2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/143601We consider the Neumann problem in $C^2$ bounded domains for fully nonlinear second order operators which are elliptic, homogenous with lower order terms. Inspired by \cite{bnv}, we define the concept of principal eigenvalue and we characterize it through the maximum principle. Moreover, Lipschitz regularity, uniqueness and existence results for solutions of the Neumann problem are given.Analysis of PDEstext