Combinatorics of generalized orthogonal polynomials of type $R_{II}$

TL;DR

This paper extends the combinatorial interpretation of moments to orthogonal polynomials of type R_{II} and generalizes their definition, unifying various classes of orthogonal polynomials through a master theorem.

Contribution

It advances the combinatorial model for R_{II} polynomials and introduces a generalization that encompasses multiple types of orthogonal polynomials.

Findings

Developed a combinatorial interpretation for R_{II} moments.

Generalized R_{II} polynomials by relaxing defining conditions.

Proved a master theorem unifying models for various orthogonal polynomial types.

Abstract

In 1995, Ismail and Masson introduced orthogonal polynomials of types \( R_I \) and \( R_{II} \), which are defined by specific three-term recurrence relations with additional conditions. Recently, Kim and Stanton found a combinatorial interpretation for the moments of orthogonal polynomials of type \( R_I \) in the spirit of the combinatorial theory of orthogonal polynomials due to Flajolet and Viennot. In this paper, we push this combinatorial model further to orthogonal polynomials of type \( R_{II} \). Moreover, we generalize orthogonal polynomials of type \( R_{II} \) by relaxing some of their conditions. We then prove a master theorem, which generalizes combinatorial models for moments of various types of orthogonal polynomials: classical orthogonal polynomials, Laurent biorthogonal polynomials, and orthogonal polynomials of types \( R_I \) and \( R_{II} \).