Conditional limit theorems for critical continuous-state branching processes

We study the conditional limit theorems for critical continuous-state branching processes with branching mechanism ψ(λ) = λ1+αL(1/λ), where α∈ [0, 1] and L is slowly varying at ∞. We prove that if α∈(0, 1], there are norming constants Qt→ 0(as t ↑ +∞) such that for every x > 0, Px(QtXt∈·| Xt> 0)converges weakly to a non-degenerate limit. The converse assertion is also true provided the regularity of ψ at0. We give a conditional limit theorem for the case α = 0. The limit theorems we obtain in this paper allow infinite variance of the branching process.

We study the conditional limit theorems for critical continuous-state branching processes with branching mechanism Ф（λ） = λ 1＋αL（1/λ）, where （α∈ [0, 1] and L is slowly varying at co. We prove that if α ∈ （0, 1], there are norming constants Qt →0 （as t ↑ ＋ ∞） such that for every x 〉 0, Px（QtXt ∈ · ｜Xt 〉 0） converges weakly to a non-degenerate limit. The converse assertion is also true provided the regularity of ψ at 0. We give a conditional limit theorem for the case α = 0. The limit theorems we obtain in this paper allow infinite variance of the branching process.