Abstract: In this expository talk I will report Simon Brendle's new curvature pinching estimates for Ricci flow on compact manifolds of dimension n>11 with positive isotropic curvature (PIC).The estimates ensure that the corresponding blow-up limits are uniformly PIC and weakly PIC2. This can be viewed as a higher-dimensional analogue of the Hamilton-Ivey pinching estimate in dimension 3，and is one of the key ingredients for the construction of Ricci flow with surgery on compact manifolds of dimension n>11 with positive isotropic curvature.
