362 research outputs found
Aperiodicity in one-way Markov cycles and repeat times of large earthquakes in faults
A common use of Markov Chains is the simulation of the seismic cycle in a
fault, i.e. as a renewal model for the repetition of its characteristic
earthquakes. This representation is consistent with Reid's elastic rebound
theory. Here it is proved that in {\it any} one-way Markov cycle, the
aperiodicity of the corresponding distribution of cycle lengths is always lower
than one. This fact concurs with observations of large earthquakes in faults
all over the world
Neutrino CP phases and lepton electric dipole moments in supersymmetric theories
We analyse the dependence of the electron electric dipole moment (EDM) on
neutrino CP violating phases in the context of supersymmetric models. We start
by studying the supersymmetric contributions to the lepton EDM and lepton
flavour violation processes tau -> mu gamma and mu -> e gamma, in the framework
of the mass insertion approximation, showing that, due to the large neutrino
mixing, mu -> e gamma leads to severe constraints on the relevant mass
insertions. We derive model independent bounds on these mass insertions and
show that once these bounds are satisfied, the present experimental limits on
electron EDM do not constraint the neutrino phases.Comment: 20 page
Prospects in space-based Gamma-Ray Astronomy
With the unequalled INTEGRAL observatory, ESA has provided a unique tool to
the astronomical community that has made Europe the world leader in the field
of gamma-ray astronomy. INTEGRAL provides an unprecedented survey of the soft
gamma-ray sky, revealing hundreds of sources of different kinds, new classes of
objects, extraordinary views of antimatter annihilation in our Galaxy, and
fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the
longly awaited global overview over the soft gamma-ray sky, there is a growing
need to perform deeper, more focused investigations of gamma-ray sources,
comparable to the step that has been taken in X-rays by going from the ROSAT
survey satellite to the more focused XMM-Newton observatory. Technological
advances in the past years in the domain of gamma-ray focusing using Laue
diffraction techniques have paved the way towards a future European gamma-ray
mission, that will outreach past missions by large factors in sensitivity and
angular resolution. Such a future Gamma-Ray Imager will allow to study particle
acceleration processes and explosion physics in unprecedented depth, providing
essential clues on the intimate nature of the most violent and most energetic
processes in the Universe.Comment: 8 pages, 7 figures, to be published in the Proceedings of the 39th
ESLAB Symposiu
Leptogenesis in Neutrino Textures with Two Zeros
The leptogenesis is studied in the neutrino textures with two zeros, which
reduce the number of independent phases of the CP violation. The
phenomenological favored neutrino textures with two zeros are decomposed into
the Dirac neutrino mass matrix and the right-handed Majorana one in the see-saw
mechanism. Putting the condition to suppress the decay
enough, the texture zeros of the Dirac neutrino mass matrix are fixed in the
framework of the MSSM with right-handed neutrinos. These textures have only one
CP violatig phase. The magnitude of each entry of the Dirac mass matrix is
determined in order to explain the baryon asymmetry of the universe by solving
the Boltzman equations. The relation between the leptogenesis and the low
energy CP violation is presented in these textures.Comment: Latex file with 20 pages, 6 eps figure
Lepton Flavor Violating Process in Bi-maximal texture of Neutrino Mixings
We investigate the lepton flavor violation in the framework of the MSSM with
right-handed neutrinos taking the large mixing angle MSW solution in the
quasi-degenerate and the inverse-hierarchical neutrino masses. We predict the
branching ratio of and processes
assuming the degenerate right-handed Majorana neutrino masses. We find that the
branching ratio in the quasi-degenerate neutrino mass spectrum is 100 times
smaller than the ones in the inverse-hierarchical and the hierarchical neutrino
spectra. We emphasize that the magnitude of is one of important
ingredients to predict BR(). The effect of the deviation
from the complete-degenerate right-handed Majorana neutrino masses are also
estimated. Furtheremore, we examine the S_{3\sL}\times S_{3\sR} model, which
gives the quasi-degenerate neutrino masses, and the Shafi-Tavartkiladze model,
which gives the inverse-hierarchical neutrino masses. Both predicted branching
ratios of are smaller than the experimantal bound.Comment: Latex file, 38 pages, 10 figures, revised versio
Neutrinoless double-beta decay with three or four neutrino mixing
Considering the scheme with mixing of three neutrinos and a mass hierarchy
that can accommodate the results of solar and atmospheric neutrino experiments,
it is shown that the results of solar neutrino experiments imply a lower bound
for the effective Majorana mass in neutrinoless double-beta decay, under the
natural assumptions that massive neutrinos are Majorana particles and there are
no unlikely fine-tuned cancellations among the contributions of the different
neutrino masses. Considering the four-neutrino schemes that can accommodate
also the results of the LSND experiment, it is shown that only one of them is
compatible with the results of neutrinoless double-beta decay experiments and
with the measurement of the abundances of primordial elements produced in
Big-Bang Nucleosynthesis. It is shown that in this scheme, under the
assumptions that massive neutrinos are Majorana particles and there are no
cancellations among the contributions of the different neutrino masses, the
results of the LSND experiment imply a lower bound for the effective Majorana
mass in neutrinoless double-beta decay.Comment: 18 pages including 2 figures, RevTe
Magnetized Kelvin-Helmholtz instability in the presence of a radiation field
The purpose of this study is to analyze the dynamical role of a radiation
field on the growth rate of the unstable Kelvin - Helmholtz (KH) perturbations.
As a first step toward this purpose, the analyze is done in a general way,
irrespective of applying the model to a specific astronomical system. The
transition zone between the two layers of the fluid is ignored. Then, we
perform a linear analysis and by imposing suitable boundary conditions and
considering a radiation field, we obtain appropriate dispersion relation.
Unstable modes are studied by solving the dispersion equation numerically, and
then growth rates of them are obtained. By analyzing our dispersion relation,
we show that for a wide range of the input parameters, the radiation field has
a destabilizing effect on KH instability. In eruptions of the galaxies or
supermassive stars, the radiation field is dynamically important and because of
the enhanced KH growth rates in the presence of the radiation; these eruptions
can inject more momentum and energy into their environment and excite more
turbulent motions.Comment: Accepted for publication in Astrophysics and Space Scienc
Search for charginos in e+e- interactions at sqrt(s) = 189 GeV
An update of the searches for charginos and gravitinos is presented, based on
a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector
in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was
found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a
centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by
combining the chargino searches with neutralino searches at the Z resonance
implies a limit on the mass of the lightest neutralino which, for a heavy
sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure
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