We study the semilinear equation Delta u + a(x)u = b(x)u(sigma) (sigma > 1)
on a complete Riemannian manifold. We determine conditions on the coeffici
ents that guarantee existence and nonexistence of positive solutions. A ver
y general uniqueness result is also established. Our main results are valid
without explicit curvature assumptions, and appear to be new even in R-m.
(C) 1998 Academic Press.