Qiaochu Yuan's user avatar
Qiaochu Yuan's user avatar
Qiaochu Yuan's user avatar
Qiaochu Yuan
  • Member for 14 years, 5 months
  • Last seen more than a month ago
  • Oakland, California, USA
37 votes
2 answers
3k views

How can I define the product of two ideals categorically?

35 votes
4 answers
3k views

How does this relationship between the Catalan numbers and SU(2) generalize?

35 votes
3 answers
3k views

If Spec Z is like a Riemann surface, what's the analogue of integration along a contour?

35 votes
3 answers
3k views

Is every abelian group a colimit of copies of Z?

34 votes
2 answers
7k views

What is the geometric meaning of integral closure?

33 votes
7 answers
3k views

Do non-associative objects have a natural notion of representation?

33 votes
2 answers
2k views

What are the "correct" conventions for defining Clifford algebras?

32 votes
2 answers
2k views

When is there a submersion from a sphere into a sphere?

32 votes
3 answers
6k views

Is the statement that every field has an algebraic closure known to be equivalent to the ultrafilter lemma?

32 votes
4 answers
4k views

Modular curves of genus zero and normal forms for elliptic curves

31 votes
2 answers
3k views

Number theory textbook based on the absolute Galois group?

31 votes
8 answers
5k views

Resources for graphical languages / Penrose notation / Feynman diagrams / birdtracks?

31 votes
2 answers
3k views

Do we expect that sufficiently large computable ordinals settle every question of arithmetic?

30 votes
1 answer
1k views

Which of the proofs of the fundamental theorem of algebra can actually produce bounds on where the roots are?

30 votes
1 answer
4k views

For which varieties is the natural map from the Chow ring to integral cohomology an isomorphism?

29 votes
1 answer
2k views

Is there a topological space X homeomorphic to the space of continuous functions from X to [0, 1]?

29 votes
7 answers
4k views

When is a monic integer polynomial the characteristic polynomial of a non-negative integer matrix?

28 votes
2 answers
3k views

Is there a "finitary" solution to the Basel problem?

28 votes
3 answers
3k views

How can simple physical "proofs" of mathematical facts be made rigorous?

27 votes
4 answers
3k views

Is any representation of a finite group defined over the algebraic integers?

26 votes
8 answers
6k views

What is the "right" definition of a ring?

26 votes
3 answers
4k views

How are these two ways of thinking about the cross product related?

26 votes
8 answers
2k views

Examples of sequences whose asymptotics can't be described by elementary functions

25 votes
5 answers
2k views

Exotic principal ideal domains

25 votes
7 answers
4k views

Can adjoint linear transformations be naturally realized as adjoint functors?

25 votes
1 answer
1k views

From the perspective of bordism categories, where does the ring structure on Thom spectra come from?

24 votes
1 answer
3k views

What kind of random matrices have rapidly decaying singular values?

24 votes
0 answers
1k views

What, precisely, do we mean when we say that a f.d. vector space is canonically isomorphic to its double dual?

24 votes
4 answers
5k views

What is a section?

23 votes
7 answers
3k views

When can we prove constructively that a ring with unity has a maximal ideal?