Abstract:
Active particles consume energy from their environment and turn it into directed motion, leading to remarkable non-equilibrium effects. These phenomena occur for systems of different scales, from molecular motors, through persistent motion of bacteria such as E. Coli, to flocking of birds. In this talk I will mostly focus on the run-and-tumble particle (RTP) model, a useful theoretical model which mimics the behavior of many active systems. I will present recent results for the nonequilibirum steady state that a single RTP reaches when confined by an external harmonic potential.
First I will present the exact steady state distribution of the position of an overdamped RTP in two dimensions with four possible orientations. Next, I will go beyond the overdamped regime, and focus on the limit in which the RTP switches its orientation very fast. While typical fluctuations of its position obey a Boltzmann distribution, I will show that large deviations do not, and are instead dominated by a single, most likely trajectory in a coarse-grained dynamical description of the system.
If time permits, I will discuss the extension of these results to arbitrary active particles in active trapping potentials (but in the overdamped regime).