Abstract:
Consider a closed 2-form that is degenerate at the points of a hypersurface and is non-degenerate outside it. In the neighbourhood of a singularity (which is called contact under
certain natural conditions) the limit behaviour of Hamiltonian fields is investigated and a canonical form of the 2-form is found (Darboux's theorem). Connections with regular Lie
structures are established. Properties of integrable structures on Liouville tori containing contact degeneracies are studied.
Bibliography: 16 titles.