Let $K$ denote a field and let $V$ denote a vector space over $K$ with finite
positive dimension. We consider an ordered pair of linear transformations
$A:V\to V$ and $A^*:V\to V$ that satisfy conditions (i), (ii) below.
(i) There exists a basis for $V$ with respect to which the matrix
representing $A$ is irreducible tridiagonal and the matrix representing $A^*$
is diagonal.
(ii) There exists a basis for $V$ with respect to which the matrix
representing $A$ is diagonal and the matrix representing $A^*$ is irreducible
tridiagonal.
We call such a pair a {\it Leonard pair} on $V$. The structure of any given
Leonard pair is deterined by a certain sequence of scalars called its {\it
parameter array}. The set of parameter arrays is an affine algebraic variety.
We give two characterizations of this variety. One involves bidiagonal matrices
and the other involves orthogonal polynomials.
@article{0306291,
author = {Terwilliger, Paul},
title = {Two linear transformations each tridiagonal with respect to an
eigenbasis of the other; comments on the parameter array},
journal = {arXiv},
volume = {2003},
number = {0},
year = {2003},
language = {en},
url = {http://dml.mathdoc.fr/item/0306291}
}
Terwilliger, Paul. Two linear transformations each tridiagonal with respect to an
eigenbasis of the other; comments on the parameter array. arXiv, Tome 2003 (2003) no. 0, . http://gdmltest.u-ga.fr/item/0306291/