Fundamental Groups in the Five Dimensional Pan-Rong Conjecture

Abstract

Let $M$ be a complete open $5$-manifold with nonnegative Ricci curvature. If its universal cover $\tilde{M}$ has Euclidean volume growth, then ${\pi }_1(M)$ is finitely generated and virtually ${\mathbb{Z}}^k$ for some $0\le k\le 4$. This confirms a conjecture of Pan and Rong \cite{PR18} in dimension five; see also \cite{BNS25,BrNaSe25}. In dimension six, under the same volume growth assumption, we also obtain a quantitative virtual abelianness result without assuming finite generation of the fundamental group.