Active Brownian Particles

In this chapter, we study Brownian active particles under confinement by means of the Fick-Jacobs approach. As part of the description, we derive an approximation formula for position-dependent diffusivity, which seems to work very well for low velocities when compared with Brownian dynamics simulations. One of the main conclusions is that particles with large Reynolds numbers propel themselves by the acceleration of the liquid that surrounds them, while particles with small Reynolds numbers use viscous shear.