Boundary TBA Equations for a Non-diagonal Theory

TL;DR

This paper calculates boundary entropies and related physical quantities for an SU(2)-invariant principal chiral model at level 1, confirming consistency with known results and providing new insights into boundary conditions and degeneracies.

Contribution

It introduces boundary TBA equations for a non-diagonal theory and computes boundary entropies, ground-state energies, and degeneracies, extending previous reflection factor results.

Findings

Boundary entropies for SU(2) principal chiral model at level 1

Ground-state energy for mixed boundary conditions

Degeneracies of the Kondo model in different regimes

Abstract

We compute the boundary entropies for the allowed boundary conditions of the SU(2)-invariant principal chiral model at level k=1. We used the reflection factors determined in a previous work. As a by-product we obtain some miscellaneous results such as the ground-state energy for mixed boundary conditions as well as the degeneracies of the Kondo model in the underscreened and exactly screened cases. All these computations are in perfect agreement with known results.