36,264 research outputs found
Aproximative solutions to the neutrino oscillation problem in matter
We present approximative solutions to the neutrino evolution equation
calculated by different methods. In a two neutrino framework, using the
physical parameters which gives the main effects to neutrino oscillations from
nu{e} to another flavors for L=3000Km and E=1GeV, the results for the
transition probability calculated by using series solutions, by to take the
neutrino evolution operator as a product of ordered partial operators and by
numerical methods, for a linearly and sinusoidally varying matter density are
compared. The extension to an arbitrary density profile is discussed and the
evolution operator as a product of partial operators in the three neutrino case
is obtained.Comment: 12 pages, 5 figure
Lattice Simulation of Nuclear Multifragmentation
Motivated by the decade-long debate over the issue of criticality supposedly
observed in nuclear multifragmentation, we propose a dynamical lattice model to
simulate the phenomenon. Its Ising Hamiltonian mimics a short range attractive
interaction which competes with a thermal-like dissipative process. The results
here presented, generated through an event-by-event analysis, are in agreement
with both experiment and those produced by a percolative (non-dynamical) model.Comment: 8 pages, 3 figure
Mapping the train model for earthquakes onto the stochastic sandpile model
We perform a computational study of a variant of the ``train'' model for
earthquakes [PRA 46, 6288 (1992)], where we assume a static friction that is a
stochastic function of position rather than being velocity dependent. The model
consists of an array of blocks coupled by springs, with the forces between
neighbouring blocks balanced by static friction. We calculate the probability,
P(s), of the occurrence of avalanches with a size s or greater, finding that
our results are consistent with the phenomenology and also with previous models
which exhibit a power law over a wide range. We show that the train model may
be mapped onto a stochastic sandpile model and study a variant of the latter
for non-spherical grains. We show that, in this case, the model has critical
behaviour only for grains with large aspect ratio, as was already shown in
experiments with real ricepiles. We also demonstrate a way to introduce
randomness in a physically motivated manner into the model.Comment: 14 pages and 6 figures. Accepted in European Physical Journal
Realidade econômica do setor rural na Amazônia Ocidental
O trabalho apresenta uma análise econômica dos estados Acre, Amapá, Rondônia e Roraima, componentes da Região Amazônia Ocidental.Editado por: Paulo Guilherme Salvador Wadt; Alaerto Luiz Marcolan; Stella Cristiani Gonçalves Matoso e Marcos Gervasio Pereira
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