Dresden 2020 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 15: Active Matter III (joint session DY/BP/CPP)

BP 15.5: Vortrag

Dienstag, 17. März 2020, 15:00–15:15, ZEU 160

Nonuniversality in scalar active matter with diffusivity edge under periodic confinement — •Benoît Mahault1 and Ramin Golestanian1,21Max Planck Institute for Dynamics and Self-Organization, Germany — 2University of Oxford, United Kingdom

Scalar active matter is often described at the mean field level by nonlinear Fokker-Planck equations with density-dependent diffusion coefficients integrating fast degrees of freedom, as well as various equilibrium and/or nonequilibrium processes. A generic class, characterized by a diffusivity vanishing above some threshold density, was recently introduced [Golestanian, Phys. Rev. E 100, 010601(R)]. In presence of harmonic confinement, such `diffusivity edge' was shown to lead to condensation in the ground state, with the associated transition exhibiting formal similarities with Bose-Einstein condensation (BEC).

Many active systems, such as self-propelled Janus particles, can however self-assemble into finite-size coexisting clusters. To account for such feature in the diffusivity edge framework, a periodic egg-crate confinement, that provides multiple sites for condensation, is considered in arbitrary dimensions. While for high barriers separating two minima the system essentially behaves as in the single harmonic trap case, for shallow potentials the transition is qualitatively different as the exponent associated to the scaling of the condensate fraction with an effective temperature is found to be nonuniversal. We nevertheless show from a generalized thermodynamic description that the overall phenomenology of BEC, such as the divergence of the isothermal compressibility at the transition, holds in both cases.

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