Let C denote the infimal value of λ0(γ), the least eigenvalue of the Schrödinger operator
Hγ=−ds2d2+κ2(s)
associated with a simple closed convex curve γ parameterized by arclength and normalized to have length 2π, where κ(s) is the curvature. Obtain upper and lower bounds for C that are as strong as possible.