A half-space Liouville theorem for anisotropic minimal graph with free boundary
Guofang Wang, Wei Wei, Chao Xia, Xuwen Zhang
TL;DR
The paper proves a half-space Liouville-type theorem for anisotropic minimal graphs with free boundary: any $C^2$ solution $u$ to the anisotropic minimal surface equation in $\mathbb{R}^n_+$ with free boundary, whose negative part has at most linear growth, must be affine. The authors develop an integral-analytic approach based on the graphical area element $W_f$ and its anisotropic gradient, establishing a boundary-tangency identity that cancels boundary terms, a mean-value inequality for $\log W_f$, and a robust gradient bound via Sobolev inequalities and De Giorgi–Nash–Moser iteration. This gradient estimate holds in full generality for any uniformly elliptic integrand $F$ and all dimensions, enabling the affine rigidity conclusion. Moreover, the method extends to anisotropic capillary graphs in the half-space, removing angle restrictions present in prior works and highlighting the sharp linear-growth condition through known counterexamples.
Abstract
In this paper we prove the following Liouville-type theorem: any anisotropic minimal graph with free boundary in the half-space must be flat, provided that the graph function has at most one-sided linear growth. This extends the classical results of Bombieri-De Giorgi-Miranda and Simon to an appropriate free boundary setting.
