User Pierre-Yves Gaillard

56 votes

Quick proofs of hard theorems

answered May 18, 2010 at 4:40

21 votes

Dimension of infinite product of vector spaces

answered May 30, 2014 at 14:23

18 votes

Errata for Atiyah–Macdonald

answered Oct 24, 2010 at 8:27

18 votes

Examples of common false beliefs in mathematics

answered May 19, 2010 at 16:02

17 votes

Cardinality of the permutations of an infinite set

answered Jun 12, 2010 at 4:51

17 votes

Accepted

"Sums-compact" objects = f.g. objects in categories of modules?

answered Nov 19, 2011 at 11:32

11 votes

Galois theory timeline

answered Jun 2, 2010 at 13:32

9 votes

Applications of the Chinese remainder theorem

answered Jul 30, 2010 at 8:39

8 votes

Accepted

When matrices commute

answered Nov 22, 2011 at 8:04

7 votes

Accepted

Closedness of finite-dimensional subspaces

answered Sep 8, 2010 at 4:21

7 votes

Suggestions for good books on class field theory

answered May 15, 2010 at 11:04

6 votes

Are there locally compact groups which have no compact open subgroups and no discrete infinite cyclic subgroups?

answered Aug 3, 2010 at 6:04

5 votes

Localizing an arbitrary additive category

answered Jul 27, 2013 at 6:14

5 votes

Accepted

Comparing $\mathcal C$ and $\mathcal C^{\mathcal C}$ (where $\mathcal C$ is a category)

answered Jun 27, 2019 at 14:45

5 votes

Posets isomorphic to their endomorphism poset

answered Jul 24, 2019 at 14:43

5 votes

If $\mathcal C^{\mathcal C}$ is equivalent to $\mathcal C$, is $\mathcal C$ necessarily equivalent to a category with one object and one morphism?

answered Aug 4, 2019 at 11:31

5 votes

Examples of common false beliefs in mathematics

answered May 19, 2010 at 16:03

5 votes

Expressing $-\operatorname{adj}(A)$ as a polynomial in $A$?

answered Jul 20, 2010 at 9:35

4 votes

Is PA consistent? do we know it?

answered Nov 8, 2014 at 6:10

4 votes

Why are (pre)sheaves defined as contravariant functors? Why not just reverse the arrows in the first place?

answered Aug 11, 2013 at 8:52

4 votes

Can a vector space over an infinite field be a finite union of proper subspaces?

answered Jul 1, 2011 at 3:44

3 votes

What are all the natural maps between iterated duals of vector spaces, and equations between these?

answered Mar 12, 2022 at 12:09

3 votes

Math paper authors' order

answered May 18, 2010 at 3:46

3 votes

Examples of common false beliefs in mathematics

answered May 12, 2010 at 14:48

3 votes

Subset of the plane that intersects every line exactly twice

answered May 14, 2010 at 5:59

2 votes

What does it mean for a mathematical statement to be true?

answered May 12, 2010 at 9:38

2 votes

Shortest/Most elegant proof for $L(1,\chi)\neq 0$

answered May 25, 2010 at 5:56

2 votes

Taylor's theorem and the symmetric group

answered Aug 10, 2013 at 13:01

1 vote

How would one even begin to try to prove that a simple number-theoretic statement is undecidable?

answered Jun 12, 2010 at 9:36

1 vote

Unbounded operator bounded in a dense subset

answered Jun 18, 2010 at 4:44

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32 Answers

Quick proofs of hard theorems

Dimension of infinite product of vector spaces

Errata for Atiyah–Macdonald

Examples of common false beliefs in mathematics

Cardinality of the permutations of an infinite set

"Sums-compact" objects = f.g. objects in categories of modules?

Galois theory timeline

Applications of the Chinese remainder theorem

When matrices commute

Closedness of finite-dimensional subspaces

Suggestions for good books on class field theory

Are there locally compact groups which have no compact open subgroups and no discrete infinite cyclic subgroups?

Localizing an arbitrary additive category

Comparing $\mathcal C$ and $\mathcal C^{\mathcal C}$ (where $\mathcal C$ is a category)

Posets isomorphic to their endomorphism poset

If $\mathcal C^{\mathcal C}$ is equivalent to $\mathcal C$, is $\mathcal C$ necessarily equivalent to a category with one object and one morphism?

Examples of common false beliefs in mathematics

Expressing $-\operatorname{adj}(A)$ as a polynomial in $A$?

Is PA consistent? do we know it?

Why are (pre)sheaves defined as contravariant functors? Why not just reverse the arrows in the first place?

Can a vector space over an infinite field be a finite union of proper subspaces?

What are all the natural maps between iterated duals of vector spaces, and equations between these?

Math paper authors' order

Examples of common false beliefs in mathematics

Subset of the plane that intersects every line exactly twice

What does it mean for a mathematical statement to be true?

Shortest/Most elegant proof for $L(1,\chi)\neq 0$

Taylor's theorem and the symmetric group

How would one even begin to try to prove that a simple number-theoretic statement is undecidable?

Unbounded operator bounded in a dense subset