On Extensions of Myers' Theorem

Let $M$ be a compact Riemannian manifold and $h$ a smooth function on $M$. Let ${\rho }^h(x)={\inf }_{\mathrm{\mid }v\mathrm{\mid }=1}(Ri{c}_x(v,v)-2Hess(h{)}_x(v,v))$. Here $Ri{c}_x$ denotes the Ricci curvature at $x$ and $Hess(h)$ is the Hessian of $h$. Then $M$ has finite fundamental group if ${\mathrm{\Delta }}^h-{\rho }^h<0$. 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.