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BP: Fachverband Biologische Physik

BP 27: Nonequilibrium Processes and Self-Organisation

BP 27.5: Talk

Friday, March 30, 2007, 11:45–12:00, H43

Optimal finite-time processes in stochastic thermodynamics — •Tim Schmiedl and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart

For a small system like a colloidal particle or a single biomolecule embedded in a heat bath, we ask for the optimal protocol of an external control parameter minimizing the mean work required to drive the system from one given equilibrium state to another in a finite time. The emphasis on a finite time is crucial since for infinite time the work spent in any quasi-static process is equal to the free energy difference of the two states. For finite time the mean work is larger and will depend on the protocol. Knowing the optimal protocol could inter alia improve the extraction of free energy differences from finite-time path sampling via the Jarzynski relation both in numerical schemes and in experimental studies.

In general, the optimal protocol obeys an integro-differential equation. We derive explicite solutions both for a moving harmonic laser trap and a time-dependent strength of such a trap. In both cases, the optimal protocol exhibits finite jumps both at the beginning and the end of the process. We expect such jumps to be generic even for nonharmonic potentials.