and on a sphere. The vortices form a polygonal equilibrium in a rotating frame of reference.
We use numerical continuation in a boundary value setting to determine the Lyapunov
families of periodic orbits that arise from the polygonal relative equilibrium. When the
frequency of a Lyapunov orbit and the frequency of the rotating frame have a rational
relationship, the orbit is also periodic in the inertial frame. A dense set of Lyapunov orbits …