MULTIVALUED OPERATORS WITH FINITE ESSENTIAL ASCENT OR ESSENTIAL DESCENT AND PERTURBATIONS

Ezzeddine Chafai

Abstract


In this work we introduce and we study the essential index of degree n 2 N
of a closed multi-valued linear operator on a Banach space. We give some algebraic
properties and we prove the stability of such index under commuting small perturbations. Also some perturbation results in the sets \xi+(resp. \xi-) of finite essential ascent (resp. finite essential descent) linear relations are given.


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