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This tag is used if a reference is needed in a paper or textbook on a specific result.

6 votes

Kummer's quartic surface and the Dirac operator

It is hard to imagine that Eddington's numbers could be anything but the imaginary part of the Clifford algebra $C$ of Minkowski space. Recall that the Clifford algebra for an n-dimensional real vec …
Richard Montgomery's user avatar
4 votes

parallel transport along $W^{1,2}$-curves

You will find a proof in Appendix D (Theorem D.1) of my book `A Tour of SubRiemannian Geometry'. It may not look like what you want at first glance, since that theorem is stated in a more general c …
Richard Montgomery's user avatar
4 votes

Navier-Stokes equations in Riemannian geometry

You are missing a $\dot u$ in your equation! We want a dynamic vector field. The sign of your $\nabla_u u$ and $\Delta u$ are usually taken to be opposite, as with the sign of your $df^*$ and $\nabla …
Richard Montgomery's user avatar
9 votes

Probing a manifold with geodesics

Fix one $u$, its resulting geodesic probe, and vary $u$ slightly. Comparing the two geodesics at the same arclength values yields a close approximation to the solution to the Jacobi equation al …
Richard Montgomery's user avatar
8 votes
Accepted

Two interacting bodies in an external field

I seriously doubt there is any general criteria. However there are more than one beautiful explicit examples of an external field which lead to an integrable problem. The simplest and probably best …
Richard Montgomery's user avatar
4 votes
0 answers
174 views

Recognize this metric? Do you have a name for this metric on the product of spheres?

Take the product $S^2 \times S^2$ of two two-spheres, but perturb the product metric as follows. Think of each $S^2$ as the unit two-sphere in Euclidean 3-space in the standard way so that for $p …
Richard Montgomery's user avatar
4 votes

What's that shape? Inferring a 3D shape from random shadows

Joseph: this `answer' is perhaps more a comment than an answer, so apologies in advance. The deepest geometric work I know of is this wonderful piece by Mohammad Ghomi. I quote from his web page: ` …
Richard Montgomery's user avatar
17 votes
Accepted

2- and 3-body problems when gravity is not inverse-square

The answers to question (1) for the 2 body problem are fine, and complete enough. Regarding (2). The 3 body problem (and N-body) with p =3 is significantly simpler than with $p \ne 3$. The added …
Richard Montgomery's user avatar
4 votes

Reference request for instantons

I think a good starting place for your question regarding the moduli space for a flat 4-torus is the Fourier-Mukai' correspondence which came out of work of Nahm and which relates the moduli space o …
Richard Montgomery's user avatar
23 votes

Good differential equations text for undergraduates who want to become pure mathematicians

Arnol'd's ODEs. Hirsch and Smale. As a second best the `supersized version' of this with Devaney added as a co-author.