Seminar - SCM

Raman Research Institute

Bangalore

Seminar

Title: Non-reciprocal Model B and the role of mobilities and non-reciprocal interfacial forces

Speaker: Bibhut Sahoo (University of Goettingen, Germany)

Date & Time: 16 June 2025 at 2:30 pm

Venue: SCM lecture hall

Abstract: 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-reciprocally interacting particle mixture. We focus on the effect of mobility, the kinetic coefficient 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 early time 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 discontinuous 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 interaction as assumed in theories to date. We show that such interfacial terms can significantly enlarge the travelling spinodal regions in the phase diagram.

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