ON VECTOR-VALUED SPECTRA

Abstract

Elements\alpha\in A\otimes E of the tensor product of a Banach algebra Aand a Banach space E induce systems \{\psi(\alpha):\psi\in E^*\}of elements of A indexed by the dual space E^*, whose jointspectrum belongs to the second dual E^{**}. In this note we investigate when thespectrum actually lies in E\subseteq E^{**}, and extend the spectral mappingtheorem P\sigma_A(\alpha)=\sigma_AP(\alpha) to polynomial mappings P:E\toF between Banach spaces. When the algebra A is commutative and the Banachspace E=B is another algebra we also reach a sort of vector-valued Gelfandtheory.