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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.

16 votes

What are the main contributions to the mathematics of general relativity by Sir Roger Penros...

I would say Penrose is a mathematical physicist and I don't think he can be considered (at least not primarily) to be a pure mathematician. For example, his argument for the Penrose inequality is a …
15 votes
2 answers
1k views

Counterexamples to the Penrose Conjecture

I have noticed that in the literature on causality in general relativity one sees apparent counterexamples to the cosmic censorship hypothesis (somehow you have models for gravitational collapse which …
Hollis Williams's user avatar
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 …
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 …
Hollis Williams's user avatar
12 votes
1 answer
566 views

Alternative approaches to topological QFTs

A while ago I read the paper 'Quantum Field Theory and the Jones Polynomial' by Edward Witten. This article uses a lot of concepts from physics like BRST symmetry and the Chern-Simons action which ar …
Hollis Williams's user avatar
8 votes
2 answers
314 views

Work on triply periodic minimal surfaces

I have seen in some engineering departments that they manufacture models of periodic minimal forms (characterised by equal and opposite curvature at every points on the surface). In pure mathematics, …
Hollis Williams's user avatar
8 votes

What is an "Instanton" in classical gauge theory? (to a mathematician)

Generally speaking, you could say they are a special type of solution to the field equations of gauge theories. More specifically, an instanton is a classical solution in a classical Euclidean field …
Hollis Williams's user avatar
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 …
Hollis Williams's user avatar
5 votes
1 answer
331 views

Ricci flow proof of isoperimetric inequality

It is well-known in geometric analysis that one can use curve-shortening flow to prove the isoperimetric inequality (where the general result requires curve-shortening flow for non-convex curves). I …
Hollis Williams's user avatar
5 votes

Which high-degree derivatives play an essential role?

I think third-order and fourth-order derivatives in particular are very common in both pure and applied mathematics. For example, I once worked with some equations modelling the local film thickness …
4 votes
1 answer
155 views

Example of a Manifold which has One Non-zero Component of Ric corresponding to Scalar Curvature

I am wondering if there is a simple example of a manifold such that, given a value for the scalar curvature $R$, I can find a manifold such that the Ricci tensor has all zero components except for one …
Hollis Williams's user avatar
4 votes
Accepted

Counterexamples to the Penrose Conjecture

Having thought about this more and discussed it with others, the answer seems to be that there are likely no counterexamples to the Penrose inequality, even if one allows for unphysical violations. Fo …
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 …
Hollis Williams's user avatar
3 votes
1 answer
155 views

Connections on bundle gerbes from cocycle data

I am reading a 2007 article of Bressler et al. on deformation quantization of gerbes. In the article, the authors state that a gerbe on a manifold is defined using certain two-cocycles $c_{ijk}$ b …
Hollis Williams's user avatar
3 votes

References for classical Yang-Mills theory

My personal suggestion is 'Differential Geometry, Gauge Theories, and Gravity' by M. Gockeler and T. Schucker. However, it assumes a fairly high degree of mathematical sophistication (it's one of the …
Hollis Williams's user avatar

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