Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 52: Poster: Active Matter, Microswimmer, Microfluidics

DY 52.2: Poster

Thursday, April 4, 2019, 15:00–18:00, Poster B2

Motion of fronts and clusters in an active Allen-Cahn model — •Fenna Stegemerten and Uwe Thiele — Institute of Theoretical Physics Westfälische Wilhelms-Universität Münster

Active matter is composed of many particles which are able to transform different types of energy into motion. This may result in motility-induced clustering or directed collective motion. Such phenomena are observable for swarming in fauna as well as for artifical microswimmers. The collective structures may consist of disordered or well ordered arrangements and are referred to as active clusters and active crystals, respectively. In order to understand aspects of the behaviour of active clusters we employ a rather simple model for active matter, namely, the active Allen-Cahn (aAC) equation: The passive Allen-Cahn equation is coupled to a polarization field similar to the active phase field model (aPFC) in [1]. We then study occurring clusters and the motion of fronts in aAC. In particular, we provide bifurcation diagrams and show that the onset of motion occurring with increasing activity corresponds to a drift-ptichfork bifurcation similar to the case of aPCF [2]. Additionally, we we find that motion is not only controlled by the activity parameter but is also affected by the chemical potential. We track the drift-pitchfork bifurcation in the corresponding parameter space. Finally, we show that depending on the chemical potential the passive AC equation generates pulled and pushed fronts and discus their existence in the active case. [1] A. M. Menzel and H. Löwen Phys. Rev. Lett. (2013) [2] L. Ophaus, et al. Phys. Rev. E (2018)