75 research outputs found
Effective Actions Near Singularities: The STU-Model
We derive the low energy effective action of the STU-model in four and five
dimensions near the line T=U, where SU(2) gauge symmetry enhancement occurs. By
`integrating in' the light W^{\pm} bosons together with their superpartners,
the quantum corrected effective action becomes non-singular at T=U and
manifestly SU(2) invariant. The four-dimensional theory is found to be
consistent with modular invariance and the five-dimensional decompactification
limit. This talk concisely summarizes results that have been obtained in
collaboration with J. Louis and T. Mohaupt.Comment: 6 pages, LaTeX. Contribution to the proceedings of the 35th Symposium
Ahrenshoop, Berlin, Germany, August 2002. v2: reference corrected, paper
format adjuste
Curvature-induced Resolution of Anti-brane Singularities
We study AdS vacua of massive type IIA string theory compactified on a
3-sphere with flux and anti-D6-branes. In such backgrounds, the
anti-brane backreaction is known to generate a singularity in the energy
density, whose interpretation has not been understood so far. We first consider
supersymmetric solutions of this setup and give an analytic proof that the flux
singularity is resolved there by a polarization of the anti-D6-branes into a
D8-brane, which wraps a finite 2-sphere inside of the compact space. To this
end, we compute the potential for a spherical probe D8-brane on top of a
background with backreacting anti-D6-branes and show that it has a local
maximum at zero radius and a local minimum at a finite radius of the 2-sphere.
The polarization is triggered by a term in the potential due to the AdS
curvature and does therefore not occur in non-compact setups where the 7d
external spacetime is Minkowski. We furthermore find numerical evidence for the
existence of non-supersymmetric solutions in our setup. This is supported by
the observation that the general solution to the equations of motion has a
continuous parameter that is suggestive of a modulus and appears to control
supersymmetry breaking. Analyzing the polarization potential for the
non-supersymmetric solutions, we find that the flux singularities are resolved
there by brane polarization as well.Comment: 25 pages, 9 figures. v2: minor changes, discussion of scalar masses
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General Matter Coupled N=4 Gauged Supergravity in Five Dimensions
We construct the general form of matter coupled N=4 gauged supergravity in
five dimensions. Depending on the structure of the gauge group, these theories
are found to involve vector and/or tensor multiplets. When self-dual tensor
fields are present, they must be charged under a one-dimensional Abelian group
and cannot transform non-trivially under any other part of the gauge group. A
short analysis of the possible ground states of the different types of theories
is given. It is found that AdS ground states are only possible when the gauge
group is a direct product of a one-dimensional Abelian group and a semi-simple
group. In the purely Abelian, as well as in the purely semi-simple gauging, at
most Minkowski ground states are possible. The existence of such Minkowski
ground states could be proven in the compact Abelian case.Comment: 30 pages, Latex, some references modified, typos in eq. (4.18) and
(5.3) corrected. Version to appear in Nuclear Physics
N=4 Supersymmetric AdS5 Vacua and their Moduli Spaces
We classify the N=4 supersymmetric AdS5 backgrounds that arise as solutions
of five-dimensional N=4 gauged supergravity. We express our results in terms of
the allowed embedding tensor components and identify the structure of the
associated gauge groups. We show that the moduli space of these AdS vacua is of
the form SU(1,m)/(U(1)x SU(m)) and discuss our results regarding
holographically dual N=2 SCFTs and their conformal manifolds.Comment: 29 pages; v2: published versio
Cosmological Constant, Near Brane Behavior and Singularities
We show that the classical cosmological constant in type II flux
compactifications can be written as a sum of terms from the action of localized
sources plus a specific contribution from non-trivial background fluxes.
Exploiting two global scaling symmetries of the classical supergravity action,
we find that the flux contribution can in many interesting cases be set to zero
such that the cosmological constant is fully determined by the boundary
conditions of the fields in the near-source region. This generalizes and makes
more explicit previous arguments in the literature. We then discuss the problem
of putting \bar{D3}-branes at the tip of the Klebanov-Strassler throat glued to
a compact space in type IIB string theory so as to engineer a de Sitter
solution. Our result for the cosmological constant and a simple global argument
indicate that inserting a fully localized and backreacting \bar{D3}-brane into
such a background yields a singular energy density for the NSNS and RR 3-form
field strengths at the \bar{D3}-brane. This argument does not rely on partial
smearing of the \bar{D3}-brane or a linearization of field equations, but on a
few general assumptions that we also discuss carefully.Comment: 30 pages, no figures, v2: Minor modifications and references added.
Version to appear in JHE
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