Infinitely many solutions for fourth-order elliptic equations with general potentials

This paper is concerned with the following fourth-order elliptic equations { Δ 2 u − Δ u + V ( x ) u = f ( x , u ) in  R N , u ∈ H 2 ( R N ) , where u : R N → R . Under general assumption on potential V ( x ) , and f ( x , u ) is indefinite sign and sublinear as | u | → ∞ , we establish the existence of infinitely many solutions by using the genus properties in critical point theory. Recent results from the literature are extended.