Combinatorial aspects of boundary loop models

TL;DR

This paper explores the combinatorial structure of boundary loop models using algebraic methods, providing new insights into their representation theory and potential links to conformal field theory.

Contribution

It introduces the two-boundary Temperley-Lieb algebra and analyzes its representations, degeneracies, and conjectures on Gram matrix determinants, advancing understanding of boundary loop models.

Findings

Dimensions of TL representations determined

Degeneracies in partition functions analyzed

Conjectures on Gram matrix determinants proposed

Abstract

We discuss in this paper combinatorial aspects of boundary loop models, that is models of self-avoiding loops on a strip where loops get different weights depending on whether they touch the left, the right, both or no boundary. These models are described algebraically by a generalization of the Temperley-Lieb algebra, dubbed the two-boundary TL algebra. We give results for the dimensions of TL representations and the corresponding degeneracies in the partition functions. We interpret these results in terms of fusion and in the light of the recently uncovered A_n large symmetry present in loop models, paving the way for the analysis of the conformal field theory properties. Finally, we propose conjectures for determinants of Gram matrices in all cases, including the two-boundary one, which has recently been discussed by de Gier and Nichols.