Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/ii/paper-2/27k/c/solution

After leaving zero, the jump chain avoids every future reset with probability
This probability is positive exactly when . If , the probability of ever returning to zero is less than one, so the irreducible chain is transient. If , a reset to zero occurs almost surely after each departure; by the Strong Markov property this happens repeatedly, so the chain is recurrent. Therefore

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