A general fusion procedure for open $\mathfrak{gl}(N)$ spin chains: Application to the ABJM spin chain
Nan Bai
TL;DR
This work develops a comprehensive fusion framework for open $\mathfrak{gl}(N)$ spin chains, constructing fused $R$-matrices, fused boundary $K^{\pm}$-matrices, and fused reflection equations, and identifies invariant subspaces carrying irreducible $\mathfrak{gl}(N)$ representations. The fused objects yield commuting families of open-chain transfer matrices and admit explicit evaluations on the full quantum space or on invariant subspaces, including a factorization into quantum determinants in reduced spaces. As a key application, the ABJM spin chain is shown to arise from an $\mathfrak{su}(4)$ fusion scheme involving fundamental and anti-fundamental representations, with explicit fused $R$- and $K^{-}$-matrix solutions on the anti-fundamental space. The results extend the fusion program to general open $\mathfrak{gl}(N)$ models and provide a concrete path to analyze open-chain spectra via boundary fusion techniques and their associated functional relations.
Abstract
We formulate a general fusion procedure for open $\mathfrak{gl}(N)$ spin chains. We construct the fused boundary reflection matrices and the corresponding fused reflection equations. By using the intertwining relation between the fused reflection matrices and the fusion operator, we identify the invariant subspace of the fused reflection matrices carrying the irreducible representations of $\mathfrak{gl}(N)$. We also construct the fused transfer matrix and evaluate it explicitly in the total tensor product space and the invariant subspaces. Finally, we demonstrate that the ABJM spin chain model originates from such fusion procedure and derive three classes of boundary reflection matrices solutions on the anti-fundamental representation space of $\mathfrak{su}(4)$.
