A Phase Reduction Method for Weakly Coupled Stochastic Oscillator Systems

We progressively propose a generalized phase reduction method for a stochastic system of weakly coupled oscillators, regardless of the noise intensity, and analyze dynamical behavior in such a system. This is because noise effects on a phase space were so far described for an uncoupled single stochastic oscillator, subjected only to weak noise. Our method is established with definition of "a phase of the distribution of state variables," rather than by defining distributions on a phase space. The stochastic system of weakly coupled oscillators can then be reduced straightforward to one dimensional phase dynamics. It is also confirmed that our method can be applied into the deterministic system without any noise intensity.