$q$-Numerical Ranges and Spectral Sets

Fuente: arXiv
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Autores principales: O'Loughlin, Ryan, Rani, Jyoti
Formato: Preprint
Publicado: 2026
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author O'Loughlin, Ryan
Rani, Jyoti
author_facet O'Loughlin, Ryan
Rani, Jyoti
contents We study spectral constants for convex domains $Ω$ containing the spectrum of an operator. We extend the Crouzeix--Palencia framework by obtaining bounds depending on a parameter $γ$ and relating these bounds to geometric properties of $Ω$ and the numerical range $W(A)$. We generalise the proof that the numerical range is a $1+\sqrt{2}$-spectral set to scaled $q$-numerical ranges. We also propose a generalisation of Crouzeix's Conjecture in the context of $q$-numerical ranges.
format Preprint
id arxiv_https___arxiv_org_abs_2603_15536
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle $q$-Numerical Ranges and Spectral Sets
O'Loughlin, Ryan
Rani, Jyoti
Functional Analysis
47A12, 47A25, 47A60
We study spectral constants for convex domains $Ω$ containing the spectrum of an operator. We extend the Crouzeix--Palencia framework by obtaining bounds depending on a parameter $γ$ and relating these bounds to geometric properties of $Ω$ and the numerical range $W(A)$. We generalise the proof that the numerical range is a $1+\sqrt{2}$-spectral set to scaled $q$-numerical ranges. We also propose a generalisation of Crouzeix's Conjecture in the context of $q$-numerical ranges.
title $q$-Numerical Ranges and Spectral Sets
topic Functional Analysis
47A12, 47A25, 47A60
url https://arxiv.org/abs/2603.15536