Abstract
In this article, we study four-dimensional complete gradient shrinking Ricci solitons. We prove that a four-dimensional complete gradient shrinking Ricci soliton satisfying a pointwise condition involving either the self-dual or anti-self-dual part of the Weyl tensor is either Einstein, or a finite quotient of either the Gaussian shrinking soliton
ℝ
4
{\mathbb{R}^{4}}
, or
𝕊
3
×
ℝ
{\mathbb{S}^{3}\times\mathbb{R}}
, or
𝕊
2
×
ℝ
2
.
{\mathbb{S}^{2}\times\mathbb{R}^{2}.}
In addition, we provide some curvature estimates for four-dimensional complete gradient Ricci solitons assuming that its scalar curvature is suitable bounded by the potential function.