12,032 research outputs found
New Gauged N=8, D=4 Supergravities
New gaugings of four dimensional N=8 supergravity are constructed, including
one which has a Minkowski space vacuum that preserves N=2 supersymmetry and in
which the gauge group is broken to . Previous gaugings used the
form of the ungauged action which is invariant under a rigid symmetry
and promoted a 28-dimensional subgroup ( or the
non-semi-simple contraction ) to a local gauge group. Here, a
dual form of the ungauged action is used which is invariant under
instead of and new theories are obtained by gauging 28-dimensional
subgroups of . The gauge groups are non-semi-simple and are different
real forms of the groups, denoted , and the new
theories have a rigid SU(2) symmetry. The five dimensional gauged N=8
supergravities are dimensionally reduced to D=4. The gauge
theories reduce, after a duality transformation, to the
gauging while the gauge theory reduces to the gauge
theory. The new theories are related to the old ones via an analytic
continuation. The non-semi-simple gaugings can be dualised to forms with
different gauge groups.Comment: 33 pages. Reference adde
Generalised Geometry for M-Theory
Generalised geometry studies structures on a d-dimensional manifold with a
metric and 2-form gauge field on which there is a natural action of the group
SO(d,d). This is generalised to d-dimensional manifolds with a metric and
3-form gauge field on which there is a natural action of the group .
This provides a framework for the discussion of M-theory solutions with flux. A
different generalisation is to d-dimensional manifolds with a metric, 2-form
gauge field and a set of p-forms for either odd or even on which there is a
natural action of the group . This is useful for type IIA or IIB
string solutions with flux. Further generalisations give extended tangent
bundles and extended spin bundles relevant for non-geometric backgrounds.
Special structures that arise for supersymmetric backgrounds are discussed.Comment: 31 page
The gauge algebra of double field theory and Courant brackets
We investigate the symmetry algebra of the recently proposed field theory on
a doubled torus that describes closed string modes on a torus with both
momentum and winding. The gauge parameters are constrained fields on the
doubled space and transform as vectors under T-duality. The gauge algebra
defines a T-duality covariant bracket. For the case in which the parameters and
fields are T-dual to ones that have momentum but no winding, we find the gauge
transformations to all orders and show that the gauge algebra reduces to one
obtained by Siegel. We show that the bracket for such restricted parameters is
the Courant bracket. We explain how these algebras are realised as symmetries
despite the failure of the Jacobi identity.Comment: 25 pages, LaTe
Flux Compactifications of M-Theory on Twisted Tori
We find the bosonic sector of the gauged supergravities that are obtained
from 11-dimensional supergravity by Scherk-Schwarz dimensional reduction with
flux to any dimension D. We show that, if certain obstructions are absent, the
Scherk-Schwarz ansatz for a finite set of D-dimensional fields can be extended
to a full compactification of M-theory, including an infinite tower of
Kaluza-Klein fields. The internal space is obtained from a group manifold
(which may be non-compact) by a discrete identification. We discuss the
symmetry algebra and the symmetry breaking patterns and illustrate these with
particular examples. We discuss the action of U-duality on these theories in
terms of symmetries of the D-dimensional supergravity, and argue that in
general it will take geometric flux compactifications to M-theory on
non-geometric backgrounds, such as U-folds with U-duality transition functions.Comment: Latex, 47 page
Gauge Symmetry, T-Duality and Doubled Geometry
String compactifications with T-duality twists are revisited and the gauge
algebra of the dimensionally reduced theories calculated. These reductions can
be viewed as string theory on T-fold backgrounds, and can be formulated in a
`doubled space' in which each circle is supplemented by a T-dual circle to
construct a geometry which is a doubled torus bundle over a circle. We discuss
a conjectured extension to include T-duality on the base circle, and propose
the introduction of a dual base coordinate, to give a doubled space which is
locally the group manifold of the gauge group. Special cases include those in
which the doubled group is a Drinfel'd double. This gives a framework to
discuss backgrounds that are not even locally geometric.Comment: 16 page
Duality Twists on a Group Manifold
We study duality-twisted dimensional reductions on a group manifold G, where
the twist is in a group \tilde{G} and examine the conditions for consistency.
We find that if the duality twist is introduced through a group element
\tilde{g} in \tilde{G}, then the flat \tilde{G}-connection A =\tilde{g}^{-1}
d\tilde{g} must have constant components M_n with respect to the basis 1-forms
on G, so that the dependence on the internal coordinates cancels out in the
lower dimensional theory. This condition can be satisfied if and only if M_n
forms a representation of the Lie algebra of G, which then ensures that the
lower dimensional gauge algebra closes. We find the form of this gauge algebra
and compare it to that arising from flux compactifications on twisted tori. As
an example of our construction, we find a new five dimensional gauged, massive
supergravity theory by dimensionally reducing the eight dimensional Type II
supergravity on a three dimensional unimodular, non-semi-simple, non-abelian
group manifold with an SL(3,R) twist.Comment: 22 page
A Geometry for Non-Geometric String Backgrounds
A geometric string solution has background fields in overlapping coordinate
patches related by diffeomorphisms and gauge transformations, while for a
non-geometric background this is generalised to allow transition functions
involving duality transformations. Non-geometric string backgrounds arise from
T-duals and mirrors of flux compactifications, from reductions with duality
twists and from asymmetric orbifolds. Strings in ` T-fold' backgrounds with a
local -torus fibration and T-duality transition functions in are
formulated in an enlarged space with a fibration which is geometric,
with spacetime emerging locally from a choice of a submanifold of each
fibre, so that it is a subspace or brane embedded in the enlarged
space. T-duality acts by changing to a different subspace of .
For a geometric background, the local choices of fit together to give a
spacetime which is a bundle, while for non-geometric string backgrounds
they do not fit together to form a manifold. In such cases spacetime geometry
only makes sense locally, and the global structure involves the doubled
geometry. For open strings, generalised D-branes wrap a subspace of each
fibre and the physical D-brane is the part of the part of the physical
space lying in the generalised D-brane subspace.Comment: 28 Pages. Minor change
Consistent reductions of IIB*/M* theory and de Sitter supergravity
We construct consistent non-linear Kaluza Klein reduction ansatze for a
subset of fields arising from the reduction of IIB* and M* theory on dS_5 x H^5
and dS_4 x AdS_7, respectively. These reductions yield four and
five-dimensional de Sitter supergravities, albeit with wrong sign kinetic
terms. We also demonstrate that the ansatze may be used to lift multi-centered
de Sitter black hole solutions to ten and eleven dimensions. The lifted dS_5
black holes correspond to rotating E4-branes of IIB* theory.Comment: 27 pages, late
Recommended from our members
Intelligent techniques in condition monitoring based on forecasting of vibrational signals
- âŠ