Forced singular oscillators and the method of lower and upper solutions.(English)Zbl 1108.34033

Summary: We study the existence of positive periodic solutions of the second-order differential equation $u''+g(u)u'+f(t,u)=h(t)$ where $$f(t,\cdot)$$ has a singularity of repulsive type at the origin. We use the method of lower and upper solutions.

MSC:

 34C25 Periodic solutions to ordinary differential equations 34B15 Nonlinear boundary value problems for ordinary differential equations
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