A note on numerical radius attaining mappings

We prove that if every bounded linear operator (or N N -homogeneous polynomials) on a Banach space X X with the compact approximation property attains its numerical radius, then X X is a finite dimensional space. Moreover, we present an improvement of the polynomial James’ theorem for numerical radi...

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Veröffentlicht in:Proceedings of the American Mathematical Society 2023-10, Vol.151 (10), p.4419-4434
1. Verfasser: Jung, Mingu
Format: Artikel
Sprache:eng
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Zusammenfassung:We prove that if every bounded linear operator (or N N -homogeneous polynomials) on a Banach space X X with the compact approximation property attains its numerical radius, then X X is a finite dimensional space. Moreover, we present an improvement of the polynomial James’ theorem for numerical radius proved by Acosta, Becerra Guerrero and Galán [Q. J. Math. 54 (2003), pp. 1–10]. Finally, the denseness of weakly (uniformly) continuous 2 2 -homogeneous polynomials on a Banach space whose Aron-Berner extensions attain their numerical radii is obtained.
ISSN:0002-9939
1088-6826
DOI:10.1090/proc/16457