On Extensions of Myers' Theorem

TL;DR

This paper extends Myers' theorem to certain Riemannian manifolds with conditions involving the Bismut-Witten Laplacian and a curvature function, providing new criteria for finiteness of the fundamental group.

Contribution

It introduces new curvature conditions involving the Bismut-Witten Laplacian that extend classical Myers' theorem to broader classes of manifolds.

Findings

Manifolds with $ ho^h$ satisfying $ riangle^h - ho^h < 0$ have finite fundamental group.

Provides a quick proof of recent Myers' theorem extensions.

Includes results applicable to noncompact manifolds.

Abstract

Let $M$ be a compact Riemannian manifold and $h$ a smooth function on $M$. Let $\rho^h(x)=\inf_{|v|=1}\left(Ric_x(v,v)-2Hess(h)_x(v,v) \right)$. Here $Ric_x$ denotes the Ricci curvature at $x$ and $Hess(h)$ is the Hessian of $h$. Then $M$ has finite fundamental group if $\Delta ^h-\rho^h<0$. Here $\Delta ^h=: \Delta +2L_{\nabla h}$ is the Bismut-Witten Laplacian. This leads to a quick proof of recent results on extension of Myers' theorem to manifolds with mostly positive curvature. There is also a similar result for noncompact manifolds.