Periodic solutions of non-autonomous second order systems
The author considers the boundary value problem of the second order system \(\ddot u(t)=\nabla F(t,u(t))\), \(u(0)-u(\tau)=\dot u(0)-\dot u(\tau)=0\). He obtains an existence theorem of periodic solutions of the system with classical theorems of variational calculus.
scientific article; zbMATH DE number 930202