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DY: Fachverband Dynamik und Statistische Physik

DY 14: Microswimmers (joint session DY/CPP)

DY 14.7: Vortrag

Montag, 16. März 2020, 17:00–17:15, ZEU 160

Chemokinesis causes trapping and avoidance by dynamic scattering — •Justus Kromer — Stanford University, Stanford, United States of America

A minimal control strategy for artificial microswimmers with limited information processing capabilities is chemokinesis: the regulation of random directional fluctuations or speed as function of local, non-directional cues. In contrast to chemotaxis, it is not well understood whether chemokinesis is beneficial for the search for hidden targets.

We present a general theory of chemokinetic search agents that regulate directional fluctuations according to distance to a target. We characterize a dynamic scattering effect that reduces the probability to penetrate regions with strong directional fluctuations. If the target is surrounded by such a region, dynamic scattering causes beneficial inward-scattering of agents that had just missed the target, but also disadvantageous outward-scattering of agents approaching the target for the first time. If agents respond instantaneously to positional cues, outward-scattering dominates and chemokinetic agents perform worse than simple ballistic search. Yet, agents with just two internal states can decouple both effects and increase the probability to find the target significantly. Interestingly, these agents violate a mean-chord-length theorem. We apply our analytical theory to the biological example of sperm chemotaxis of marine invertebrates. Sperm cells need to pass a 'noise zone' surrounding the egg, where chemokinesis masks chemotaxis.

Kromer et al. arXiv:1904.11020