Abstract

We consider semistable, radially symmetric and increasing solutions of Sk(D2u) = g(u) in the unit ball of Rn, where Sk(D2u) is the k-Hessian operator of u and g ϵ C1is a general positive nonlinearity. We establish sharp pointwise estimates for such solutions in a proper weighted Sobolev space, which are optimal and do not depend on the specific nonlinearity g. As an application of these results, we obtain pointwise estimates for the extremal solution and its derivatives (up to order three) of the equation Sk(D2u) = γg(u), posed in B1, with Dirichlet data u|B1 = 0, where g is a continuous, positive, nonincreasing function such that limt→-∞ g(t)/ |t|k= +∞.