Positive solutions and multiple solutions for periodic problems driven by scalar p-Laplacian

In this paper we study a nonlinear second order periodic problem driven by a scalar p-Laplacian and with a nonsmooth, locally Lipschitz potential function. Using a variational approach based on the nonsmooth critical point theory for locally Lipschitz functions, we first prove the existence of nontrivial positive solutions and then establish the existence of a second distinct solution (multiplicity theorem) by strengthening further the hypotheses. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.