Multi-component phase separation and small deformations of a spherical biomembrane

TL;DR

This paper develops a mathematical model for multi-component phase separation on biological membranes, incorporating membrane curvature and small deformations, and proves well-posedness and convergence of solutions.

Contribution

It introduces a coupled energy functional for membrane composition and curvature, deriving a multi-component Cahn-Hilliard model with small deformation analysis.

Findings

Proves global well-posedness of the model in a weak setting.

Shows solutions regularize and satisfy strict separation in finite time.

Demonstrates convergence to stationary states using Lojasiewicz-Simon inequality.

Abstract

We focus on the derivation and analysis of a model for multi-component phase separation occurring on biological membranes, inspired by observations of lipid raft formation. The model integrates local membrane composition with local membrane curvature, describing the membrane's geometry through a perturbation method represented as a graph over an undeformed Helfrich minimising surface, such as a sphere. The resulting energy consists of a small deformation functional coupled to a Cahn-Hilliard functional. By applying Onsager's variational principle, we obtain a multi-component Cahn-Hilliard equation for the vector $\boldsymbol\varphi$ of protein concentrations coupled to an evolution equation for the small deformation $u$ along the normal direction to the reference membrane. Then, in the case of a constant mobility matrix, we consider the Cauchy problem and we prove that it is (globally) well posed in a weak setting. We also demonstrate that any weak solution regularises in finite time and satisfies the so-called "strict separation property". This property allows usto show that any weak solution converges to a single stationary state by a suitable version of the Lojasiewicz-Simon inequality.