Defect interactions in the non-reciprocal Cahn-Hilliard model

TL;DR

This study computationally investigates defect interactions in a non-reciprocal Cahn-Hilliard model, revealing how defect behavior depends on charges, initial conditions, and non-reciprocity strength, with implications for active matter systems.

Contribution

It provides the first detailed analysis of defect interactions in a non-reciprocal Cahn-Hilliard model, highlighting the effects of non-reciprocity on defect stability and dynamics.

Findings

Defect interactions depend on charges, initial separation, and non-reciprocity parameter.

Oppositely charged defects merge into a single target at close proximity.

High non-reciprocity leads to formation of rotating bound pairs and complex defect behaviors.

Abstract

We present a computational study of the pairwise interactions between defects in the recently introduced non-reciprocal Cahn-Hilliard model. The evolution of a defect pair exhibits dependence upon their corresponding topological charges, initial separation, and the non-reciprocity coupling constant $\alpha$. We find that the stability of isolated topologically neutral targets significantly affects the pairwise defect interactions. At large separations, defect interactions are negligible and a defect pair is stable. When positioned in relatively close proximity, a pair of oppositely charged spirals or targets merge to form a single target. At low $\alpha$, like-charged spirals form rotating bound pairs, which are however torn apart by spontaneously formed targets at high $\alpha$. Similar preference for charged or neutral solutions is also seen for a spiral target pair where the spiral dominates at low $\alpha$, but concedes to the target at large $\alpha$. Our work sheds light on the complex phenomenology of non-reciprocal active matter systems when their collective dynamics involves topological defects.