36,101 research outputs found
Zero-energy peak of the density of states and localization properties of a one-dimensional Frenkel exciton: Off-diagonal disorder
We study a one-dimensional Frenkel Hamiltonian with off-diagonal disorder,
focusing our attention on the physical nature of the zero-energy peak of the
density of states. The character of excitonic states (localized or delocalized)
is also examined in the vicinity of this peak. It is shown that the state being
responsible for the peak is localized. A detailed comparison of the
nearest-neighbor approach with the long-range dipole-dipole coupling is
performed.Comment: 15 pages with 7 figures (REVTeX). To appear in Physical Review
Nariai--Bertotti--Robinson spacetimes as a building material for one-way wormholes with horizons, but without singularity
We discuss the problem of wormholes from the viewpoint of gluing together two
Reissner--Nordstr\"om-type universes while putting between them a segment of
the Nariai-type world (in both cases there are also present electromagnetic
fields as well as the cosmological constant). Such a toy wormhole represents an
example of one-way topological communication free from causal paradoxes, though
involving a travel to next spacetime sheet since one has to cross at least a
pair of horizons through which the spacetimes' junction occurs. We also
consider the use of thin shells in these constructions. Such a ``material'' for
wormholes we choose taking into account specific properties of the
Nariai--Bertotti--Robinson spacetimes.Comment: 5 pages, a talk delivered at the 11th Marcel Grossmann Meeting (2006
Intermittent quakes and record dynamics in the thermoremanent magnetization of a spin-glass
A novel method for analyzing the intermittent behavior of linear response
data in aging systems is presented and applied to spin-glass thermoremanent
magnetization (TRM) (Rodriguez et al. Phys. Rev. Lett. 91, 037203, 2003).
The probability density function (PDF) of magnetic fluctuations is shown to
have an asymmetric exponential tail, demonstrating that the demagnetization
process is carried by intermittent, significant, spin rearrangements or
\emph{quakes}. These quakes are most pronounced shortly after the field
removal, and in the non-equilibrium aging regime .
For a broad temperature range, we study the dependence of the TRM decay rate on
, the time since the initial quench and on , the time at which the
magnetic field is cut. The and dependence of the rate is extracted
numerically from the data and described analytically using the assumption that
the linear response is subordinated to the intermittent process which
spasmodically release the initial imbalances created by the quench.Comment: 8 pages, 9 figures. The paper has been expanded and restructured, the
figures have been enlarged and improved. Final version, to appear in Phy.
Rev.
Simbol-X Background Minimization: Mirror Spacecraft Passive Shielding Trade-Off Study
The present work shows a quantitative trade-off analysis of the Simbol-X
Mirror Spacecraft (MSC) passive shielding, in the phase space of the various
parameters: mass budget, dimension, geometry, and composition. A simplified
physical (and geometrical) model of the sky screen, implemented by means of a
GEANT4 simulation, has been developed to perform a performance-driven mass
optimization and evaluate the residual background level on Simbol-X focal
plane.Comment: 3 pages, 6 figures, to appear in the proceedings of the second
Simbol-X International Symposium "Simbol-X - Focusing on the Hard X-ray
Universe", AIP Conf. Proc. Series, P. Ferrando and J. Rodriguez ed
Socioeconomic Factors and the Consumption of Wine in Tenerife
In this paper we measure the impact of an individual's socioeconomic conditions on the decision to consume wine in a traditionally wine-producing area. Based on the data obtained in an exhaustive survey on wine consumption and through discrete choice models, we assess the changes which come about in the decisions to consume the different types of wine under consideration, and we obtain the most relevant distinctive and differentiated characteristics for each one of them.wine consumption, socioeconomic characteristics, discrete choice models, Food Consumption/Nutrition/Food Safety,
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