310 research outputs found
More on Massive 3D Gravity
We explore the space of static solutions of the recently discovered
three-dimensional `New Massive Gravity' (NMG), allowing for either sign of the
Einstein-Hilbert term and a cosmological term parametrized by a dimensionless
constant . For we find black hole solutions asymptotic
(but not isometric) to the unique (anti) de Sitter vacuum, including extremal
black holes that interpolate between this vacuum and (a)dS. We
also investigate unitarity of linearized NMG in (a)dS vacua. We find unitary
theories for some dS vacua, but (bulk) unitarity in adS implies negative
central charge of the dual CFT, except for where the central charge
vanishes and the bulk gravitons are replaced by `massive photons'. A similar
phenomenon is found in the massless limit of NMG, for which the linearized
equations become equivalent to Maxwell's equations.Comment: 25 pages, 4 figures; v2: minor improvements and extensions,
references added; v3: version to appear in PR
Gravitons in Flatland
We review some features of three-dimensional (3D) massive gravity theories.
In particular, we stress the role of the Schouten tensor, explore an analogy
with Lovelock gravity and discuss renormalizabilty.Comment: 11 pages, Contribution to proceedings of the workshop {\it Cosmology,
the Quantum Vacuum and Zeta Functions} in celebration of the 60th birthday of
Emilio Elizalde; Barcelona, 8-10 March, 2010. Additional references in v
Massive Gravity in Three Dimensions
A particular higher-derivative extension of the Einstein-Hilbert action in
three spacetime dimensions is shown to be equivalent at the linearized level to
the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general
model, which also includes `topologically-massive' gravity as a special case,
propagates the two spin 2 helicity states with different masses. We discuss the
extension to massive -extended supergravity, and we present a
`cosmological' extension that admits an anti-de Sitter vacuum.Comment: Minor corrections plus a further correction to discussion of
supersymmetry in adS vacua, Version to be publishe
Ramond-Ramond Cohomology and O(D,D) T-duality
In the name of supersymmetric double field theory, superstring effective
actions can be reformulated into simple forms. They feature a pair of vielbeins
corresponding to the same spacetime metric, and hence enjoy double local
Lorentz symmetries. In a manifestly covariant manner --with regard to O(D,D)
T-duality, diffeomorphism, B-field gauge symmetry and the pair of local Lorentz
symmetries-- we incorporate R-R potentials into double field theory. We take
them as a single object which is in a bi-fundamental spinorial representation
of the double Lorentz groups. We identify cohomological structure relevant to
the field strength. A priori, the R-R sector as well as all the fermions are
O(D,D) singlet. Yet, gauge fixing the two vielbeins equal to each other
modifies the O(D,D) transformation rule to call for a compensating local
Lorentz rotation, such that the R-R potential may turn into an O(D,D) spinor
and T-duality can flip the chirality exchanging type IIA and IIB
supergravities.Comment: 1+37 pages, no figure; Structure reorganized, References added, To
appear in JHEP. cf. Gong Show of Strings 2012
(http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/Talks/Thursday/Gongshow/Lee.pdf
Gauged diffeomorphisms and hidden symmetries in Kaluza-Klein theories
We analyze the symmetries that are realized on the massive Kaluza-Klein modes
in generic D-dimensional backgrounds with three non-compact directions. For
this we construct the unbroken phase given by the decompactification limit, in
which the higher Kaluza-Klein modes are massless. The latter admits an
infinite-dimensional extension of the three-dimensional diffeomorphism group as
local symmetry and, moreover, a current algebra associated to SL(D-2,R)
together with the diffeomorphism algebra of the internal manifold as global
symmetries. It is shown that the `broken phase' can be reconstructed by gauging
a certain subgroup of the global symmetries. This deforms the three-dimensional
diffeomorphisms to a gauged version, and it is shown that they can be governed
by a Chern-Simons theory, which unifies the spin-2 modes with the Kaluza-Klein
vectors. This provides a reformulation of D-dimensional Einstein gravity, in
which the physical degrees of freedom are described by the scalars of a gauged
non-linear sigma model based on SL(D-2,R)/SO(D-2), while the metric appears in
a purely topological Chern-Simons form.Comment: 23 pages, minor changes, v3: published versio
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
On higher derivatives in 3D gravity and higher-spin gauge theories
The general second-order massive field equations for arbitrary positive
integer spin in three spacetime dimensions, and their "self-dual" limit to
first-order equations, are shown to be equivalent to gauge-invariant
higher-derivative field equations. We recover most known equivalences for spins
1 and 2, and find some new ones. In particular, we find a non-unitary massive
3D gravity theory with a 5th order term obtained by contraction of the Ricci
and Cotton tensors; this term is part of an N=2 super-invariant that includes
the "extended Chern-Simons" term of 3D electrodynamics. We also find a new
unitary 6th order gauge theory for "self-dual" spin 3.Comment: 23 pp. New references, improved spin-3 discussion. Minor additional
corrections in v
Duality Invariant M-theory: Gauged supergravities and Scherk-Schwarz reductions
We consider the reduction of the duality invariant approach to M-theory by a
U-duality group valued Scherk-Schwarz twist. The result is to produce
potentials for gauged supergravities that are normally associated with
non-geometric compactifications. The local symmetry reduces to gauge
transformations with the gaugings exactly matching those of the embedding
tensor approach to gauged supergravity. Importantly, this approach now includes
a nontrivial dependence of the fields on the extra coordinates of the extended
space.Comment: 22 pages Latex; v2: typos corrected and references adde
A Topologically Massive Gauge Theory with 32 Supercharges
We construct a novel topologically massive abelian Chern-Simons gauge theory
with 32 global supersymmetries in three spacetime dimensions. In spite of the
32 supercharges, the theory exhibits massive excitations only up to spin 1. The
possibility of such a multiplet shortening is due to the presence of
non-central R-symmetry generators in the Poincare superalgebra, whose
supermultiplets are determined.Comment: 20 pages; v2: minor changes, ref. added, to appear in Phys. Rev.
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