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BP: Fachverband Biologische Physik
BP 17: Statistical Physics of Biological Systems I (joint session DY/BP)
BP 17.1: Vortrag
Mittwoch, 11. März 2026, 09:30–09:45, ZEU/0114
Metastability in the mixing/demixing of two species with reciprocally concentration-dependent diffusivity — •Benjamin Lindner1,2, Alexander B. Neiman3,4, and Xiaochen Dong2 — 1Department of Physics, Humboldt University Berlin, Berlin, Germany — 2Bernstein Center for Computational Neuroscience Berlin — 3Department of Physics and Astronomy, Ohio University, Athens, OH, United States — 4Neuroscience Program, Ohio University, Athens, OH, United States
It is known that two species of diffusing particles can separate from each other by a reciprocally concentration-dependent diffusivity: the presence of one species at a certain location amplifies the diffusion coefficient of the respective other one in this location, causing the two densities of particles to separate spontaneously. In a minimal model, Schimansky-Geier et al. (2021) observed this with a quadratic dependence of the diffusion coefficient on the density of the other species. Here, we consider a sigmoidal dependence in the form of a logistic function on the other particle’s density averaged over a finite sensing radius. The sigmoidal dependence leads to a new regime in which a homogeneous disordered (well-mixed) state and a spontaneously separated ordered (demixed) state coexist, forming two long-lived metastable configurations. In systems with a finite number of particles, random fluctuations induce repeated transitions between these two states. By tracking an order parameter that distinguishes mixed from demixed phases, we measure the corresponding mean residence in each state.
Keywords: particle separation; active motion; Brownian particles; reciprocally concentration-dependent diffusivity; Metastability of order and disorder