500 research outputs found
Static Quantities of the W bosons in the MSSM
I discuss the static quantities of the W boson, magnetic dipole and electric
quadrupole moments, in the context of the minimal supersymmetric standard
model, in which supersymmetry is broken by soft terms .
Following a renormalization group analysis it is found that the supersymmetric
values of and can be largely different,
in some cases, from the standard model predictions but of the same order of
magnitude for values of \quad .
Therefore possible supersymmetric structure can be probed provided the accuracy
of measurements for , reaches
and hence hard to be detected at LEP2. In cases where
, the charginos and neutralinos may give substantial
contributions saturating the LEP2 sensitivity limits. This occurs when their
masses turn out to be both light satisfying
. However these extreme cases are
perturbatively untrustworthy and besides unnatural for they occupy a small
region in the parameter space.Comment: 14 pages+2 figures , Latex, uses revtex[aps,aipbook,floats,epsfig]
(The two figures in a separate uuencode file ). Talk given at the
International Symposium on Gauge Boson self-interactions, UCLA, February 1-3,
1995 Los Angele
Inflation in no-scale supergravity
Supergravity is known to be equivalent to standard Supergravity
coupled to two chiral supermultiples with a no-scale K\"ahler potential. Within
this framework, that can accomodate vanishing vacuum energy and spontaneous
supersymmetry breaking, we consider modifications of the associated
superpotential and study the resulting models, which, viewed as generalizations
of the Starobinsky model, for a range of the superpotential parameters,
describe viable single-field slow-roll inflation. In all models studied in this
work the tensor to scalar ratio is found to be small, well below the upper
bound established by the very recent PLANCK and BICEP2 data.Comment: 15 pages, 6 figures, references and comments adde
Non-critical String Cosmologies
Non-critical String Cosmologies are offered as an alternative to Standard Big
Bang Cosmology. The new features encompassed within the dilaton dependent
non-critical terms affect the dynamics of the Universe\'s evolution in an
unconventional manner being in agreement with the cosmological data.
Non-criticality is responsible for a late transition to acceleration at
redshifts z=0.2. The role of the uncoupled rolling dilaton to relic abundance
calculations is discussed. The uncoupled rolling dilaton dilutes the neutralino
relic densities in supersymmetric theories by factors of ten, relaxing
considerably the severe WMAP Dark Matter constraints, while at the same time
leaves almost unaffected the baryon density in agreement with primordial
Nucleosynthesis.Comment: 16 pages, 7 figures, conference tal
Dilaton dominance in the early Universe dilutes Dark Matter relic abundances
The role of the dilaton field and its coupling to matter may result to a
dilution of Dark Matter (DM) relic densities. This is to be contrasted with
quintessence scenarios in which relic densities are augmented, due to
modification of the expansion rate, since Universe is not radiation dominated
at DM decoupling. Dilaton field, besides this, affects relic densities through
its coupling to dust which tends to decrease relic abundances. Thus two
separate mechanisms compete each other resulting, in general, to a decrease of
the relic density. This feature may be welcome and can rescue the situation if
Direct Dark Matter experiments point towards small neutralino-nucleon cross
sections, implying small neutralino annihilation rates and hence large relic
densities, at least in the popular supersymmetric scenarios. In the presence of
a diluting mechanism both experimental constraints can be met. The role of the
dilaton for this mechanism has been studied in the context of the non-critical
string theory but in this work we follow a rather general approach assuming
that the dilaton dominates only at early eras long before Big Bang
Nucleosynthesis.Comment: 11 pages, Latex, 4 figures: Comments and references added, version to
appear in Phys. Rev.
Static and non-static quantum effects in two-dimensional dilaton gravity
We study backreaction effects in two-dimensional dilaton gravity. The
backreaction comes from an term which is a part of the one-loop effective
action arising from massive scalar field quantization in a certain
approximation. The peculiarity of this term is that it does not contribute to
the Hawking radiation of the classical black hole solution of the field
equations. In the static case we examine the horizon and the physical
singularity of the new black hole solutions. Studying the possibility of time
dependence we see the generation of a new singularity. The particular solution
found still has the structure of a black hole, indicating that non-thermal
effects cannot lead, at least in this approximation, to black hole evaporation.Comment: 10 pages, no figure
Weak and electromagnetic interactions in the quarkbarton model
This thesis deals with the naive quark parton model as means of explaining deep inelastic scattering phenomena. The formalism of the quark model is reviewed as is the parton model and its main results. The Kuti-Weisskopf quark parton model is introduced and used to make predictions for charged and neutral current neutrino experiments. An attempt is made to improve the Kuti-Weisskopf model predictions and we propose a model in which new hadronic constituents, besides the p,n,λ and charmed p' quarks participate. In this model the new particles are classified in SU(2) triplets of the Weinberg model. Wu an.ilyee charged and neutral current neutrino experiments and construct a model which is a modification of a quark model proposed by R.Mc. Elhaney and S.F. Tuan. In the light of recent work on nonleptonic interactions of the electron we consider both electron positron annihilation and deepinelastic scattering. Finally, we propose a scheme in which "naive quark parton model' techniques can give (logs)(^2) behaviour for the hadronic total cross sections
- …