1,035 research outputs found
Duality Symmetric String and M-Theory
We review recent developments in duality symmetric string theory. We begin
with the world sheet doubled formalism which describes strings in an extended
space time with extra coordinates conjugate to winding modes. This formalism is
T-duality symmetric and can accommodate non-geometric T-fold backgrounds which
are beyond the scope of Riemannian geometry. Vanishing of the conformal anomaly
of this theory can be interpreted as a set of spacetime equations for the
background fields. These equations follow from an action principle that has
been dubbed Double Field Theory (DFT). We review the aspects of generalised
geometry relevant for DFT. We outline recent extensions of DFT and explain how,
by relaxing the so-called strong constraint with a Scherk Schwarz ansatz, one
can obtain backgrounds that simultaneously depend on both the regular and
T-dual coordinates. This provides a purely geometric higher dimensional origin
to gauged supergravities that arise from non-geometric compactification. We
then turn to M-theory and describe recent progress in formulating an E_{n(n)}
U-duality covariant description of the dynamics. We describe how spacetime may
be extended to accommodate coordinates conjugate to brane wrapping modes and
the construction of generalised metrics in this extend space that unite the
bosonic fields of supergravity into a single object. We review the action
principles for these theories and their novel gauge symmetries. We also
describe how a Scherk Schwarz reduction can be applied in the M-theory context
and the resulting relationship to the embedding tensor formulation of maximal
gauged supergravities.Comment: Review article. 122 pages. V2 Published Version in Physics Report
The gauge structure of generalised diffeomorphisms
We investigate the generalised diffeomorphisms in M-theory, which are gauge
transformations unifying diffeomorphisms and tensor gauge transformations.
After giving an En(n)-covariant description of the gauge transformations and
their commutators, we show that the gauge algebra is infinitely reducible,
i.e., the tower of ghosts for ghosts is infinite. The Jacobiator of generalised
diffeomorphisms gives such a reducibility transformation. We give a concrete
description of the ghost structure, and demonstrate that the infinite sums give
the correct (regularised) number of degrees of freedom. The ghost towers belong
to the sequences of rep- resentations previously observed appearing in tensor
hierarchies and Borcherds algebras. All calculations rely on the section
condition, which we reformulate as a linear condition on the cotangent
directions. The analysis holds for n < 8. At n = 8, where the dual gravity
field becomes relevant, the natural guess for the gauge parameter and its
reducibility still yields the correct counting of gauge parameters.Comment: 24 pp., plain tex, 1 figure. v2: minor changes, including a few added
ref
Membranes with a boundary
We investigate the recently developed theory of multiple membranes. In
particular, we consider open membranes, i.e. the theory defined on a membrane
world volume with a boundary. We first restrict our attention to the gauge
sector of the theory. We obtain a boundary action from the Chern-Simons terms.
Secondly, we consider the addition of certain boundary terms to various
Chern-Simons theories coupled to matter. These terms ensure the full bulk plus
boundary action has the correct amount of supersymmetry. For the ABJM model,
this construction motivates the inclusion of a boundary quartic scalar
potential. The boundary dynamics obtained from our modified theory produce
Basu-Harvey type equations describing membranes ending on a fivebrane. The
ultimate goal of this work is to throw light on the theory of fivebranes using
the theory of open membranes.Comment: 48 pages, Latex, v2 references adde
Duality Symmetric Strings, Dilatons and O(d,d) Effective Actions
We calculate the background field equations for the T-duality symmetric
string building on previous work by including the effect of the Dilaton up to
two-loops. Inclusion of the Dilaton allows us to obtain the full beta
functionals of the duality symmetric sigma model. We are able to interpret the
result in terms of a dimensionally reduced O(d,d) invariant target space
effective action.Comment: 15 pages, latex; v2 reference added, typos fixe
Aspects of Multiple Membranes
This paper examines various aspects of the recently proposed theory of
coincident membranes by Bagger and Lambert. These include the properties of
open membranes and the resulting boundary theory with an interpretation in
terms of the fivebrane and marginal supersymmetric deformations of the
interactions with the relation to the holographic dual.Comment: latex, 24 page
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
Background Field Equations for the Duality Symmetric String
This paper describes the background field equations for strings in T-duality
symmetric formalisms in which the dimension of target space is doubled and the
sigma model supplemented with constraints. These are calculated by demanding
the vanishing of the beta-functional of the sigma model couplings in the
doubled target space. We demonstrate the equivalence with the background field
equations of the standard string sigma model.Comment: 26 pages, latex, v2 typos correcte
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