Semi-global symplectic invariant of the champagne bottle

Fuente: arXiv
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Autor principal: Christov, Ognyan
Formato: Preprint
Publicado: 2026
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author Christov, Ognyan
author_facet Christov, Ognyan
contents We study a two degrees of freedom Hamiltonian system describing the motion of a particle in a potential field of the form of $S^1$ symmetric double well, namely $V = - (x_1^2 + x_2^2) + (x_1^2 + x_2^2)^2$, known also as a champagne bottle potential. This system is completely integrable. The champagne bottle is the simplest member of a class of integrable systems that have no global action variables due to a non-trivial monodromy, Bates (1991). Beyond that, the geometric and dynamical properties of the system near the equilibrium are of primary interest. We calculate the Birkhoff normal form and the nontrivial action near the focus-focus singularity and obtain the semi-global symplectic invariant near focus-focus point, which is introduced by Vũ Ng\d{o}c (2003). Examples of such calculations are still few. We compare our result with the semi-global symplectic invariant of the spherical pendulum, calculated by Dullin (2013).
format Preprint
id arxiv_https___arxiv_org_abs_2605_21985
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Semi-global symplectic invariant of the champagne bottle
Christov, Ognyan
Exactly Solvable and Integrable Systems
Mathematical Physics
37j35, 37j40, 70H06, 70H08
We study a two degrees of freedom Hamiltonian system describing the motion of a particle in a potential field of the form of $S^1$ symmetric double well, namely $V = - (x_1^2 + x_2^2) + (x_1^2 + x_2^2)^2$, known also as a champagne bottle potential. This system is completely integrable. The champagne bottle is the simplest member of a class of integrable systems that have no global action variables due to a non-trivial monodromy, Bates (1991). Beyond that, the geometric and dynamical properties of the system near the equilibrium are of primary interest. We calculate the Birkhoff normal form and the nontrivial action near the focus-focus singularity and obtain the semi-global symplectic invariant near focus-focus point, which is introduced by Vũ Ng\d{o}c (2003). Examples of such calculations are still few. We compare our result with the semi-global symplectic invariant of the spherical pendulum, calculated by Dullin (2013).
title Semi-global symplectic invariant of the champagne bottle
topic Exactly Solvable and Integrable Systems
Mathematical Physics
37j35, 37j40, 70H06, 70H08
url https://arxiv.org/abs/2605.21985