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Equisummability for linear operators in Banach spaces

Published online by Cambridge University Press:  14 November 2011

M. A. Kon
Affiliation:
Department of Mathematics, Columbia University, New York, NY 10027, U.S.A.
A. G. Ramm
Affiliation:
Department of Mathematics, Kansas State University, Manhattan, KS 66506, U.S.A.
L. A. Raphael
Affiliation:
Department of Mathematics, Howard University, Washington, DC 20059, U.S.A.

Synopsis

Let A and B be closed linear operators on a Banach space X. Assume that ε(εIA)−1ff as |ε|→ ∞ for all f in X, ζ∊∑ ⊂ℂ. Under what conditions on BA does the same relationship hold for B? When does [ε(εIA)−1 − ε(εIB)−1 ] f→ 0 in some stronger norm than that of X? The questions are discussed in an abstract setting and the results are generalised to other analytic functions of A. Applications are given to second order elliptic operators.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1987

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