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arXiv · 2511.18947

Conservation laws and slow dynamics determine the universality class of interfaces in active matter

Raphaël Maire·Andrea Plati·Frank Smallenburg·Giuseppe Foffi
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Abstract

While equilibrium interfaces display universal large-scale statistics, interfaces in phase-separated active and driven systems are predicted to belong to distinct non-equilibrium universality classes. Yet, such behavior has proven difficult to observe, with most systems exhibiting equilibrium-like fluctuations despite their strongly non-equilibrium microscopic dynamics. We introduce a hard-disk model driven by active collisions, conceived as an effective 2D description of a vibrofluidized granular system that, contrary to self-propelled models, displays clear non-equilibrium interfacial scaling. We observe for the first time, the $|\boldsymbol q|$KPZ and wet-$|\boldsymbol q|$KPZ universality classes while revealing a new, previously overlooked universality class arising in systems with slow solid-like or glassy dynamics. Conservation laws and slow dynamics select these distinct classes.

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Raphaël Maire, Andrea Plati, Frank Smallenburg, Giuseppe Foffi. 2025-11-24. Conservation laws and slow dynamics determine the universality class of interfaces in active matter. https://doi.org/10.1103/b7s9-4l4q

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