Dresden 2020 – scientific programme
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BP: Fachverband Biologische Physik
BP 24: Active Matter IV (joint session DY/BP/CPP)
BP 24.4: Talk
Wednesday, March 18, 2020, 10:45–11:00, ZEU 160
Statistical mechanical sum rules for active colloids at surfaces - a touch of equilibrium — •René Wittmann1,2, Frank Smallenburg3, and Joseph Brader2 — 1Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Germany — 2Soft Matter Theory, Université de Fribourg, Switzerland — 3Laboratoire de Physique des Solides, Université Paris Sud, France
We study the mechanical properties of active particles in the presence of curved walls by computer simulation of Active Brownian Particles (ABPs), Active Ornstein-Uhlenbeck Particles (AOUPs) and a passive system with effective interactions [R. Wittmann, F. Smallenburg and J. M. Brader, J. Chem. Phys. 150, 174908 (2019)]. The effective theory admits analytic results for pressure, surface tension and adsorption of an active ideal gas at a two-dimensional circular wall. It further predicts that an equilibrium sum rule also holds for active fluids, which we confirm numerically for both ABPs and AOUPs in the limit of small curvature.
More precisely, we find within each model that the slope of the pressure as a function of the curvature equals the surface tension and adsorption (up to an effective temperature scale) on a planar wall. Intriguingly, the explicit value of these coefficients is model-dependent, which can be explained by the different velocity distributions. We also discuss the influence of interactions and find that the effect of curvature on the wall pressure is reduced when increasing the density. Within numerical accuracy, the equality of the slope of the pressure and the planar surface tension appears to hold at finite density.