Exponential Asymptotics of Ricci Flow Neckpinch

In this article we examine the formation of cylindrical neckpinch singularities in Ricci flow in compact manifolds. Rigorous examples of neckpinch sigularity for rotationally symmetric initial data were first constructed by Angenent and Knopf, and examples with given asymptotic behaviour were constructed by them and Isenberg. Here we discuss the asymptotic behavior of the flow under Type-I assumption for general symmetric initial data, and show the previously constructed asymptotic profiles and are the only possibilities.