Log-Concavity and Fundamental Gaps on Surfaces of Positive Curvature
We study the log-concavity of the first Dirichlet eigenfunction of the Laplacian for convex domains. For positively curved surfaces satisfying a condition involving the curvature and its second derivative, we show that the first eigenfunction is strongly log-concave. Previously, the log-concavity of these eigenfunctions were only known for convex domains of $\mathbb{R}^n$ and $\mathbb{S}^n$. Using this estimate, we establish lower bounds on the fundamental gap of such regions. Furthermore, we study the behavior of these estimates under Ricci flow and other deformations of the metric.