(Vanishing) Twist in the Saddle-Centre and Period-Doubling Bifurcation

Abstract

The lowest order resonant bifurcations of a periodic orbit of a Hamiltonian system with two degrees of freedom have frequency ratio 1:1 (saddle-centre) and 1:2 (period-doubling). The twist, which is the derivative of the rotation number with respect to the action, is studied near these bifurcations. When the twist vanishes the nondegeneracy condition of the (isoenergetic) KAM theorem is not satisfied, with interesting consequences for the dynamics. We show that near the saddle-centre bifurcation the twist always vanishes. At this bifurcation a ``twistless'' torus is created, when the resonance is passed. The twistless torus replaces the colliding periodic orbits in phase space. We explicitly derive the position of the twistless torus depending on the resonance parameter, and show that the shape of this curve is universal. For the period doubling bifurcation the situation is different. Here we show that the twist does not vanish in a neighborhood of the bifurcation.

arXiv comment18 pages, 9 figures

References in corpus (3)

• Meanders and Reconnection-Collision Sequences in the Standard Nontwist Map
• Generic Twistless Bifurcations
• Vanishing Twist in the Hamiltonian Hopf Bifurcation

Cited by in corpus (8)

• Symplectic invariants for parabolic orbits and cusp singularities of integrable systems with two degrees of freedom
• Hidden toric symmetry and structural stability of singularities in integrable systems
• The 1:+2 / 1:-2 resonance
• Generating hyperbolic singularities in completely integrable systems
• Existence of a smooth Hamiltonian circle action near parabolic orbits
• Vanishing Twist in the Hamiltonian Hopf Bifurcation
• The Vanishing Twist in the Restricted Three Body Problem
• Behaviour of circular chains of nonlinear oscillators with Kuramoto-like local coupling