Balanced metrics, Zoll deformations and isosystolic inequalities in $\mathbb{C}P^n$

Abstract: The $k$-systole of a Riemannian manifold is the infimum of the volume over all homologically non-trivial $k$-cycles. In this paper we discuss the behavior of the dimension two and co-dimension two systole of the complex projective space for distinguished classes of metrics, namely the homogeneous metrics and the Balanced metrics. In particular, we argue that every homogeneous metric maximizes the systole in its volume-normalized conformal class, as well as that each K\"ahler metric locally minimizes the systole on the set of volume-normalized Balanced metrics. The proof demands the implementation of integral geometric techniques, and a careful analysis of the second variation of the systole functional. As an application, we characterize the systolic behavior of almost-Hermitian 1-parameter Zoll-like deformations of the Fubini-Study metric.