Robustness of topological entropy under small area deformations
Abstract
In this paper, we establish a new type of stability phenomenon for the topological entropy of Hamiltonian diffeomorphisms of closed surfaces. For a closed surface endowed with an area form (Σ,ω) and a Hamiltonian diffeomorphism ϕ of (Σ,ω), we show that for every ε>0 there exists A=A(ϕ,ε)>0 such that htop(ϕ') > htop(ϕ)−ε for every Hamiltonian diffeomorphism ϕ' obtained from ϕ by a deformation supported in a disjoint union of disks, each of area less than A. In particular, if htop(ϕ)>0, then ϕ cannot be made to have zero entropy by an area-preserving deformation supported in disks of small area. This follows from the new braid stability result established in this paper with respect to the spectral distance recently introduced by Connery-Grigg.
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BibTeX
@misc{alves2026robustness,
title = {{Robustness of topological entropy under small area deformations}},
author = {Marcelo R. R. Alves and Matthias Meiwes and Beomjun Sohn},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.31132},
eprint = {2608.31132},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.31132},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Robustness of topological entropy under small area deformations
AU - Marcelo R. R. Alves
AU - Matthias Meiwes
AU - Beomjun Sohn
PY - 2026
DA - 2026/08/31
PB - arXiv
DO - 10.48550/arxiv.2608.31132
UR - https://arxiv.org/abs/2608.31132
AB - In this paper, we establish a new type of stability phenomenon for the topological entropy of Hamiltonian diffeomorphisms of closed surfaces. For a closed surface endowed with an area form (Σ,ω) and a Hamiltonian diffeomorphism ϕ of (Σ,ω), we show that for every ε>0 there exists A=A(ϕ,ε)>0 such that h_top(ϕ') > h_top(ϕ)−ε for every Hamiltonian diffeomorphism ϕ' obtained from ϕ by a deformation supported in a disjoint union of disks, each of area less than A. In particular, if h_top(ϕ)>0, then ϕ cannot be made to have zero entropy by an area-preserving deformation supported in disks of small area. This follows from the new braid stability result established in this paper with respect to the spectral distance recently introduced by Connery-Grigg.
ER -