Coupled fixed points of multivalued operators and first--order ODEs with state--dependent deviating arguments

TL;DR

This paper develops a coupled fixed points theorem for multivalued operators and applies it to establish the existence of solutions for first-order functional differential equations with state-dependent delays, including discontinuous cases.

Contribution

It introduces a new coupled fixed points theorem for multivalued operators and applies it to solve complex differential equations with state-dependent deviating arguments.

Findings

Established a general coupled fixed points theorem for multivalued operators.

Derived existence results for solutions to differential equations with state-dependent delays.

Applicable to equations with discontinuities in all arguments.

Abstract

We establish a coupled fixed points theorem for a meaningful class of mixed monotone multivalued operators and then we use it to derive some results on existence of quasisolutions and solutions to first--order functional differential equations with state--dependent deviating arguments. Our results are very general and can be applied to functional equations featuring discontinuities with respect to all of their arguments, but we emphasize that they are new even for differential equations with continuously state--dependent delays.