Symmetry, Integrability and Geometry: Methods and Applications (Jun 2009)
Non-Hamiltonian Actions and Lie-Algebra Cohomology of Vector Fields
Abstract
Two examples of Diff^+S^1-invariant closed two-forms obtained from forms on jet bundles, which does not admit equivariant moment maps are presented. The corresponding cohomological obstruction is computed and shown to coincide with a nontrivial Lie algebra cohomology class on H^2(X(S^1)).
