Real linear operators and numerical ranges

Fuente: arXiv
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Auteurs principaux: Kołaczek, Damian, Müller, Vladimir
Format: Preprint
Publié: 2025
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author Kołaczek, Damian
Müller, Vladimir
author_facet Kołaczek, Damian
Müller, Vladimir
contents Real linear operators between two complex Banach spaces unify naturally two important classes of linear operators and antilinear operators. We give a survey of basic geometric, spectral and duality properties of real linear operators. The main goal of the paper is to introduce the numerical range of real linear operators on both Hilbert and Banach spaces and to study its properties. In particular, we show that the numerical range of real linear operators on complex Hilbert space is always a convex set (on at least two-dimensional spaces). This generalizes the classical result of Hausdorff and Toeplitz for linear operators.
format Preprint
id arxiv_https___arxiv_org_abs_2508_04347
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Real linear operators and numerical ranges
Kołaczek, Damian
Müller, Vladimir
Functional Analysis
47A12 (Primary), 47A05 (Secondary)
Real linear operators between two complex Banach spaces unify naturally two important classes of linear operators and antilinear operators. We give a survey of basic geometric, spectral and duality properties of real linear operators. The main goal of the paper is to introduce the numerical range of real linear operators on both Hilbert and Banach spaces and to study its properties. In particular, we show that the numerical range of real linear operators on complex Hilbert space is always a convex set (on at least two-dimensional spaces). This generalizes the classical result of Hausdorff and Toeplitz for linear operators.
title Real linear operators and numerical ranges
topic Functional Analysis
47A12 (Primary), 47A05 (Secondary)
url https://arxiv.org/abs/2508.04347