Regensburg 2025 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 23: Poster: Active Matter, Soft Matter, Fluids (joint session DY/CPP)

DY 23.11: Poster

Wednesday, March 19, 2025, 10:00–12:00, P3

Pumping currents and formation of flocks in 1D Ising model — •Adrian Morais Cabral and Achim Rosch — Institute for Theoretical Physics, University of Cologne, Germany

Non equilibrium systems create phenomena that are not observed in equilibrium counterparts, such as long range order in two or less dimensions and breaking of detailed balance.

We use an effective description of coupled Langevin equations to study a 1D system where an Ising order parameter is coupled to a charge density. Our assumption is that the charge current has a contribution proportional to the order parameter for the driven system. The formation of domain walls leads to a source of dynamical frustration for the charge. Driving disallows the formation of domain walls and creates flocking blob like states in addition to constant ordered and disordered states and a non moving spike phase. These solutions are studied numerically in 1D for T≥0.

At T=0, we characterize existing flocking solutions and compare analytical predictions to numerical simulations which agree well with only one fitting parameter.

At finite temperatures we find new dynamics for the flocking state such as reversals similar to the active Ising model and (quasi) crossings. However, we have not yet been able to answer whether the existing ordered phase is stable in 1D.

Keywords: flocking; active Ising; numerical simulations