## Abstract

We elucidate the close connection between the repulsive lattice gas in equilibrium statistical mechanics and the Lovász local lemma in probabilistic combinatorics. We show that the conclusion of the Lovász local lemma holds for dependency graph G and probabilities {p _{x} } if and only if the independent-set polynomial for G is nonvanishing in the polydisc of radii {p _{x} }. Furthermore, we show that the usual proof of the Lovász local lemma - which provides a sufficient condition for this to occur - corresponds to a simple inductive argument for the nonvanishing of the independent-set polynomial in a polydisc, which was discovered implicitly by Shearer^{(98)} and explicitly by Dobrushin.^{(37,38)} We also present some refinements and extensions of both arguments, including a generalization of the Lovász local lemma that allows for ''soft'' dependencies. In addition, we prove some general properties of the partition function of a repulsive lattice gas, most of which are consequences of the alternating-sign property for the Mayer coefficients. We conclude with a brief discussion of the repulsive lattice gas on countably infinite graphs.

Original language | English (US) |
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Pages (from-to) | 1151-1261 |

Number of pages | 111 |

Journal | Journal of Statistical Physics |

Volume | 118 |

Issue number | 5-6 |

DOIs | |

State | Published - Mar 2005 |

## Keywords

- Cluster expansion
- Graph
- Hard-core interaction
- Independent-set polynomial
- Lattice gas
- Lovász local lemma
- Mayer expansion
- Polymer expansion
- Probabilistic method

## ASJC Scopus subject areas

- Statistical and Nonlinear Physics
- Mathematical Physics