Lyapunov functions for Morse-Smale synchronisation diffeomorphisms

This paper investigates the dynamical system governing the phase differences between three identical oscillators arranged symmetrically and coupled by burst interactions. By constructing a discrete Lyapunov function, we prove the existence of two asymptotically stable fixed points on the 2-torus T^2, which correspond to Huygens synchronisation of three clocks. The locked states have phase differences of (2 pi/3,4 pi/3) and (4 pi/3,2 pi/3). Each fixed point possesses an open basin of attraction. The closure of the union of the basins of attraction of the two asymptotically stable attractors is the torus T^2, implying that Huygens synchronisation occurs generically and with full Lebesgue measure with respect to initial conditions.