116 research outputs found
Constraints on Supersymmetric Theories from
In the absence of any additional assumption it is natural to conjecture that
sizeable flavour-mixing mass entries, , may appear in the mass
matrices of the scalars of the MSSM, i.e. . This flavour
violation can still be reconciled with the experiment if the gaugino mass,
, is large enough, leading to a {\em gaugino dominance} framework
(i.e. ), which permits a remarkably model--independent
analysis. We study this possibility focussing our attention on the
decay. In this way we obtain very strong and general
constraints, in particular \frac{M_{1/2}^2}{\Delta m}\simgt 34\ {\rm TeV}. On
the other hand, we show that our analysis and results remain valid for values
of much larger than , namely for \frac{\Delta
m^2}{m^2}\simgt \frac{m^2} {10\ {\rm TeV^2}}, thus extending enormously their
scope of application. Finally, we discuss the implications for superstring
scenarios.Comment: 12 pages, Latex, 5 figures as uuencoded compressed postscript files,
uses psfig.st
Model for a Universe described by a non-minimally coupled scalar field and interacting dark matter
In this work it is investigated the evolution of a Universe where a scalar
field, non-minimally coupled to space-time curvature, plays the role of
quintessence and drives the Universe to a present accelerated expansion. A
non-relativistic dark matter constituent that interacts directly with dark
energy is also considered, where the dark matter particle mass is assumed to be
proportional to the value of the scalar field. Two models for dark matter
pressure are considered: the usual one, pressureless, and another that comes
from a thermodynamic theory and relates the pressure with the coupling between
the scalar field and the curvature scalar. Although the model has a strong
dependence on the initial conditions, it is shown that the mixture consisted of
dark components plus baryonic matter and radiation can reproduce the expected
red-shift behavior of the deceleration parameter, density parameters and
luminosity distance.Comment: 11 pages and 6 figures. To appear in GR
Anomalous U(1) D-term Contribution in Type I String Models
We study the -term contribution for anomalous U(1) symmetries in type I
string models and derive general formula for the -term contribution,
assuming that the dominant source of SUSY breaking is given by -terms of the
dilaton, (overall) moduli or twisted moduli fields. On the basis of the
formula, we also point out that there are several different features from the
case in heterotic string models. The differences originate from the different
forms of K\"ahler potential between twisted moduli fields in type I string
models and the dilaton field in heterotic string models.Comment: 16 pages, latex, no figur
Late-time cosmology in (phantom) scalar-tensor theory: dark energy and the cosmic speed-up
We consider late-time cosmology in a (phantom) scalar-tensor theory with an
exponential potential, as a dark energy model with equation of state parameter
close to -1 (a bit above or below this value). Scalar (and also other kinds of)
matter can be easily taken into account. An exact spatially-flat FRW cosmology
is constructed for such theory, which admits (eternal or transient)
acceleration phases for the current universe, in correspondence with
observational results. Some remarks on the possible origin of the phantom,
starting from a more fundamental theory, are also made. It is shown that
quantum gravity effects may prevent (or, at least, delay or soften) the cosmic
doomsday catastrophe associated with the phantom, i.e. the otherwise
unavoidable finite-time future singularity (Big Rip). A novel dark energy model
(higher-derivative scalar-tensor theory) is introduced and it is shown to admit
an effective phantom/quintessence description with a transient acceleration
phase. In this case, gravity favors that an initially insignificant portion of
dark energy becomes dominant over the standard matter/radiation components in
the evolution process.Comment: LaTeX file, 48 pages, discussion of Big Rip is enlarged, a reference
is adde
The b--->s{\gamma} constraint in effective supergravities from string theory
We study the constraints from the decay in the
parameter space of effective supergravities from orbifold string theory and
with minimal supesymmetric particle content. Both the general dilaton-dominated
universal scenario as well as a non-universal scenario for the soft terms are
investigated. It is found that the recently reported CLEO upper and lower
bounds constrain the parameter space of the models under scrutiny. In
particular we find constraints on the values of the parameter and
the gluino masses. In this class of string scenarios the negative sign of the
Higgs mixing parameter , is phenomenologically preferred.Comment: LaTeX 11 pages, figures uuencoded included in a separate file, some
typos have been corrected,1 figure adde
Cosmology With Non-Minimally Coupled K-Field
We consider non-minimally coupled (with gravity) scalar field with
non-canonical kinetic energy. The form of the kinetic term is of
Dirac-Born-Infeld (DBI) form.We study the early evolution of the universe when
it is sourced only by the k-field, as well as late time evolution when both the
matter and k-field are present. For the k-field, we have considered constant
potential as well as potential inspired from Boundary String Field Theory
(B-SFT). We show that it is possible to have inflationary solution in early
time as well as late time accelerating phase. The solutions also exhibit
attractor property in a sense that it does not depend on the initial conditions
for a certain values of the parameters.Comment: 10 pages, Revtex style, 14 eps figures, to appear in General
Relativity and Gravitatio
Low-Energy Effective Lagrangian from Non-Minimal Supergravity with Unified Gauge Symmetry
From general supergravity theory with unified gauge symmetry, we obtain the
low-energy effective Lagrangian by taking the flat limit and integrating out
the superheavy fields in model-independent manner. The scalar potential
possesses some excellent features. Some light fields classified by using
supersymmetric fermion mass, in general, would get intermediate masses at the
tree level after the supersymmetry is broken. We show that the stability of
weak scale can be guaranteed under some conditions. There exist extra
non-universal contributions to soft supersymmetry breaking terms which can give
an impact on phenomenological study.Comment: 37 pages, Figures not include
Risk assessment of the lead intake by consumption of red deer and wild boar meat in Southern Spain
Pb and Cd on growth, leaf ultrastructure and essential oil yield mint (Mentha arvensis L.)
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