Locally conformally flat ancient Ricci flows
arXiv:1308.2374 · doi:10.2140/apde.2015.8.365
Abstract
We show that any locally conformally flat ancient solution to the Ricci flow must be rotationally symmetric. As a by-product, we prove that any locally conformally flat Ricci soliton is a gradient soliton in the shrinking and steady cases as well as in the expanding case, provided the soliton has nonnegative curvature.
Final version, to appear on Anal. PDE