On a fourth‐order nonlinear Helmholtz equation
On a fourth‐order nonlinear Helmholtz equation
In this paper, we study the mixed dispersion fourth-order nonlinear Helmholtz equation Δ 2 u − β Δ u + α u = Γ | u | p − 2 u in R N , for positive, bounded and Z N -periodic functions Γ in the following three cases: ( …