Existence of two positive solutions of a singular nonlinear periodic boundary value problem
The author deals with the existence of two periodic solutions to the second-order scalar differential equation \(x''= f(t,x,x')\) under the assumption that \(f\) has a repulsive singularity at \(x= 0^+\). The results are derived via some a priori estimates, from some author's theorems [Preprint 22 (1998), Palacký Univ. Olomouc] which are based on a connection between lower and upper solutions and the topological degree.
singular nonlinear periodic boundary value problem
scientific article; zbMATH DE number 1398393