Boundary singularities for weak solutions of semilinear elliptic problems

Abstract

Let Omega be a bounded domain in R-N, N >= 2, with smooth boundary partial derivative Omega. We construct positive weak solutions of the problem Delta u + u(p) = 0 in Omega, which vanish in a suitable trace sense on partial derivative Omega, but which are singular at prescribed isolated points if p is equal or slightly above N+1/N-1. Similar constructions are carried out for solutions which are singular at any given embedded submanifold of partial derivative Omega of dimension k epsilon [0, N -2], if p equals or it is slightly above N-k-1/N-k-1, and even on countable families of these objects, dense on a given closed set. The role of the exponent N+1/N-1 (first discovered by Brezis and Turner [H. Brezis, R. Turner, N-1 On a class of superlinear elliptic problems, Comm. Partial Differential Equations 2 (1977) 601-614]) for boundary regularity, parallels that of N/N-2 for interior singularities. (c) 2007 Elsevier Inc. All rights reserved.