Module 1:Concepts of Random walks, Markov Chains, Markov Processes
  Lecture 3:Markov Chains

 

Theorem 1.3
A state  is recurrent iff

Proof of Theorem 1.3

Assume state  is recurrent then we must have must have , which is what we need to prove. Now pay close attention to the concept of generating function from where we see that, ,  and this is the generic form,from which we have (i) , , i.e., (ii) , (proof given above),would also imply , which would immediately prove that , as  for  (refer above prove). Now using the second proof which is: if  and ,