We build a Markovian system of particles entirely characterized by their masses, in which each pair of particles with masses $x$ and $y$ coalesce at rate $K(x,y)\simeq x^\lambda+y^\lambda$, for some $\lambda \in $, and such that the system is initially composed of infinitesimally small particles.
"Standard stochastic coalescence with sum kernels." Electron. Commun. Probab. 11 141 - 148, 2006. https://doi.org/10.1214/ECP.v11-1206