements of a Lorentzian Coxeter group. Such
Coxeter groups are the Weyl groups of infinite-dimensional Kac-Moody algebras,
suggesting that these algebras yield symmetries of gravitational theories. Our
presentation is aimed to be a self-contained and comprehensive treatment of the
subject, with all the relevant mathematical background material introduced and
explained in detail. We also review attempts at making the infinite-dimensional
symmetries manifest, through the construction of a geodesic sigma model based
on a Lorentzian Kac-Moody algebra. An explicit example is provided for the case
of the hyperbolic algebra E10, which is conjectured to be an underlying
symmetry of M-theory. Illustrations of this conjecture are also discussed in
the context of cosmological solutions to eleven-dimensional supergravity.Comment: 228 pages. Typos corrected. References added. Subject index added.
Published versio
Categorizing Different Approaches to the Cosmological Constant Problem
We have found that proposals addressing the old cosmological constant problem
come in various categories. The aim of this paper is to identify as many
different, credible mechanisms as possible and to provide them with a code for
future reference. We find that they all can be classified into five different
schemes of which we indicate the advantages and drawbacks.
Besides, we add a new approach based on a symmetry principle mapping real to
imaginary spacetime.Comment: updated version, accepted for publicatio
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