644 research outputs found
Type IIB Flows with N=1 Supersymmetry
We write general and explicit equations which solve the supersymmetry
transformations with two arbitrary complex-proportional Weyl spinors on
supersymmetric type IIB strings backgrounds with all R-R ,
, and NS-NS fluxes turned on using SU(3) structures. The
equations are generalizations of the ones found for specific relations between
the two spinors by Grana, Minasian, Petrini and Tomasiello in [1] and by Butti,
Grana, Minasian, Petrini and Zaffaroni in [2]. The general equations allow to
study systematically generic type IIB backgrounds with
supersymmetry. We then explore some specific classes of flows with constant
axion, flows with constant dilaton, flows on conformally Calabi-Yau
backgrounds, flows with imaginary self-dual 3-form flux, flows with constant
ratio of the two spinors, the corresponding equations are written down and some
of their features and relations are discussed.Comment: 28 page
AdS Vacua, Attractor Mechanism and Generalized Geometries
We consider flux vacua attractor equations in type IIA string theory
compactified on generalized geometries with orientifold projections. The
four-dimensional N=1 superpotential in this compactification can be written as
the sum of the Ramond-Ramond superpotential and a term described by
(non)geometric flux charges. We exhibit a simple model in which supersymmetric
AdS and Minkowski solutions are classified by means of discriminants of the two
superpotentials. We further study various configurations without Ramond-Ramond
flux charges. In this case we find supersymmetric AdS vacua both in the case of
compactifications on generalized geometries with SU(3) x SU(3) structures and
on manifolds with an SU(3)-structure without nongeometric flux charges. In the
latter case, we have to introduce correction terms into the prepotential in
order to realize consistent vacua.Comment: 35 pages, accepted version in JHE
New families of interpolating type IIB backgrounds
We construct new families of interpolating two-parameter solutions of type
IIB supergravity. These correspond to D3-D5 systems on non-compact
six-dimensional manifolds which are T^2 fibrations over Eguchi-Hanson and
multi-center Taub-NUT spaces, respectively. One end of the interpolation
corresponds to a solution with only D5 branes and vanishing NS three-form flux.
A topology changing transition occurs at the other end, where the internal
space becomes a direct product of the four-dimensional surface and the
two-torus and the complexified NS-RR three-form flux becomes imaginary
self-dual. Depending on the choice of the connections on the torus fibre, the
interpolating family has either N=2 or N=1 supersymmetry. In the N=2 case it
can be shown that the solutions are regular.Comment: 20 page
D3-brane action in a supergravity background: the fermionic story
Using the kappa-symmetric action for a D3-brane, we study the interaction
between its world-volume fermions and a bosonic type IIB supergravity
background preserving 4-dimensional Lorentz invariance. We find that the
renormalizable terms in the action include only coupling between the fermions
and the 3-form flux in the combination *G_3-iG_3, which is zero for a class of
supersymmetric and nonsupersymmetric solutions. We also find the magnetic and
electric dipole moments for the fermions, which are proportional to the
derivative of the dilaton-axion. We show that different gauges to fix the
kappa-symmetry give the same interaction terms, and prove that these terms are
also SL(2,R) self-dual. We interpret our results in terms of N=1 supersymmetric
gauge theory on the D-brane.Comment: 23 pages. Minor corrections, references adde
Contact line depinning from sharp edges
With aim of finding mathematical criteria for contact line depinning from
sharp corners, we have studied the equilibrium and stability of a semi-infinite
planar liquid layer pinned at the vertex of a wedge. Equilibrium is compatible
with a fan of apparent contact angles bracketed by the equilibrium
contact angles of both flanks of the wedge, so the contact line could remain
pinned if is within this fan. However, the analysis of the stability
of these solutions, studied exploiting the variational structure of the problem
through turning-point arguments, shows that the equilibrium becomes unstable at
critical depinning advancing and receding contact
angles, which are found as subcritical saddle-node bifurcations. Equilibrium is
thus possible (stable) within the interval
but the contact line depins from the vertex beyond these critical angles if
they occur within the equilibrium fan.Comment: 9 pages, 5 figure
Supersymmetric sources, integrability and generalized-structure compactifications
In the context of supersymmetric compactifications of type II supergravity to
four dimensions, we show that orientifold sources can be compatible with a
generalized SU(3) x SU(3)-structure that is neither strictly SU(3) nor static
SU(2). We illustrate this with explicit examples, obtained by suitably
T-dualizing known solutions on the six-torus. In addition we prove the
following integrability statements, valid under certain mild assumptions: (a)
for general type II supergravity backgrounds with orientifold and/or D-brane
generalized-calibrated sources, the source-corrected Einstein and dilaton
equations of motion follow automatically from the supersymmetry equations once
the likewise source-corrected form equations of motion and Bianchi identities
are imposed; (b) in the special case of supersymmetric compactifications to
four-dimensional Minkowski space, the equations of motion of all fields,
including the NSNS three-form, follow automatically once the supersymmetry and
the Bianchi identities of the forms are imposed. Both (a) and (b) are equally
valid whether the sources are smeared or localized. As a byproduct we obtain
the calibration form for a space-filling NS5-brane.Comment: 32 pages, 1 table, v2: added references, v3: corrected mistake in
(4.1) leading to factor 2 mistake in (B.6), corrected (B.5), smaller typo
Type IIB Solutions with Interpolating Supersymmetries
We study type IIB supergravity solutions with four supersymmetries that
interpolate between two types widely considered in the literature: the dual of
Becker and Becker's compactifications of M-theory to 3 dimensions and the dual
of Strominger's torsion compactifications of heterotic theory to 4 dimensions.
