MEAN CURVATURE FLOW

∂X/∂t = H·n — curves shrink to circles, dumbbells pinch and split
MCF in 2D:
κ = curvature at each point.
Points move inward at rate κ.

Gage-Hamilton-Grayson (1987):
Any smooth embedded closed curve flows to a round point.

Dumbbell: neck pinches in finite time — topology change!

Perimeter:
Area:
Isoperimetric:

4πA/L² → 1 as → circle