K-spectral sets and intersections of disks of the Riemann sphere

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dc.creatorBadea, Catalin
dc.creatorBeckermann, Bernhard
dc.creatorCrouzeix, Michel
dc.date2007-12-04
dc.date.accessioned2026-07-07T08:47:14Z
dc.date.available2026-07-07T08:47:14Z
dc.descriptionWe prove that if two closed disks X_1 and X_2 of the Riemann sphere are spectral sets for a bounded linear operator A on a Hilbert space, then the intersection X_1\cap X_2 is a complete (2+2/\sqrt{3})-spectral set for A. When the intersection of X_1 and X_2 is an annulus, this result gives a positive answer to a question of A.L. Shields (1974).
dc.description10 pages
dc.identifierhttps://arxiv.org/abs/0712.0522
dc.identifierhttp://arxiv.org/abs/0712.0522
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/143524
dc.subjectSpectral Theory
dc.subjectFunctional Analysis
dc.subject47A25
dc.titleK-spectral sets and intersections of disks of the Riemann sphere
dc.typetext

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