English

Braid stability for periodic orbits of area-preserving surface diffeomorphisms

Dynamical Systems 2025-06-03 v4 Symplectic Geometry

Abstract

We consider an area-preserving diffeomorphism of a compact surface, which is assumed to be an irrational rotation near each boundary component. A finite set of periodic orbits of the diffeomorphism gives rise to a braid in the mapping torus. We show that under some nondegeneracy hypotheses, the isotopy classes of braids that arise from finite sets of periodic orbits are stable under Hamiltonian perturbations that are small with respect to the Hofer metric. A corollary is that for a Hamiltonian isotopy class of such maps, the topological entropy is lower semicontinuous with respect to the Hofer metric. This extends results of Alves-Meiwes for braids arising from finite sets of fixed points of Hamiltonian surface diffeomorphisms.

Keywords

Cite

@article{arxiv.2303.07133,
  title  = {Braid stability for periodic orbits of area-preserving surface diffeomorphisms},
  author = {Michael Hutchings},
  journal= {arXiv preprint arXiv:2303.07133},
  year   = {2025}
}

Comments

v4 has additional corrections and clarifications

R2 v1 2026-06-28T09:14:10.803Z