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JOURNALS // Chebyshevskii Sbornik // Archive

Chebyshevskii Sb., 2020 Volume 21, Issue 2, Pages 228–243 (Mi cheb906)

This article is cited in 4 papers

Classification of saddle-focus singularities

I. K. Kozlov, A. A. Oshemkov

Faculty of Mechanics and Mathematics, Lomonosov Moscow State University (Moscow)

Abstract: The paper presents an algorithm for topological classification of nondegenerate saddle-focus singularities of integrable Hamiltonian systems with three degrees of freedom up to semilocal equivalence. In particular, we prove that any singularity of saddle-focus type can be represented as an almost direct product in which the acting group is cyclic. Based on constructed algorithm, a complete list of singularities of saddle-focus type of complexity 1, 2, and 3, i. e., singularities whose leaf contains one, two, or three singular points of rank 0, is obtained. Earlier, both singularities of saddle-focus type of complexity 1 were also described by L. M. Lerman.

Keywords: integrable system, Liouville foliation, saddle-focus singularity.

UDC: 517.938.5+515.164.15

Received: 01.12.2019
Accepted: 11.03.2020

DOI: 10.22405/2226-8383-2018-21-2-228-243



© Steklov Math. Inst. of RAS, 2026