English

$H_q-$semiclassical orthogonal polynomials via polynomial mappings

Classical Analysis and ODEs 2017-12-19 v1

Abstract

In this work we study orthogonal polynomials via polynomial mappings in the framework of the HqH_q-semiclassical class. We consider two monic orthogonal polynomial sequences {pn(x)}n0\{p_n (x)\}_{n\geq0} and {qn(x)}n0\{q_n(x)\}_{n\geq0} such that pkn(x)=qn(xk)  ,n=0,1,2,  , p_{kn}(x)=q_n(x^k)\;,\quad n=0,1,2,\ldots\;, being kk a fixed integer number such that k2k\geq2, and we prove that if one of the sequences {pn(x)}n0\{p_n (x)\}_{n\geq0} or {qn(x)}n0\{q_n(x)\}_{n\geq0} is HqH_q-semiclassical, then so is the other one. In particular, we show that if {pn(x)}n0\{p_n(x)\}_{n\geq0} is HqH_q-semiclassical of class sk1s\leq k-1, then {qn(x)}n0\{q_n (x)\}_{n\geq0} is HqkH_{q^k}-classical. This fact allows us to recover and extend recent results in the framework of cubic transformations, whenever we consider the above equality with k=3k=3. The idea of blocks of recurrence relations introduced by Charris and Ismail plays a key role in our study.

Keywords

Cite

@article{arxiv.1712.06474,
  title  = {$H_q-$semiclassical orthogonal polynomials via polynomial mappings},
  author = {K. Castillo and M. N. De Jesus and F. Marcellán and J. Petronilho},
  journal= {arXiv preprint arXiv:1712.06474},
  year   = {2017}
}
R2 v1 2026-06-22T23:21:46.258Z