Multitype branching processes in random environment: probability of survaval for the critical case

We investigate the asymptotic behavior of the survival probability of a critical multitype branching process evolving in an environment generated by a sequence of independent identically distributed random variables. Under fairly general assumptions on the form of the offspring generating functions of particles, we show that the probability of survival up to generation n of the process initiated at moment. zero by a single particle of type i is equivalent to beta i(n-1/2), where beta(i) is a positive constant. This assertion essentially generalizes a number of previously known results.