On steady and expanding Ricci solitons with asymptotic symmetries

Abstract

We establish a symmetry principle for asymptotically cylindrical steady gradient Ricci solitons (GRSs) and asymptotically conical expanding GRSs with homogeneous links. Using this, we show that the Bryant steady soliton is the unique asymptotically cylindrical steady GRS that has a round spherical link and satisfies a particular quantitative rigidity condition. A similar characterization is proved for Bryant's expanding solitons. Finally, we establish a global symmetry result for GRSs which exhibit the aforementioned asymptotics with quotient-Berger sphere asymptotic links.

29 pages. v3 is a substantial rewrite of the paper. Versions 1 and 2 contain a fatal error in Lemma 3.11 (old numbering), so the main claims of those versions are invalid as stated. This version gives a revised symmetry result and includes results for expanders