Multiple solutions for nonhomogeneous schrödinger-poisson equations with sign-changing potential

In this article, we study the following nonhomogeneous Schrodinger-Poisson equations {-Δu+λV(x)u+K(x)ϕu=f(x,u)+g(x),x∈R3,-Δϕ=K(x)u2,x∈R3,where λ > 0 is a parameter. Under some suitable assumptions on V, K, f and g, the existence of multiple solutions is proved by using the Ekeland's variational principle and the Mountain Pass Theorem in critical point theory. In particular, the potential V is allowed to be sign-changing.