Exchangeable arrays and integrable systems for characteristic polynomials of random matrices

TL;DR

This paper establishes a comprehensive probabilistic and combinatorial framework for analyzing the asymptotics of joint moments of derivatives of characteristic polynomials of random matrices, connecting them to integrable systems and Painlevé equations.

Contribution

It introduces a novel exchangeable array structure to analyze joint moments, providing explicit formulas and exact representations involving Painlevé transcendents.

Findings

Proves convergence of joint moments for arbitrary derivatives and exponents.

Derives explicit formulas for leading order asymptotics using combinatorial integrals.

Expresses finite-size joint moments in terms of Painlevé V and  Painleve9 III' transcendents.

Abstract

The joint moments of the derivatives of the characteristic polynomial of a random unitary matrix, and also a variant of the characteristic polynomial that is real on the unit circle, in the large matrix size limit, have been studied intensively in the past twenty five years, partly in relation to conjectural connections to the Riemann zeta-function and Hardy's function. We completely settle the most general version of the problem of convergence of these joint moments, after they are suitably rescaled, for an arbitrary number of derivatives and with arbitrary positive real exponents. Our approach relies on a hidden, higher-order exchangeable structure, that of an exchangeable array. Using these probabilistic techniques, we then give a combinatorial formula for the leading order coefficient in the asymptotics of the joint moments, when the power on the characteristic polynomial itself is a positive real number and the exponents of the derivatives are integers, in terms of a finite number of finite-dimensional integrals which are explicitly computable. Finally, we develop a method, based on a class of Hankel determinants shifted by partitions, that allows us to give an exact representation of all these joint moments, for finite matrix size, in terms of derivatives of Painlev\'e V transcendents, and then for the leading order coefficient in the large-matrix limit in terms of derivatives of solutions of the $\sigma$-Painlev\'e III' equation. Equivalently, we can represent all the joint moments of power sum linear statistics of a certain determinantal point process behind this problem in terms of derivatives of $\sigma$-Painlev\'e III' transcendents. This gives an efficient way to compute all these quantities explicitly. Our methods can be used to obtain analogous results for a number of other models sharing the same features.