605 research outputs found
Anomaly Mediated Supersymmetry Breaking without R-Parity
We analyze the low energy features of a supersymmetric standard model where
the anomaly--induced contributions to the soft parameters are dominant in a
scenario with bilinear --parity violation. This class of models leads to
mixings between the standard model particles and supersymmetric ones which
change the low energy phenomenology and searches for supersymmetry. In
addition, --parity violation interactions give rise to small neutrino masses
which we show to be consistent with the present observations.Comment: 38 pages, 15 figures. For higher resolution figures go to
http://www.fma.if.usp.br/~magro/figures
Top-Quark Phenomenology in Models with Bilinearly and Spontaneously Broken R-parity
We study unconventional decays of the top-quark in the framework of SUSY
models with spontaneously broken R-parity. In particular we discuss an
effective theory which consists of the MSSM plus bilinearly broken R-parity. We
demonstrate that the decay modes t -> stau + b and t -> tau + sbottom can have
large branching ratios even in scenarios where the tau-neutrino mass is very
small. We show that existing Tevatron data already probe the theoretical
parameters, with promising prospects for further improvement at the Run 2 of
the Tevatron.Comment: 12 pages, 6 eps-figure
Classical and quantum quintessence cosmology
This paper implements the idea of considering the instantonic creation of
brane worlds whose five-dimensional bulk contains a negative cosmological
constant and a scalar quintessence field with time-dependent equation of state,
restricting to the case that the quintessence field couples minimally to
Hilbert-Einstein gravity. We construct an Euclidean formalism, both for the
four- and five-dimensional cases, singling out a Hamiltonian constraint that
depends on the parameter defining the quintessence state equation. Specializing
at several particular values of that parameter, we obtain solutions to the
constraint equation and analyse them both classically and quantum mechanically.
It is found that these solutions can represent either asymptotically anti-de
Sitter wormholes or pure anti-de Sitter spaces whose quantum states are
obtained by means of the Wheeler de Witt equation. Starting with the different
five-dimensional solutions, an instantonic procedure is applied to describe the
creation of geometrically equivalent inflating de Sitter branes whose quantum
states are also evaluated in some cases. We thus consider the quantum state of
the universe to be contributed by all the instantonic paths that correspond to
these particular brane worlds.Comment: 12 pages, RevTex, 1 figure incorporate
Quintessence in brane cosmology
In order to reconcile the non conventional character of brane cosmology with
standard Friedmann cosmology, we introduce in this paper a slowly-varying
quintessence scalar field in the brane and analyse the cosmological solutions
corresponding to some equations of state for the scalar field. Different
compensation mechanisms between the cosmological constant in the bulk and the
constant tension resulting from the combined effect of ordinary matter and the
quintessence scalar field are derived or assumed. It has been checked that the
Randall-Sundrum approach is not necessarily the best procedure to reconcile
brane and standard cosmologies, and that there exists at least another
compensating mechanism that reproduces a rather conventional behaviour for an
accelerating universe.Comment: 10 pages, additional physical motivation and connections to high
energy physics and observations, to appear in Phys. Lett.
Shape Theory via QR decomposition
This work sets the non isotropic noncentral elliptical shape distributions
via QR decomposition in the context of zonal polynomials, avoiding the
invariant polynomials and the open problems for their computation. The new
shape distributions are easily computable and then the inference procedure can
be studied under exact densities instead under the published approximations and
asymptotic densities under isotropic models. An application in Biology is
studied under the classical gaussian approach and a two non gaussian models.Comment: 13 page
Shape Theory Via SV Decomposition II
The non isotropic and non central elliptical shape distributions via the Le
and Kendall SVD decomposition approach are derived in this paper in the context
of invariant polynomials and zonal polynomials. The so termed cone and disk
densities here obtained generalise some results of the literature. Finally,
some particular densities are applied in a classical data of Biology, and the
inference is performed after choosing the best model by using a modified BIC
criterion.Comment: 16 page
Shape theory via polar decomposition
This work proposes a new model in the context of statistical theory of shape,
based on the polar decomposition. The non isotropic noncentral elliptical shape
distributions via polar decomposition is derived in the context of zonal
polynomials, avoiding the invariant polynomials and the open problems for their
computation. The new polar shape distributions are easily computable and then
the inference procedure can be studied under exact densities. As an example of
the technique, a classical application in Biology is studied under three
models, the usual Gaussian and two non normal Kotz models; the best model is
selected by a modified BIC criterion, then a test for equality in polar shapes
is performed.Comment: 14 page
Growing interfaces in quenched disordered media
We present the microscopic equation of growing interface with quenched noise
for the Tang and Leschhorn model [{\em Phys. Rev.} {\bf A 45}, R8309 (1992)].
The evolution equations for the mean heigth and the roughness are reached in a
simple way. Also, an equation for the interface activity density (i.e.
interface density of free sites) as function of time is obtained. The
microscopic equation allows us to express these equations in two contributions:
the diffusion and the substratum one. All the equation shows the strong
interplay between both contributions in the dynamics. A macroscopic evolution
equation for the roughness is presented for this model for the critical
pressure . The dynamical exponent is analitically
obtained in a simple way. Theoretical results are in excellent agreement with
the Monte Carlo simulation.Comment: 6 pages and 3 figures. Conference on Percolation and disordered
systems: theory and applications, Giessen, Germany, (July, 1998
Supersymmetry Unification Predictions for M_top V_cb and tan(beta)
We study the predictions for M_top, tan(beta) and V_cb in a popular texture
ansatze for the fermion mass matrices. We do this both for the Minimal
Supersymmetric Standard Model (MSSM) and for the simplest model (MSSM-BRpV)
where a bilinear R-Parity violating term is added to the superpotential. We
find that taking the experimental values for M_top and V_cb at 99 % C.L. and
the GUT relations h_b=h_tau and (V_cb)^2=h_c/h_t within 5 %, the large
tan(beta) solution, characteristic in the MSSM with bottom--tau unification,
becomes disallowed. In contrast the corresponding allowed region for the
MSSM-BRpV is slightly larger. We also find that important modifications occur
if we relax the texture conditions at the GUT scale. For example, if the GUT
relations are imposed at 40 %, the large tan(beta) branch in the MSSM becomes
fully allowed. In addition, in MSSM-BRpV the whole tan(beta)-M_top plane become
allowed, finding unification at any value of tan(beta).Comment: 15 pages, including 6 figures. Late
Some results in topology optimization applied to biomechanics
This paper presents the application of a topology optimization algorithm based in homogenization theory. Three examples in structural design will be solved numerically. The first two are formulated such that analytical solutions can also be developed. To obtain this goal, the microscopic structure that we considered is formed of laminates because for this type of composite materials there is an explicit dependence of the homogenized coefficients on the design variables. The last example regards bone remodelling. Here, where it is impossible to obtain the analytical solution, the applied algorithm produces numerical results which are in good agreement with Wolffs Law.info:eu-repo/semantics/publishedVersio
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