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14 votes
1 answer
395 views

Does the Cheeger constant satisfy a heat-type equation?

It was shown by Hamilton in the 1990s that the isoperimetric ratio $C_H$ on the $2$-sphere improves along the Ricci flow. A way to prove this is to use the fact that if $(M^2, g(t))$ is a solution of …
3 votes
Accepted

Does the Cheeger constant satisfy a heat-type equation?

Answer to (2) is negative. For a counterexample, consider a $2$-sphere and blow up the radius. The isoperimetric ratio $C_H$ remains the same, but the Cheeger constant $h$ shrinks, essentially becau …
Hollis Williams's user avatar
13 votes
2 answers
2k views

Is there a solution of the Yamabe problem using Ricci flow?

Someone told me that it is possible to solve the Yamabe problem using Ricci flow. The proof I know of is the one originally proposed by Yamabe and then completed by Trudinger, Aubin and Schoen (in pa …
5 votes
1 answer
260 views

Neckpinch singularity of Ricci flow

I apologise if this question is unclear as I do not know much about the Ricci flow and am only asking out of curiosity. My understanding is that a neckpinch singularity is a local singularity in the …
0 votes

Rigorous solution to Ricci Flow on dumbbell $S^3$

Yes, these pictures have now been made rigorous. Another paper which you might be interested in on this topic is Simon, M. (2000). A class of Riemannian manifolds that pinch when evolved by Ricci flo …
Hollis Williams's user avatar
4 votes
0 answers
283 views

Is there a version of Ricci Flow for Pseudo-Riemannian Metrics?

The Ricci flow deforms a Riemannian metric. I was wondering if there was something very similar which deforms a pseudo-Riemannian metric or if not, is there reason why such a geometric flow cannot ex …
0 votes
0 answers
287 views

Does the Volume Ratio of a Geodesic Ball for a Complete Riemannian Manifold tend to the volu...

I am reading Peter Topping's notes on Ricci flow: on page 99 a statement is made which is needed for his proof of a version of Perelman's no local volume collapse theorem, but I am not sure why it hol …
2 votes
1 answer
243 views

Principal Symbol for the Ricci-DeTurck Flow

I am following some lecture notes on Ricci flow and reached the section where we linearize the Ricci tensor and obtain the principal symbol for the resulting operator. We have $T \in \: \Gamma(Sym^2 …
2 votes
1 answer
248 views

What is the Weak Maximum Principle for Scalars and how is it Derived?

I am currently reading 'Lectures on Ricci Flow' by Peter Topping and I have got to Chapter 3 where he states the 'weak maximum principle for scalars'. Suppose for $t \in [0,T]$ for finite $T$ that $g …