Generalized Gibbs ensemble of the Ablowitz-Ladik lattice, Circular $\beta$-ensemble and double confluent Heun equation

TL;DR

This paper studies the statistical properties of the integrable Ablowitz-Ladik lattice under the Generalized Gibbs ensemble, connecting it to random matrix theory, log-gas models, and special functions like the double-confluent Heun equation.

Contribution

It introduces a novel analysis of the Ablowitz-Ladik lattice's free energy and density of states using mappings to log-gas models and special functions, linking integrable systems with random matrix ensembles.

Findings

Derived the generalized free energy of the Ablowitz-Ladik lattice.

Established the density of states via the double-confluent Heun equation.

Connected the Lax matrix to the Circular β-ensemble at high temperature.

Abstract

We consider the discrete defocusing nonlinear Schr\"odinger equation in its integrable version, which is called defocusing Ablowitz-Ladik lattice. We consider periodic boundary conditions with period $N$ and initial data sample according to the Generalized Gibbs ensemble. In this setting, the Lax matrix of the Ablowitz-Ladik lattice is a random CMV-periodic matrix and it is related to the Killip-Nenciu Circular $\beta$-ensemble at high-temperature. We obtain the generalized free energy of the Ablowitz-Ladik lattice and the density of states of the random Lax matrix by establishing a mapping to the one-dimensional log-gas. For the Gibbs measure related to the Hamiltonian of the Ablowitz-Ladik flow, we obtain the density of states via a particular solution of the double-confluent Heun equation.