Stable $(r+1)$-th capillary hypersurfaces
Jinyu Guo, Haizhong Li, Chao Xia
TL;DR
The paper develops a variational framework for higher-order capillary hypersurfaces by introducing the $(r+1)$-th energy functional $\mathcal{E}_{r+1}$ and restricting to volume-preserving and angle-preserving variations. It derives the first and second variation formulas, establishing a stability notion on a constrained function space and expressing the second variation via the Jacobi-type operator $L_r$ and Newton tensors $P_r$. Central to the results are higher-order Minkowski-type formulas in both Euclidean half-spaces and hyperbolic horoballs, which yield admissible test functions and enable rigidity classifications. Consequently, stable $(r+1)$-th capillary hypersurfaces in the Euclidean half-space are spherical caps, while in hyperbolic space the stability analysis on horospheres implies total umbilicity (not totally geodesic under elliptic-point assumptions), extending classical capillary stability to higher order with precise geometric-analytic tools.
Abstract
In this paper, we propose a new definition of stable $(r+1)$-th capillary hypersurfaces from variational perspective for any $1\leq r\leq n-1$. More precisely, we define stable $(r+1)$-th capillary hypersurfaces to be smooth local minimizers of a new energy functional under volume-preserving and contact angle-preserving variations. Using the new concept of the stable $(r+1)$-th capillary hypersurfaces, we generalize the stability results of Souam \cite{Souam} in a Euclidean half-space and Guo-Wang-Xia \cite{GWX} in a horoball in hyperbolic space for capillary hypersurface to $(r+1)$-th capillary hypersurface case.
