Speaker
Description
In the linear overdamped Langevin equation, the effect on a mesoscopic particle (e.g., a colloid) of its collisions with the molecules of the surrounding medium is described by instantaneous friction accompanied by a random force modeled by Gaussian white
noise, yielding a Markovian dynamics of the particle. Such a description hinges on the assumption of time-scale separation, i.e., that the motion of the molecules occurs on
time-scales much shorter than the one at which the motion of the particle is described.
Media undergoing a second-order phase transition exhibit collective fluctuations characterized by long-range correlations across the distance set by the correlation length $\xi$, and macroscopic relaxation times, comparable with the typical time-scale of the motion of a colloidal particle. The coupling between a tracer particle and such slow collective fluctuations breaks time-scale separation and leads to an effective non-Markovian dynamics of the colloid.
We investigate the dynamics of a colloidal particle in a harmonic trap coupled with a fluctuating Gaussian field with a tunable correlation length $\xi$ following relaxational dynamics. The proposed model allows us to analytically describe emergent memory effects and the interplay between stochasticity and fluctuation-induced critical Casimir forces, both in- and out-of-equilibrium. Among them, we demonstrate the emerging memory-induced term in the time-correlator of the particle position, its behavior in the bulk and in the presence of a wall. Also, we derive a backwards motion of a particle released from a trap moving with constant velocity through a near-critical medium.
