Editing Ricci flow (section)

===Singularities in 3d Ricci flow===
In 3d the possible blow-up limits of Ricci flow singularities are well-understood. From the work of Hamilton, Perelman and Brendle, blowing up at points of maximum curvature leads to one of the following three singularity models:
* The shrinking round spherical space form <math> S^3/\Gamma </math>
* The shrinking round cylinder <math> S^2 \times \mathbb{R} </math> 
* The Bryant soliton
The first two singularity models arise from Type I singularities, whereas the last one arises from a Type II singularity.