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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 63: Active Matter IV (joint session DY/BP/CPP)
CPP 63.7: Talk
Wednesday, March 18, 2020, 11:45–12:00, ZEU 160
Continuum model for bacterial suspensions with density variations — •Vasco Marius Worlitzer1, Avraham Be'er2, Gil Ariel3, Markus Bär1, Holger Stark4, and Sebastian Heidenreich1 — 1Physikalisch-Technische Bundesanstalt — 2Ben-Gurion University — 3Bar-Ilan University — 4Technical University of Berlin
The various dynamical states found in bacterial suspensions are a fascinating illustration of the rich dynamics exhibited by active polar fluids. A recent study explored the phase space experimentally, identifying three major states: single-cell motion, collective swarming, biofilm formation and mixtures between them [1]. While a continuum model presented in [2] has been proven to describe the statistical features of the swarming phase quite successfully, it is not applicable outside this regime as a constant density is assumed. We show that new dynamical states are accessible by relaxing this assumption. In particular a regime similar to the mixed state of swarming and biofilm formation is covered, showing the same anomalous statistics as found experimentally. The new model is inspired by work on scalar active matter [3] and consist of a generic continuity equation for the density. The density is coupled to a local polar order parameter through a density dependent self-propulsion speed and an active pressure.
[1] H Jeckel et al., PNAS 116 (5) (2019) [2] J Dunkel et al., Phys. Rev. Lett. 110 (2013) 228102. [3] J Bialké et al., EPL 103 (2013) 30008.