Published online by Cambridge University Press: 01 March 2022
Let $(Z_n)_{n\geq 0}$ be a critical branching process in a random environment defined by a Markov chain
$(X_n)_{n\geq 0}$ with values in a finite state space
$\mathbb{X}$. Let
$ S_n = \sum_{k=1}^n \ln f_{X_k}^{\prime}(1)$ be the Markov walk associated to
$(X_n)_{n\geq 0}$, where
$f_i$ is the offspring generating function when the environment is
$i \in \mathbb{X}$. Conditioned on the event
$\{ Z_n>0\}$, we show the nondegeneracy of the limit law of the normalized number of particles
${Z_n}/{e^{S_n}}$ and determine the limit of the law of
$\frac{S_n}{\sqrt{n}} $ jointly with
$X_n$. Based on these results we establish a Yaglom-type theorem which specifies the limit of the joint law of
$ \log Z_n$ and
$X_n$ given
$Z_n>0$.