English

Circular bidiagonal pairs

Quantum Algebra 2024-07-04 v1 Combinatorics

Abstract

A square matrix is said to be circular bidiagonal whenever (i) each nonzero entry is on the diagonal, or the subdiagonal, or in the top-right corner; (ii) each subdiagonal entry is nonzero, and the entry in the top-right corner is nonzero. Let F\mathbb F denote a field, and let VV denote a nonzero finite-dimensional vector space over F\mathbb F. We consider an ordered pair of F\mathbb F-linear maps A:VVA: V \to V and A:VVA^*: V \to V that satisfy the following two conditions: (i) there exists a basis for VV with respect to which the matrix representing AA is circular bidiagonal and the matrix representing AA^* is diagonal; (ii) there exists a basis for VV with respect to which the matrix representing AA^* is circular bidiagonal and the matrix representing AA is diagonal. We call such a pair a circular bidiagonal pair on VV. We classify the circular bidiagonal pairs up to affine equivalence. There are two infinite families of solutions, which we describe in detail.

Keywords

Cite

@article{arxiv.2301.00121,
  title  = {Circular bidiagonal pairs},
  author = {Paul Terwilliger and Arjana Žitnik},
  journal= {arXiv preprint arXiv:2301.00121},
  year   = {2024}
}

Comments

30 pages

R2 v1 2026-06-28T07:57:59.602Z