Algebra and Topology Seminar

4pm Tuesday 12 November 2002

Emmanuel Farjoun
The Hebrew University

Homotopy (co-)limits in Algebra and topology

In order to formulate some general geometric theorems about quotient spaces and more general co-limit constructions it is useful to look at a notion of homotopy limit of, say, digrams of groups or modules. We will examine such constructions which are purely algebraic and show how they help to formulate and prove some algebraic classification problems. We then demonstrate their further utility by formulating a very general version of the classical Seifert van Kampen theorem about fundamental groups.




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