A singular perturbation problem in integrodifferential equations.
We extend the classical Leighton comparison theorem to a class of quasilinear forced second order differential equations where the endpoints , of the interval are allowed to be singular. Some applications of this statement in the oscillation theory of (*) are suggested.
We consider differential inclusions where a positive semidefinite function of the solutions satisfies a class- estimate in terms of time and a second positive semidefinite function of the initial condition. We show that a smooth converse Lyapunov function, i.e., one whose derivative along solutions can be used to establish the class- estimate, exists if and only if the class- estimate is robust, i.e., it holds for a larger, perturbed differential inclusion. It remains an open question whether...