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arXiv · 2605.15903

Active Model B$^-$ from Mass-Conserving Reaction-Diffusion Systems

Davide Toffenetti·Beatrice Nettuno·Henrik Weyer·Erwin Frey
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Abstract

We show that the late-time dynamics of a minimal three-component mass-conserving reaction--diffusion system reduce to a scalar active field theory, Active Model B$^-$ (AMB$^-$), in which a density-dependent interfacial coefficient $\kappa(\phi)$ turns negative at high density. This drives a finite-wavelength instability and stabilises microphase-separated patterns, in contrast to the unbounded coarsening of two-component mass-conserving systems. Unlike Active Model B$^+$, AMB$^-$ retains a chemical potential that remains a state function, inherited from the underlying conservation law, but admits no equation of state for the pressure.

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Davide Toffenetti, Beatrice Nettuno, Henrik Weyer, Erwin Frey. 2026-05-15. Active Model B$^-$ from Mass-Conserving Reaction-Diffusion Systems. https://arxiv.org/abs/2605.15903

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