We investigate the Schrödinger operator H = −d 2 /dx 2 +(γ/x) sin αx+V , acting in L p (R), 1 ≤ p < ∞, where γ ∈ R \ {0}, α > 0, and V ∈ L 1 (R). For |γ| ≤ 2α/p we show that H does not have positive eigenvalues. For |γ| > 2α/p we show that the set of functions V ∈ L 1 (R), such that H has a positive eigenvalue embedded in the essential spectrum σess(H) = [0, ∞), is a smooth unbounded sub-manifold of L 1 (R) of codimension one.
Résumé. On examine l'opérateur de SchrödingerSi |γ| ≤ 2α/p, on montre que H n'a aucune valeur caractéristique positive. Si |γ| > 2α/p, on montre que l'ensemble des fonctions V ∈ L 1 (R), telles que H a une valeur caractéristique positive immergée dans le spectre essentiel σess(H) = [0, ∞), est une sous-variété lisse non-bornée de L 1 (R) de codimensionégaleà un.Proof of Theorem 1.1. For p ≥ 1, α > 0, and γ ∈ R \ {0}, let M p (α, γ) be the set of functions V ∈ L 1 (R) for which the operator H Q,p has a positive eigenvalue. It follows from Theorem 2.1 and Proposition A.1 that