4,957 research outputs found
Large-q series expansion for the ground state degeneracy of the q-state Potts antiferromagnet on the (3.12^2) lattice
We calculate the large- series expansion for the ground state degeneracy
(= exponent of the ground state entropy) per site of the -state Potts
antiferromagnet on the lattice, to order , where
. We note a remarkable agreement, to , between this
series and a rigorous lower bound derived recently.Comment: 10 pages, Latex, 3 encapsulated postscript figures, to appear in
Phys. Rev.
Simulations of a classical spin system with competing superexchange and double-exchange interactions
Monte-Carlo simulations and ground-state calculations have been used to map
out the phase diagram of a system of classical spins, on a simple cubic
lattice, where nearest-neighbor pairs of spins are coupled via competing
antiferromagnetic superexchange and ferromagnetic double-exchange interactions.
For a certain range of parameters, this model is relevant for some magnetic
materials, such as doped manganites, which exhibit the remarkable colossal
magnetoresistance effect. The phase diagram includes two regions in which the
two sublattice magnetizations differ in magnitude. Spin-dynamics simulations
have been used to compute the time- and space-displaced spin-spin correlation
functions, and their Fourier transforms, which yield the dynamic structure
factor for this system. Effects of the double-exchange
interaction on the dispersion curves are shown.Comment: Latex, 3 pages, 3 figure
Local gauge symmetry on optical lattices?
The versatile technology of cold atoms confined in optical lattices allows
the creation of a vast number of lattice geometries and interactions, providing
a promising platform for emulating various lattice models. This opens the
possibility of letting nature take care of sign problems and real time
evolution in carefully prepared situations. Up to now, experimentalists have
succeeded to implement several types of Hubbard models considered by condensed
matter theorists. In this proceeding, we discuss the possibility of extending
this effort to lattice gauge theory. We report recent efforts to establish the
strong coupling equivalence between the Fermi Hubbard model and SU(2) pure
gauge theory in 2+1 dimensions by standard determinantal methods developed by
Robert Sugar and collaborators. We discuss the possibility of using dipolar
molecules and external fields to build models where the equivalence holds
beyond the leading order in the strong coupling expansion.Comment: 6 pages, 3 figures,poster presented at the 30th International
Symposium on Lattice Field Theory, June 24 - 29, 2012, Cairns, Australi
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