Thin-film limit of the parabolic $p$-Laplace equation in a moving thin domain
Tatsu-Hiko Miura
TL;DR
The paper proves a rigorous thin-film limit for the parabolic $p$-Laplace equation in moving thin domains when $p>2$, showing that the weighted normal average of the solution converges to a pair $(v, zeta)$ on the moving surface that solves a nonlinear diffusion system coupled to an algebraic constraint. The limit problem on the moving hypersurface consists of a nonlinear tangential diffusion term with flux $w=|_{v, zeta}|^{p-2}_{v, zeta}$ and a normal-velocity constraint that yields a local mass conservation law on $igl\Gamma_tigr)$ through $ zeta$, the normal component of the flux. The analysis extends prior linear ($p=2$) thin-film results to the nonlinear regime, employing the evolving Bochner-space framework, a weighted-thin-direction average, and a careful characterization of the limit flux to overcome the nonlinearity and moving-domain geometry. The findings provide a rigorous reduction of dimension that preserves mass balance on moving surfaces and offer a foundation for approximating nonlinear diffusion on evolving manifolds in thin-geometry settings.
Abstract
We consider the parabolic $p$-Laplace equation with $p>2$ in a moving thin domain under a Neumann type boundary condition corresponding to the total mass conservation. When the moving thin domain shrinks to a given closed moving hypersurface as its thickness tends to zero, we rigorously derive a limit problem by showing the weak convergence of the weighted average of a weak solution to the thin-domain problem and characterizing the limit function as a unique weak solution to the limit problem. The limit problem obtained in this paper is a system of a nonlinear partial differential equation and an algebraic equation on the moving hypersurface. This seems to be somewhat strange, but we also find that the limit problem can be seen as a new kind of local mass conservation law on the moving hypersurface with a normal flux.
