Optical tuning of timescale separation in non-equilibrium steady states

Driven colloidal suspensions serve as a paradigmatic model for the study of statistical mechanics out of thermal equilibrium. It is usually assumed that driving velocity is slow compared to the suspending fluid's relaxation time, i.e. the time it takes the fluid to equilibrate after an external perturbation. This timescale separation is an underlying assumption often made in the growing framework of non-equilibrium statistical mechanics. However, this timescale separation need not exist in general, as is, for example, the case in active biolmaterials such as the cytoskeleton. In this talk, I will discuss several approached to study system which couple fluctuation and driving: feedback based driving, optically induced fluctuations, and driving in dense colloidal suspensions.