Orthogonal polynomials associated with an inverse spectral transform. the cubic case


Mabrouk Sghaier, Lamaa Khaled




The purpose of this work is to give some new algebraic properties of the orthogonality of a monic polynomial sequence {Qn } n≥0 defined by Qn (x) = Pn (x) + sn Pn−1 (x) + tn Pn−2 (x) + rn Pn−3 (x), n ≥ 1, where r n 0, n ≥ 3, and {Pn } n≥0 is a given sequence of monic orthogonal polynomials. Essentially, we consider some cases in which the parameters r n , s n , and t n can be computed more easily. Also, as a consequence, a matrix interpretation using LU and UL factorization is done. Some applications for Laguerre, Bessel and Tchebychev orthogonal polynomials of second kind are obtained.