Title: Fluctuations in out of equilibrium systems: from theory to experiments Speaker: S. Ciliberto, Ecole Normale Supérieure de Lyon, Laboratoire de Physique Time: Wednesday, 26 October, 2011 at 3:15 p.m. Place: Auditorium G2, Department of Mathematics Abstract The study of the fluctuations in out of equilibrium systems is a subject of current interest ranging from dynamical systems to stochastic systems. I will discuss the very general problem of the fluctuations of injected and dissipated power in these systems. There are presently rather few theoretical results which may predict several statistical properties of these fluctuations. One such case is the Fluctuation Theorem (FT) which has been first found in the context of dynamical systems and later extended to stochastic ones. The proof relies upon several hypothesis which merit to be experimental test. I will focus, from the experimental point of view, on stochastic systems dominated by thermal fluctuations. I describe a rather general case, that is the work fluctuations of an oscillator in contact with a heat reservoir and driven out of equilibrium by an external force. I will also consider the fluctuations of the heat dissipated towards the heat bath. The experimental analysis in the context of Fluctuation Theorem (FT) allows us to highlight the general properties of this theorem and emphasise the importance of the theorem for experi-mental systems. We discuss the finite time corrections that depend on the observable and show that for the total entropy production rate the FT is verified for all times. The role of non-linearities is considered by briefly describing the experimental results of a Brownian particle confined in a double well potential and driven out of equilibrium by an external force. The important con-sequences of the fluctuation theorem and some useful applications to the analysis of experi-mental data will be described. We will finally discuss the applications to a dynamical system. _____ Coffee/tea and cake will be served at 3 p.m. David Field