Complete gradient expanding Ricci solitons with finite asymptotic scalar curvature ratio
Huai-Dong Cao, Tianbo Liu, Junming Xie
Abstract
Let $(M^n, g, f)$, $n\geq 5$, be a complete gradient expanding Ricci soliton with nonnegative Ricci curvature $Rc\geq 0$. In this paper, we show that if the asymptotic scalar curvature ratio of $(M^n, g, f)$ is finite (i.e., $ \limsup_{r\to \infty} R r^2< \infty $), then the Riemann curvature tensor must have at least sub-quadratic decay, namely, $\limsup_{r\to \infty} |Rm| \ \! r^α< \infty$ for any $0<α<2$.