We find that for all intermediate solutions the internal manifold is not
Calabi-Yau, but has SU(3) holonomy in a connection with a torsion given by the
3-form flux. All 3-form and 5-form fluxes, as well as the dilaton, depend on
one function appearing in the supersymmetry spinor, which satisfies a nonlinear
differential equation. We check that the fields corresponding to a flat bound
state of D3/D5-branes lie in our class of solutions. The relations among
supergravity fields that we derive should be useful in studying new gravity
duals of gauge theories, as well as possibly compactifications.Comment: 27pp, v2 REVTeX4, typographical fixes and minor clarifications, v3
added ref, modified discussion of RR axion slightl
From ten to four and back again: how to generalize the geometry
We discuss the four-dimensional N=1 effective approach in the study of warped
type II flux compactifications with SU(3)x SU(3)-structure to AdS_4 or flat
Minkowski space-time. The non-trivial warping makes it natural to use a
supergravity formulation invariant under local complexified Weyl
transformations. We obtain the classical superpotential from a standard
argument involving domain walls and generalized calibrations and show how the
resulting F-flatness and D-flatness equations exactly reproduce the full
ten-dimensional supersymmetry equations. Furthermore, we consider the effect of
non-perturbative corrections to this superpotential arising from gaugino
condensation or Euclidean D-brane instantons. For the latter we derive the
supersymmetry conditions in N=1 flux vacua in full generality. We find that the
non-perturbative corrections induce a quantum deformation of the internal
generalized geometry. Smeared instantons allow to understand KKLT-like AdS
vacua from a ten-dimensional point of view. On the other hand, non-smeared
instantons in IIB warped Calabi-Yau compactifications 'destabilize' the
Calabi-Yau complex structure into a genuine generalized complex one. This
deformation gives a geometrical explanation of the non-trivial superpotential
for mobile D3-branes induced by the non-perturbative corrections.Comment: LaTeX, 47 pages, v2, references, hyperref added, v3, correcting small
inaccuracies in eqs. (2.6a) and (5.16
On the Existence of Meta-stable Vacua in Klebanov-Strassler
We solve for the complete space of linearized deformations of the
Klebanov-Strassler background consistent with the symmetries preserved by a
stack of anti-D3 branes smeared on the of the deformed conifold. We find
that the only solution whose UV physics is consistent with that of a
perturbation produced by anti-D3 branes must have a singularity in the
infrared, coming from NS and RR three-form field strengths whose energy density
diverges. If this singularity is admissible, our solution describes the
backreaction of the anti-D3 branes, and is thus likely to be dual to the
conjectured metastable vacuum in the Klebanov-Strassler field theory. If this
singularity is not admissible, then our analysis strongly suggests that anti-D3
branes do not give rise to metastable Klebanov-Strassler vacua, which would
have dramatic consequences for some string theory constructions of de Sitter
space. Key to this result is a simple, universal form for the force on a probe
D3-brane in our ansatz.Comment: 35 pages, LaTeX. v2: further details provided regarding the IR
singularity and the discussion modified accordingly. typos corrected, refs
adde
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