Numerical Ranges and Spectral Sets: the unbounded case
Functional Analysis
2025-09-25 v1 Numerical Analysis
Numerical Analysis
Abstract
It is known that, if C is a convex set containing the numerical range of an operator A, then is a C -spectral set for A with C 1+ \sqrt 2. We improve this estimate in unbounded cases.
Cite
@article{arxiv.2509.19792,
title = {Numerical Ranges and Spectral Sets: the unbounded case},
author = {Michel Crouzeix},
journal= {arXiv preprint arXiv:2509.19792},
year = {2025}
}