Nonequilibrium Dynamics of a Tracer in an Active Environment

Furman Hall 109

In systems driven out of equilibrium symmetries such as detail balance, action-reaction principle, and gradient-type stochastic forces are violated. However, in nature one finds many examples of colloids immersed in nonequilibrium environments. Finding the effective temperature of the system allows us to recover these symmetries. We present a theoretical and computational model of an interacting Brownian particle, the tracer, embedded in a nonequilibrium bath of active particles. We develop a mathematical framework using the nonequilibrium linear response theory to derive the generalized Langevin equation for the tracer which is coupled with the many-body active particles acting as the environment. The probe itself is constrained by a harmonic potential. We studied both weak and strong coupling potentials such as Gaussian and Weeks-Chandler-Anderson. As a baseline, derive the linear coupling model, which has an analytical solution. We study the long-term and average properties of the system and find that an effective temperature can be found.