1 2 Fe b 20 02 NIELSEN NUMBERS AND NIELSEN GROUPS
نویسنده
چکیده
X : f (x) = g(x)} is a compact subset of X\∂X. In case of codimension 0, the Nielsen number is the lower estimate of the number of points in this set. We suggest a generalization of the classical Nielsen theory for the coincidence and as well as the preimage problems in order to provide a framework for some recent Wecken type results for codimension 1. The Nielsen equivalence on the set of coincidence/preimage points becomes an equivalence on the bordism classes. We consider topologically and algebraically essential Nielsen classes and define higher order Nielsen numbers.
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