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| In this talk existence results for nonlinear differential problems are presented. Precisely, under a suitable behaviour of the nonlinearity, the existence of a non zero solution is proved for wide classes of differential problems. The main tool is a local minimum theorem. However, in some case, also a coincidence point theorem for weakly sequentially continuous maps, obtained by
set-valued arguments, is applied. Finally, multiplicity results are established by using suitable remarks on the classical mountain pass theorem. |
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