Abstract

    Exchangeable fragmentation-coagulation (EFC) processes are partition-valued stochastic processes first introduced by Berestycki. In this talk we consider the EFC processes for which the coagulations are multiple and not simultaneous, as in a A-coalescent, and the fragmentations dislocate at finite rate an individual block into sub-blocks of infinite size. Sufficient conditions are found for the block counting process to explode (i.e., to reach ∞) or not and for ∞ to be either an exit boundary or an entrance boundary. In a case of regularly varying fragmentation and coagulation mechanisms, we find regimes where the boundary ∞ can be either an exit, an entrance or a regular boundary.

    This talk is based on joint work with Clement Foucart.