Acta Universitatis Sapientiae: Mathematica (Dec 2016)
Study of periodic and nonnegative periodic solutions of nonlinear neutral functional differential equations via fixed points
Abstract
In this paper, we study the existence of periodic and non-negative periodic solutions of the nonlinear neutral differential equation ddtx(t)=−a (t) h (x (t))+ddtQ (t, x (t−τ (t)))+G (t, x(t), x (t−τ (t))).$${{\rm{d}} \over {{\rm{dt}}}}{\rm{x}}({\rm{t}}) = - {\rm{a}}\;({\rm{t}})\;{\rm{h}}\;({\rm{x}}\;({\rm{t}})) + {{\rm{d}} \over {{\rm{dt}}}}{\rm{Q}}\;({\rm{t}},\;{\rm{x}}\;({\rm{t}} - {\rm \tau} \;({\rm{t}}))) + {\rm{G}}\;({\rm{t}},\;{\rm{x}}({\rm{t}}),\;{\rm{x}}\;({\rm{t}} - {\rm \tau} \;({\rm{t}}))).$$ We invert this equation to construct a sum of a completely continuous map and a large contraction which is suitable for applying the modificatition of Krasnoselskii’s theorem. The Caratheodory condition is used for the functions Q and G.
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