1,179 research outputs found
Gluino Condensation in Strongly Coupled Heterotic String Theory
Strongly coupled heterotic string theory, compactified to
four dimensions on a large Calabi-Yau manifold , may represent a
viable candidate for the description of low-energy particle phenomenology. In
this regime, heterotic string theory is adequately described by low-energy
-theory on , with the two
's supported at the two boundaries of the world. In this paper we study
the effects of gluino condensation, as a mechanism for supersymmetry breaking
in this -theory regime. We show that when a gluino condensate forms in
-theory, the conditions for unbroken supersymmetry can still be satisfied
locally in the orbifold dimension . Supersymmetry is then
only broken by the global topology of the orbifold dimension, in a mechanism
similar to the Casimir effect. This mechanism leads to a natural hierarchy of
scales, and elucidates some aspects of heterotic string theory that might be
relevant to the stabilization of moduli and the smallness of the cosmological
constant.Comment: 22 pages, harvmac, no figure
Small SUSY phases in string-inspired supergravity
In supersymmetric models, there are new CP violating phases which, if
unsuppressed, would give a too large neutron electric dipole moment. We examine
the possibility of small SUSY phases in string-inspired supergravity models in
which supersymmetry is broken by the auxiliary components of the dilaton and
moduli superfields. It is found that the SUSY phases can be suppressed by a
small factor governing the breakdown of the approximate Peccei Quinn symmetries
nonlinearly realized for the moduli superfields that participate in
supersymmetry breaking. In many cases, the symmetry breaking factors are
exponentially small for moderately large values of the moduli, leading to small
phase values in a natural way.Comment: 15pages, Latex, SNUTP 93-8
Possible astrophysical signatures of heavy stable neutral relics in supergravity models
We consider heavy stable neutral particles in the context of supergravity and
show that a gravitationally suppressed inflaton decay can produce such
particles in cosmologically interesting abundances within a wide mass range
. In gravity-mediated
supersymmetry breaking models, a heavy particle can decay into its superpartner
and a photon-photino pair or a gravitino. Such decays only change the identity
of a possible dark matter candidate. However, for , astrophysical bounds from gamma-ray background and
photodissociation of light elements can be more stringent than the overclosure
bound, thus ruling out the particle as a dark matter candidate.Comment: 12 page
Supergravity Inflation Free from Harmful Relics
We present a realistic supergravity inflation model which is free from the
overproduction of potentially dangerous relics in cosmology, namely moduli and
gravitinos which can lead to the inconsistencies with the predictions of baryon
asymmetry and nucleosynthesis. The radiative correction turns out to play a
crucial role in our analysis which raises the mass of supersymmetry breaking
field to intermediate scale. We pay a particular attention to the non-thermal
production of gravitinos using the non-minimal Kahler potential we obtained
from loop correction. This non-thermal gravitino production however is
diminished because of the relatively small scale of inflaton mass and small
amplitudes of hidden sector fields.Comment: 10 pages, revtex, 1 eps figure, references added, conclusion section
expande
SUSY dark matter(s)
We review here the status of different dark matter candidates in the context
of supersymmetric models, in particular the neutralino as a realization of the
WIMP-mechanism and the gravitino. We give a summary of the recent bounds in
direct and indirect detection and also of the LHC searches relevant for the
dark matter question. We discuss also the implications of the Higgs discovery
for the supersymmetric dark matter models and give the prospects for the future
years.Comment: 16 pages, 3 figure
Top squark and neutralino decays in a R-parity violating model constrained by neutrino oscillation data
In a R-parity violating (RPV) model of neutrino mass with three bilinear
couplings and three trilinear couplings , where is
the lepton index, we find six generic scenarios each with a distinctive pattern
of the trilinear couplings consistent with the oscillation data. These patterns
may be reflected in direct RPV decays of the lighter top squark or in the RPV
decays of the lightest superparticle, assumed to be the lightest neutralino.
Typical signal sizes at the Tevatron RUN II and the LHC have been estimated
and the results turn out to be encouraging.Comment: 20 pages, 4 figures, LaTex,typos corrected and reference added for
section 2, a paragraph has been added in the conclusion par
Singlet superfield extension of the minimal supersymmetric standard model with Peccei-Quinn symmetry and a light pseudoscalar Higgs boson at the LHC
Motivated by the mu-problem and the axion solution to the strong CP-problem,
we extend the MSSM with one more chiral singlet field . The underlying
PQ-symmetry allows only one more term in the superpotential. The
spectrum of the Higgs system includes a light pseudoscalar (in addition
to the standard CP-even Higgs boson), predominantly decaying to two photons:
. Both Higgs bosons might be in the range accessible to
current LHC experiments.Comment: 5 pages with 3 figure
Gauged extended supergravity without cosmological constant: no-scale structure and supersymmetry breaking
We consider the interplay of duality symmetries and gauged isometries of
supergravity models giving N-extended, spontaneously broken supergravity with a
no-scale structure. Some examples, motivated by superstring and M-theory
compactifications are described.Comment: AMS-LaTeX, 16 pages. Invited paper to appear in the review section of
the IJMP
String corrections to gauge couplings from a field theory approach
An effective field theory approach is introduced to compute one-loop
radiative corrections to the gauge couplings due to Kaluza-Klein states
associated with a two-torus compactification. The results are compared with
those of the string in the field theory ``limit'' alpha'-> 0. The whole U and
the leading T moduli dependence of the gauge dependent part of the string
corrections to gauge couplings can be recovered using the effective field
theory approach.Comment: 8 pages, Late
Four-Dimensional Effective Supergravity and Soft Terms in M-Theory
We provide a simple macroscopic analysis of the four-dimensional effective
supergravity of the Ho\v{r}ava-Witten M-theory which is expanded in powers of
and where ,
and denote the eleven-dimensional gravitational coupling, the
Calabi-Yau volume and the eleventh length respectively. Possible higher order
terms in the K\"ahler potential are identified and matched with the heterotic
string corrections. In the context of this M-theory expansion, we analyze the
soft supersymmetry-breaking terms under the assumption that supersymmetry is
spontaneously broken by the auxiliary components of the bulk moduli
superfields. It is examined how the pattern of soft terms changes when one
moves from the weakly coupled heterotic string limit to the M-theory limit.Comment: Latex, 23 pages, 3 figures. References are added and the discussion
of the M-theory expansion parameters is enlarge
- âŠ