Open Access

Merging of degree and index theory

Fixed Point Theory and Applications20062006:36361

Received: 14 January 2006

Accepted: 24 April 2006

Published: 5 September 2006


The topological approaches to find solutions of a coincidence equation can roughly be divided into degree and index theories. We describe how these methods can be combined. We are led to a concept of an extended degree theory for function triples which turns out to be natural in many respects. In particular, this approach is useful to find solutions of inclusion problems . As a side result, we obtain a necessary condition for a compact AR to be a topological group.


Authors’ Affiliations

Institute of Mathematics, University of Würzburg
Department of Mathematics and Computer Science (WE1), Free University of Berlin


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© Martin Väth. 2006

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