Electronic Journal of Differential Equations,
Conference 06 (2001), pp. 243-255.

Title: On a fourth order superlinear elliptic problem.

Authors: M. Ramos (Univ. de Lisboa, Lisboa, Portugal)
  P. Rodrigues (Univ. Nova de Lisboa, Caparica, Portugal)
 
Abstract: 
  We prove the existence of a nonzero solution for the fourth order
  elliptic equation
  $$\Delta^2u= \mu u +a(x)g(u)$$
  with boundary conditions $u=\Delta u=0$.
  Here, $\mu$ is a real parameter, $g$ is superlinear both at zero and
  infinity and $a(x)$ changes sign in $\Omega$. The proof uses a
  variational argument based on the argument by Bahri-Lions \cite{BL}.

Published January 8, 2001.
Math Subject Classifications: 35J25, 35J20, 58E05.
Key Words: Superlinear elliptic problems; Morse index; biharmonic operator.