On a periodic boundary value problem for third order linear functional differential equations Original Research Article

Unimprovable sufficient conditions are established for the unique solvability of the periodic problem View the MathML sourceu‴(t)=∑i=02ℓi(u(i))(t)+q(t),u(j)(0)=u(j)(ω)+cj(j=0,2¯), Turn MathJax on where ℓi:C([0,ω])→L([0,ω])ℓi:C([0,ω])→L([0,ω]) are the linear bounded operators, q∈L([0,ω])q∈L([0,ω]) and cj∈Rcj∈R.