2 problems

Let $T$ be the selfadjoint operator associated with a singular Sturm–Liouville expression, and let $A$ be the corresponding indefinite Sturm–Liouville operator. Spectral lower-boun…

Let $L$ be the operator on $L^2[-\pi,\pi]$ defined by … with periodic boundary conditions $y(-\pi)=y(\pi)$ and parameter $\epsilon>0$. Pure-imaginary spectrum conjecture. All eigen…