We investigate the growth of clusters within the mean field forest fire model of Ráth and Tóth. The model is a continuous-time Markov process, similar to the dynamical Erdös-Rényi random graph process but with the addition of so-called fires. A vertex may catch fire at any moment and, when it does so, causes all edges within its connected cluster to burn, meaning that they instantaneously disappear. Each burned edge may later reappear. We give a precise description of the process C_t of the size of the cluster of a tagged vertex, in the limit as the number of vertices in the model tends to infinity. We show that C_t is an explosive branching process with a time-inhomogeneous offspring distribution and instantaneous return to 1 on each explosion. Additionally, we show that the characteristic curves used to analyse the Smoluchowski-type coagulation equations associated to the model have a probabilistic interpretation in terms of the process Ct .
- Erdos-Renyi random graph
- forest fire
- self-organized criticality
- moluchowski coagulation equation