Three positive radial solutions for elliptic equations in a ball

In this work we deal with a class of second-order elliptic problems of the form −Δu=λk(|x|)f(u) in Ω, with non-homogeneous boundary condition u=a on ∂Ω where Ω is the ball of radius R0 centered at origin, λ,a are positive parameters, f∈C([0,+∞),[0,+∞)) is an increasing function and k∈C([0,R0],[0,+∞)) is not identically zero on any subinterval of [0,R0]. We obtain via a fixed point theorem of cone expansion/compression type the existence of at least three positive radial solutions.