We study the Ricci flow on \({\mathbb {R}}^{4}\) starting at an SU(2)-cohomogeneity 1 metric \(g_{0}\) whose restriction to any hypersphere is a Berger metric. We prove that if \(g_{0}\) has no necks and is bounded by a cylinder, then the solution develops a global Type-II singularity and converges to the Bryant soliton when suitably dilated at the origin. This is the first example in dimension \(n > 3\) of a non-rotationally symmetric Type-II flow converging to a rotationally symmetric singularity model. Next, we show that if instead \(g_{0}\) has no necks, its curvature decays and the Hopf fibres are not collapsed, then the solution is immortal. Finally, we prove that if the flow is Type-I, then there exist minimal 3-spheres for times close to the maximal time.

我们研究从SU（2）-同质性1度量\（g_ {0} \）开始的\（{\ mathbb {R}} ^ {4} \）上的Ricci流，其对任何超球面的限制都是Berger度量。我们证明，如果\（g_ {0} \）没有颈并且被圆柱包围，则该解决方案会产生整体II型奇点，并且在原点进行适当扩张时会收敛到科比孤子。这是收敛到旋转对称奇异模型的非旋转对称II型流的尺寸\（n> 3 \）的第一个示例。接下来，我们将显示\（g_ {0} \）没有脖子，它的曲率衰减并且霍普夫纤维不塌陷，那么这个解决方案是不朽的。最后，我们证明如果流是类型I，那么在接近最大时间的时间内存在最小的3个球。