LMP Seminar: Enhanced diffusion of tracer particles in nonequilibrium mixtures

In many situations of biophysical interest, describing accurately the dynamics of tagged particles (or 'tracers') in nonequilibrium suspensions is of crucial importance. From a theoretical perspective, it represents a major challenge, since the combination of interparticle couplings and nonequilibrium drive requires refined levels of descriptions. We design a generic analytical framework to study the dynamics of a tracer in a dense mixture of particles which evolves far from equilibrium. Starting from the overdamped Langevin equations that describe the evolution of the system, we derive the expression of the self-diffusion coefficient of a tagged particle in the suspension, in the limit of soft interactions between the particles. Our derivation relies on the linearization of the Dean-Kawasaki equations obeyed by the density fields and on a path-integral representation of the dynamics of the tracer. We apply this scheme to two types of nonequilibrium mixtures which have received a lot of interest recently: two-temperature mixtures, and non-reciprocal mixtures. In both situations, our analytical model combined with Brownian dynamics reveals the emergence of enhanced diffusion, and the condition for its observation.

References:

Jardat et al., Phys. Rev. E 106, 064608 (2022), arXiv:2209.00929
Benois et al., to appear in Phys. Rev. E (2023), arXiv:2307.05408