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In naturally reproducing populations one usually encounters an aver­age number of more than one offspring per individual. However, given non-extinction, classical super-critical branching processes grow beyond all bounds. This is unrealistic because of bounded resources. We consider a model for a population with subpopulations living in separated regions and with migration between the regions. In addition to the births and deaths in a super-critical branching mecha­nism, there are deaths resulting from competition between any two individuals in one subpopulation. We prove that there is...

Many stochastic differential equations (SDEs) in the literature have a superlinearly growing nonlinearity in their drift or diffusion coefficient. Unfortunately, moments of the computationally efficient Euler-Maruyama approximation method diverge for these SDEs in finite time. This article develops a general theory based on rare events for studying integrability properties such as moment bounds for discrete-time stochastic processes. Using this approach, the authors establish moment bounds for fully and partially drift-implicit Euler methods and for a class of new explicit approximation...