33,318 research outputs found
Soliton attenuation and emergent hydrodynamics in fragile matter
Disordered packings of soft grains are fragile mechanical systems that loose
rigidity upon lowering the external pressure towards zero. At zero pressure, we
find that any infinitesimal strain-impulse propagates initially as a non-linear
solitary wave progressively attenuated by disorder. We demonstrate that the
particle fluctuations generated by the solitary-wave decay, can be viewed as a
granular analogue of temperature. Their presence is manifested by two emergent
macroscopic properties absent in the unperturbed granular packing: a finite
pressure that scales with the injected energy (akin to a granular temperature)
and an anomalous viscosity that arises even when the microscopic mechanisms of
energy dissipation are negligible. Consistent with the interpretation of this
state as a fluid-like thermalized state, the shear modulus remains zero.
Further, we follow in detail the attenuation of the initial solitary wave
identifying two distinct regimes : an initial exponential decay, followed by a
longer power law decay and suggest simple models to explain these two regimes.Comment: 8 pages, 3 Figure
Electromagnetic quasinormal modes of five-dimensional topological black holes
We calculate exactly the QNF of the vector type and scalar type
electromagnetic fields propagating on a family of five-dimensional topological
black holes. To get a discrete spectrum of quasinormal frequencies for the
scalar type electromagnetic field we find that it is necessary to change the
boundary condition usually imposed at the asymptotic region. Furthermore for
the vector type electromagnetic field we impose the usual boundary condition at
the asymptotic region and we discuss the existence of unstable quasinormal
modes in the five-dimensional topological black holes.Comment: 16 pages. Already published in Revista Mexicana de Fisic
Maximal-entropy random walks in complex networks with limited information
J.G.-G. was supported by MICINN through the Ramon y Cajal program and by grants FIS2008-01240 and MTM2009-13848
Muon g-2 through a flavor structure on soft SUSY terms
In this work we analyze the possibility to explain the muon anomalous
magnetic moment discrepancy within theory and experiment through lepton flavor
violation processes. We propose a flavor extended MSSM by considering a
hierarchical family structure for the trilinear scalar Soft-Supersymmetric
terms of the Lagranagian, present at the SUSY breaking scale. We obtain
analytical results for the rotation mass matrix, with the consequence of having
non-universal slepton masses and the possibility of leptonic flavour mixing.
The one-loop supersymmetric contributions to the leptonic flavour violating
process are calculated in the physical basis, with slepton
flavour mixed states, instead of using the well known Mass Insertion Method. We
present the regions in parameter space where the muon g-2 problem is either
entirely solved or partially reduced through the contribution of these flavor
violating processes.Comment: 21 pages, 7 figures. Changes on version 3: In order to obtain the
complete result for muon g-2 in the limit of non-flavor violation we added
the terms given in the appendix. We redid the graphics and numerical analysis
including these changes. We also corrected some typos and changed the order
of figure
Large Shell Model Calculations for Calcium Isotopes: Spectral Statistics and Chaos
We perform large shell model calculations for Calcium isotopes in the full fp
shell by using the realistic Kuo-Brown interaction. The Calcium isotopes are
especially interesting because the nearest-neighbour spacing distribution P(s)
of low-lying energy levels shows significant deviations from the predictions of
the Gaussian Orthogonal Ensemble of random--matrix theory. This contrasts with
other neighbouring nuclei which show fully chaotic spectral distributions. We
study the chaotic behaviour as a function of the excitation energy. In
addition, a clear signature of chaos suppression is obtained when the
single-particle spacings are increased. In our opinion the relatively weak
strength of the neutron-neutron interaction is unable to destroy the regular
single-particle mean-field motion completely. In the neighbouring nuclei with
both protons and neutrons in valence orbits, on the other hand, the stronger
proton-neutron interaction would appear to be sufficient to destroy the regular
mean-field motion.Comment: Latex, 7 pages, 2 postscript figures, to be published in the
Proceedings 'Highlights of Modern Nuclear Structure', S. Agata sui due Golfi
(italy), Ed. A. Covello (World Scientific
Spectral Statistics in Large Shell Model Calculations
The spectral statistics of low--lying states of shell nuclei are studied
by performing large shell--model calculations with a realistic nuclear
interaction. For isotopes, we find deviations from the predictions of the
random--matrix theory which suggest that some spherical nuclei are not as
chaotic in nature as the conventional view assumes.Comment: 9 pages, LaTex, 3 figures available upon request, to appear in
Proceedings of the V International Spring Seminar on Nuclear Physics, Ed. by
A. Covello (World Scientific
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