22 research outputs found
Extended gaussian ensemble solution and tricritical points of a system with long-range interactions
The gaussian ensemble and its extended version theoretically play the
important role of interpolating ensembles between the microcanonical and the
canonical ensembles. Here, the thermodynamic properties yielded by the extended
gaussian ensemble (EGE) for the Blume-Capel (BC) model with infinite-range
interactions are analyzed. This model presents different predictions for the
first-order phase transition line according to the microcanonical and canonical
ensembles. From the EGE approach, we explicitly work out the analytical
microcanonical solution. Moreover, the general EGE solution allows one to
illustrate in details how the stable microcanonical states are continuously
recovered as the gaussian parameter is increased. We found out that it
is not necessary to take the theoretically expected limit
to recover the microcanonical states in the region between the canonical and
microcanonical tricritical points of the phase diagram. By analyzing the
entropy as a function of the magnetization we realize the existence of
unaccessible magnetic states as the energy is lowered, leading to a treaking of
ergodicity.Comment: 8 pages, 5 eps figures. Title modified, sections rewritten,
tricritical point calculations added. To appear in EPJ
Nonextensive Entropies derived from Form Invariance of Pseudoadditivity
The form invariance of pseudoadditivity is shown to determine the structure
of nonextensive entropies. Nonextensive entropy is defined as the appropriate
expectation value of nonextensive information content, similar to the
definition of Shannon entropy. Information content in a nonextensive system is
obtained uniquely from generalized axioms by replacing the usual additivity
with pseudoadditivity. The satisfaction of the form invariance of the
pseudoadditivity of nonextensive entropy and its information content is found
to require the normalization of nonextensive entropies. The proposed principle
requires the same normalization as that derived in [A.K. Rajagopal and S. Abe,
Phys. Rev. Lett. {\bf 83}, 1711 (1999)], but is simpler and establishes a basis
for the systematic definition of various entropies in nonextensive systems.Comment: 16 pages, accepted for publication in Physical Review
Correlation functions in the factorization approach of nonextensive quantum statistics
We study the long range behavior of a gas whose partition function depends on
a parameter q and it has been claimed to be a good approximation to the
partition function proposed in the formulation of nonextensive statistical
mechanics. We compare our results, at large temperatures and at the critical
point, with the case of Boltzmann-Gibbs thermodynamics for the case of a
Bose-Einstein gas. In particular, we find that for all temperatures the long
range correlations in a Bose gas decrease when the value of q departs from the
standard value q=1.Comment: revtex file, 10 pages, two eps style figures, packaged as a single
tar.gz fil
Onsager coefficients of a Brownian Carnot cycle
We study a Brownian Carnot cycle introduced by T. Schmiedl and U. Seifert
[Europhys. Lett. \textbf{81}, 20003 (2008)] from a viewpoint of the linear
irreversible thermodynamics. By considering the entropy production rate of this
cycle, we can determine thermodynamic forces and fluxes of the cycle and
calculate the Onsager coefficients for general protocols, that is, arbitrary
schedules to change the potential confining the Brownian particle. We show that
these Onsager coefficients contain the information of the protocol shape and
they satisfy the tight-coupling condition irrespective of whatever protocol
shape we choose. These properties may give an explanation why the
Curzon-Ahlborn efficiency often appears in the finite-time heat engines
Termodinâmica do modelo de Ising com interações de alcance infinito via ensemble canônico generalizado
Acúmulo de nutrientes em soja convencional e soja RR em diferentes tipos de controle de planta daninha
Prevenção de injúrias causadas por glyphosate em soja RR por meio do uso de aminoácido
Adult education, community development and rural regeneration Synopsis report of the Rural Development and Regeneration Project
An Interreg Project funded by the European UnionAvailable from British Library Document Supply Centre- DSC:q95/16766 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo