Periodic solutions for a class of second-order Hamiltonian systems.
We deal with a bifurcation result for the Dirichlet problem ⎧ a.e. in Ω, ⎨ ⎩. Starting from a weak lower semicontinuity result by E. Montefusco, which allows us to apply a general variational principle by B. Ricceri, we prove that, for μ close to zero, there exists a positive number such that for every the above problem admits a nonzero weak solution in satisfying .
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