18,376 research outputs found
Loop-corrected belief propagation for lattice spin models
Belief propagation (BP) is a message-passing method for solving probabilistic
graphical models. It is very successful in treating disordered models (such as
spin glasses) on random graphs. On the other hand, finite-dimensional lattice
models have an abundant number of short loops, and the BP method is still far
from being satisfactory in treating the complicated loop-induced correlations
in these systems. Here we propose a loop-corrected BP method to take into
account the effect of short loops in lattice spin models. We demonstrate,
through an application to the square-lattice Ising model, that loop-corrected
BP improves over the naive BP method significantly. We also implement
loop-corrected BP at the coarse-grained region graph level to further boost its
performance.Comment: 11 pages, minor changes with new references added. Final version as
published in EPJ
Superfluidity and Stabilities of a Bose-Einstein condensate with periodically modulated interatomic interaction
We study theoretically the superfluidity and stability of a Bose-Einstein
condensate (BEC) whose interatomic scattering length is periodically modulated
with optical Feshbach resonance. Our numerical study finds that the properties
of this periodic BEC are strongly influenced by the modulation strength. When
the modulation strength is small, only the Bloch waves close to the Brillouin
zone edge suffer both Landau and dynamical instabilities. When the modulation
strength is strong enough, all Bloch waves become dynamically unstable. In
other words, the periodic BEC loses its superfluidity completely.Comment: 5 pages, 5 figure
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