3,395 research outputs found
One-step replica symmetry breaking solution for fermionic Ising spin glass in a transverse field
The fermionic Ising spin glass models in a transverse field are investigated
in a Grassmann path integral formalism. The Parisi's scheme of one-step replica
symmetry breaking (RSB) is used within the static ansatz. This formalism has
already been applied in a theory in which (Parisi's block-size parameter)
is taken as a constant (PRB 72, 014447 (2005)). Now, it is extended to consider
as a variational parameter. In this case, the results show that RSB is
present when , in which the system is driven by quantum fluctuations.Comment: 8 pages, 3 figures, accepted for publication as a Brief Report in
Phys. Rev.
Role of the transverse field in inverse freezing in the fermionic Ising spin-glass model
We investigate the inverse freezing in the fermionic Ising spin-glass (FISG)
model in a transverse field . The grand canonical potential is
calculated in the static approximation, replica symmetry and one-step replica
symmetry breaking Parisi scheme. It is argued that the average occupation per
site is strongly affected by . As consequence, the boundary phase
is modified and, therefore, the reentrance associated with the inverse freezing
is modified too.Comment: 6 pages, 3 figures, accepted for publication in PR
A van Hemmen-Kondo model for disordered strongly correlated electron systems
We present here a theoretical model in order to describe the competition
between the Kondo effect and the spin glass behavior. The spin glass part of
the starting Hamiltonian contains Ising spins with an intersite exchange
interaction given by the local van Hemmen model, while the Kondo effect is
described as usual by the intrasite exchange . We obtain, for large
values, a Kondo phase and, for smaller values, a succession, with
decreasingComment: 14 pages, 4 figures, accepted for publication in Phys. Rev.
Explaining operational modal analysis with data from an arch bridge
This tutorial paper aims to introduce the topic of operational modal analysis to non-specialists on the subject. First of all, it is stressed the relevance of this experimental technique particularly in the assessment of important civil infrastructure. Then, after a synthesis of required theoretical background, three of the most powerful algorithms for output-only modal identification are presented. The several steps of these identification procedures are illustrated with the processing of data collected on a concrete arch bridge with a span of 280 m. As the use of operational modal analysis in the context of structural health monitoring is a subject under active research, this theme is also introduced and briefly exemplified with data continuously recorded at the same bridge
Fosfatos naturais no Brasil.
Foi feita uma apreciação sobre a validade de utilização dos principais fosfatos naturais, seja como corretivos do solo na chamada "fosfatagem" ou em combinações adequadas onde tais fosfatos podem ser usados como fertilizantes substituindo no total ou em parte as fontes solúveis convencionais. Também foram mostrados aspectos do mercado nacional de fertilizantes fosfatados, bem como das reservas mundiais e duração das reservas nacionais.bitstream/item/81543/1/Fosfatos-Naturais-Antonia-Magalhaes-Documentos-53-1993.pdfMemória
Spin Glass and antiferromagnetism in Kondo lattice disordered systems
The competition between spin glass (SG), antiferromagnetism (AF) and Kondo
effect is studied here in a model which consists of two Kondo sublattices with
a gaussian random interaction between spins in differents sublattices with an
antiferromagnetic mean Jo and standard deviation J. In the present approach
there is no hopping of the conduction electrons between the sublattices and
only spins in different sublattices can interact. The problem is formulated in
the path integral formalism where the spin operators are expressed as bilinear
combinations of Grassmann fields which can be solved at mean field level within
the static approximation and the replica symmetry ansatz. The obtained phase
diagram shows the sequence of phases SG, AF and Kondo state for increasing
Kondo coupling. This sequence agrees qualitatively with experimental data of
the Ce_{2} Au_{1-x} Co_{x} Si_{3} compound.Comment: 7 pages, 1 figure, submitted to EPJ
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