English

Transition maps between the 24 bases for a Leonard pair

Rings and Algebras 2007-05-29 v1 Combinatorics

Abstract

Let VV denote a vector space with finite positive dimension. We consider a pair of linear transformations A:VVA : V \to V and A:VVA^* : V \to V that satisfy (i) and (ii) below: (i) There exists a basis for VV with respect to which the matrix representing AA is irreducible tridiagonal and the matrix representing AA^* is diagonal. (ii) There exists a basis for VV with respect to which the matrix representing AA^* is irreducible tridiagonal and the matrix representing AA is diagonal. We call such a pair a Leonard pair on VV. In an earlier paper we described 24 special bases for VV. One feature of these bases is that with respect to each of them the matrices that represent AA and AA^* are (i) diagonal and irreducible tridiagonal or (ii) irreducible tridiagonal and diagonal or (iii) lower bidiagonal and upper bidiagonal or (iv) upper bidiagonal and lower bidiagonal. For each ordered pair of bases among the 24, there exists a unique linear transformation from VV to VV that sends the first basis to the second basis; we call this the transition map. In this paper we find each transition map explicitly as a polynomial in A,AA,A^*.

Keywords

Cite

@article{arxiv.0705.3918,
  title  = {Transition maps between the 24 bases for a Leonard pair},
  author = {Kazumasa Nomura and Paul Terwilliger},
  journal= {arXiv preprint arXiv:0705.3918},
  year   = {2007}
}
R2 v1 2026-06-21T08:32:22.698Z