User Bjorn Poonen

105 votes

Accepted

Conceptual reason why the sign of a permutation is well-defined?

answered Mar 9, 2022 at 4:15

97 votes

Experimental mathematics leading to major advances

answered Jan 17, 2010 at 9:46

76 votes

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Is there an "elementary" proof of the infinitude of completely split primes?

answered Feb 14, 2010 at 1:49

76 votes

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Polynomial with the primes as coefficients irreducible?

answered Mar 14, 2010 at 7:25

55 votes

Accepted

How can I define the product of two ideals categorically?

answered Feb 9, 2010 at 6:12

48 votes

Intuition for the last step in Serre's proof of the three-squares theorem

answered Dec 31, 2009 at 23:08

47 votes

Expected determinant of a random NxN matrix

answered Jan 26, 2010 at 4:32

46 votes

Roots of truncations of $ e^x - 1$

answered Feb 26, 2010 at 5:46

41 votes

Accepted

Bringing Number and Graph Theory Together: A Conjecture on Prime Numbers

answered Mar 23, 2010 at 2:11

35 votes

Accepted

Order of the Tate-Shafarevich group

answered Dec 28, 2009 at 20:50

34 votes

Accepted

When a formal power series is a rational function in disguise

answered Feb 10, 2010 at 8:18

33 votes

Is there a Whitney theorem type theorem for projective schemes?

answered Feb 6, 2010 at 17:37

33 votes

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non principally polarized complex abelian varieties

answered Mar 3, 2010 at 21:21

30 votes

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What's the probability that k + n^2 is squarefree, for fixed k?

answered Mar 1, 2010 at 22:48

30 votes

Integer matrices with no integer eigenvalues

answered May 16, 2010 at 4:34

29 votes

Are there any nonlinear solutions to $f(x+1) - f(x) = f'(x)$?

answered Jan 14, 2010 at 7:41

28 votes

What are interesting families of subsets of a given set?

answered Feb 1, 2010 at 5:16

28 votes

Accepted

Is a universally closed morphism of schemes quasi-compact ?

answered May 5, 2010 at 1:42

27 votes

Theorems with unexpected conclusions

answered Mar 14, 2010 at 2:14

26 votes

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Everywhere locally isomorphic abelian varieties

answered Dec 30, 2009 at 2:23

25 votes

Is a 'generic' variety nonsingular? Or singular?

answered Mar 8, 2010 at 3:12

24 votes

Accepted

When f(x)-a and f(x)-b yield the same field extension

answered Dec 27, 2009 at 16:11

24 votes

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Example of a smooth morphism where you can't lift a map from a nilpotent thickening?

answered Apr 21, 2010 at 19:08

23 votes

Are most cubic plane curves over the rationals elliptic?

answered Jan 10, 2010 at 17:41

23 votes

Is the theory of categories decidable?

answered Jan 24, 2010 at 0:25

22 votes

Accepted

Is there a matrix C so that the trace of C^n is dense in R?

answered Feb 12, 2010 at 0:39

22 votes

Size of the smallest group not satisfying an identity.

answered Feb 12, 2010 at 2:31

22 votes

Least number of non-zero coefficients to describe a degree n polynomial

answered Mar 26, 2010 at 22:25

22 votes

Accepted

Images of action of Galois on the Tate module of Elliptic Curve,

answered May 7, 2010 at 2:13

21 votes

Accepted

When does a p-adic function have a Mahler expansion?

answered Feb 13, 2010 at 21:28

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95 Answers

Conceptual reason why the sign of a permutation is well-defined?

Experimental mathematics leading to major advances

Is there an "elementary" proof of the infinitude of completely split primes?

Polynomial with the primes as coefficients irreducible?

How can I define the product of two ideals categorically?

Intuition for the last step in Serre's proof of the three-squares theorem

Expected determinant of a random NxN matrix

Roots of truncations of $ e^x - 1$

Bringing Number and Graph Theory Together: A Conjecture on Prime Numbers

Order of the Tate-Shafarevich group

When a formal power series is a rational function in disguise

Is there a Whitney theorem type theorem for projective schemes?

non principally polarized complex abelian varieties

What's the probability that k + n^2 is squarefree, for fixed k?

Integer matrices with no integer eigenvalues

Are there any nonlinear solutions to $f(x+1) - f(x) = f'(x)$?

What are interesting families of subsets of a given set?

Is a universally closed morphism of schemes quasi-compact ?

Theorems with unexpected conclusions

Everywhere locally isomorphic abelian varieties

Is a 'generic' variety nonsingular? Or singular?

When f(x)-a and f(x)-b yield the same field extension

Example of a smooth morphism where you can't lift a map from a nilpotent thickening?

Are most cubic plane curves over the rationals elliptic?

Is the theory of categories decidable?

Is there a matrix C so that the trace of C^n is dense in R?

Size of the smallest group not satisfying an identity.

Least number of non-zero coefficients to describe a degree n polynomial

Images of action of Galois on the Tate module of Elliptic Curve,

When does a p-adic function have a Mahler expansion?