Combinatorial Solution of the Eclectic Spin Chain

TL;DR

This paper analyzes the eclectic spin chain Hamiltonian in the fishnet theory, revealing its non-diagonalisable nature and spectrum, and provides combinatorial tools to understand its Jordan block structure.

Contribution

It introduces a generating function for the Jordan block spectrum of the hypereclectic spin chain, supporting the conjecture of spectral equivalence with the eclectic model.

Findings

Spectrum characterized by Jordan blocks with logarithmic correlators

A combinatorial generating function related to q-binomial coefficients

Evidence supporting spectral equivalence between models

Abstract

The one-loop dilatation operator in the holomorphic 3-scalar sector of the dynamical fishnet theory is studied. Due to the non-unitary nature of the underlying field theory this operator, dubbed the eclectic spin chain Hamiltonian, is non-diagonalisable. The corresponding spectrum of Jordan blocks leads to logarithms in the two-point functions, which is characteristic of logarithmic conformal field theories. It was previously conjectured that for certain filling conditions and generic couplings the spectrum of the eclectic model is equivalent to the spectrum of a simpler model, the hypereclectic spin chain. We provide further evidence for this conjecture, and introduce a generating function which fully characterises the Jordan block spectrum of the simplified model. This function is found by purely combinatorial means and is simply related to the q-binomial coefficient.