Recurrence relations and zeros of Gegenbauer–Sobolev orthogonal polynomials
摘要
Gegenbauer–Sobolev polynomials are an important class of Sobolev orthogonal polynomials. We prove a novel recurrence relation for this sequence of polynomials that allows a more accurate construction of the sequence. This new recurrence relation allows us to decompose the recurrence matrix of the sequence as the product of three structured matrices. By computing the eigenvalues of the recurrence matrix, we obtain the zeros of the Gegenbauer–Sobolev polynomials. However, the eigenvalue problem formulated with this recurrence matrix is ill-conditioned and thus cannot lead to reliable approximations of the actual zeros. We deal with this ill-conditioning by reformulating the eigenvalue problem as a generalized eigenvalue problem, involving the three structured matrices that decompose the recurrence matrix, and applying a balancing technique to this generalized eigenvalue problem.