The Neumann problem for a class of Hessian quotient type equations
Jiabao Gong, Zixuan Liu, Qiang Tu
TL;DR
This work addresses the Neumann problem for a Hessian quotient type equation in a Euclidean domain, where the right-hand side depends on $(x,u,Du)$. The authors derive interior gradient estimates under a growth condition, then establish global gradient and second-order estimates by reducing the problem to boundary double normal derivatives and performing a meticulous boundary analysis. The combination of these a priori estimates with Evans–Krylov theory and the method of continuity yields existence and uniqueness of a $(\Lambda,k)$-convex solution in $C^{2,\alpha}(\overline{\Omega})$ to the Neumann problem, along with corollaries for specific right-hand side forms. Overall, the paper extends the Neumann theory for Hessian quotient equations, providing a robust framework for interior and boundary regularity and a priori control in this nonlinear setting.
Abstract
In this paper, we consider the Neumann problem for a class of Hessian quotient equations involving a gradient term on the right-hand side in Euclidean space. More precisely, we derive the interior gradient estimates for the $(Λ, k)$-convex solution of Hessian quotient equation $\frac{σ_k(Λ(D^2 u))}{σ_l(Λ(D^2 u))}=ψ(x,u,D u)$ with $0\leq l<k\leq C^{p-1}_{n-1}$ under the assumption of the growth condition. As an application, we obtain the global a priori estimates and the existence theorem for the Neumann problem of this Hessian quotient type equation.
