131 research outputs found
Universal dS vacua in STU-models
Stable de Sitter solutions in minimal F-term supergravity are known to lie
close to Minkowski critical points. We consider a class of STU-models arising
from type IIB compactifications with generalised fluxes. There, we apply an
analytical method for solving the equations of motion for the moduli fields
based on the idea of treating derivatives of the superpotential of different
orders up to third as independent objects. In particular, supersymmetric and
no-scale Minkowski solutions are singled out by physical reasons. Focusing on
the study of dS vacua close to supersymmetric Minkowski points, we are able to
elaborate a complete analytical treatment of the mass matrix based on the
sGoldstino bound. This leads to a class of interesting universal dS vacua. We
finally explore a similar possibility around no-scale Minkowski points and
discuss some examples.Comment: 31 pages, 4 figures and 7 table
Out of the swampland with multifield quintessence?
Multifield models with a curved field space have already been shown to be able to provide viable quintessence models for steep potentials that satisfy swampland bounds. The simplest dynamical systems of this type are obtained by coupling Einstein gravity to two scalar fields with a curved field space. In this paper we study the stability properties of the non-trivial fixed points of this dynamical system for a general functional dependence of the kinetic coupling function and the scalar potential. We find the existence of non-geodesic trajectories with a sharp turning rate in field space which can give rise to late-time cosmic acceleration with no need for flat potentials. In particular, we discuss the properties of the phase diagram of the system and the corresponding time evolution when varying the functional dependence of the kinetic coupling. Interestingly, upon properly tuning the initial conditions of the field values, we find trajectories that can describe the current state of the universe. This could represent a promising avenue to build viable quintessence models out of the swampland if they could be consistently embedded in explicit string constructions
Stringy multifield quintessence and the Swampland
We consider quintessence models within 4D effective descriptions of gravity coupled to two scalar fields. These theories are known to give rise to viable models of late-time cosmic acceleration without any need for flat potentials, and so they are potentially in agreement with the dS Swampland conjecture. In this paper we investigate the possibility of consistently embedding such constructions in string theory. We identify situations where the quintessence fields are either closed string universal moduli or non-universal moduli such as blow-up modes. We generically show that no trajectories compatible with today’s cosmological parameters exist, if one starts from matter-dominated initial conditions. It is worth remarking that universal trajectories compatible with observations do appear, provided that the starting point at early times is a phase of kinetic domination. However, justifying this choice of initial conditions on solid grounds is far from easy. We conclude by studying Q-ball formation in this class of models and discuss constraints coming from Q-ball safety in all cases analyzed here
Stringy multifield quintessence and the Swampland
We consider quintessence models within 4D effective descriptions of gravity
coupled to two scalar fields. These theories are known to give rise to viable
models of late-time cosmic acceleration without any need for flat potentials,
and so they are potentially in agreement with the dS Swampland conjecture. In
this paper we investigate the possibility of consistently embedding such
constructions in string theory. We identify situations where the quintessence
fields are either closed string universal moduli or non-universal moduli such
as blow-up modes. We generically show that no trajectories compatible with
today's cosmological parameters exist, if one starts from matter-dominated
initial conditions. It is worth remarking that universal trajectories
compatible with observations do appear, provided that the starting point at
early times is a phase of kinetic domination. However, justifying this choice
of initial conditions on solid grounds is far from easy. We conclude by
studying Q-ball formation in this class of models and discuss constraints
coming from Q-ball safety in all cases analyzed here.Comment: 23 pages, 5 figure
Exceptional Flux Compactifications
We consider type II (non-)geometric flux backgrounds in the absence of brane
sources, and construct their explicit embedding into maximal gauged D=4
supergravity. This enables one to investigate the critical points, mass spectra
and gauge groups of such backgrounds. We focus on a class of type IIA geometric
vacua and find a novel, non-supersymmetric and stable AdS vacuum in maximal
supergravity with a non-semisimple gauge group. Our construction relies on a
non-trivial mapping between SL(2) x SO(6,6) fluxes, SU(8) mass spectra and
gaugings of E7(7) subgroups.Comment: 51 pages, 2 figures and 4 tables. v3: change of SO(6,6) spinorial
conventions, published versio
Charting the landscape of N=4 flux compactifications
We analyse the vacuum structure of isotropic Z_2 x Z_2 flux
compactifications, allowing for a single set of sources. Combining algebraic
geometry with supergravity techniques, we are able to classify all vacua for
both type IIA and IIB backgrounds with arbitrary gauge and geometric fluxes.
Surprisingly, geometric IIA compactifications lead to a unique theory with four
different vacua. In this case we also perform the general analysis allowing for
sources compatible with minimal supersymmetry. Moreover, some relevant examples
of type IIB non-geometric compactifications are studied. The computation of the
full N=4 mass spectrum reveals the presence of a number of non-supersymmetric
and nevertheless stable AdS_4 vacua. In addition we find a novel dS_4 solution
based on a non-semisimple gauging.Comment: Minor corrections and references added. Version published in JHE
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