Resumen de Examples of the nonexistence of a solution in the presence of upper and lower solutions

Patrick Habets, Rodrigo López Pouso

• Standard results for boundary value problems involving second-order ordinary differential equations ensure that the existence of a well-ordered pair of lower and upper solutions together with a Nagumo condition imply existence of a solution. In this note we introduce some examples which show that existence is not guaranteed if no Nagumo condition is satisfied.