Abstract. We consider a bounded domain Ω of R N , N ≥ 3, and h a continuous function on Ω. Let Γ be a closed curve contained in Ω. We study existence of positive solutions u ∈ H 1 0 (Ω) to the equation, σ ∈ (0, 2), and ρ Γ is the distance function to Γ. For N ≥ 4, we find a sufficient condition, given by the local geometry of the curve, for the existence of a ground-state solution. In the case N = 3, we obtain existence of ground-state solution provided the trace of the regular part of the Green of −∆ + h is positive at a point of the curve.