zbMATH — the first resource for mathematics

An angle’s maximum principle for the gradient of solutions of elliptic equations. (English) Zbl 0628.35034
It is shown that the angle between the gradient of the solutions to certain nonlinear second-order elliptic equations and a given direction in space satisfies another elliptic equation and a strong maximum principle. This result, as well as its proof, is related to recent results concerning the geometric properties of the level sets of these solutions.
Reviewer: Simeon Reich

35J60 Nonlinear elliptic equations
35B50 Maximum principles in context of PDEs
35A30 Geometric theory, characteristics, transformations in context of PDEs