一阶微分方程周期边值问题的解的存在性

该文用拓扑度理论证明了一阶微分方程周期边值问题关于下解与上解之间解的存在性的两个定理，这里下解α(t)与上解β(t)可以不满足关系α(0)≤α(2π)，β(0)≥β(2π)

On the Existence of Solutions for PBVP of First Order Differential Equations

Using the topological degree theory, the author  proves several existence theorems of solutions between lower and upper solutions for periodic boundary value problems of first order differential equations, where the lower and upper solutions  $α(t)$ and  $β(t)$ need not satisfy relations $α(0)≤α(2π)，β(0)≥β(2π).$