Isolated singularities of positive solutions of p-Laplacian type equations in R^d (1008.3873v3)

Abstract: We study the behavior of positive solutions of p-Laplacian type elliptic equations of the form Q'(u) := -p-Laplacian(u) + V |u|^p-2 u = 0 in Omega near an isolated singular point zeta, where 1 < p < inf, Omega is a domain in R^d with d > 1, and zeta = 0 or zeta = inf. We obtain removable singularity theorems for positive solutions near zeta. In particular, using a new three-spheres theorems for certain solutions of the above equation near zeta we prove that if V belongs to a certain Kato class near zeta and p>d (respectively, p<d), then any positive solution u of the equation Q'(u)=0 in a punctured neighborhood of zeta=0 (respectively, zeta=inf) is in fact continuous at zeta. Under further assumptions we find the asymptotic behavior of u near zeta.