Fusion hierarchies, $T$-systems and $Y$-systems for the dilute $A_2^{(2)}$ loop models on a strip

TL;DR

This paper develops fusion hierarchies, T- and Y-systems for dilute A2^{(2)} loop models on a strip with boundary conditions, deriving finite relations at roots of unity and computing bulk and boundary free energies.

Contribution

It constructs the fusion hierarchy, T- and Y-systems for the dilute A2^{(2)} loop models with boundary conditions and derives finite relations at roots of unity.

Findings

Fusion hierarchy and T-, Y-systems constructed for boundary conditions.

Finite relations at roots of unity close the hierarchy.

Bulk and boundary free energies computed and match numerical data.

Abstract

We study the dilute $A_2^{(2)}$ loop models on the geometry of a strip of width $N$. Two families of boundary conditions are known to satisfy the boundary Yang-Baxter equation. Fixing the boundary condition on the two ends of the strip leads to four models. We construct the fusion hierarchy of commuting transfer matrices for the model as well as its $T$- and $Y$-systems, for these four boundary conditions and with a generic crossing parameter $\lambda$. For $\lambda/\pi$ rational and thus $q=-e^{4i\lambda}$ a root of unity, we prove a linear relation satisfied by the fused transfer matrices that closes the fusion hierarchy into a finite system. The fusion relations allow us to compute the two leading terms in the large-$N$ expansion of the free energy, namely the bulk and boundary free energies. These are found to be in agreement with numerical data obtained for small $N$. The present work complements a previous study (A. Morin-Duchesne, P.A. Pearce, J. Stat. Mech. (2019)) that investigated the dilute $A_2^{(2)}$ loop models with periodic boundary conditions.