(1) Department of Mathematics, University of Glasgow, Glasgow, G12 8QW, UK
Abstract:
We show that the concept of a linear operator being u0-positive, and refinements of some classical results of Krasnosel’skiĭ, can be used, in conjunction with the theory of fixed point index, to give some short proofs of existence and nonexistence of positive solutions for nonlinear maps. Dedicated to Felix Browder on the occasion of his 80th birthday