English

Leonard pairs having LB-TD form

Rings and Algebras 2014-04-29 v1

Abstract

Fix an algebraically closed field F\mathbb{F} and an integer d3d \geq 3. Let Matd+1(F)\text{Mat}_{d+1}(\mathbb{F}) denote the F\mathbb{F}-algebra consisting of the (d+1)×(d+1)(d+1) \times (d+1) matrices that have all entries in F\mathbb{F}. We consider a pair of diagonalizable matrices A,AA,A^* in Matd+1(F)\text{Mat}_{d+1}(\mathbb{F}), each acts in an irreducible tridiagonal fashion on an eigenbasis for the other one. Such a pair is called a Leonard pair in Matd+1(F)\text{Mat}_{d+1}(\mathbb{F}). For a Leonard pair A,AA,A^* there is a nonzero scalar qq that is used to describe the eigenvalues of AA and AA^*. In the present paper we find all Leonard pairs A,AA,A^* in Matd+1(F)\text{Mat}_{d+1}(\mathbb{F}) such that AA is lower bidiagonal with subdiagonal entries all 11 and AA^* is irreducible tridiagonal, under the assumption that qq is not a root of unity. This gives a partial solution of a problem given by Paul Terwilliger.

Keywords

Cite

@article{arxiv.1404.6794,
  title  = {Leonard pairs having LB-TD form},
  author = {Kazumasa Nomura},
  journal= {arXiv preprint arXiv:1404.6794},
  year   = {2014}
}
R2 v1 2026-06-22T03:59:46.762Z