The “footprints” of irreversibility

We reformulate the result for the entropy production given in Phys. Rev. Lett. , 98 (2007) 080602 in terms of the relative entropy of microscopic trajectories. By a combination with the Crook's theorem, we identify the path variables that are sufficient to fully identify irreversibility. We show that work saturates the relative entropy, and derive the entropy production for stochastic descriptions.