Periodic groups of operators in Banach spaces

Nagy, B.

doi:10.1090/S0002-9939-98-04298-1

Periodic groups of operators in Banach spaces
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Proc. Amer. Math. Soc. 126 (1998), 1433-1444 Request permission

Abstract:

Spectral operators of scalar type in the sense of Dunford often occur in connection with unconditionally convergent series expansions, whereas conditionally convergent expansions under similar conditions may be described with the help of operators having a more general type of spectral decomposition. We show that under certain conditions even in the latter case we can restrict our considerations to a dense linear submanifold of the original Banach space with a stronger topology, where the convergence of the expansion under study will be unconditional. Though our conditions could be formulated in terms of a single operator, it seems to be more natural to state them in terms of (the generator of) a periodic group of operators.

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