Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 43: Colloids and Complex Liquids II

CPP 43.13: Talk

Thursday, March 25, 2010, 17:15–17:30, H39

Experimental accessible variables for testing a generalized fluctuation-dissipation theorem — •Jakob Mehl, Valentin Blickle, and Clemens Bechinger — 2. Physikalisches Institut, Universität Stuttgart, Germany

One cornerstone of statistical physics is the fluctuation-dissipation theorem (FDT). Generally true for all systems slightly perturbted around their equilibrium state, it connects the response of any observable to a small perturbation to equilibrium correlations involving the observable conjugated to the perturbation with respect to energy.

When leaving thermal equilibrium the FDT breaks down. Recently it was shown, that the FDT can be generalized to nonequilibrium steady states (NESS) by choosing the conjugated variable with respect to entropy. By combining colloidal particles, rotating laser tweezers, and video microscopy, we confirm experimentally the generalized FDT for a NESS. In principle the restored formulation allows infinitely many variants of the FDT. However, our experiments demonstrate, that the right choice of variables is crucial to determine the nonequilibrium response via forced fluctuations out of a NESS.