Berlin 2024 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 32: Poster: Active Matter, Soft Matter, Fluids
DY 32.4: Poster
Wednesday, March 20, 2024, 15:00–18:00, Poster C
Nonreciprocal Model B and the role of nonreciprocal interfacial forces — •Bibhut Sahoo1 and Peter Sollich1,2 — 1Institut für Theoretische Physik, Georg-August-Universität Göttingen, 37077 Göttingen — 2Department of Mathematics, King's College London, London
Recently it has been shown that the Cahn-Hilliard model for phase separation with nonreciprocal interaction can give rise to travelling states. While the Cahn-Hilliard description comes from a magnetic analogy, we explore here the corresponding nonreciprocal model B dynamics as the continuum theory for a particle mixture. We explore the topology of the phase diagram for binary mixtures, determining where spinodal instabilities occur and where these lead to travelling states because the relevant eigenvalues are complex. Simulations show that in addition to pure travelling states, coexistence of stable, equilibrium-like domains with strongly fluctuating patterns in the rest of the system can also occur, a feature that has not been observed in the Cahn-Hilliard setting. We argue further, based on a nonreciprocal version of Dean's equation, that coarse graining into a model B description should generically lead to nonreciprocal forces also at interfaces, rather than only in the bulk as assumed in nonreciprocal field theories to date. We explore the effects of such nonreciprocal interfacial forces and find that they can convert conventional spinodal instabilities into ones producing travelling patterns. This indicates that interfacial nonreciprocity can have important implications for the spinodal dynamics of phase separating mixtures, and potentially also for their long-time dynamics.
Keywords: Phase Separation; Model B; Nonreciprocal interaction; Conserved dynamics; Interfacial effects