Generalised higher-order Freud weights

TL;DR

This paper studies polynomials orthogonal with respect to a family of generalized higher order Freud weights, deriving their properties, recurrence relations, asymptotics, and connections to Painlevé equations.

Contribution

It introduces a hierarchy of generalized Freud weights, characterizes their moments and recurrence coefficients, and links these to discrete Painlevé equations.

Findings

First moment expressed as a finite hypergeometric sum

Recurrence coefficients satisfy discrete Painlevé hierarchy

Asymptotic zero distribution analyzed

Abstract

We discuss polynomials orthogonal with respect to a semi-classical generalised higher order Freud weight \[\omega(x;t,\lambda)=|x|^{2\lambda+1}\exp\left(tx^2-x^{2m}\right),\qquad x\in\mathbb{R},\] with parameters $\lambda > -1$, $t\in\mathbb{R}$ and $m=2,3,\dots$\ . The sequence of generalised higher order Freud weights for $m=2,3,\dots$, forms a hierarchy of weights, with associated hierarchies for the first moment and the recurrence coefficient. We prove that the first moment can be written as a finite partition sum of generalised hypergeometric $_1F_m$ functions and show that the recurrence coefficients satisfy difference equations which are members of the first discrete Painlev\'e hierarchy. We analyse the asymptotic behaviour of the recurrence coefficients and the limiting distribution of the zeros as $n \to \infty$. We also investigate structure and other mixed recurrence relations satisfied by the polynomials and related properties.