Lecturer: Prof. Yael Roichman, Dept. of physical chemistry, Tel-Aviv University

Abstract:
In this talk, I will present a series of experimental systems driven by athermal (nonequilibrium) fluctuations. For each system, we explore the conditions under which one can define a physically meaningful effective temperature. Specifically, in one system, we compare different definitions of temperature and identify when they converge. In a second system, we test the predictive power of an effective temperature in describing the relaxation towards a steady state when a diffusive contact is formed. Finally, we focus on transitions between different steady-states. We develop a consistent non-equilibrium thermodynamic framework by examining the interplay of thermal and non-equilibrium fluctuations at the level of individual trajectories. Remarkably, this approach leads to a generalized notion of temperature—one that varies with the system's state while remaining consistent with the Second Law of thermodynamics.