A maximum principle for some fully nonlinear elliptic equations with applications to Weingarten hypersurfaces

In this article, we investigate a general class of fully nonlinear elliptic equations, including Weingarten equations. Our first aim is to construct a general elliptic inequality for an appropriate functional combination of u(x) and |delta u(x)|, i.e. a kind of P-function P(x), in the sense of L.E. Payne (see the book of Sperb [Sperb, Maximum Principles and Their Applications, Academic Press, New York, 1981]), where u(x) is a given solution of our class of fully nonlinear equations. From this inequality, making use of Hopf's first maximum principle, we derive a maximum principle for P(x), which extend some similar results obtained by Philippin and Safoui [Philippin and Safoui, Some maximum principles and symmetry results for a class of boundary value problems involving the Monge-Ampere equation, Math. Models Methods Appl. Sci. 11 (2001), pp. 1073-1080; Philippin and Safoui, Some applications of the maximum principle to a variety of fully nonlinear elliptic PDE's, Z. Angew. Math. Phys. 54 (2003), pp. 739-755], Porru et al. [Porru, Safoui and Vernier-Piro, Best possible maximum principles for fully nonlinear elliptic partial differential equations, Zeit. Anal. Anwend. 25 (2006), pp. 421-434] and Enache [Enache, Maximum principles and symmetry results for a class of fully nonlinear elliptic PDEs, Nonlinear Differ. Eqns Appl. 17 (2010), pp. 591-600]. This maximum principle is then used to obtain various a priori estimates with applications to some class of Weingarten hypersurfaces.