Freezing lakes as analogue models of $\Lambda$CDM cosmology and beyond

TL;DR

This paper develops an analogy between ice growth in lakes with buoyancy-driven heat transport and cosmological expansion, deriving equations that mimic Friedmann equations and introduce effective cosmological constants and exotic matter components.

Contribution

It extends previous conduction-based analogies by incorporating convection, resulting in a more comprehensive model that reproduces various cosmological behaviors and introduces novel effective terms.

Findings

Derived an evolution equation for ice thickness analogous to Friedmann equations.

Identified a constant term analogous to a cosmological constant from buoyancy-driven transport.

Introduced a negative energy density component with w=-2/3, resembling exotic matter or domain walls.

Abstract

We extend previous conduction-based analogies between ice growth in a lake and cosmological expansion by incorporating buoyancy-driven heat transport. Reformulating the Stefan problem with both conductive and convective fluxes yields an evolution equation for the ice thickness $s(t)$ that is structurally analogous to the Friedmann equations for the cosmological scale factor $a(t)$. Beyond reproducing radiation-, matter-, and curvature-like behaviors, we introduce a reduced description of convection in which the vertically integrated heat flux reaching the moving ice-water interface is modeled as a power-law function of the instantaneous liquid-layer thickness, generating two additional effective contributions. The first is a constant term, directly analogous to a cosmological constant, arising from the persistence of buoyancy-driven transport under geometric confinement. The second is a $s^{-1}$ contribution originating from the coupling between the moving ice boundary and the convective boundary layer. This term reflects the specific reduced flux-height Ansatz adopted, rather than a universal physical prediction. When expressed in Friedmann-like cosmological form, this term entails a fluid with negative energy density and equation-of-state parameter $w=-2/3$. In cosmology this term may be an effective one associated to a network of domain walls made of exotic energy/matter, but it might also arise from an energy exchange between cosmological components. Overall, the results should be interpreted as a structural analogy between evolution equations, showing how nonlinear transport mechanisms in a classical moving-boundary problem can reproduce the hierarchy of scaling terms familiar from cosmology within a reduced and analytically tractable framework.