11 research outputs found
Moduli Decays and Gravitinos
One proposed solution of the moduli problem of string cosmology requires that
the moduli are quite heavy, their decays reheating the universe to temperatures
above the scale of nucleosynthesis. In many of these scenarios, the moduli are
approximately supersymmetric; it is then crucial that the decays to gravitinos
are helicity suppressed. In this paper, we discuss situations where these
decays are, and are not, suppressed. We also comment on a possible gravitino
problem from inflaton decay.Comment: 16 pages, version to appear in Physical Review
IIA moduli stabilization with badly broken supersymmetry
Scherk-Schwarz compactification in string theory can be defined as
orbifolding by an R symmetry, a symmetry that acts differently on bosons and
fermions. Such a symmetry can arise in many situations, including toroidal and
orbifold compactifications, as well as smooth Calabi-Yau spaces. If the
symmetry acts freely then for large radius there are no tachyons in the
spectrum. We focus mainly on stabilization by fluxes, and give examples with
all moduli stabilized where the coupling is small and the internal manifold is
large. Such models appear to be perturbatively stable with supersymmetry broken
at the Kaluza-Klein scale. These are interesting laboratories for a variety of
theoretical questions and provide models of a non-supersymmetric landscape.Comment: 18 pages, LATEX, no figures. several refs added to earlier literature
on Scherk Schwarz in string theory, discussion of smooth CY made more precis
Towards a quantum theory of de Sitter space
We describe progress towards constructing a quantum theory of de Sitter space
in four dimensions. In particular we indicate how both particle states and
Schwarzschild de Sitter black holes can arise as excitations in a theory of a
finite number of fermionic oscillators. The results about particle states
depend on a conjecture about algebras of Grassmann variables, which we state,
but do not prove.Comment: JHEP3 LaTex - 19 page
Symmetric Points in the Landscape as Cosmological Attractors
In the landscape, if there is to be any prospect of scientific prediction, it
is crucial that there be states which are distinguished in some way. The
obvious candidates are states which exhibit symmetries. Here we focus on states
which exhibit discrete symmetries. Such states are rare, but one can speculate
that they are cosmological attractors. We investigate the problem in model
landscapes and cosmologies which capture some of the features of candidate flux
landscapes. In non-supersymmetric theories we find no evidence that such states
might be cosmologically favored. In supersymmetric theories, simple arguments
suggest that states which exhibit symmetries might be. Our considerations
lead us to raise questions about some popular models of eternal inflation.Comment: 27 pages, latex, minor typo correcte
Metastable Domains of the Landscape
We argue that the vast majority of flux vacua with small cosmological
constant are unstable to rapid decay to a big crunch. Exceptions are states
with large compactification volume and supersymmetric and approximately
supersymmetric states. Neither weak string coupling, warping, or the existence
of very light particles are, by themselves, enough to render states reasonably
metastable. We speculate, as well, about states which might be cosmological
attractors.Comment: 20 page
The Fate of Nearly Supersymmetric Vacua
Supersymmetric vacua are stable. It is interesting to ask: how long-lived are
vacua which are nearly supersymmetric? This question is relevant if our
universe is approximately supersymmetric. It is also of importance for a number
of issues of the physics of the landscape and eternal inflation. In this note,
we distinguish a variety of cases. In all of them the decay is slow. For a flat
space theory decaying to a deep AdS vacuum, the leading behavior of the decay
amplitude, if a thin wall approximation is valid, is (where the phase of is defined in the
text) for , and zero otherwise. Metastable supersymmetry
breaking generally yields parametrically more rapid decays. For nearly
supersymmetric decays, we will see that it is necessary to compute subleading
terms in the exponential to extraordinarily high accuracy before one can
meaningfully discuss the prefactor.Comment: 19 page
Strings on Bubbling Geometries
We study gauge theory operators which take the form of a product of a trace
with a Schur polynomial, and their string theory duals. These states represent
strings excited on bubbling AdS geometries which are dual to the Schur
polynomials. These geometries generically take the form of multiple annuli in
the phase space plane. We study the coherent state wavefunction of the lattice,
which labels the trace part of the operator, for a general Young tableau and
their dual description on the droplet plane with a general concentric ring
pattern. In addition we identify a density matrix over the coherent states on
all the geometries within a fixed constraint. This density matrix may be used
to calculate the entropy of a given ensemble of operators. We finally recover
the BMN string spectrum along the geodesic near any circle from the ansatz of
the coherent state wavefunction.Comment: 41 pages, 12 figures, published version in JHE
Moduli Decays and Gravitinos
One proposed solution of the moduli problem of string cosmology requires that the moduli are quite heavy, their decays reheating the universe to temperatures above the scale of nucleosynthesis. In many of these scenarios, the moduli are approximately supersymmetric; it is then crucial that the decays to gravitinos are helicity suppressed. In this paper, we discuss situations where these decays are, and are not, suppressed. We also comment on a possible gravitino problem from inaton decay