278 research outputs found
The Gauged (2,1) Heterotic Sigma-Model
The geometry of (2,1) supersymmetric sigma-models with isometry symmetries is
discussed. The gauging of such symmetries in superspace is then studied. We
find that the coupling to the (2,1) Yang-Mills supermultiplet can be achieved
provided certain geometric conditions are satisfied. We construct the general
gauged action, using an auxiliary vector to generate the full non-polynomial
structure.Comment: LaTeX, 25 pages, no figures; version to appear in Nuclear Physics
Einstein Supergravity and New Twistor String Theories
A family of new twistor string theories is constructed and shown to be free
from world-sheet anomalies. The spectra in space-time are calculated and shown
to give Einstein supergravities with second order field equations instead of
the higher derivative conformal supergravities that arose from earlier twistor
strings. The theories include one with the spectrum of N=8 supergravity,
another with the spectrum of N=4 supergravity coupled to N=4 super-Yang-Mills,
and a family with supersymmetries with the spectra of self-dual
supergravity coupled to self-dual super-Yang-Mills. The non-supersymmetric
string with N=0 gives self-dual gravity coupled to self-dual Yang-Mills and a
scalar. A three-graviton amplitude is calculated for the N=8 and N=4 theories
and shown to give a result consistent with the cubic interaction of Einstein
supergravity.Comment: LaTeX, 69 pages, no figures; v2: minor corrections made, footnotes
and references adde
Sigma models with non-commuting complex structures and extended supersymmetry
We discuss additional supersymmetries for N = (2, 2) supersymmetric
non-linear sigma models described by left and right semichiral superfields.Comment: 11 pages. Talk presented by U.L. at "30th Winter School on Geometry
and Physics" Srni, Czech Republic January 2010
BPS states of D=4 N=1 supersymmetry
We find the combinations of momentum and domain-wall charges corresponding to
BPS states preserving 1/4, 1/2 or 3/4 of D=4 N=1 supersymmetry, and we show how
the supersymmetry algebra implies their stability. These states form the
boundary of the convex cone associated with the Jordan algebra of
real symmetric matrices, and we explore some implications of the associated
geometry. For the Wess-Zumino model we derive the conditions for preservation
of 1/4 supersymmetry when one of two parallel domain-walls is rotated and in
addition show that this model does not admit any classical configurations with
3/4 supersymmetry. Our analysis also provides information about BPS states of
N=1 D=4 anti-de Sitter supersymmetry.Comment: Latex, 27 pages. Various corrections and improvements including an
expanded discussion on BPS states in ad
Black Holes and U-Duality
We find the general charged rotating black hole solutions of the maximal
supergravities in dimensions arising from toroidally compactified
Type II string or M-theories. In each dimension, these are obtained by acting
on a generating solution with classical duality symmetries. In D=4, D=5 and
the generating solution is specified by the ADM mass,
-angular momentum components and five, three and two charges,
respectively. We discuss the BPS-saturated (static) black holes and derive the
U-duality invariant form of the area of the horizon. We also comment on the
U-duality invariant form of the BPS mass formulae.Comment: Minor corrections. Version to appear in Nuclear Physics
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
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
A new maximally supersymmetric background of IIB superstring theory
We present a maximally supersymmetric IIB string background. The geometry is
that of a conformally flat lorentzian symmetric space G/K with solvable G, with
a homogeneous five-form flux. We give the explicit supergravity solution,
compute the isometries, the 32 Killing spinors, and the symmetry superalgebra,
and then discuss T-duality and the relation to M-theory.Comment: 17 page
Wrapped Branes and Supersymmetry
Configurations of two or more branes wrapping different homology cycles of
space-time are considered and the amount of supersymmetry preserved is
analysed, generalising the analysis of multiple branes in flat space. For K3
compactifications, these give the Type II or M theory origin of certain
supersymmetric four-dimensional heterotic string solutions that fit into
spin-3/2 multiplets and which become massless at certain points in moduli
space. The interpretation of these BPS states and the possibility of
supersymmetry enhancement are discussed.Comment: 18 pages, Latex with Revtex, minor corrections and references added,
version to appear in Nuclear Physics
Global Aspects of T-Duality, Gauged Sigma Models and T-Folds
The gauged sigma-model argument that string backgrounds related by T-dual
give equivalent quantum theories is revisited, taking careful account of global
considerations. The topological obstructions to gauging sigma-models give rise
to obstructions to T-duality, but these are milder than those for gauging: it
is possible to T-dualise a large class of sigma-models that cannot be gauged.
For backgrounds that are torus fibrations, it is expected that T-duality can be
applied fibrewise in the general case in which there are no globally-defined
Killing vector fields, so that there is no isometry symmetry that can be
gauged; the derivation of T-duality is extended to this case. The T-duality
transformations are presented in terms of globally-defined quantities. The
generalisation to non-geometric string backgrounds is discussed, the conditions
for the T-dual background to be geometric found and the topology of T-folds
analysed.Comment: Minor corrections and addition
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