85 research outputs found
Geometric non-geometry
We consider a class of (orbifolds of) M-theory compactifications on with gauge fluxes yielding minimally supersymmetric STU-models
in 4D. We present a group-theoretical derivation of the corresponding
flux-induced superpotentials and argue that the aforementioned backgrounds
provide a (globally) geometric origin for 4D theories that only look locally
geometric from the perspective of twisted tori. In particular, we show that
Q-flux can be used to generate compactifications on . We
thus conclude that the effect of turning on non-geometric fluxes, at least when
the section condition is solved, may be recovered by considering reductions on
different topologies other than toroidal.Comment: 20 pages, 5 table
An alternative to anti-branes and O-planes?
In this paper we consider type IIA compactifications in the isotropic Z2 x Z2
orbifold with a flux-induced perturbative superpotential combined with
non-perturbative effects. Without requiring the presence of O-planes, and
simply having D6-branes as local sources, we demonstrate the existence of de
Sitter (dS) critical points, where the non-perturbative contributions to the
cosmological constant have negligible size. We note, however, that these
solutions generically have tachyons. By means of a more systematic search, we
are able to find two examples of stable dS vacua with no need for anti-branes
or O-planes, which, however, exhibit important non-perturbative corrections.
The examples that we present turn out to remain stable even after opening up
the fourteen non-isotropic moduli.Comment: 12 pages, 4 tables; v2: typos corrected, published versio
Accelerated Universes from type IIA Compactifications
We study slow-roll accelerating cosmologies arising from geometric
compactifications of type IIA string theory on
. With the aid of a genetic
algorithm, we are able to find quasi-de Sitter backgrounds with both slow-roll
parameters of order . Furthermore, we study their evolution by numerically
solving the corresponding time-dependent equations of motion, and we show that
they actually display a few e-folds of accelerated expansion. Finally, we
comment on their perturbative reliability.Comment: 22 pages, 3 figures and 5 table
KK-monopoles and G-structures in M-theory/type IIA reductions
We argue that M-theory/massive IIA backgrounds including KK-monopoles are
suitably described in the language of G-structures and their intrinsic torsion.
To this end, we study classes of minimal supergravity models that admit an
interpretation as twisted reductions in which the twist parameters are not
restricted to satisfy the Jacobi constraints required by an
ordinary Scherk-Schwarz reduction. We first derive the correspondence between
four-dimensional data and torsion classes of the internal space and, then,
check the one-to-one correspondence between higher-dimensional and
four-dimensional equations of motion. Remarkably, the whole construction holds
regardless of the Jacobi constraints, thus shedding light upon the
string/M-theory interpretation of (smeared) KK-monopoles.Comment: 38 pages, 1 figure, 1 table; v2: refs added, published versio
Lobotomy of Flux Compactifications
We provide the dictionary between four-dimensional gauged supergravity and
type II compactifications on with metric and gauge fluxes in the
absence of supersymmetry breaking sources, such as branes and orientifold
planes. Secondly, we prove that there is a unique isotropic compactification
allowing for critical points. It corresponds to a type IIA background given by
a product of two 3-tori with SO(3) twists and results in a unique theory
(gauging) with a non-semisimple gauge algebra. Besides the known four AdS
solutions surviving the orientifold projection to induced by
O6-planes, this theory contains a novel AdS solution that requires non-trivial
orientifold-odd fluxes, hence being a genuine critical point of the
theory.Comment: 44 pages (33 pages + appendices), 13 tables, 3 figure
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