Roles of Dry Friction in Fluctuating Motion of Adiabatic Piston

by Tomohiko Sano (Yukawa Institute, Kyoto)

Friday 31 Jan 2014, 11:00 → 12:00 Europe/Rome

Aula Corbino (DIP. di Fisica - edificio E. Fermi)

Recent developments in experimental technique enable us to control small systems and non-equilibrium systems to clarify their thermodynamic structures, in detail. One of the most important applications of manipulation techniques for small systems is the design of nano-machines or sub-micron machines. The difficulty to realize efficient small machines is the existence of dry friction when two solids are in contact, because the dry friction wears down the small machines. Because the dry friction is ubiquitous throughout nature, to control systems under dry friction is indispensable to make small machines. Experiments for macroscopic systems under the dry friction reveal that the dry friction has an important role to rectify unbiased fluctuations, i.e. to extract work from an equilibrium environment. Although the dry friction plays essential roles in non-equilibrium transport, the energetics for the systems under the dry friction has been elusive so far. In this seminar, we consider the fluctuating motion of an adiabatic piston under dry friction to clarify the roles of dry friction in non-equilibrium steady states. Introducing the stochastic equation of motion for the piston driven by white non-Gaussian noises, we clarify that the dry friction can reverse the direction of the piston motion and causes a discontinuity or a cusp-like singularity for velocity distribution functions of the piston. We also show that the heat fluctuation relation is modified under the dry friction. In the last part of the talk, the thermodynamic efficiency or power for the engine which contains the fluctuating boundary are analyzed through the extension of the model for the fluctuating piston.