Exactly Solvable Lattice Models with Crossing Symmetry

TL;DR

This paper introduces a method to exactly compute partition functions for certain lattice models with crossing symmetry, enabling analysis of complex systems like nets, dimers, and loop models through graph transformations.

Contribution

It presents a novel approach to exactly solve lattice models with crossing symmetry, including methods to generate such models and restore symmetry after deviations.

Findings

Exact partition functions for models with crossing symmetry

Methods to construct models using group theory and anyon fusion

Restoration of crossing symmetry via real-space decimation

Abstract

We show how to compute the exact partition function for lattice statistical-mechanical models whose Boltzmann weights obey a special "crossing" symmetry. The crossing symmetry equates partition functions on different trivalent graphs, allowing a transformation to a graph where the partition function is easily computed. The simplest example is counting the number of nets without ends on the honeycomb lattice, including a weight per branching. Other examples include an Ising model on the Kagome' lattice with three-spin interactions, dimers on any graph of corner-sharing triangles, and non-crossing loops on the honeycomb lattice, where multiple loops on each edge are allowed. We give several methods for obtaining models with this crossing symmetry, one utilizing discrete groups and another anyon fusion rules. We also present results indicating that for models which deviate slightly from having crossing symmetry, a real-space decimation (renormalization-group-like) procedure restores the crossing symmetry.