Markov branching process with infinite variance and non-homogeneous immigration with infinite mean

Abstract: The paper studies a class of critical Markov branching processes with infinite variance of the offspring distribution. The processes admit also an immigration component at the jump-points of a non-homogeneous Poisson process, assuming that the mean number of immigrants is infinite and the intensity of the Poisson process converges to zero. The asymptotic behavior of the probability for non-visiting zero is obtained. Limiting distributions are proved, under suitable normalization of the sample paths, depending on the offspring distribution, on the distribution of the immigrants and on the intensity of the Poisson process.