181 research outputs found
Twin Supergravities
We study the phenomenon that pairs of supergravities can have identical
bosonic field content but different fermionic extensions. Such twin theories
are classified and shown to originate as truncations of a common theory with
more supersymmetry. Moreover, we discuss the possible gaugings and scalar
potentials of twin theories. This allows to pinpoint to which extent these
structures are determined by the purely bosonic structure of the underlying
Kac-Moody algebras and where supersymmetry comes to plays its role. As an
example, we analyze the gaugings of the six-dimensional N=(0,1) and N=(2,1)
theories with identical bosonic sector and explicitly work out their scalar
potentials. The discrepancy between the potentials finds a natural explanation
within maximal supergravity, in which both theories may be embedded.Comment: 27 pages. v2: ref added, published versio
Universality Classes of Scale Invariant Inflation
We investigate the inflationary implications of extensions of Poincare
symmetry. The simplest constructions with local scale invariance lead to
universal predictions: the spectral index is , in excellent
agreement with Planck data, while the tensor-to-scalar ratio is determined by a
free parameter to . For the special value one
finds symmetry enhancement to the full conformal group. We show that these
findings hold both for two-derivative scalar-tensor theories as well as
higher-derivative gravity. Therefore scale invariance underlies a promising set
of inflationary models.Comment: 6 pages, 1 figur
General sGoldstino Inflation
We prove that all inflationary models, including those with dark energy after
the end of inflation, can be embedded in minimal supergravity with a single
chiral superfield. Moreover, the amount of supersymmetry breaking is
independently tunable due to a degeneracy in the choice for the superpotential.
The inflaton is a scalar partner of the Goldstino in this set-up. We illustrate
our general procedure with two examples that are favoured by the Planck data.Comment: 6 pages, 6 figures; v2: refs added, published versio
Cosmological Attractors from -Scale Supergravity
The Planck value of the spectral index can be interpreted as
in terms of the number of e-foldings . An appealing explanation for this
phenomenological observation is provided by -attractors: the
inflationary predictions of these supergravity models are fully determined by
the curvature of the Kahler manifold. We provide a novel formulation of
-attractors which only involves a single chiral superfield. Our
construction involves a natural deformation of no-scale models, and employs
these to construct a De Sitter plateau with an exponential fall-off. Finally,
we show how analogous structures with a flat Kahler geometry arise as a
singular limit of such -scale models.Comment: 6 pages, 3 figures. v3: minor clarifications and refs added. PRD
versio
Gaugings at angles from orientifold reductions
We consider orientifold reductions to N=4 gauged supergravity in four
dimensions. A special feature of this theory is that different factors of the
gauge group can have relative angles with respect to the electro-magnetic SL(2)
symmetry. These are crucial for moduli stabilisation and De Sitter vacua. We
show how such gaugings at angles generically arise in orientifold reductions.Comment: 15 pages. v4: refs added, minor improvements, published versio
The special Galileon as Goldstone of diffeomorphisms
The special Galileon stands out amongst scalar field theories due to its soft
limits, non-linear symmetries and scattering amplitudes. This prompts the
question what the origin of its underlying symmetry is. We show that it is
intimately connected to general relativity: the special Galileon is the
Goldstone mode of the affine group, consisting of linear coordinate
transformations, analogous to the dilaton for conformal symmetries. We
construct the corresponding metric, and discuss various relations to gravity,
Yang-Mills and the non-linear sigma-model.Comment: 6 pages; v2: ref added, published versio
Galileons as the Scalar Analogue of General Relativity
We establish a correspondence between general relativity with diffeomorphism
invariance and scalar field theories with Galilean invariance: notions such as
the Levi-Civita connection and the Riemann tensor have a Galilean counterpart.
This suggests Galilean theories as the unique nontrivial alternative to gauge
theories (including general relativity). Moreover, it is shown that the
requirement of first-order Palatini formalism uniquely determines the Galileon
models with second-order field equations, similar to the Lovelock gravity
theories. Possible extensions are discussed.Comment: 6 pages, v2: Version appeared in Phys. Rev.
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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