Kinetic locking of dissipation in viscous aerosols: a frenesy reading of a reacto-diffusive transition

Plain-language summary. A long-standing idea in physics holds that a driven system settles into whichever state dissipates energy fastest—the state of maximum entropy production. But this rule holds only conditionally. Which state a system actually selects depends on the full statistics of its possible histories, in which a time-symmetric quantity—the "frenesy," or dynamical activity—counts on an equal footing with dissipation. When the activity cost of reaching a high-dissipation state is too large, the system can lock into a low-dissipation state instead, even though a faster channel for dissipation is open and energetically favored. Until now this counterintuitive locking had been demonstrated only in deliberately constructed models.

This paper identifies a real, climate-relevant example: a microscopic organic haze that itself forms in the air through oxidation—secondary organic aerosol—as that same chemistry continues to age it. Depending on humidity and temperature, these particles range from liquid to syrupy to glassy. Oxidation supplies the dissipative drive, but its rate is set by how fast the particle's interior can resupply fresh material to the thin surface layer where the reaction occurs—and that resupply slows to a halt as the particle turns glassy. Using independently measured viscosity data, with nothing fitted to the chemistry, the paper locates a "locking line" in the humidity–temperature plane that separates a chemically active regime from a kinetically frozen one, consistent with where laboratory aerosols are observed to switch from reacting throughout the particle to reacting only at the surface. A minimal solvable model reproduces the same effect and predicts a distinctive fingerprint—hysteresis under humidity cycling—that the conventional smooth picture lacks.

Why it matters. Secondary organic aerosol is among the most abundant fine particulate matter in the atmosphere—it scatters sunlight, seeds cloud droplets, and stores reactive organic carbon—so the rate at which it ages bears on climate-relevant properties and on how long it persists in the air. Many atmospheric and climate models assume aerosols remain in instantaneous gas–particle equilibrium, an assumption already known to fail. This work reframes that failure as a kinetic-locking effect and supplies falsifiable orderings—in oxidant, particle size, and temperature—that mark where such diffusion limitation must be retained. The contribution is conceptual and diagnostic: a unified, testable account of when aerosol aging is kinetically locked, and a concrete physical instance of a universal obstruction to maximum entropy production—not a new parameterization or a quantitative climate forecast.