Existence of multi-bump solutions for a class of elliptic problems   involving the biharmonic operator
  Using variational methods, we establish existence of multi-bump solutions for the following class of problems   $$   \left\{   \begin{array}{l}   \Delta^2 u +(\lambda V(x)+1)u = f(u), \quad \mbox{in} \quad \mathbb{R}^{N}, u \in H^{2}(\mathbb{R}^{N}),   \end{array}   \right.   $$ where $N \geq 1$, $\Delta^2$ is the biharmonic operator, $f$ is a continuous function with subcritical growth and $V : \mathbb{R}^N \rightarrow \mathbb{R}$ is a continuous function verifying some conditions. 
Claudianor O. Alves and Al\^annio B. N\'obrega
math.AP