Title
Matrix orthogonal polynomials satisfying second-order differential equations: Coping without help from group representation theory
Abstract
The method developed in Duran and Grunbaum [Orthogonal matrix polynomials satisfying second order differential equations, Internat. Math. Res. Notices 10 (2004) 461-484] led us to consider polynomials that are orthogonal with respect to weight matrices W(t) of the form e^-^t^^^2T(t)T^*(t), t^@ae^-^tT(t)T^*(t) and t^@a(1-t)^@bT(t)T^*(t), with T satisfying T^'=(2Bt+A)T, T(0)=I, T^'=(A+B/t)T, T(1)=I and T^'(t)=(A/t+B/(1-t))T, T(1/2)=I, respectively. Here A and B are in general two non-commuting matrices. To proceed further and find situations where these polynomials satisfied second-order differential equations, we needed to impose commutativity assumptions on the pair of matrices A,B. In fact, we only dealt with the case when one of the matrices vanishes. The only exception to this arose as a gift from group representation theory: one automatically gets a situation where A and B do not commute, see Grunbaum et al. [Matrix valued orthogonal polynomials of the Jacobi type: the role of group representation theory, Ann. Inst. Fourier Grenoble 55 (6) (2005) 2051-2068]. This corresponds to the last of the three cases mentioned above. The purpose of this paper is to consider the other two situations and since now we do not get any assistance from representation theory we make a direct attack on certain differential equations in Duran and Grunbaum [Orthogonal matrix polynomials satisfying second order differential equations, Internat. Math. Res. Notices 10 (2004) 461-484]. By solving these equations we get the appropriate weight matrices W(t), where the matrices A,B give rise to a solvable Lie algebra.
Year
DOI
Venue
2007
10.1016/j.jat.2007.02.003
Journal of Approximation Theory
Keywords
Field
DocType
representation theory,group representation theory,differential operator,differential operators,orthogonal polynomial,differential equation,satisfiability,matrix polynomial
Group representation,Orthogonal matrix,Orthogonal polynomials,Polynomial,Matrix (mathematics),Mathematical analysis,Differential operator,Representation theory,Mathematics,Solvable Lie algebra
Journal
Volume
Issue
ISSN
148
1
0021-9045
Citations 
PageRank 
References 
6
1.04
1
Authors
2
Name
Order
Citations
PageRank
Antonio J. Durán13613.73
F. Alberto Grünbaum2199.14