Hiroshi Nakazato

activity

20182023

most citedThe numerical range of a periodic tridiagonal operator reduces to the numerical range of a finite matrix

2 citations · 3 across the 4 of their papers we have counts for

collaborators

5 papers

math.FA2023

The numerical range of periodic banded Toeplitz operators

Benjamín A. Itzá-Ortiz, Rubén A. Martínez-Avendaño, Hiroshi Nakazato

We prove that the closure of the numerical range of a $(n + 1)$ -periodic and $(2 m + 1)$ -banded Toeplitz operator can be expressed as the closure of the convex hull of the uncountable u…

math.CO2023

Numerical ranges of cyclic shift matrices

Mao-Ting Chien, Steve Kirkland, Chi-Kwong Li +1

We study the numerical range of an $n \times n$ cyclic shift matrix, which can be viewed as the adjacency matrix of a directed cycle with $n$ weighted arcs. In particular, we consid…

math.FA2021★ 1 cited

The numerical range of some periodic tridiagonal operators is the convex hull of the numerical ranges of two finite matrices

Benjamín A. Itzá-Ortiz, Rubén A. Martínez-Avendaño, Hiroshi Nakazato

In this paper we prove a conjecture stated by the first two authors establishing the closure of the numerical range of a certain class of $n + 1$ -periodic tridiagonal operators as th…

math.FA2021★ 2 cited

The numerical range of a periodic tridiagonal operator reduces to the numerical range of a finite matrix

Benjamín A. Itzá-Ortiz, Rubén A. Martínez-Avendaño, Hiroshi Nakazato

In this paper we show that the closure of the numerical range of an $n + 1$ -periodic tridiagonal operator is equal to the numerical range of a $2 (n + 1) \times 2 (n + 1)$ complex matrix.

math.FA2018

Norm-parallelism and the Davis--Wielandt radius of Hilbert space operators

A. Zamani, M. S. Moslehian, M. T. Chien +1

We present a necessary and sufficient condition for the norm-parallelism of bounded linear operators on a Hilbert space. We also give a characterization of the Birkhoff--James orth…