This article is cited in 11 papers

On the 65th birthday of R.Cushman

Symplectic Invariants Near Hyperbolic-Hyperbolic Points

H.R. Dullin^a, S.Vũ Ngoc<sup>b

a</sup> Department of Mathematical Sciences, Loughborough University, LE11 3TU, UK
^b IRMAR, Université de Rennes 1, 35042 Rennes cedex, France

Abstract: We construct symplectic invariants for Hamiltonian integrable systems of 2 degrees of freedom possessing a fixed point of hyperbolic-hyperbolic type. These invariants consist in some signs which determine the topology of the critical Lagrangian fibre, together with several Taylor series which can be computed from the dynamics of the system. We show how these series are related to the singular asymptotics of the action integrals at the critical value of the energy-momentum map. This gives general conditions under which the non-degeneracy conditions arising in the KAM theorem (Kolmogorov condition, twist condition) are satisfied. Using this approach, we obtain new asymptotic formulae for the action integrals of the C. Neumann system. As a corollary, we show that the Arnold twist condition holds for generic frequencies of this system.

Keywords: completely integrable systems, hyperbolic-hyperbolic point, KAM, isoenergetic non-degeneracy, vanishing twist.

MSC: 37J35, 37J15, 37J40, 70H06, 70H08, 37G20

Received: 15.08.2007
Accepted: 10.10.2007

Language: English

DOI: 10.1134/S1560354707060111

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