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arXiv · 2401.09929

Expansions for random walks conditioned to stay positive

Denis Denisov·Alexander Tarasov·Vitali Wachtel
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Abstract

We consider a one-dimensional random walk $S_n$ with i.i.d. increments with zero mean and finite variance. We study the asymptotic expansion for the tail distribution $\mathbf P(\tau_x>n)$ of the first passage times $\tau_x:=\inf\{n\ge1:x+S_n\le0\}$ for $\ x\ge0.$ We also derive asymptotic expansion for local probabilities $\mathbf P(S_n=x,\tau_0>n)$. Studying the asymptotic expansions we obtain a sequence of discrete polyharmonic functions and obtain analogues of renewal theorem for them.

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Denis Denisov, Alexander Tarasov, Vitali Wachtel. 2024-01-18. Expansions for random walks conditioned to stay positive. https://arxiv.org/abs/2401.09929

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