A Two-Dimensional Map of Arbitrary Period

We introduce a two-dimensional discrete-time dynamical system which represents the evolution of an angle and angular velocity. While the angle evolves by a fixed amount in every step, the evolution of the angular velocity is governed by a nonlinear map. We study the periodicity and stability of solutions to the system for a range of parameter values and initial conditions. The coupled system is shown to be periodic for certain parameter choices and initial conditions. In the limit, when the change in the angle tends to zero, the map is equivalent to the dynamics of a simple pendulum. Based on the integral of motion of the pendulum, an approximate invariant for the system is obtained. Simulations showing the behavior of the system for different parameter values and initial conditions are presented.