Testing the irreversibility of a Gibbsian process via hitting and return   times
  We introduce estimators for the entropy production of a Gibbsian process based on the observation of a single or two typical trajectories. These estimators are built with adequate hitting and return times. We then study their convergence and fluctuation properties. This provides statisticals test for the irreversibility of Gibbsian processes. 
J.-R. Chazottes, F. Redig