Active phase separation from concentration-dependent diffusion in chemical networks

Giulia Pisegna; Ramin Golestanian

Home/Archive/arXiv

arXiv · 2610.30958

Active phase separation from concentration-dependent diffusion in chemical networks

Giulia Pisegna·Ramin Golestanian

View original source ↗Read source document ↗Export metadata ↓

Abstract

Active phase separation in living systems is ubiquitous, yet the microscopic origins of the non-equilibrium terms in active field theories remain largely unknown. Here, starting from stochastic mass-conserving reaction-diffusion dynamics of two interacting chemical species, we perform a systematic slow-mode reduction and derive the complete Active Model B+ field theory, with all phenomenological coefficients expressed in terms of microscopic parameters. We identify concentration-dependent diffusivities and asymmetric inter-species chemotactic couplings as the minimal microscopic ingredients generating the genuinely non-equilibrium coefficient responsible for microphase separation, cluster phases, and arrested coarsening. Our framework recovers the equilibrium limit consistently and is validated by stochastic numerical simulations. These results establish a direct, bottom-up link between the architecture of chemical reaction networks and the universality class of their emergent large-scale dynamics.

Explore related subjects

cond-mat.stat-mech cond-mat.soft

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Giulia Pisegna, Ramin Golestanian. 2026-10-22. Active phase separation from concentration-dependent diffusion in chemical networks. https://arxiv.org/abs/2610.30958

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Universal winding laws in chiral active motion

Chiral active particles, from bacteria and sperm cells to engineered microswimmers, undergo persistent motion that breaks both time-reversal and mirror symmetries. This broken mirror symmetry leaves geometric signatures in trajectories that cannot be captured by conventional measures like position fluctuations. Here we identify the signed area and winding angle as key observables to characterize the geometric and topological aspects of the trajectories of chiral active particles. Combining theory, experiment, and computer simulations, we demonstrate that these observables exhibit universal growth laws and fluctuation statistics that are independent of propulsion details. The presence of chirality generates multiple off-centred closed loops in the trajectories, resulting in a linear temporal growth of the signed area and a much slower logarithmic growth for the winding angle. Our work uncovers universal trajectory-level signatures of chirality and provides a unifying description of chiral dynamics in active matter.

cond-mat.stat-mech↗

arXiv2026

Accelerating stochastic processes through nonequilibrium driving: Thermodynamic constraints on the maximum speed-up

We derive a new set of bounds controlling the speed-up of the survival rate of trajectory-dependent observables induced by the application of a perturbation. Via the study of survival probabilities in two different contexts, continuous-time Markov jump processes and overdamped diffusions, we obtain different fashions of the bound on the achievable boost. These bounds, obtained by a nonlinear response theory of constrained path probabilities, are explicitly linked to thermodynamics. For arbitrary time-dependent survival rates, we find a linear bound that depends on both the perturbation strength and the entropy production rate prior to the perturbation. For rare processes characterized by a constant survival rate, the bound is exponential and is determined by the excess heat generated by the perturbation. We exemplify the inequalities on two prototypical model systems, namely, a unicyclic network and forced diffusion in a bistable potential.

cond-mat.stat-mech↗

arXiv2026

Origins of Faceted Anomalous Scaling

Fluctuating interfaces are typically characterized by their global, spectral, and local roughness exponents. Faceted anomalous scaling, characterized by $α_s>1$, $α_s\neqα$, and $α_{\mathrm{loc}}=1$, owes its name to the tendency of such interfaces to develop long, nearly linear segments called facets. Its statistical origin, and whether facets are required, have remained unclear. We show that this exponent structure is determined by the spatial statistics of the slope field. Slope increments split into typical fluctuations and rare, larger jumps. This anomalous scaling arises either when the typical slope increment displays genuine system-size-dependent anomalous scaling or when the rare jumps dominate the second moment. The two contributions can coexist, and their competition leads to bifractal scaling of the slopes. We establish this framework analytically in the generalized anharmonic Larkin model and the columnar Kardar--Parisi--Zhang equation, and we derive exactly the global, spectral, and local roughness exponents in both cases. The Larkin model realizes both mechanisms and produces anomalous interfaces with or without facets, whereas columnar KPZ belongs to the jump-dominated case and yields $α_s=3/2$.

cond-mat.stat-mech↗