Bounds on the cover time

A particle that moves on a connected unidirected graph G with n vertices is considered. At each step the particle goes from the current vertex to one of its neighbors, chosen uniformly at random. The cover time is the first time when the particle has visited all the vertices in the graph, starting from a given vertex. Upper and lower bounds are presented that relate the expected cover time for a graph to the eigenvalues of the Markov chain that describes the above random walk. An interesting consequence is that regular expander graphs have expected cover time θ(n log n)