Tunneling and Metastability of continuous time Markov chains II, the   nonreversible case
  We proposed in \cite{bl2} a new approach to prove the metastable behavior of reversible dynamics based on potential theory and local ergodicity. In this article we extend this theory to nonreversible dynamics based on the Dirichlet principle proved in \cite{gl2}. 
J. Beltr\'an and C. Landim
math.PR cond-mat.stat-mech