Surfactant renormalization of the square-gradient coefficient
= Surfactant renormalization of the square-gradient coefficient
If a nonconserved surfactant polarization has local energy $\nu|\mathbf p|^2/2+\lambda\mathbf p\cdot\nabla\phi$, eliminating $\mathbf p$ changes the composition-gradient coefficient from $\kappa$ to $\widetilde\kappa=\kappa-\lambda^2/\nu$. This expresses the surfactant's reduction of interfacial energy.