Analytic genericity of diffusing orbits in a priori unstable Hamiltonian systems

Qinbo Chen, Rafael de la Llave

Published 2021-03-05Version 1

We study the problem of instability in the following a priori unstable Hamiltonian system with a time-periodic perturbation \[\mathcal{H}_\varepsilon(p,q,I,\varphi,t)=h(I)+\sum_{i=1}^n\pm \left(\frac{1}{2}p_i^2+V_i(q_i)\right)+\varepsilon H_1(p,q,I,\varphi, t), \] where $(p,q)\in \mathbb{R}^n\times\mathbb{T}^n$, $(I,\varphi)\in\mathbb{R}^d\times\mathbb{T}^d$ with $n, d\geq 1$, $V_i$ are Morse potentials, and $\varepsilon$ is a small non-zero parameter. Using geometric methods we prove that Arnold diffusion occurs for generic analytic perturbations $H_1$. Indeed, the set of admissible $H_1$ is $C^\omega$ dense and $C^3$ open. The proof also works for arbitrarily small $V_i$. Our perturbative technique for the genericity is valid in the $C^k$ topology for all $k\in [3,\infty)\cup\{\infty, \omega\}$.