81 research outputs found
A second look at gauged supergravities from fluxes in M-theory
We investigate reductions of M-theory beyond twisted tori by allowing the
presence of KK6 monopoles (KKO6-planes) compatible with N=4 supersymmetry in
four dimensions. The presence of KKO6-planes proves crucial to achieve full
moduli stabilisation as they generate new universal moduli powers in the scalar
potential. The resulting gauged supergravities turn out to be compatible with a
weak G2 holonomy at N=1 as well as at some non-supersymmetric AdS4 vacua. The
M-theory flux vacua we present here cannot be obtained from ordinary type IIA
orientifold reductions including background fluxes, D6-branes (O6-planes)
and/or KK5 (KKO5) sources. However, from a four-dimensional point of view, they
still admit a description in terms of so-called non-geometric fluxes. In this
sense we provide the M-theory interpretation for such non-geometric type IIA
flux vacua.Comment: 46 pages. Published version. Minor changes, references adde
(Weak) G_2 Holonomy from Self-duality, Flux and Supersymmetry
The aim of this paper is two-fold. First, we provide a simple and pedagogical
discussion of how compactifications of M-theory or supergravity preserving some
four-dimensional supersymmetry naturally lead to reduced holonomy or its
generalization, reduced weak holonomy. We relate the existence of a (conformal)
Killing spinor to the existence of certain closed and co-closed p-forms, and to
the metric being Ricci flat or Einstein. Then, for seven-dimensional manifolds,
we show that octonionic self-duality conditions on the spin connection are
equivalent to G_2 holonomy and certain generalized self-duality conditions to
weak G_2 holonomy. The latter lift to self-duality conditions for
cohomogeneity-one spin(7) metrics. To illustrate the power of this approach, we
present several examples where the self-duality condition largely simplifies
the derivation of a G_2 or weak G_2 metric.Comment: references added, 25 pages, no figures, Late
Potentials and superpotentials in the effective N=1 supergravities from higher dimensions
We consider N=1 superpotentials corresponding to gaugings of an underlying
extended supergravity for a chiral multiplet in the SU(1,1)/U(1) manifold of
curvature 2/3. We analyze the resulting D=4 scalar potentials, and show that
they can describe different N=1 phases of higher-dimensional supergravities,
with broken or unbroken supersymmetry, flat or curved backgrounds, sliding or
stabilized radius. As an application, we discuss the D=4 effective theory of
the detuned supersymmetric Randall-Sundrum model in two different approximation
schemes.Comment: 20 pages; one reference added. To appear in Nuclear Physics
New Fayet-Iliopoulos terms in supergravity
We present a new type of Fayet-Iliopoulos (FI) terms in
supergravity that do not require the gauging of the -symmetry. We elaborate
on the impact of such terms on the vacuum structure of the
theory and compare their properties with the standard Fayet-Iliopoulos terms
that arise from gaugings. In particular, we show that, with the use of the new
FI terms, models with a single physical vector multiplet can
be constructed that give stable de Sitter vacua.Comment: 50 page
Five-Brane Thresholds and Membrane Instantons in Four-Dimensional Heterotic M-Theory
The effective four-dimensional supergravity of M-theory compactified on the
orbifold S^1/Z_2 and a Calabi-Yau threefold includes in general moduli
supermultiplets describing massless modes of five-branes. For each brane, one
of these fields corresponds to fluctuations along the interval. The five-brane
also leads to modifications of the anomaly-cancelling terms in the
eleven-dimensional theory, including gauge contributions located on their
world-volumes. We obtain the interactions of the brane "interval modulus"
predicted by these five-brane-induced anomaly-cancelling terms and we construct
their effective supergravity description. In the condensed phase, these
interaction terms generate an effective non-perturbative superpotential which
can also be interpreted as instanton effects of open membranes stretching
between five-branes and the S^1/Z_2 fixed hyperplanes. Aspects of the vacuum
structure of the effective supergravity are also briefly discussed.Comment: 39 pages. Published version. Changes in introduction, appendix and
reference
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