M. Ramos et al., SUPERLINEAR ELLIPTIC PROBLEMS WITH SIGN C HANGING NONLINEARITY, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 325(3), 1997, pp. 283-286
We prove the existence of a nontrivial solution for a nonlinear ellipt
ic problem - Delta u = mu u + a(x)g(u) with Dirichlet boundary conditi
on on a bounded domain, where g is superlinear both at zero and at inf
inity, and where a(x) changes sign and mu > 0.