Periodic solutions of first order functional differential equations with periodic deviations
The paper is concerned with the functional differential equation u '(t) = a(t)g(u(h(1) (t)))u(t) - lambda b(t)f(u(h(2)(t))), where lambda > 0, a(t), b(t), h(1) (t) and h(2)(t) are periodic functions. Applying Leggett-Williams fixed point theorem to the equation, we show the explicit open intervals of lambda such that the equation has at least three nonnegative periodic solutions. (c) 2007 Published by Elsevier Ltd.
periodic solution functional differential equation periodic deviation fixed point cone