Jordan blocks and the Bethe ansatz: The eclectic spin chain as a limit

Abstract

Abstract We present a procedure to extract generalised eigenvectors of a non-diagonalisable matrix by considering a diagonalisable perturbation and computing the non-diagonalisable limit of its eigenvectors. As an example, we show how to obtain a subset of the spectrum of the eclectic spin chain from the spectrum of a twisted 𝔰𝔲(3) spin chain.