A Crossed Module giving the Godbillon-Vey Cocycle
Abstract
We find crossed modules, i.e. certain 4 term exact sequences, associated to the Godbillon-Vey class for W1, Vect(S1), Vect1,0() and Hol(r), i.e. for the Lie algebras of formal vector fields in 1 variable, vector fields on the circle, differentiable vector fields of holomorphic type on a Riemann surface and holomorphic vector fields on an open Riemann surface.
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