A Krein space approach to symmetric ordinary differential operators with an indefinite weigth function (Q584485)

The authors study spectral properties of the differential equation \[ (- 1)^ n(p_ 0f^{(n)})^{(n)}+(-1)^{n-1}(p_ 1f^{(n-1)})^{(n- 1)}+...+p_ nf=\lambda rf \] considered in the Hilbert space \(L^ 2(a,b)\) with a weight function \(| r|\) where \(-\infty \leq a<b\leq +\infty\), \(1/p_ 0,p_ 1,...,p_ n\) and r are locally summable, \(p_ 0>0\) and r changes its sign.