On the Existence of Periodic Quasi Solutions for First Order Systems
Abstract
**Please note that the full text is embargoed** ABSTRACT: Recently the method of upper and lower solutions and Lyapunov-Schmitt
method have been fruitfully employed to prove the existence of periodic solutions for scalar first and second order equations in [2,4]. In this paper we shall
use this technique to prove the existence of periodic solutions for first order systems which is the generalisation of Müller's result [3] for periodic case. We shall also develop monotone iterative technique to obtain coupled minimal and maximal periodic quasisoltions for system of first order equations. Further, under a uniqueness assumption, our results yield a unique periodic solution for the first order system.