Journal of Statistical Physics

, Volume 155, Issue 4, pp 666–686

Approximation Algorithms for Two-State Anti-Ferromagnetic Spin Systems on Bounded Degree Graphs

  • Alistair Sinclair
  • Piyush Srivastava
  • Marc Thurley
Article

DOI: 10.1007/s10955-014-0947-5

Cite this article as:
Sinclair, A., Srivastava, P. & Thurley, M. J Stat Phys (2014) 155: 666. doi:10.1007/s10955-014-0947-5

Abstract

We show that for the anti-ferromagnetic Ising model on the Bethe lattice, weak spatial mixing implies strong spatial mixing. As a by-product of our analysis, we obtain what is to the best of our knowledge the first rigorous proof of the uniqueness threshold for the anti-ferromagnetic Ising model (with non-zero external field) on the Bethe lattice. Following a method due to Weitz [15], we then use the equivalence between weak and strong spatial mixing to give a deterministic fully polynomial time approximation scheme for the partition function of the anti-ferromagnetic Ising model with arbitrary field on graphs of degree at most \(d\), throughout the uniqueness region of the Gibbs measure on the infinite \(d\)-regular tree. By a standard correspondence, our results translate to arbitrary two-state anti-ferromagnetic spin systems with soft constraints. Subsequent to a preliminary version of this paper, Sly and Sun [13] have shown that our results are optimal in the sense that, under standard complexity theoretic assumptions, there does not exist a fully polynomial time approximation scheme for the partition function of such spin systems on graphs of maximum degree \(d\) for parameters outside the uniqueness region. Taken together, the results of [13] and of this paper therefore indicate a tight relationship between complexity theory and phase transition phenomena in two-state anti-ferromagnetic spin systems.

Keywords

Phase transitions Complexity theory Approximation algorithms  Decay of correlations Two-spin systems on trees 

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Alistair Sinclair
    • 1
  • Piyush Srivastava
    • 1
  • Marc Thurley
    • 2
  1. 1.Soda Hall, University of California BerkeleyBerkeleyUSA
  2. 2.Medallia, Inc.Buenos AiresArgentina

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