Area and the length of the shortest closed geodesic (Q1101697)

The main result of the paper is that the inequality 31\(\sqrt{A}\geq L\) is satisfied for any Riemannian metric on the two-sphere where A denotes its area and L the length of its shortest nontrivial closed geodesic. This is closely related to so-called isosystolic inequalities which relate area (or volume) to the length of the shortest not null-homotopic closed geodesic, see \textit{M. Gromov} [J. Differ. Geom. 18, 1-147 (1983; Zbl 0515.53037)]. The author also shows for any Riemannian metric on the two- sphere that 9D\(\geq L\) where D denotes its diameter. Furthermore, he proves that there is a constant \(c(n)^ n\sqrt{Vol(M)}\geq L\) for any closed convex hypersurface in \({\mathbb{R}}^{n+1}\). The last result was proved independently by \textit{A. Treibergs} [Invent. Math. 80, 481-488 (1985; Zbl 0563.53035)].