Let Xn be a MC s.t. (Xn)n≥0∼\mboxMarkov(λ,P), and m≥0 be a fixed integer. Then conditional on {Xm=i} 1. (Xm+n)n≥0 is independent of X0,⋯,Xm−1 2. (Xm+n)n≥0 is \mboxMarkov(δi,P)
where δi is the Dirac Distribution at state i.
Let λ be a distribution on S, and P be a stochastic matrix. Assume for any N≥0, and any states i0,⋯,iN∈S P(X0=i0,⋯,XN=iN)=λi0pi0i1⋯piN−1iN Then Xn,n≥0∼Markov(λ,P), or Xn,n≥0 is a MC.
Let (Xn)n≥0∼\mboxMarkov(λ,P) be a time homogeneous MC, and T be a stopping time. Then for any integer m≥0 and state i∈S, conditional on {T=m,XT=i}, 1. (XT+n)n≥0 is conditionally independent of X0,⋯,XT,T 2. (XT+n)n≥0 is \mboxMarkov(δi,P)
where δi is the Dirac Distribution at state i.
Let (Xn)n≥0∼\mboxMarkov(λ,P) be a time homogeneous MC, and T be a stopping time such that P(T<∞)=1. Then for any state i∈S, conditional on XT=i, 1. (XT+n)n≥0 is conditionally independent of X0,⋯,XT,T 2. (XT+n)n≥0 is \mboxMarkov(δi,P)
where δi is the Dirac Distribution at state i.
Intuition
This generalizes the Markov Property to also handle random times (i.e. the stopping time T).
If {Xt:t≥0}∼\mboxMarkov(λ,Q), then fix a time s≥0, conditional on {Xs=i}, we have that - {Xt+s:t≥0}∼\mboxMarkov(δi,Q) - {Xt+s:t≥0} is conditionally independent of {Xr:t<s}