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DY: Fachverband Dynamik und Statistische Physik

DY 53: Posters - Active Matter

DY 53.2: Poster

Donnerstag, 23. März 2017, 17:00–19:30, P1A

Bifurcations in a Model for Active Crystals: The Onset of Motion — •Lukas Ophaus, Svetlana Gurevich, and Uwe Thiele — Institut für Theoretische Physik, WWU, Münster, Germany

The conserved Swift-Hohenberg equation (or Phase-Field-Crystal [PFC] model) provides a simple microscopic description of the thermodynamic transition from a fluid to a crystalline state [1]. The model can be combined with the Toner-Tu theory for self-propelled particles to obtain a model for crystallization (swarm formation) in active systems [2]. Within the resulting active PFC model, resting and traveling crystals can be identified. Above a critical value of activity, crystals migrate with a well-defined velocity while keeping their spatial periodicity.

Like the passive PFC model [3], the active version describes a variety of localized clusters besides spatially extended crystals. We use a 1d model to explore how the bifurcation structure (slanted homoclinic snaking of localized states) is amended by activity. Numerical continuation is applied to follow resting and traveling localized states while varying the activity and mean concentration. In addition, we provide a general analytical criterion for the onset of motion in the nonlinear regime, that corresponds to a drift pitchfork bifurcation.

[1] M.J. Robbins et al., Phys Rev E 85, 061408 (2012)

[2] A.M. Menzel and H. Löwen, Phys. Rev. Lett. 110, 055702 (2013)

[3] U. Thiele et al., Phys Rev E 87, 042915 (2013)