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Sensitivity of mixing times in Eulerian digraphs. (English) Zbl 1390.05219

Summary: Let \(X\) be a lazy random walk on a graph \(G\). If \(G\) is undirected, then the mixing time is upper bounded by the maximum hitting time of the graph. This fails for directed chains, as the biased random walk on the cycle \(\mathbb{Z}_n\) shows. However, we establish that for Eulerian digraphs, the mixing time is \(O(mn)\), where \(m\) is the number of edges and \(n\) is the number of vertices. In the reversible case, the mixing time is robust to the change of the laziness parameter. Surprisingly, in the directed setting the mixing time can be sensitive to such changes. We also study exploration and cover times for random walks on Eulerian digraphs and prove universal upper bounds in analogy to the undirected case.

MSC:

05C81 Random walks on graphs
05C20 Directed graphs (digraphs), tournaments
05C45 Eulerian and Hamiltonian graphs
60J10 Markov chains (discrete-time Markov processes on discrete state spaces)

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