Coincidence degree and periodic solutions of neutral equations

摘要: This paper is devoted to the problem of existence periodic solutions for some nonautonomous neutral functional differential equations. It essentially an application a basic theorem on Fredholm alternative linear equations recently obtained by one authors [2] and generalized Leray-Schauder theory developed second [3, 41. Although their proofs are surprisingly simple, results nontrivial extensions case number recent theorems In particular, Section 3 generalizes criteria due [5] corresponding extension J. Cronin [6], example following Theorem 4.1 improves condition given Lopes [ 141 equation transmission line problem, 5.1 result R. E. Fennel1 [7]. Lastly, analogous 5.2 retarded can be found in [8]. For partly related concerning equations, see [9].