Random Walks on Directed Covers of Graphs |
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Authors: | Lorenz A Gilch Sebastian Müller |
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Institution: | 1.Institut für Mathematische Strukturtheorie,Graz University of Technology,Graz,Austria |
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Abstract: | Directed covers of finite graphs are also known as periodic trees or trees with finitely many cone types. We expand the existing
theory of directed covers of finite graphs to those of infinite graphs. While the lower growth rate still equals the branching
number, upper and lower growth rates no longer coincide in general. Furthermore, the behavior of random walks on directed
covers of infinite graphs is more subtle. We provide a classification in terms of recurrence and transience and point out
that the critical random walk may be recurrent or transient. Our proof is based on the observation that recurrence of the
random walk is equivalent to the almost sure extinction of an appropriate branching process. Two examples in random environment
are provided: homesick random walk on infinite percolation clusters and random walk in random environment on directed covers.
Furthermore, we calculate, under reasonable assumptions, the rate of escape with respect to suitable length functions and
prove the existence of the asymptotic entropy providing an explicit formula which is also a new result for directed covers
of finite graphs. In particular, the asymptotic entropy of random walks on directed covers of finite graphs is positive if
and only if the random walk is transient. |
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