Abstract

A solution of the operator equation $L(u)=N(u)$ is called a coincidence point of $L$ and $N$, which are two operators between some spaces $X$ and $Y$. One aim of the talk is to give a short presentation of the thesis Coincidence Principles and Applications (presented at Babes-Bolyai University, Cluj-Napoca, Romania), where we have established some abstract coincidence theorems in metric spaces, ordered spaces or Banach spaces. Other aim is to present in more detail the coincidence degree theory with its applications for finding periodic solutions of differential systems.