Randomly evolving trees II

Generating function equation has been derived for the probability distribution of the number of nodes with k ≥ 0 outgoing lines in randomly evolving special trees defined in an earlier paper arXiv:condmat/0205650. The stochastic properties of the end-nodes (k = 0) have been analyzed, and it was shown that the relative variance of the number of end-nodes vs. time has a maximum when the evolution is either subcritical or supercritical. On the contrary, the time dependence of the relative dispersion of the number of dead end-nodes shows a minimum at the beginning of the evolution independently of its type. For the sake of better understanding of the evolution dynamics the survival probability of random trees has been investigated, and asymptotic expressions have been derived for this probability in the cases of subcritical, critical and supercritical evolutions. In critical evolution it was shown that the probability to find the tree lifetime larger than x, is decreasing to zero as 1/x, if x → ∞. Approaching the critical state it has been found the fluctuations of the tree lifetime to become extremely large, and so near the critical state the average lifetime could be hardly used for the characterization of the process. PACS: 02.50.-r, 02.50.Ey, 05.40.-a