K. Nomura

activity

20242026

collaborators

4 papers

math.CO2026

Variations on a circular Hessenberg pair

Kazumasa Nomura, Paul Terwilliger

A square matrix is called Hessenberg whenever each entry below the subdiagonal is zero and each entry on the subdiagonal is nonzero. A Hessenberg pair is an ordered pair of diagona…

math.CO2026

Circular Hessenberg pairs and the tridiagonal relations

Kazumasa Nomura, Paul Terwilliger

A square matrix is said to be Hessenberg whenever each entry below the subdiagonal is zero, and each entry on the subdiagonal is nonzero. A Hessenberg matrix is called circular whe…

math.CO2025

Spin Leonard pairs and the zero diagonal space

Kazumasa Nomura, Paul Terwilliger

We consider a Leonard pair $A, A^{*}$ of linear maps on a vector space $V$ that has finite positive dimension. This Leonard pair $A, A^{*}$ is said to have spin whenever there exist inv…

math.RA2024

The nucleus of the Johnson graph $J (N, D)$

Kazumasa Nomura, Paul Terwilliger

In this paper, we describe the nucleus of the Johnson graph $I^ = J (N, D)$ with $N > 2 D$ . Let $X$ denote the vertex set of $I^$ . Let $A \in Mat_{X} (C)$ denote the adja…

Variations on a circular Hessenberg pair

Circular Hessenberg pairs and the tridiagonal relations

Spin Leonard pairs and the zero diagonal space

The nucleus of the Johnson graph J(N,D)

The nucleus of the Johnson graph $J (N, D)$