A friendly introduction to condensing operators

Subject Functional analysis
Title A friendly introduction to condensing operators
Author(s) Jürgen Appell
Keywords measure of noncompactness, condensing operator, fixed point theory
Abstract Condensing operators contain both compact and contracting operators as special cases. Therefore Darbo's celebrated fixed point theorem [1] and Sadovskij's generalization [2] bridge the gap between Schauder's fixed point principle and the Banach-Caccioppoli contaction mapping theorem. The aim of this talk is to illustrate the usefulness of the Darbo-Sadovskij theorem by means of a large variety of applications, ranging from integral equations over boundary value problems to spectral theory, for details see [3]. The presentation is throughout elementary and requires only a modest background in functional analysis and operator theory.