On coupled and tripled fixed point theory of multi-valued contraction mappings in partially ordered metric spaces

In this paper, we present a new and simple approach to coupled fixed point theory of multi-valued maps. By using our method, we first give a very simple proof of the recent coupled fixed point theorems established by Samet and Vetro [B. Samet, C. Vetro, Coupled fixed point theorems for multi-valued nonlinear contraction mappings in partially ordered metric spaces, Nonlinear Analysis 74(2011), 4260-4268.] Then, we use our technique to present a new tripled fixed point theorem in a general setting.