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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 25: Poster: Active Matter, Soft Matter, Fluids (joint session DY/CPP)
CPP 25.2: Poster
Mittwoch, 19. März 2025, 10:00–12:00, P3
Non-reciprocal Model B and the role of mobilities and non-reciprocal 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 the effects of non-reciprocal interactions have been widely studied in the Cahn-Hilliard model for phase separation, which is based on a magnetic analogy. Here we explore the corresponding nonreciprocal model B, as the continuum theory for non-reciprocal particle mixture. We focus on the effect of mobility matrix on topology of the phase diagram and find that changing mobility can change stability of a homogeneous state, which for reciprocal interactions would be impossible. We study spinodal dynamics in regions of instability, where static or travelling spinodal patterns can occur. This aspect is as in non-reciprocal Cahn-Hilliard but, the transitions between these instabilities are novel: they occur not via exceptional points, but via first order transitions in the length scale of the dominant unstable modes. At transition, a static and a travelling spinodal pattern with two different scales coexist. We show that more complicated transitions involving coexistence of three length scales can also occur. We finally argue, based on a nonreciprocal version of Dean's equation, that coarse graining into a model B description should lead to non-reciprocal interface terms, rather than only in the bulk as assumed in theories to date. We show that such interfacial terms can significantly enlarge the travelling spinodal regions in the phase diagram.
Keywords: Phase Separation; Conserved Dynamics; Nonreciprocal interaction; Kinetic Effects; Phase Transitions