Abstract. Benguria and Loss have conjectured that, amongst all smooth closed curves in R 2 of length 2π, the lowest possible eigenvalue of the operator L = −∆ + κ 2 is 1. They observed that this value was achieved on a twoparameter family, O, of geometrically distinct ovals containing the round circle and collapsing to a multiplicity-two line segment. We characterize the curves in O as absolute minima of two related geometric functionals. We also discuss a connection with projective differential geometry and use it to explain the natural symmetries of all three problems.