Abstract
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 |∇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-Ampère 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.
Acknowledgements
The authors thank the anonymous referees for their valuable suggestions to improve clarity in several points. The second author was supported by the strategic grant POSDRU/88/1.5/S/49516 Project ID 49516 (2009), co-financed by the European Social Fund Investing in People, within the Sectorial Operational Programme Human Resources Development 2007–2013.