We deal with the existence of nonnegative and nontrivial $ T $–periodic solutions for the equation $ x'' = r(t)x^{\alpha}-s(t)x^{\beta} $ where $ r $ and $ s $ are continuous $ T $–periodic functions and $ 0<\alpha<\beta<1 $. This equation has been studied in connection with the valveless pumping phenomenon and we will take advantage of its variational structure in order to guarantee its solvability by means of the mountain pass theorem of Ambrosetti and Rabinowitz.
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Graph of the potential
Phase plane for (3) with the values