174 research outputs found
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
Quantum Mechanics of the Doubled Torus
We investigate the quantum mechanics of the doubled torus system, introduced
by Hull [1] to describe T-folds in a more geometric way. Classically, this
system consists of a world-sheet Lagrangian together with some constraints,
which reduce the number of degrees of freedom to the correct physical number.
We consider this system from the point of view of constrained Hamiltonian
dynamics. In this case the constraints are second class, and we can quantize on
the constrained surface using Dirac brackets. We perform the quantization for a
simple T-fold background and compare to results for the conventional
non-doubled torus system. Finally, we formulate a consistent supersymmetric
version of the doubled torus system, including supersymmetric constraints.Comment: 31 pages, 1 figure; v2: references added, minor corrections to final
sectio
NS-NS fluxes in Hitchin's generalized geometry
The standard notion of NS-NS 3-form flux is lifted to Hitchin's generalized
geometry. This generalized flux is given in terms of an integral of a modified
Nijenhuis operator over a generalized 3-cycle. Explicitly evaluating the
generalized flux in a number of familiar examples, we show that it can compute
three-form flux, geometric flux and non-geometric Q-flux. Finally, a
generalized connection that acts on generalized vectors is described and we
show how the flux arises from it.Comment: 21 pages, 1 figure; v3: minor change
Heterotic-type IIA duality with fluxes
In this paper we study a possible non-perturbative dual of the heterotic
string compactified on K3 x T^2 in the presence of background fluxes. We show
that type IIA string theory compactified on manifolds with SU(3) structure can
account for a subset of the possible heterotic fluxes. This extends our
previous analysis to a case of a non-perturbative duality with fluxes.Comment: 26 pages, minor corrections; version to appear in JHE
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
Nongeometry, Duality Twists, and the Worldsheet
In this paper, we use orbifold methods to construct nongeometric backgrounds,
and argue that they correspond to the spacetimes discussed in \cite{dh,wwf}.
More precisely, we make explicit through several examples the connection
between interpolating orbifolds and spacetime duality twists. We argue that
generic nongeometric backgrounds arising from duality twists will not have
simple orbifold constructions and then proceed to construct several examples
which do have a consistent worldsheet description.Comment: v2-references added; v3-minor correction (eqn. 4.17
Backreacted T-folds and non-geometric regions in configuration space
We provide the backreaction of the T-fold doubly T-dual to a background with
NSNS three-form flux on a three-torus. We extend the backreacted T-fold to
include cases with a flux localized in one out of three directions. We analyze
the resulting monodromy domain walls and vortices. In these backgrounds, we
give an analysis of the action of T-duality on observables like charges and
Wilson surfaces. We analyze arguments for the existence of regions in the
configuration space of second quantized string theory that cannot be reduced to
geometry. Finally, by allowing for space-dependent moduli, we find a
supergravity solution which is a T-fold with hyperbolic monodromies.Comment: 25 pages, 4 figures; v2: minor changes, reference adde
Superstring partition functions in the doubled formalism
Computation of superstring partition function for the non-linear sigma model
on the product of a two-torus and its dual within the scope of the doubled
formalism is presented. We verify that it reproduces the partition functions of
the toroidally compactified type--IIA and type--IIB theories for appropriate
choices of the GSO projection.Comment: 15 page
Toroidal Orientifolds in IIA with General NS-NS Fluxes
Type IIA toroidal orientifolds offer a promising toolkit for model builders,
especially when one includes not only the usual fluxes from NS-NS and R-R field
strengths, but also fluxes that are T-dual to the NS-NS three-form flux. These
new ingredients are known as metric fluxes and non-geometric fluxes, and can
help stabilize moduli or can lead to other new features. In this paper we study
two approaches to these constructions, by effective field theory or by toroidal
fibers twisted over a toroidal base. Each approach leads us to important
observations, in particular the presence of D-terms in the four-dimensional
effective potential in some cases, and a more subtle treatment of the
quantization of the general NS-NS fluxes. Though our methods are general, we
illustrate each approach on the example of an orientifold of T^6/Z_4.Comment: 59 pages, references 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
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