2,028 research outputs found
Gravitational Couplings, Orientifolds and M-Planes
We examine string-theory orientifold planes of various types including the Sp
and SO-odd planes, and deduce the gravitational Chern-Simons couplings on their
world-volumes. Consistency checks are carried out in different spacetime
dimensions using various dualities, including those relating string theory with
F-theory and M-theory. It is shown that when an orientifold 3-plane crosses a
5-brane, the jump in the charge is accompanied by a corresponding change in the
gravitational couplings.Comment: 14 pages, harvmac (b), 2 figures, referencing improved and a
reference added, no changes in conten
Gauge-Invariant Couplings of Noncommutative Branes to Ramond-Ramond Backgrounds
We derive the couplings of noncommutative D-branes to spatially varying
Ramond-Ramond fields, extending our earlier results in hep-th/0009101. These
couplings are expressed in terms of *n products of operators involving open
Wilson lines. Equivalence of the noncommutative to the commutative couplings
implies interesting identities as well as an expression for the Seiberg-Witten
map that was previously conjectured. We generalise our couplings to include
transverse scalars, thereby obtaining a Seiberg-Witten map relating commutative
and noncommutative descriptions of these scalars. RR couplings for unstable
non-BPS branes are also proposed.Comment: harvmac, 22 pages, v2: typos corrected, references and
acknowledgements adde
Holographic chiral induced W-gravities
We study boundary conditions for 3-dimensional higher spin gravity that admit
asymptotic symmetry algebras expected of 2-dimensional induced higher spin
theories in the light cone gauge. For the higher spin theory based on sl(3, R)
plus sl(3,R) algebra, our boundary conditions give rise to one copy of
classical W3 and a copy of sl(3,R) or su(1,2) Kac-Moody symmetry algebra. We
propose that the higher spin theories with these boundary conditions describe
appropriate chiral induced W-gravity theories on the boundary. We also consider
boundary conditions of spin-3 higher spin gravity that admit u(1) plus u(1)
current algebra.Comment: 19 page
On Asymptotic Symmetries of 3d Extended Supergravities
We study asymptotic symmetry algebras for classes of three dimensional
supergravities with and without cosmological constant. In the first part we
generalise some of the non-Dirichlet boundary conditions of gravity to
extended supergravity theories, and compute their asymptotic symmetries. In
particular, we show that the boundary conditions proposed to holographically
describe the chiral induced gravity and Liouville gravity do admit extension to
the supergravity contexts with appropriate superalgebras as their asymptotic
symmetry algebras. In the second part we consider generalisation of the 3d
computation to extended supergravities without cosmological constant, and
show that their asymptotic symmetry algebras provide examples of nonlinear
extended superalgebras containing the algebra
Counterterms, critical gravity and holography
We consider counterterms for odd dimensional holographic CFTs. These
counterterms are derived by demanding cut-off independence of the CFT partition
function on and . The same choice of counterterms
leads to a cut-off independent Schwarzschild black hole entropy. When treated
as independent actions, these counterterm actions resemble critical theories of
gravity, i.e., higher curvature gravity theories where the additional massive
spin-2 modes become massless. Equivalently, in the context of AdS/CFT, these
are theories where at least one of the central charges associated with the
trace anomaly vanishes. Connections between these theories and logarithmic CFTs
are discussed. For a specific choice of parameters, the theories arising from
counterterms are non-dynamical and resemble a DBI generalization of gravity.
For even dimensional CFTs, analogous counterterms cancel log-independent
cut-off dependence.Comment: 28 pages, v2: references added, v3: minor changes, version to appear
in PR
Brane-Antibrane Constructions
In type II string theories, we examine intersecting brane constructions
containing brane-antibrane pairs suspended between 5-branes, and more general
non-BPS constructions. The tree-level spectra are obtained in each case. We
identify various models with distinct physics: parallel brane-antibrane pairs,
adjacent pairs, non-adjacent pairs, and configurations which break all
supersymmetry even though any pair of branes preserves some supersymmetry. In
each case we examine the possible decay modes. Some of these configurations
turn out to be tachyon-free, stable non-BPS states. We use T-duality to map
some of our brane constructions to brane-antibrane pairs at ALE singularities.
This enables us to explicitly derive the spectra by the analogue of the quiver
construction, and to compute the sign of the brane-antibrane force in each
case.Comment: 40 pages, harvmac (b), 14 eps figures (included), v2: references
added and report no. corrected, no other change
An sl(2, R) current algebra from AdS_3 gravity
We provide a set of chiral boundary conditions for three-dimensional gravity
that allow for asymptotic symmetries identical to those of two-dimensional
induced gravity in light-cone gauge considered by Polyakov. These are the most
general boundary conditions consistent with the boundary terms introduced by
Compere, Song and Strominger recently. We show that the asymptotic symmetry
algebra of our boundary conditions is an sl(2,R) current algebra with level
given by c/6. The fully non-linear solution in Fefferman--Graham coordinates is
also provided along with its charges.Comment: 8 page
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