Classification of general Wentzell boundary conditions for fourth order operators in one space dimension (Q886176)

The authors classify when a fourth order linear ordinary differential operator in one space dimension is symmetric, semibounded or quasiaccretive. It is imposed at each endpoint one general Wentzell boundary condition, as well as one other linear boundary condition. These extend other known boundary conditions under which the one-dimensional beam equation \(u_{tt}+c^2u_{xxxx}=0\) is well-posed and governed by a strongly continuous cosine function.