84 research outputs found
Mean Field in Long-Range Ferromagnets and Periodic Boundary Conditions
Periodic boundary conditions are applied to a ferromagnetic spin lattice. A
symmetrical lattice and its contributions all over space are being used.
Results, for the Ising model with ferromagnetic interaction that decays as a
law, are discussed in the mean field approximatio
Caloric Curves in two and three-dimensional Lennard-Jones-like systems including Long-range forces
We present a systematic study of the thermodynamics of two and
three-dimensional generalized Lennard-Jones () systems focusing on the
relationship between the range of the potential, the system density and its
dimension. We found that the existence of negative specific heats depends on
these three factors and not only on the potential range and the density of the
system as stated in recent contributions.Comment: LaTex, 12 pages, 7 figure
Thermodynamics from a scaling Hamiltonian
There are problems with defining the thermodynamic limit of systems with
long-range interactions; as a result, the thermodynamic behavior of these types
of systems is anomalous. In the present work, we review some concepts from both
extensive and nonextensive thermodynamic perspectives. We use a model, whose
Hamiltonian takes into account spins ferromagnetically coupled in a chain via a
power law that decays at large interparticle distance as for
. Here, we review old nonextensive scaling. In addition, we
propose a new Hamiltonian scaled by that
explicitly includes symmetry of the lattice and dependence on the size, , of
the system. The new approach enabled us to improve upon previous results. A
numerical test is conducted through Monte Carlo simulations. In the model,
periodic boundary conditions are adopted to eliminate surface effects.Comment: 12 pages, 2 figures, submitted for publication to Phys. Rev.
Fisher information, Wehrl entropy, and Landau Diamagnetism
Using information theoretic quantities like the Wehrl entropy and Fisher's
information measure we study the thermodynamics of the problem leading to
Landau's diamagnetism, namely, a free spinless electron in a uniform magnetic
field. It is shown that such a problem can be "translated" into that of the
thermal harmonic oscillator. We discover a new Fisher-uncertainty relation,
derived via the Cramer-Rao inequality, that involves phase space localization
and energy fluctuations.Comment: no figures. Physical Review B (2005) in pres
Thermodynamic Consistency of the -Deformed Fermi-Dirac Distribution in Nonextensive Thermostatics
The -deformed statistics for fermions arising within the non-extensive
thermostatistical formalism has been applied to the study of various quantum
many-body systems recently. The aim of the present note is to point out some
subtle difficulties presented by this approach in connection with the problem
of thermodynamic consistency. Different possible ways to apply the -deformed
quantum distributions in a thermodynamically consistent way are considered.Comment: 4 pages, 1 figur
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