Zoll Manifolds of Type $\mathbb{CP}^n$ with Entire Grauert Tubes
Chi Li, Kyobeom Song
TL;DR
This work proves a rigidity result for Zoll manifolds of type $\mathbb{CP}^n$ under the entire Grauert tube condition. By constructing the complexified tangent bundle $X=TM\cup D$ and analyzing its cohomology, the authors show $X$ is a $2n$-dimensional Fano manifold with index $n+1$, and then apply Wiśniewski's classification to identify $X\cong \mathbb{CP}^n\times\mathbb{CP}^n$. The algebro-geometric identification of the divisor $D$ and the action of the anti-holomorphic involution $N_{-1}$ lead to a rigidity that forces $M$ to be $\mathbb{CP}^n$ with the Fubini–Study metric, up to scaling. The result extends previous uniqueness findings for Zoll spheres to the CP^n type, consolidating the role of complexification and Fano geometry in metric rigidity for Zoll manifolds.
Abstract
We show that a Zoll manifold of type $\mathbb{CP}^n$ with an entire Grauert tube is isometric to $\mathbb{CP}^n$ with the canonical Fubini-Study metric, up to constant multiplication.
