Singularities of Integrable Hamiltonian Systems with the Same Boundary Foliation. An Infinite Series / M. A. Tuzhilin. // Vestnik Moskovskogo Universiteta. Seriya 1. Matematika. Mekhanika. 2016. № 5. P. 14-20 [Moscow Univ. Math. Bulletin. Vol. 72, N 2, 2017. P. 185-190].

Four-dimensional momentum mapping singularities of integrable Hamiltonian systems with two degrees of freedom are considered. An infinite series of pairs of 4-dimensional saddle–saddle singularities is constructed so that 4-singularities from each pair are not Liouville equivalent, but 2-foliations on their 3-boundaries are Liouville equivalent.

Key words: Liouville equivalence, almost direct product of atoms, circular molecules, saddle-saddle singularities of the momentum map.