A generalization of formulas for the discriminants of quasi-orthogonal polynomials with applications to hypergeometric polynomials

Abstract

In this article, we extend the classical framework for computing discriminants of special quasi-orthogonal polynomials from Schur’s resultant formula, and establish a framework for computing discriminants of a sufficiently broader class of polynomials from the resultant formulas that are proven by Ulas and Turaj. More precisely, we derive a formula for the discriminant of a sequence \(\{r_{A,n}+c r_{A,n-1}\}\) of polynomials. Here, c is an element of a field K and \(\{r_{A,n}\}\) is a sequence of polynomials satisfying a certain recurrence relation. There are several works computing the discriminants of given polynomials. For example, Kaneko–Niiho and Mahlburg–Ono independently proved the formula for the discriminants of certain hypergeometric polynomials that are related to j-invariants of supersingular elliptic curves. Sawa–Uchida proved the formula for the discriminants of quasi-Jacobi polynomials and applied it to prove the nonexistence of certain rational quadrature formulas. Our main theorem presents a uniform way to prove a vast generalization of the above formulas for the discriminants.