D. R. Farenick, B. E. Forrest, L. W. Marcoux
Amenable operators on Hilbert spaces
In this paper, we study the closed subalgebra AT of ?(?) generated by an operator T. We show that AT is amenable if and only if T is similar to a normal operator whose spectrum has connected complement and no interior. Furthermore, if AT is amenable, then AT is similar to a C*-algebra. We also prove that if T has finite spectrum, then AT is weakly amenable if and only if AT is amenable. In particular, if Q ? ?(?) is quasinilpotent, then AQ is weakly amenable if and only if Q = 0.
Journal fur die reine und angewandte Mathematik (Crelles Journal), Walter de Gruyter
Print ISSN: 0075-4102
Volume: 2005, 05/2005
Pages: 201 - 228
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