Mathis Guéneau (Max Planck, Dresden)

Spatiotemporal Characterization of Active Dynamics in Channels: Theory and Experiments

Swimming microorganisms often live in confined, complex environments, where they transition between bulk and near-surface dynamics. Their dynamics can be quantified in terms of first-passage statistics. In this talk, I will first consider run-and-tumble bacteria confined in a channel. Combining theoretical predictions based on a renewal framework with experimental observations of Escherichia coli, we study the statistics of the time required, after leaving one wall, to encounter either wall. I will discuss how incorporating heterogeneity in tumbling rates or non-exponential run-duration distributions affects the survival probability. In the second part of the talk, I will consider active Brownian dynamics between two walls. Using a systematic expansion, we compute first-passage properties. Exploiting Siegmund duality, we infer the corresponding spatial properties for active Brownian particles confined between hard walls and reveal a transition towards a wall-accumulated state, reminiscent of experimental observations.