Paper detail

Zeroes of the spectral density of the Schroedinger operator with the slowly decaying Wigner-von Neumann potential

We consider the Schrödinger operator $\mathcal L_α$ on the half-line with a periodic background potential and a perturbation which consists of two parts: a summable potential and the slowly decaying Wigner--von Neumann potential $\frac{c\sin(2ωx+δ)}{x^γ}$, where $γ\in(\frac12,1)$. The continuous spectrum of this operator has the same band-gap structure as the continuous spectrum of the unperturbed periodic operator. In every band there exist two points, called critical, where the eigenfunction equation has square summable solutions. Every critical point $ν_{cr}$ is an eigenvalue of the operator $\mathcal L_α$ for some value of the boundary parameter $α=α_{cr}$, specific to that particular point. We prove that for $α\neqα_{cr}$ the spectral density of the operator $\mathcal L_α$ has a zero of the exponential type at $ν_{cr}$.