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On a periodic boundary value problem for cyclic feedback type linear functional differential systems. (English) Zbl 1132.34045

The authors are interested in the study of the following system
\[ \begin{aligned} u_i^{\prime\prime}(t)&= l_i(u_{i+1})(t) +q_i(t), \quad i=1,\dots,n-1,\\ u_n^{\prime\prime}& =l_n(u_1)(t)+q_n(t)\end{aligned} \]
with periodic conditions
\[ u_j(t+\omega)=u_j(t),\quad j=1,\dots,n,\;t\in\mathbb R. \]
They give integral sufficient conditions for unique solvability of this problem in case that \( l_i \) are monotone linear operators.

MSC:

34K10 Boundary value problems for functional-differential equations
34K13 Periodic solutions to functional-differential equations
34K06 Linear functional-differential equations