11,370 research outputs found
3D Effects Of The Entropic Force
This work analyzes the classical statistical mechanics associated to
phase-space curves in three dimensions. Special attention is paid to the
entropic force. Strange effects like confinement, hard core, and asymptotic
freedom are uncovered. Negative specific heats, that were previously seen to
emerge in a one-dimensional setting, disappear in 3D, and with them,
gravitational effects of the entropic force.Comment: arXiv admin note: substantial text overlap with arXiv:1306.203
Physical peculiarities of divergences emerging in q-deformed statistics
It was found in [Europhysics Letters {\bf 104}, (2013), 60003] that classical
Tsallis theory exhibits poles in the partition function and the mean
energy . These occur at a countably set of the q-line. We give
here, via a simple procedure, a mathematical account of them. Further, by
focusing attention upon the pole-physics, we encounter interesting effects. In
particular, for the specific heat, we uncover hidden gravitational effects.Comment: 21 pages, 3 figures. Title has changed. Text has change
A first order Tsallis theory
We investigate first-order approximations to both i) Tsallis' entropy
and ii) the -MaxEnt solution (called q-exponential functions ). It is
shown that the functions arising from the procedure ii) are the MaxEnt
solutions to the entropy emerging from i). The present treatment is free of the
poles that, for classic quadratic Hamiltonians, appear in Tsallis' approach, as
demonstrated in [Europhysics Letters {\bf 104}, (2013), 60003]. Additionally,
we show that our treatment is compatible with extant date on the ozone layer.Comment: 4 figures adde
Interplay of disorder and geometrical frustration in doped Gadolinium Gallium Garnet
The geometrically-frustrated, triangular antiferromagnet GGG exhibits a rich
mix of short-range order and isolated quantum states. We investigate the
effects of up to 1% Neodymium substitution for Gallium on the ac magnetic
response at temperatures below 1 K in both the linear and nonlinear regimes.
Substitutional disorder actually drives the system towards a more perfectly
frustrated state, apparently compensating for the effect of imperfect
Gadolinium/Gallium stoichiometry, while at the same time more closely
demarcating the boundaries of isolated, coherent clusters composed of hundreds
of spins. Optical measurements of the local Nd environment substantiate the
picture of an increased frustration index with doping.Comment: 5 pages, 5 figure
Combined Effects of the North Atlantic Oscillation and the Arctic Oscillation on Sea Surface Temperature in the Alborán Sea
We explored the possible effects of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) on interannual sea
surface temperature (SST) variations in the Albora´n Sea, both separately and combined. The probability of observing mean
annual SST values higher than average was related to NAO and AO values of the previous year. The effect of NAO on SST
was negative, while that of AO was positive. The pure effects of NAO and AO on SST are obscuring each other, due to the
positive correlation between them. When decomposing SST, NAO and AO in seasonal values, we found that variation in
mean annual SST and mean winter SST was significantly related to the mean autumn NAO of the previous year, while mean
summer SST was related to mean autumn AO of the previous year. The one year delay in the effect of the NAO and AO on
the SST could be partially related to the amount of accumulated snow, as we found a significant correlation between the
total snow in the North Albora´n watershed for a year with the annual average SST of the subsequent year. A positive AO
implies a colder atmosphere in the Polar Regions, which could favour occasional cold waves over the Iberian Peninsula
which, when coupled with precipitations favoured by a negative NAO, may result in snow precipitation. This snow may be
accumulated in the high peaks and melt down in spring-summer of the following year, which consequently increases the
runoff of freshwater to the sea, which in turn causes a diminution of sea surface salinity and density, and blocks the local
upwelling of colder water, resulting in a higher SST.CGL2009-11316 (Ministerio de Ciencia e Innovación, Spain, and FEDER
Tuning the atomic and domain structure of epitaxial films of multiferroic BiFeO3
Recent works have shown that the domain walls of room-temperature
multiferroic BiFeO3 (BFO) thin films can display distinct and promising
functionalities. It is thus important to understand the mechanisms underlying
domain formation in these films. High-resolution x-ray diffraction and
piezo-force microscopy, combined with first-principles simulations, have
allowed us to characterize both the atomic and domain structure of BFO films
grown under compressive strain on (001)-SrTiO3, as a function of thickness. We
derive a twining model that describes the experimental observations and
explains why the 71o domain walls are the ones commonly observed in these
films. This understanding provides us with a new degree of freedom to control
the structure and, thus, the properties of BiFeO3 thin films.Comment: RevTeX; 4 two-column pages; 4 color figures. Figure 2b does not seem
to display well. A proper version can be found in the source fil
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