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Questions designed to get an overview of a specific subject or body of results or to understand the relations among similar definitions, techniques or concepts appearing in different sub-fields of mathematics. While such questions by their very nature sometimes cannot be made very narrow and focused, it can be helpful to keep in mind that the design of MathOverflow does not make it a good fit for questions that are too broad.

10 votes

Linear/Non-linear sigma model

The sigma model started life as a model for pions and derives its name from one of the fields in the theory (denoted $\sigma$). This, however, is another story and not the reason why I would get "exc …
Glorfindel's user avatar
  • 2,821
53 votes

How to find ICM talks?

Years ago I received for free a CD-ROM from World Scientific containing a PDF file with some Fields medalists' talks at the ICM. It contains talks up to and including the 1994 ICM. I have just manag …
José Figueroa-O'Farrill's user avatar
9 votes

Surprising and Useful Physical Intuition for Mathematical Objects

Mr. McGuire: Benjamin. Benjamin: Mr. McGuire. Mr. McGuire: Benjamin. Benjamin: Mr. McGuire. Mr. McGuire: I want to say two words to you. Benjamin: Yes, sir. Mr. McGuir …
José Figueroa-O'Farrill's user avatar
5 votes

What do whitehead towers have to do with physics?

I finally got a hold of the paper in question: Edward Witten's Global anomalies in string theory, where the cases of the particle and the string are discussed. The model in question is a supersymmetr …
José Figueroa-O'Farrill's user avatar
1 vote

Theorems that are 'obvious' but hard to prove

The Hodge decomposition theorem It is obvious that there is a unique point in any given affine plane in a finite-dimensional euclidean vector space which is closest to the origin. Therefore it would …
José Figueroa-O'Farrill's user avatar
1 vote

Is the dual notion of a presheaf useful?

Edit I seem to have misunderstood the nature of the duality in the question. This answer is not relevant. I'll keep it in case it has any archaeological interest. In local quantum field theory, …
José Figueroa-O'Farrill's user avatar
77 votes
Accepted

What is an integrable system?

This is, of course, a very good question. I should preface with the disclaimer that despite having worked on some aspects of integrability, I do not consider myself an expert. However I have thought …
José Figueroa-O'Farrill's user avatar
2 votes

Are rings really more fundamental objects than semi-rings?

Although not a ring, the renormalisation group of quantum field theory is really a semigroup. Moreover, there is no compelling physical reason to add inverses, since in fact physically inverses need …
José Figueroa-O'Farrill's user avatar
5 votes

Doing geometry using Feynman Path Integral?

You might find Witten's lectures on the The Dirac index on manifolds and loop spaces from the IAS course on quantum field theory useful.
José Figueroa-O'Farrill's user avatar
35 votes

The 'real' use of Quantum Algebra, Non-commutative Geometry, Representation Theory, and Alge...

Of the topics you mentioned, perhaps Representation Theory (of Lie (super)algebras) has been the most useful. I realise that this is not the point of your question, but some people may not be aware o …
José Figueroa-O'Farrill's user avatar
19 votes
Accepted

What are important examples of filtered/graded rings in physics?

It is debatable that a physicist would use those very words, and if they did one would hope their meaning would be the same as for a mathematician, since it means that they are trying to speak the sam …
José Figueroa-O'Farrill's user avatar
8 votes

Heuristic behind the Fourier-Mukai transform

You may want to look at Tom Bridgeland's PhD thesis.
José Figueroa-O'Farrill's user avatar
2 votes

Justifying a theory by a seemingly unrelated example

Many geometric problems cannot be solved without hard analysis. Perhaps the best known example is the Calabi Conjecture proved by Yau.
José Figueroa-O'Farrill's user avatar
2 votes

Justifying a theory by a seemingly unrelated example

The Poincaré conjecture is an example of a purely topological statement which apparently cannot be proved only by topological means.
José Figueroa-O'Farrill's user avatar
11 votes

Justifying a theory by a seemingly unrelated example

There are a number of algebraic theorems which are easier to prove using topology. The best known is probably the fundamental theorem of algebra, but there are others. For example, an $n\times n$ ma …
José Figueroa-O'Farrill's user avatar

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