39,398 research outputs found
Supergravity Unified Models
The development of supergravity unified models and their implications for
current and future experiments are discussed.Comment: Latex, 21 pages, to appear in book "Perspectives on Supergravity",
World Scientific, Editor G. Kane; reference numbers and minor typos correcte
On Asymmetric Orbifolds and the D=5 No-modulus Supergravity
We examine whether any type II asymmetric orbifolds have the same massless
spectrum as the dimensional reduction of D=5 simple supergravity, which,
besides the eleven-dimensional supergravity, is the only known supergravity
above four dimensions with no moduli. We attempt to construct such models by
further twisting the orbifolds which yield D=4, N=4 pure supergravity to find
that, unfortunately, none of the models have that spectrum. We provide
supergravity arguments explaining why this is so. As a by-product, we list all
possible momentum-winding lattices that give D=4, N=4 pure supergravity.Comment: 10 page
in supergravity models
We compute the supersymmetric contribution to
in a
variety of supergravity models. We find R^{\rm susy}_b\lsim0.0004, which does
not shift significantly the Standard Model prediction
( for m_t=160\GeV). An improvement in experimental
precision by a factor of four would be required to be sensitive to such an
effect.Comment: 5 pages, LaTeX, 1 figure (included)
Fine-Tuning Constraints on Supergravity Models
We discuss fine-tuning constraints on supergravity models. The tightest
constraints come from the experimental mass limits on two key particles: the
lightest CP even Higgs boson and the gluino. We also include the lightest
chargino which is relevant when universal gaugino masses are assumed. For each
of these particles we show how fine-tuning increases with the experimental mass
limit, for four types of supergravity model: minimal supergravity, no-scale
supergravity (relaxing the universal gaugino mass assumption), D-brane models
and anomaly mediated supersymmetry breaking models. Among these models, the
D-brane model is less fine tuned.The experimental propects for an early
discovery of Higgs and supersymmetry at LEP and the Tevatron are discussed in
this framework.Comment: 17 pages, Latex, including 5 eps figure
Quintessence models in Supergravity
Scalar field models of quintessence typically require that the expectation
value of the field today is of order the Planck mass, if we want them to
explain the observed acceleration of the Universe. This suggests that we should
be considering models in the context of supergravity. We discuss a particular
class of supergravity models and analyze their behavior under different choices
of the Kahler metric.Comment: 6 pages, revised version to appear in PR
Phenomenological Aspects of Heterotic Orbifold Models at One Loop
We provide a detailed study of the phenomenology of orbifold
compactifications of the heterotic string within the context of supergravity
effective theories. Our investigation focuses on those models where the soft
Lagrangian is dominated by loop contributions to the various soft supersymmetry
breaking parameters. Such models typically predict non-universal soft masses
and are thus significantly different from minimal supergravity and other
universal models. We consider the pattern of masses that are governed by these
soft terms and investigate the implications of certain indirect constraints on
supersymmetric models, such as flavor-changing neutral currents, the anomalous
magnetic moment of the muon and the density of thermal relic neutralinos. These
string-motivated models show novel behavior that interpolates between the
phenomenology of unified supergravity models and models dominated by the
superconformal anomaly.Comment: 47 pages, 14 figure
False Vacuum Chaotic Inflation: The New Paradigm?
Recent work is reported on inflation model building in the context of
supergravity and superstrings, with special emphasis on False Vacuum (`Hybrid')
Chaotic Inflation. Globally supersymmetric models do not survive in generic
supergravity theories, but fairly simple conditions can be formulated which do
ensure successful supergravity inflation. The conditions are met in some of the
versions of supergravity that emerge from superstrings.Comment: 4 pages, LATEX, LANCASTER-TH 94-1
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