# Berlin 2012 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 15: Statistical Physics far from equilibrium

### DY 15.10: Vortrag

### Mittwoch, 28. März 2012, 12:15–12:30, MA 004

**Thermodynamics of genuine non-equilibrium states under feedback control** — •David Abreu and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart, Germany

The work extracted from a thermodynamic system can exceed the free energy difference between final and initial states if feedback control is implemented. For transitions between equilibrium states, Sagawa and Ueda showed that the Jarzynski equality - and therefore the second law of thermodynamics - can be generalized to take into account the information obtained through measurements [1].

In the case of transitions between genuine non-equilibrium states that even at fixed external control parameter exhibit dissipation, we extend the Hatano-Sasa equality to processes with feedback control [2]. The resulting bound on the maximal extractable work is substantially sharper than what would follow from applying the Sagawa-Ueda equality to transitions involving such states. For repeated measurements at short enough intervals, the power thus extracted can even exceed the average cost of driving as demonstrated explicitly with a simple, analytically solvable example.

[1] T. Sagawa and M. Ueda. Phys. Rev. Lett. 104, 090602 (2010).

[2] D. Abreu and U. Seifert. arXiv: 1109.5892 (2011).