Dresden 2026 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 49: Active Matter V (joint session DY/BP)

DY 49.1: Invited Talk

Thursday, March 12, 2026, 09:30–10:00, ZEU/0160

Active memory and non-reciprocity as pathways to pattern formation in conserved scalar fields — •Suropriya Saha and Vaishnavi Gajendragad — Max Planck Institute for Dynamics and Self-organisation

Active phase separation has emerged as a field within active matter that investigates pattern formation in number-conserving scalar fields. The field has also gained momentum from developments in biological systems, where phase separation has been implicated in the formation of biological condensates. In this talk, I will explore two different paths to non-Hermiticity in number-conserving scalar fields. Non-Hermiticity, or the emergence of complex eigenvalues in the linear dynamics of scalar densities, is associated with traveling patterns that break time-reversal symmetry and parity.

The first pathway I will discuss is a feedback mechanism in which particles store and use information about their past trajectories to influence their time evolution. I will present a model in which the particle velocity acquires an active contribution that depends on its past trajectory, weighted by a memory kernel. This memory kernel is independent of the thermal noise acting on the particle, implying a microscopic violation of detailed balance. The number density of these particles is described by a modified Cahn*Hilliard equation that incorporates this non-equilibrium effect. The second pathway involves non-reciprocal interactions between two or more species. I will describe the phenomenology observed in both cases, focusing on the role of fluctuations, nonlinearities, and the stability of the resulting patterns.

Keywords: Active matter; Phase separation; Memory, Nonreciprocity; Spinodal decomposition