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Floer homologies for Lagrangian intersections and instantons

Ronnie Lee, Weiping Li

math.GTarXiv:math/9506221

Abstract

In 1985 lectures at MSRI, A. Casson introduced an interesting integer valued invariant for any oriented integral homology 3-sphere Y via beautiful constructions on representation spaces (see [1] for an exposition). The Casson invariant λ(Y) is roughly defined by measuring the oriented number of irreducible representations of the fundamental group π1(Y) in SU(2). Such an invariant generalized the Rohlin invariant and gives surprising corollaries in low dimensional topology.

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