Shearless barriers in the conservative Ikeda map

Abstract

We investigate the dynamics of the Ikeda map in the conservative limit, where it is represented as a two-dimensional area-preserving map governed by two control parameters, $\theta$ and $\phi$. We demonstrate that the map can be interpreted as a composition of a rotation and a translation of the state vector. In the integrable case ($\phi = 0$), the map reduces to a uniform rotation by angle $\theta$ about a fixed point, independent of initial conditions. For $\phi \ne 0$, the system becomes nonintegrable, and the rotation angle acquires a coordinate dependence. The resulting rotation number profile exhibits extrema as a function of position, indicating the formation of shearless barriers. We analyze the emergence, persistence, and breakup of these barriers as the control parameters vary.