Quasi-periodic solutions for nonlinear wave equation with Liouvillean frequency
The authors show that under certain conditions the equation \(u_{tt}-u_{xx}+m u+\epsilon f(\omega t,x,u;\xi)=0\), with Dirichlet boundary conditions, has \(C^\infty\) smooth quasi-periodic solutions. The main result is Theorem 1, whose demonstration is given in section 3.
scientific article; zbMATH DE number 7360588