# Applied Math Seminar (AMS)

#### Shake your hips: an active particle with a fluctuating propulsion force

Speaker: Jean-Luc Thiffeault, U. Wisconsin (host: Childress)

Location: TBA

Date: Friday, March 5, 2021, 2:30 p.m.

Synopsis:

The active Brownian particle (ABP) model describes a swimmer,
synthetic or living, whose direction of swimming is a Brownian motion.
The swimming is due to a propulsion force, and the fluctuations are
typically thermal in origin.  We present a 2D model where the
fluctuations arise from nonthermal noise in a propelling force acting
at a single point, such as that due to a flagellum.  We take the
overdamped limit and find several modifications to the traditional ABP
model.  Since the fluctuating force causes a fluctuating torque, the
diffusion tensor describing the process has a coupling between
translational and rotational degrees of freedom.  An anisotropic
particle also exhibits a noise-induced drift.  We show that these
effects have measurable consequences for the long-time diffusivity of
active particles, in particular adding a contribution that is
independent of where the force acts.  This is joint work with Jiajia
Guo.