Rigidity of the Suris' potential in the Frenkel-Kontorova Model
Corentin Fierobe, Daniel Tsodikovich
TL;DR
The paper proves a local rigidity principle for the integrability of standard-like twist maps in the Frenkel-Kontorova setting, showing that a Suris potential $V_S$ with small eccentricity remains the only admissible integrable perturbation under $C^{r}$-small deformations when rational integrability on $[\tfrac{1}{6},\tfrac{1}{3}]$ is preserved. Central to the approach are action-angle coordinates adapted to Suris maps, a deformed Riesz basis in $L^2$ aligned with these coordinates, and precise action estimates that control how perturbations affect integrable structure. The results yield spectral rigidity statements: same action spectrum or same Mather beta function implies the perturbation is still a Suris potential, and any smooth isospectral deformation stays within the Suris class. Additionally, a periodic-rigidity statement excludes nontrivial short-period integrable perturbations, and the work shows higher-order integrability cannot occur within this framework. The methods parallel strategies used in billiards (e.g., ellipse) and contribute to a broader rigidity program for integrable twist maps.
Abstract
The goal of this paper is to establish a local rigidity result for the integrability of standard-like maps. The main focus of the paper is the remarkable integrable potential discovered by Suris in the 80's. We show that locally, the integrability of this potential is rigid. The proof relies on a similar strategy that was used for billiards in an ellipse, and involves developing the action-angle coordinates for this system, and exploiting it to construct a Riesz basis for $L^2$. As a corollary, we obtain a spectral rigidity result for this setting. Finally, we study the integrability question in the setting of potentials that are periodic.
