Using Leray–Schauder degree theory we obtain various existence and multiplicity results for nonlinear periodic boundary-value problems of the form
View the MathML source(ϕ(u′))′=f(t,u,u′),u(0)−u(T)=0=u′(0)−u′(T),
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where View the MathML sourceϕ:R→]−a,a[(0
Keywords :
Periodic solutions , continuation theorem , Leray–Schauder degree , ??-Laplacian