Electronic Journal of Probability

Random walks colliding before getting trapped

Louigi Addario-Berry, Roberto I. Oliveira, Yuval Peres, and Perla Sousi

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Let $P$ be the transition matrix of a finite, irreducible and reversible Markov chain. We say the continuous time Markov chain $X$ has transition matrix $P$ and speed $\lambda $ if it jumps at rate $\lambda $ according to the matrix $P$. Fix $\lambda _X,\lambda _Y,\lambda _Z\geq 0$, then let $X,Y$ and $Z$ be independent Markov chains with transition matrix $P$ and speeds $\lambda _X,\lambda _Y$ and $\lambda _Z$ respectively, all started from the stationary distribution. What is the chance that $X$ and $Y$ meet before either of them collides with $Z$? For each choice of $\lambda _X,\lambda _Y$ and $\lambda _Z$ with $\max (\lambda _X,\lambda _Y)>0$, we prove a lower bound for this probability which is uniform over all transitive, irreducible and reversible chains. In the case that $\lambda _X=\lambda _Y=1$ and $\lambda _Z=0$ we prove a strengthening of our main theorem using a martingale argument. We provide an example showing the transitivity assumption cannot be removed for general $\lambda _X,\lambda _Y$ and $\lambda _Z$.

Article information

Electron. J. Probab., Volume 21 (2016), paper no. 42, 19 pp.

Received: 15 July 2015
Accepted: 1 May 2016
First available in Project Euclid: 22 July 2016

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 60J10: Markov chains (discrete-time Markov processes on discrete state spaces)

transitive Markov chains mixing time hitting times meeting times martingale

Creative Commons Attribution 4.0 International License.


Addario-Berry, Louigi; Oliveira, Roberto I.; Peres, Yuval; Sousi, Perla. Random walks colliding before getting trapped. Electron. J. Probab. 21 (2016), paper no. 42, 19 pp. doi:10.1214/16-EJP4414. https://projecteuclid.org/euclid.ejp/1469199632

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