1,228 research outputs found
Background independent action for double field theory
Double field theory describes a massless subsector of closed string theory
with both momentum and winding excitations. The gauge algebra is governed by
the Courant bracket in certain subsectors of this double field theory. We
construct the associated nonlinear background-independent action that is
T-duality invariant and realizes the Courant gauge algebra. The action is the
sum of a standard action for gravity, antisymmetric tensor, and dilaton fields
written with ordinary derivatives, a similar action for dual fields with dual
derivatives, and a mixed term that is needed for gauge invariance.Comment: 45 pages, v2: minor corrections, refs. added, to appear in JHE
Heterotic type IIA duality with fluxes - towards the complete story
In this paper we study the heterotic type IIA duality when fluxes are turned
on. We show that many of the known fluxes are dual to each other and claim that
certain fluxes on the heterotic side require that the type IIA picture is
lifted to M or even F-theory compactifications with geometric fluxes.Comment: 31 pages, references adde
T-duality in the weakly curved background
We consider the closed string propagating in the weakly curved background
which consists of constant metric and Kalb-Ramond field with infinitesimally
small coordinate dependent part. We propose the procedure for constructing the
T-dual theory, performing T-duality transformations along coordinates on which
the Kalb-Ramond field depends. The obtained theory is defined in the
non-geometric double space, described by the Lagrange multiplier and
its -dual . We apply the proposed T-duality procedure to the
T-dual theory and obtain the initial one. We discuss the standard relations
between T-dual theories that the equations of motion and momenta modes of one
theory are the Bianchi identities and the winding modes of the other
Generalized Geometry and M theory
We reformulate the Hamiltonian form of bosonic eleven dimensional
supergravity in terms of an object that unifies the three-form and the metric.
For the case of four spatial dimensions, the duality group is manifest and the
metric and C-field are on an equal footing even though no dimensional reduction
is required for our results to hold. One may also describe our results using
the generalized geometry that emerges from membrane duality. The relationship
between the twisted Courant algebra and the gauge symmetries of eleven
dimensional supergravity are described in detail.Comment: 29 pages of Latex, v2 References added, typos fixed, v3 corrected
kinetic term and references adde
Open String Creation by S-Branes
An sp-brane can be viewed as the creation and decay of an unstable
D(p+1)-brane. It is argued that the decaying half of an sp-brane can be
described by a variant of boundary Liouville theory. The pair creation of open
strings by a decaying s-brane is studied in the minisuperspace approximation to
the Liouville theory. In this approximation a Hagedorn-like divergence is found
in the pair creation rate, suggesting the s-brane energy is rapidly transferred
into closed string radiation.Comment: Talk presented at the Hangzhou String 2002 Conference, August 12-1
D-Brane Wess-Zumino Terms and U-Duality
We construct gauge-invariant and U-duality covariant expressions for
Wess-Zumino terms corresponding to general Dp-branes (for any p<D) in arbitrary
2<D<11 dimensions. A distinguishing feature of these Wess-Zumino terms is that
they contain twice as many scalars as the 10-D compactified dimensions, in line
with doubled geometry. We find that for D<10 the charges of the
higher-dimensional branes can all be expressed as products of the 0-brane
charges, which include the D0-brane and the NS-NS 0-brane charges. We give the
general expressions for these charges and show how they determine the
non-trivial conjugacy class to which some of the higher-dimensional D-branes
belong.Comment: 42 pages. Typos corrected, an error in table 6 corrected, comments in
the conclusions adde
Branes at conical singularities and holography
For supergavrity solutions which are the product of an anti-de Sitter space
with an Einstein space X, we study the relation between the amount of
supersymmetry preserved and the geometry of X. Depending on the dimension and
the amount of supersymmetry, the following geometries for X are possible, in
addition to the maximally supersymmetric spherical geometry: Einstein-Sasaki in
dimension 2k+1, 3-Sasaki in dimension 4k+3, 7-dimensional manifolds of weak G_2
holonomy and 6-dimensional nearly Kaehler manifolds. Many new examples of such
manifolds are presented which are not homogeneous and have escaped earlier
classification efforts. String or M theory in these vacua are conjectured to be
dual to superconformal field theories. The brane solutions interpolating
between these anti-de Sitter near-horizon geometries and the product of
Minkowski space with a cone over X lead to an interpretation of the dual
superconformal field theory as the world-volume theory for branes at a conical
singularity (cone branes). We propose a description of those field theories
whose associated cones are obtained by (hyper-)Kaehler quotients.Comment: 38 pages (published version
2d Gauge Theories and Generalized Geometry
We show that in the context of two-dimensional sigma models minimal coupling
of an ordinary rigid symmetry Lie algebra leads naturally to the
appearance of the "generalized tangent bundle" by means of composite fields. Gauge transformations of the composite
fields follow the Courant bracket, closing upon the choice of a Dirac structure
(or, more generally, the choide of a "small
Dirac-Rinehart sheaf" ), in which the fields as well as the symmetry
parameters are to take values. In these new variables, the gauge theory takes
the form of a (non-topological) Dirac sigma model, which is applicable in a
more general context and proves to be universal in two space-time dimensions: A
gauging of of a standard sigma model with Wess-Zumino term
exists, \emph{iff} there is a prolongation of the rigid symmetry to a Lie
algebroid morphism from the action Lie algebroid
into (or the algebraic analogue of the morphism in the case of
). The gauged sigma model results from a pullback by this morphism
from the Dirac sigma model, which proves to be universal in two-spacetime
dimensions in this sense.Comment: 22 pages, 2 figures; To appear in Journal of High Energy Physic
U-dual fluxes and Generalized Geometry
We perform a systematic analysis of generic string flux compactifications,
making use of Exceptional Generalized Geometry (EGG) as an organizing
principle. In particular, we establish the precise map between fluxes, gaugings
of maximal 4d supergravity and EGG, identifying the complete set of gaugings
that admit an uplift to 10d heterotic or type IIB supegravity backgrounds. Our
results reveal a rich structure, involving new deformations of 10d supergravity
backgrounds, such as the RR counterparts of the -deformation. These new
deformations are expected to provide the natural extension of the
-deformation to full-fledged F-theory backgrounds. Our analysis also
provides some clues on the 10d origin of some of the particularly less
understood gaugings of 4d supergravity. Finally, we derive the explicit
expression for the effective superpotential in arbitrary N = 1 heterotic or
type IIB orientifold compactifications, for all the allowed fluxes.Comment: 58 pages, 6 table
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