343 research outputs found
The R-map and the Coupling of N=2 Tensor Multiplets in 5 and 4 Dimensions
We study the dimensional reduction of five dimensional N=2
Yang-Mills-Einstein supergravity theories (YMESGT) coupled to tensor
multiplets. The resulting 4D theories involve first order interactions among
tensor and vector fields with mass terms. If the 5D gauge group, K, does not
mix the 5D tensor and vector fields, the 4D tensor fields can be integrated out
in favor of 4D vector fields and the resulting theory is dual to a standard 4D
YMESGT. The gauge group has a block diagonal symplectic embedding and is a
semi-direct product of the 5D gauge group K with a Heisenberg group of
dimension (2P+1), where 2P is the number of tensor fields in five dimensions.
There exists an infinite family of theories, thus obtained, whose gauge groups
are pp-wave contractions of the simple noncompact groups of type SO*(2M). If,
on the other hand, the 5D gauge group does mix the 5D tensor and vector fields,
the resulting 4D theory is dual to a 4D YMESGT whose gauge group does, in
general,NOT have a block diagonal symplectic embedding and involves additional
topological terms. The scalar potentials of the dimensionally reduced theories
naturally have some of the ingredients that were found necessary for stable de
Sitter ground states. We comment on the relation between the known 5D and 4D,
N=2 supergravities with stable de Sitter ground states.Comment: 42 pages;latex fil
Charting the landscape of N=4 flux compactifications
We analyse the vacuum structure of isotropic Z_2 x Z_2 flux
compactifications, allowing for a single set of sources. Combining algebraic
geometry with supergravity techniques, we are able to classify all vacua for
both type IIA and IIB backgrounds with arbitrary gauge and geometric fluxes.
Surprisingly, geometric IIA compactifications lead to a unique theory with four
different vacua. In this case we also perform the general analysis allowing for
sources compatible with minimal supersymmetry. Moreover, some relevant examples
of type IIB non-geometric compactifications are studied. The computation of the
full N=4 mass spectrum reveals the presence of a number of non-supersymmetric
and nevertheless stable AdS_4 vacua. In addition we find a novel dS_4 solution
based on a non-semisimple gauging.Comment: Minor corrections and references added. Version published in JHE
Universal de Sitter solutions at tree-level
Type IIA string theory compactified on SU(3)-structure manifolds with
orientifolds allows for classical de Sitter solutions in four dimensions. In
this paper we investigate these solutions from a ten-dimensional point of view.
In particular, we demonstrate that there exists an attractive class of de
Sitter solutions, whose geometry, fluxes and source terms can be entirely
written in terms of the universal forms that are defined on all SU(3)-structure
manifolds. These are the forms J and Omega, defining the SU(3)-structure
itself, and the torsion classes. The existence of such universal de Sitter
solutions is governed by easy-to-verify conditions on the SU(3)-structure,
rendering the problem of finding dS solutions purely geometrical. We point out
that the known (unstable) solution coming from the compactification on SU(2)x
SU(2) is of this kind.Comment: 20 pages, 3 figures, v2: added reference
Higher order contributions to the effective action of N=2 super Yang-Mills
We apply heat kernel techniques in N=1 superspace to compute the one-loop
effective action to order for chiral superfields coupled to a non-Abelian
super Yang-Mills background. The results, when combined with those of
hep-th/0210146, yield the one-loop effective action to order for any N=2
super Yang-Mills theory coupled to matter hypermultiplets.Comment: 23 pages, references adde
On duality symmetry in perturbative quantum theory
Non-compact symmetries of extended 4d supergravities involve duality
rotations of vectors and thus are not manifest off-shell invariances in
standard "second-order" formulation. To study how such symmetries are realised
in the quantum theory we consider examples in 2 dimensions where vector-vector
duality is replaced by scalar-scalar one. Using a "doubled" formulation, where
fields and their momenta are treated on an equal footing and the duality
becomes a manifest symmetry of the action (at the expense of Lorentz symmetry),
we argue that the corresponding on-shell quantum effective action or S-matrix
are duality symmetric as well as Lorentz invariant. The simplest case of
discrete Z_2 duality corresponds to a symmetry of the S-matrix under flipping
the sign of the negative-chirality scalars in 2 dimensions or phase rotations
of chiral (definite-helicity) parts of vectors in 4 dimensions. We also briefly
discuss some 4d models and comment on implications of our analysis for extended
supergravities.Comment: 21 pages, Latex v2: comments and references added v3: references and
minor comments adde
Localized Branes and Black Holes
We address the delocalization of low dimensional D-branes and NS-branes when
they are a part of a higher dimensional BPS black brane, and the homogeneity of
the resulting horizon. We show that the effective delocalization of such branes
is a classical effect that occurs when localized branes are brought together.
Thus, the fact that the few known solutions with inhomogeneous horizons are
highly singular need not indicate a singularity of generic D- and NS-brane
states. Rather, these singular solutions are likely to be unphysical as they
cannot be constructed from localized branes which are brought together from a
finite separation.Comment: 13 pages, RevTex, no figures, few references and comments adde
Thermodynamics of Born-Infeld Black Holes
We discuss the horizon structure for Born-Infeld black holes, in the context
of Einstein-Born-Infeld gravity. We show that the entropy function formalism
agrees with a direct calculation of the entropy. With the entropy function
formalism we also obtain the entropy when an axion-dilaton system as well as
gravitational derivative corrections are included.Comment: Latex, 13 pages, 1 figure, added reference
Rotating Black Holes which Saturate a Bogomol'nyi Bound
We construct and study the electrically charged, rotating black hole solution
in heterotic string theory compactified on a dimensional torus. This
black hole is characterized by its mass, angular momentum, and a
dimensional electric charge vector. One of the novel features of this solution
is that for , its extremal limit saturates the Bogomol'nyi bound. This is
in contrast with the case where the rotating black hole solution develops
a naked singularity before the Bogomol'nyi bound is reached. The extremal black
holes can be superposed, and by taking a periodic array in , one obtains
effectively four dimensional solutions without naked singularities.Comment: 13 pages, no figure
Lectures on Gauged Supergravity and Flux Compactifications
The low-energy effective theories describing string compactifications in the
presence of fluxes are so-called gauged supergravities: deformations of the
standard abelian supergravity theories. The deformation parameters can be
identified with the various possible (geometric and non-geometric) flux
components. In these lecture notes we review the construction of gauged
supergravities in a manifestly duality covariant way and illustrate the
construction in several examples.Comment: 48 pages, lectures given at the RTN Winter School on Strings,
Supergravity and Gauge Theories, CERN, January 200
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