# 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.