Došlý, Ondřej Oscillation and spectral properties of self-adjoint even order differential operators with middle terms. (English) Zbl 1072.34032 Electron. J. Qual. Theory Differ. Equ. 2003, Suppl., Paper No. 7, 21 p. (2003). Summary: Oscillation and spectral properties of even-order selfadjoint differential operators of the form \[ L(y):=\frac{1}{w(t)}\sum_{k=0}^n (-1)^k \left(r_k(t)y^{(k)}\right)^{(k)},\quad r_n(t)>0,\;w(t)>0, \tag{L} \] are investigated. A particular attention is devoted to the fourth-order operators with a middle term, for which new (non)oscillation criteria are derived. Some open problems and perspectives of further research are discussed. MSC: 34C10 Oscillation theory, zeros, disconjugacy and comparison theory for ordinary differential equations PDFBibTeX XMLCite \textit{O. Došlý}, Electron. J. Qual. Theory Differ. Equ. 2003, Paper No. 7, 21 p. (2003; Zbl 1072.34032) Full Text: EMIS