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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.

3 votes

Visualizing how Cech cohomology detects holes

Here's an idea; I'm not sure if all of the steps are possible, but I think it should work. Take a simplicial complex of dimension $n$ (all simplices are of dimension $\leq n$). "Thicken" the simplici …
Kevin H. Lin's user avatar
53 votes
Accepted

Heuristic behind the Fourier-Mukai transform

First, recall the classical Fourier transform. It's something like this: Take a function $f(x)$, and then the Fourier transform is the function $g(y) := \int f(x)e^{2\pi i xy} dx$. I really know almos …
Kevin H. Lin's user avatar
7 votes

What's a groupoid? What's a good example of a groupoid?

Let me expand a bit on what Dave said. The Yoneda lemma tells us that given an object $X$ of a category $\mathcal C$, the (covariant, contravariant, whatever) functor $h_X : \mathcal C \to \mathsf{Se …
9 votes

What is a cohomology theory (seriously)?

Urs Schreiber has already addressed parts of this question here. There's lots of good stuff to mine through in the nLab entry on cohomology.
Kevin H. Lin's user avatar
11 votes

Mathematics of path integral: state of the art

Recently I have been reading Kevin Costello's book (draft) Renormalization of Quantum Field Theories, which claims to work out some foundations of perturbative quantum field theory following the "Wils …
18 votes
Accepted

Doing geometry using Feynman Path Integral?

Try: Witten, Quantum field theory and the Jones polynomial Witten, The index of the Dirac operator in loop space I have found both of these papers quite difficult to understand. I don't know any ea …
Kevin H. Lin's user avatar
36 votes

Fundamental Examples

Someone has already mentioned tori, but I think elliptic curves in algebraic geometry merit their own separate mention. Answered by Kevin Lin
28 votes

Why is it useful to study vector bundles?

I think many of the other answers boil down to the same underlying idea: Sections of vector bundles are "generalized functions" or "twisted functions" on your manifold/variety/whatever. For example, …
Kevin H. Lin's user avatar