Cuoghi, PaolaSalani, Paolo2021-07-202021-07-202006-10-11Cuoghi, P., & Salani, P. (2006). Convexity of level sets for solutions to nonlinear elliptic problems in convex rings. <i>Electronic Journal of Differential Equations, 2006</i>(124), pp. 1-12.1072-6691https://hdl.handle.net/10877/13997We find suitable assumptions for the quasi-concave envelope u* of a solution (or a subsolution) u of an elliptic equation F(x, u, ∇u, D2u) = 0 (possibly fully nonlinear) to be a viscosity subsolution of the same equation. We apply this result to study the convexity of level sets of solutions to elliptic Dirichlet problems in a convex ring Ω = Ω0 \ Ω‾1.Text12 pages1 file (.pdf)enAttribution 4.0 InternationalElliptic equationsConvexity of level setsQuasi-concave envelopeArticle