The annulus as a K-spectral set

Michel Crouzeix (1)

1 IRMAR - Institut de Recherche Mathématique de Rennes

We consider the annulus [\mathcal{A}_R] of complex numbers with modulus and inverse of modulus bounded by [R>1] . We present some situations, in which this annulus is a K-spectral set for an operator [A] , and some related estimates.

Mots clés: Numerical range; numerical radius; spectral set

Domaines: Analyse numérique [math.NA]

Michel Crouzeix. The annulus as a K-spectral set. Communications on Pure and Applied Mathematics, 2012, 11 (6), pp.2291-2303. ⟨10.3934/cpaa.2012.11.2291⟩. ⟨hal-00730931⟩