On a certain nonlinear problem for two-dimensional differential systems
The Leray-Schauder degree theory is used to obtain sufficient conditions for the existence and uniqueness of solutions for the boundary value problem x'' = f(t,x,x',x'',λ), α(x) = 0, β(x̅) = 0, γ(x̿)=0, depending on the parameter λ. Here α, β, γ are linear bounded functionals defined on the Banach space of C⁰-functions on [0,1] and x̅(t) = x(0) - x(t), x̿(t)=x(1)-x(t).
We investigate the existence of positive solutions for a nonlinear second-order differential system subject to some -point boundary conditions. The nonexistence of positive solutions is also studied.