## Abstract

We present exact calculations of the zero-temperature partition function (chromatic polynomial) and [Formula Presented] the exponent of the ground-state entropy, for the q-state Potts antiferromagnet with next-nearest-neighbor spin-spin couplings on square lattice strips, of width [Formula Presented] and [Formula Presented] vertices and arbitrarily great length [Formula Presented] vertices, with both free and periodic boundary conditions. The resultant values of W for a range of physical q values are compared with each other and with the values for the full two-dimensional lattice. These results give insight into the effect of such nonnearest-neighbor couplings on the ground-state entropy. We show that the [Formula Presented] (Ising) and [Formula Presented] Potts antiferromagnets have zero-temperature critical points on the [Formula Presented] limits of the strips that we study. With the generalization of q from [Formula Presented] to C, we determine the analytic structure of [Formula Presented] in the q plane for the various cases.

Original language | English |
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Pages (from-to) | 4650-4664 |

Number of pages | 15 |

Journal | Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics |

Volume | 62 |

Issue number | 4 |

DOIs | |

Publication status | Published - 2000 |

## All Science Journal Classification (ASJC) codes

- Statistical and Nonlinear Physics
- Statistics and Probability
- Condensed Matter Physics