User Simon Rose

56 votes

3 answers

8k views

What are the benefits of viewing a sheaf from the "espace étalé" perspective?

asked May 7, 2012 at 21:01

51 votes

3 answers

7k views

What is the purpose of the flat/fppf/fpqc topologies?

asked Jan 29, 2015 at 10:33

32 votes

3 answers

3k views

Is there a nice explanation for this curious fact about cyclic subgroups?

asked Jun 3, 2016 at 9:43

21 votes

1 answer

320 views

How many ways can I factor a matrix (over $\mathbb{Z}$)?

asked Mar 29, 2016 at 14:01

16 votes

1 answer

869 views

Can one determine the dimension of a manifold given its 1-skeleton?

asked Jan 6, 2019 at 19:31

16 votes

0 answers

1k views

How many sporadic simple groups are there, really?

asked Dec 10, 2013 at 18:02

16 votes

3 answers

2k views

How do modular forms of half-integral weight relate to the (quasi-modular) Eisenstein series?

asked Sep 8, 2010 at 18:28

14 votes

0 answers

520 views

Am I missing something about this notion of Mirror Symmetry for abelian varieties?

asked Dec 1, 2014 at 12:48

13 votes

1 answer

2k views

Why isn't the orbifold cohomology of $pt/G$ equal to the cohomology of $BG$?

asked Mar 3, 2011 at 0:02

13 votes

1 answer

627 views

What relations exist among (quasi-) modular forms of different levels?

asked Mar 22, 2011 at 22:39

12 votes

2 answers

1k views

What classes am I missing in the Picard lattice of a Kummer K3 surface?

asked Feb 16, 2010 at 18:52

10 votes

1 answer

2k views

What is the geometry behind psi classes in Gromov-Witten theory?

asked May 13, 2010 at 22:07

10 votes

1 answer

290 views

What can we say about tropical maps $\mathbb{P}^1 \to A$ for an Abelian variety $A$?

asked Oct 5, 2015 at 11:11

9 votes

1 answer

268 views

How is the propagator computed on an elliptic curve?

asked May 13, 2014 at 20:08

9 votes

3 answers

982 views

Is there an intrinsic way to define the group law on Abelian varieties?

asked May 19, 2010 at 18:14

9 votes

1 answer

700 views

How do the rings of level $N$ quasi-modular forms related to the rings of modular forms?

asked Oct 31, 2011 at 2:48

8 votes

1 answer

758 views

To what extent does Poincare duality hold on moduli stacks?

asked Nov 24, 2011 at 0:03

8 votes

3 answers

3k views

Why can we define the moment map in this way (i.e. why is this form exact)?

asked Feb 14, 2011 at 20:41

8 votes

0 answers

392 views

Mirror symmetry for polarized abelian surfaces and Shioda-Inose K3s

asked Nov 19, 2014 at 14:11

7 votes

2 answers

2k views

Is there any literature on multivariable theta functions?

asked Jun 22, 2010 at 19:01

7 votes

1 answer

942 views

Trivial obstructions and virtual fundamental classes

asked Dec 19, 2011 at 22:25

7 votes

2 answers

2k views

What is a good reference (preferably thorough) for the Derived Category of a scheme/orbifold/stack?

asked May 10, 2013 at 15:04

6 votes

1 answer

279 views

Does the following operation on modular forms yield something modular?

asked Nov 20, 2013 at 21:34

6 votes

3 answers

3k views

What is this restricted sum of multinomial coefficients?

asked Aug 24, 2011 at 22:06

4 votes

2 answers

734 views

What is a reference for the Hasse-Minkowski classification of indefinite forms?

asked Mar 5, 2010 at 21:26

4 votes

2 answers

830 views

What literature is known about MacMahon's generalized sum-of-divisors function?

asked Oct 7, 2010 at 21:15

4 votes

0 answers

107 views

Is there a nice way to invert this expression?

asked Sep 8, 2015 at 8:30

3 votes

1 answer

306 views

Is there a nice way to write the generating function obtained by taking the quadratic coefficients of another one?

asked Jun 12, 2014 at 23:09

3 votes

2 answers

422 views

Is there a nice generating function proof of the following identity?

asked Oct 28, 2015 at 12:40

3 votes

2 answers

1k views

Is there a lower bound for the computational complexity of the traveling salesman problem?

asked Nov 12, 2017 at 14:26

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35 Questions

What are the benefits of viewing a sheaf from the "espace étalé" perspective?

What is the purpose of the flat/fppf/fpqc topologies?

Is there a nice explanation for this curious fact about cyclic subgroups?

How many ways can I factor a matrix (over $\mathbb{Z}$)?

Can one determine the dimension of a manifold given its 1-skeleton?

How many sporadic simple groups are there, really?

How do modular forms of half-integral weight relate to the (quasi-modular) Eisenstein series?

Am I missing something about this notion of Mirror Symmetry for abelian varieties?

Why isn't the orbifold cohomology of $pt/G$ equal to the cohomology of $BG$?

What relations exist among (quasi-) modular forms of different levels?

What classes am I missing in the Picard lattice of a Kummer K3 surface?

What is the geometry behind psi classes in Gromov-Witten theory?

What can we say about tropical maps $\mathbb{P}^1 \to A$ for an Abelian variety $A$?

How is the propagator computed on an elliptic curve?

Is there an intrinsic way to define the group law on Abelian varieties?

How do the rings of level $N$ quasi-modular forms related to the rings of modular forms?

To what extent does Poincare duality hold on moduli stacks?

Why can we define the moment map in this way (i.e. why is this form exact)?

Mirror symmetry for polarized abelian surfaces and Shioda-Inose K3s

Is there any literature on multivariable theta functions?

Trivial obstructions and virtual fundamental classes

What is a good reference (preferably thorough) for the Derived Category of a scheme/orbifold/stack?

Does the following operation on modular forms yield something modular?

What is this restricted sum of multinomial coefficients?

What is a reference for the Hasse-Minkowski classification of indefinite forms?

What literature is known about MacMahon's generalized sum-of-divisors function?

Is there a nice way to invert this expression?

Is there a nice way to write the generating function obtained by taking the quadratic coefficients of another one?

Is there a nice generating function proof of the following identity?

Is there a lower bound for the computational complexity of the traveling salesman problem?