On the Einstein relation between mobility and diffusion coefficient in an active bath

An active bath, made of self-propelling units, is a nonequilibrium medium in which the Einstein relation D = mu k (B) T between the mobility mu and the diffusivity D of a tracer particle cannot be expected to hold a priori. We consider here heavy tracers for which these coefficients can be related to correlation functions which we estimate. We show that, to a good approximation, an Einstein relation does hold in an active bath upon using a different temperature which is defined mechanically, through the pressure exerted on the tracer.

Automated summary

The study investigates the relationship between mobility and diffusivity in an active bath, and finds that the Einstein relation can approximately hold when a mechanically defined different temperature is used.