Assume there is a radioactive material which emits particles according to a Poisson process at rate $\lambda$. Each particle stays alive for 1/μ time units (deterministic time).
Define $X=\{X_t,t\geq0\}$ to be the number of live particles at time $t$.
Is $X$ is Markov jumping process? Does the fact that the lifetime of particles is deterministic (and not exponentially distributed) cause a problem?