On a singular sublinear polyharmonic problem

This paper deals with a class of singular nonlinear polyharmonic equations on the unit ball B in R-n (n >= 2) where the combined effects of a singular and a sublinear term allow us by using the Schauder fixed point theorem to establish an existence result for the following problem: (-Delta)(m)u = phi(center dot, u) + psi(center dot, u) in B (in the sense of distributions), u > 0, lim(|x|-> 1) u(x)/(1-|x|)(m-1) = 0. Our approach is based on estimates for the polyharmonic Green function on B with zero Dirichlet boundary conditions.