Validity of the Law of Mass Action in Three-Dimensional Coagulation Processes

Diffusion-limited reactions are studied in detail on the classical
coalescing process. We demonstrate how, with the aid of a recent
renormalization group approach, fluctuations can be integrated
systematically. We thereby obtain an exact relation between the
microscopic physics (lattice structure and particle shape and size)
and the macroscopic decay rate in the law of mass action. Moreover,
we find a strong violation of the law of mass action. The
corresponding term in the kinetic equations originates in
longwavelength fluctuations and is a universal function of the
macroscopic decay rate.