A robust spectral method for finding lumpings and meta stable states of   non-reversible Markov chains
  A spectral method for identifying lumping in large Markov chains is presented. Identification of meta stable states is treated as a special case. The method is based on spectral analysis of a self-adjoint matrix that is a function of the original transition matrix. It is demonstrated that the technique is more robust than existing methods when applied to noisy non-reversible Markov chains. 
Martin Nilsson Jacobi