Clusters in Markov Chains via Singular Vectors of Laplacian Matrices

Suppose that $T$ is a stochastic matrix. We propose an algorithm for identifying clusters in the Markov chain associated with $T$. The algorithm is recursive in nature, and in order to identify clusters, it uses the sign pattern of a left singular vector associated with the second smallest singular value of the Laplacian matrix $I-T\mathrm{.}$ We prove a number of results that justify the algorithm’s approach, and illustrate the algorithm’s performance with several numerical examples.