A certain functional derivative equation corresponding to \(\square u+cu+bu^ 2+au^ 3=g\) on \(R^{d+1}\)
The author of this short note formulates two problems for functionals and measures, respectively, which are in some sense connected with the Klein- Gordon equation \[ \square u+cu+bu^ 2+au^ 3=g. \] He gives the corresponding notions of solution and conditions for solvability. Proofs are only sketched.
scientific article; zbMATH DE number 4157148