5,896 research outputs found
Compressible Sherrington-Kirkpatrick spin-glass model
We introduce a Sherrington-Kirkpatrick spin-glass model with the addition of
elastic degrees of freedom. The problem is formulated in terms of an effective
four-spin Hamiltonian in the pressure ensemble, which can be treated by the
replica method. In the replica-symmetric approximation, we analyze the
pressure-temperature phase diagram, and obtain expressions for the critical
boundaries between the disordered and the ordered (spin-glass and
ferromagnetic) phases. The second-order para-ferromagnetic border ends at a
tricritical point, beyond which the transition becomes discontinuous. We use
these results to make contact with the temperature-concentration phase diagrams
of mixtures of hydrogen-bonded crystals.Comment: 8 pages, 2 figures; added references, added conten
Replica Symmetry Breaking in the Critical Behaviour of the Random Ferromagnet
We study the critical properties of the weakly disordered -component
random Heisenberg ferromagnet. It is shown that if the specific heat critical
exponent of the pure system is positive, the traditional renormalization group
(RG) flows at dimensions D=4-\e, which are usually considered as describing
the disorder-induced universal critical behavior, are {\it unstable} with
respect to replica symmetry breaking (RSB) potentials as found in spin glasses.
It is demonstrated that the RG flows involving RSB potentials lead to fixed
points which have the structure known as the 1 step RSB, and there exists a
whole spectrum of such fixed points. It is argued that spontaneous RSB can
occur due to the interactions of the fluctuating fields with the local
non-perturbative degrees of freedom coming from the multiple local minima
solutions of the mean-field equations. However, it is not clear whether or not
RSB occurs for infinitesimally weak disorder. Physical consequences of these
conclusions are discussed.Comment: 20 pages, late
Seleção de linhagens-elite de arroz para o sistema de cultivo irrigado em condições tropicais.
O objetivo deste trabalho foi identificar as melhores linhagens de arroz irrigado para cultivo nas várzeas do Tocantins, pela análise de ensaios de avaliação do valor de cultivo e uso (VCU) dos últimos três anos conduzidos naquele Estado
A Transfer Matrix Method for Resonances in Randall-Sundrum Models
In this paper we discuss in detail a numerical method to study resonances in
membranes generated by domain walls in Randall-Sundrum-like scenarios. It is
based on similar works to understand the quantum mechanics of electrons subject
to the potential barriers that exist in heterostructures in semiconductors.
This method was used recently to study resonances of a three form field and
lately generalized to arbitrary forms. We apply it to a lot of important
models, namely those that contain the Gauge, Gravity and Spinor fields. In many
cases we find a rich structure of resonances which depends on the parameters
involved.Comment: 25 pages, 17 figure
The Yang-Lee zeros of the 1D Blume-Capel model on connected and non-connected rings
We carry out a numerical and analytic analysis of the Yang-Lee zeros of the
1D Blume-Capel model with periodic boundary conditions and its generalization
on Feynman diagrams for which we include sums over all connected and
non-connected rings for a given number of spins. In both cases, for a specific
range of the parameters, the zeros originally on the unit circle are shown to
departure from it as we increase the temperature beyond some limit. The curve
of zeros can bifurcate and become two disjoint arcs as in the 2D case. We also
show that in the thermodynamic limit the zeros of both Blume-Capel models on
the static (connected ring) and on the dynamical (Feynman diagrams) lattice
tend to overlap. In the special case of the 1D Ising model on Feynman diagrams
we can prove for arbitrary number of spins that the Yang-Lee zeros must be on
the unit circle. The proof is based on a property of the zeros of Legendre
Polynomials.Comment: 19 pages, 5 figure
Validação de ferramenta computacional para contagem de esporos e calibração de suspensão de inóculo - CALIBRA*
Aptidão tecnológica de cultivares do Ensaio de Qualidade de Trigo do Paraná (EQT-PR) - safra 2011.
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