The rigidity of under ancient Ricci flow
arXiv:1708.05459
Abstract
In this paper we generalize the neck-stability theorem of Kleiner-Lott to a special class of four-dimensional nonnegatively curved Type I -solutions, namely, those whose asymptotic shrinkers are the standard cylinder . We use this stability result to prove a rigidity theorem: if a four-dimensional Type I -solution with nonnegative curvature operator has the standard cylinder as its asymptotic shrinker, then it is exactly the cylinder with its standard shrinking metric.