We prove that time dynamics of a stochastic process of pure coagulation is
given by a time dependent Gibbs distribution if and only if rates of single
coagulations have the form ψ(i,j)=if(j)+jf(i), where f is an arbitrary
nonnegative function on the set of integers ≥1. We also obtained a
recurrence relation for weights of these Gibbs distributions, that allowed
explicit solutions in three particular cases of the function f. For the three
corresponding models, we study the probability of coagulation into one giant
cluster, at time t>0.Comment: 22 pages. Changes made implementing referee's suggestions and
remarks.This is a final version to be published in the Advances of Applied
probabilit