# The non-hyperbolicity of irrational invariant curves for twist maps and all that follows

Abstract : The key result of this article is key lemma: if a Jordan curve γ is invariant by a given C 1+α -diffeomorphism f of a surface and if γ carries an ergodic hyperbolic probability µ, then µ is supported on a periodic orbit. From this Lemma we deduce three new results for the C 1+α symplectic twist maps f of the annulus: 1. if γ is a loop at the boundary of an instability zone such that f |γ has an irrational rotation number, then the convergence of any orbit to γ is slower than exponential; 2. if µ is an invariant probability that is supported in an invariant curve γ with an irrational rotation number, then γ is C 1 µ-almost everywhere; 3. we prove a part of the so-called "Greene criterion", introduced by J. M. Greene in [16] in 1978 and never proved: assume that (pn qn) is a sequence of rational numbers converging to an irrational number ω; let (f k (x n)) 1≤k≤qn be a minimizing periodic orbit with rotation number pn qn and let us denote by R n its mean residue R n = |1/2 − Tr(Df qn (x n))/4|
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https://hal-univ-avignon.archives-ouvertes.fr/hal-01087349
Contributor : Marie-Claude Arnaud Connect in order to contact the contributor
Submitted on : Tuesday, November 25, 2014 - 8:19:03 PM
Last modification on : Tuesday, February 22, 2022 - 11:36:03 AM
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• HAL Id : hal-01087349, version 1
• ARXIV : 1411.7072

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M.-C Arnaud, P Berger. The non-hyperbolicity of irrational invariant curves for twist maps and all that follows. Revista Matemática Iberoamericana, European Mathematical Society, 2016, 32 (4 ), pp.1295-1310. ⟨hal-01087349⟩

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