  A general theory is presented for the coupling among nonlinear oscillators
mediated by a diffusing chemical substance. We extend a model originally
developed by Kuramoto, who supposed that the diffusion characteristic time is
much shorter than the oscillator main period, such that diffusion occurs very
fast. We eliminate this constraint and consider diffusion to have an arbitrary
characteristic time, by solving exactly the diffusion equation using suitable
Green functions. We present results in one, two and three dimension, with and
without boundary conditions.
