In this paper, we give a sufficient condition for the existence of a quasi-ergodic distribution for absorbing Markov processes. Using an orthogonal-polynomial approach, we prove that the previous main result is valid for the birth-death process on the nonnegative integers with 0 an absorbing boundary and ∞ an entrance boundary. We also show that the quasi-ergodic distribution is stochastically larger than the unique quasi-stationary distribution in the sense of monotone likelihood-ratio ordering for the birth-death process.
IntroductionLet (Ω, (F t ) t≥0 , (X t ) t≥0 , (P t ) t≥0 , (P x ) x∈E∪{∂} ) be a time-homogeneous Markov process with state space E ∪ {∂}, where (E, E) is a measurable space and ∂ ∈ E is a cemetery state. Let P x and E x stand for the probability and the expectation, respectively, associated with the process X when initiated from x. We assume that the process X has a finite lifetime T , i.e., for allx ∈ E,where T = inf{t ≥ 0 : X t = ∂}. We also assume that for all t ≥ 0 and x ∈ E, P x (t < T ) > 0.