Homological $(n-2)$-systole in $n$-manifolds with positive triRic curvature
Jingche Chen, Han Hong
TL;DR
The article proves an optimal homological $(n-2)$-systole inequality for closed oriented $n$-manifolds with positive $\operatorname{triRic}$ curvature in dimensions $n=4,5$ (and $n=6$ under a $\gamma$-range). It combines stable weighted $2$-slicings with a refined Antonelli–Xu type volume comparison and a metric-deformation scheme to bound the $(n-2)$-systole by $|\mathbb{S}^{n-2}|$, and characterizes equality via a two-step isometric splitting, ultimately showing $M$ is covered by $\mathbb{S}^{n-2}\times \mathbb{R}^2$. The topological hypothesis on cohomology classes is essential to avoid counterexamples from products like $\mathbb{S}^{n-2}(r_1)\times \mathbb{S}^2(r_2)$. Overall, the work extends prior two-dimensional and higher-codimension systolic results to codimension two, using a blend of variational, geometric-analytic, and splitting arguments.
Abstract
In this paper, we prove an optimal systolic inequality and characterize the case of equality on closed Riemannian manifolds with positive triRic curvature. This extends prior work of Bray-Brendle-Neves \cite{BrayBrenleNevesrigidity} and Chu-Lee-Zhu \cite{chuleezhu_n_systole} to higher codimensions. The proof relies on the notion of stable weighted $k$-slicing, a weighted volume comparison theorem and metric-deformation.
