User Yuhao Huang

50 votes

7 answers

10k views

Why forgetful functors usually have LEFT adjoint?

asked Nov 21, 2009 at 16:36

31 votes

8 answers

5k views

Is there a "knot theory" for graphs?

asked Oct 30, 2011 at 0:46

28 votes

6 answers

3k views

Why are finiteness conditions important (and how to recognize them)?

asked May 2, 2011 at 18:09

25 votes

5 answers

5k views

Why does the (S2) property of a ring correspond to the Hartogs phenomenon?

asked Nov 8, 2010 at 19:57

25 votes

5 answers

3k views

Which algebraic varieties admit a morphism to a curve?

asked Aug 13, 2010 at 2:55

24 votes

2 answers

3k views

Why is the decomposition theorem awesome?

asked Dec 9, 2009 at 2:10

17 votes

3 answers

1k views

What are the auto-equivalences of the category of groups?

asked Dec 4, 2009 at 18:18

15 votes

6 answers

3k views

Representation of Groupoids

asked Feb 26, 2010 at 6:34

15 votes

4 answers

3k views

How does one motivates the method of separation of variables when teaching PDE's?

asked Nov 16, 2010 at 6:03

14 votes

2 answers

804 views

What's the easiest example of a morphism of topoi that is not from that of a site?

asked Oct 31, 2011 at 1:24

14 votes

1 answer

2k views

What are p-adic period rings?

asked Mar 15, 2012 at 0:20

14 votes

2 answers

1k views

Can one find the hodge number by counting points over finite fields?

asked Apr 3, 2012 at 3:15

13 votes

4 answers

2k views

Is there any generalization of the Dold-Kan correspondence?

asked Jul 21, 2010 at 7:01

13 votes

4 answers

6k views

"Counter"-example for Gauss's Lemma on irreducible polynomials

asked Nov 24, 2009 at 4:07

13 votes

3 answers

3k views

What functor does Grassmannian represent?

asked Nov 24, 2009 at 21:07

12 votes

1 answer

1k views

Cohomological functor from triangulated category

asked Apr 14, 2011 at 4:59

11 votes

3 answers

2k views

Why is a variety of general type hyperbolic?

asked Dec 5, 2009 at 20:45

10 votes

2 answers

2k views

Does the derived category remember the homological dimension?

asked Mar 5, 2011 at 6:48

10 votes

6 answers

3k views

How do you present a non-existence theorem?

asked Oct 27, 2011 at 20:09

10 votes

2 answers

3k views

What are unramified morphisms like?

asked Nov 16, 2010 at 2:31

10 votes

1 answer

915 views

Characterization of schemes whose dualizing complex is perfect

asked Sep 15, 2012 at 3:57

9 votes

1 answer

429 views

Reverse Engineering to find deformation problem (from cohomology groups)?

asked Apr 11, 2011 at 2:20

9 votes

6 answers

5k views

Figure out the roots from the Dynkin diagram

asked Jan 26, 2010 at 22:12

8 votes

1 answer

984 views

obstruction to smooth lifting of smooth schemes

asked Jan 4, 2010 at 13:47

8 votes

1 answer

623 views

Is it possible to do intersection theory in the derived category of a scheme?

asked Feb 23, 2011 at 2:18

8 votes

3 answers

484 views

Can irreducibility of polynomials be figured out in polynomial time?

asked Aug 17, 2011 at 4:47

7 votes

3 answers

3k views

How many commuting nilpotent matrices are there?

asked Sep 18, 2010 at 22:04

7 votes

6 answers

932 views

Why are the following varieties symplectomorphic?

asked Oct 22, 2010 at 6:12

7 votes

8 answers

708 views

What is an example of a function on M_g?

asked Oct 13, 2009 at 21:15

7 votes

1 answer

256 views

Is there a cohomological criterion of nefness?

asked Nov 10, 2009 at 7:22

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39 Questions

Why forgetful functors usually have LEFT adjoint?

Is there a "knot theory" for graphs?

Why are finiteness conditions important (and how to recognize them)?

Why does the (S2) property of a ring correspond to the Hartogs phenomenon?

Which algebraic varieties admit a morphism to a curve?

Why is the decomposition theorem awesome?

What are the auto-equivalences of the category of groups?

Representation of Groupoids

How does one motivates the method of separation of variables when teaching PDE's?

What's the easiest example of a morphism of topoi that is not from that of a site?

What are p-adic period rings?

Can one find the hodge number by counting points over finite fields?

Is there any generalization of the Dold-Kan correspondence?

"Counter"-example for Gauss's Lemma on irreducible polynomials

What functor does Grassmannian represent?

Cohomological functor from triangulated category

Why is a variety of general type hyperbolic?

Does the derived category remember the homological dimension?

How do you present a non-existence theorem?

What are unramified morphisms like?

Characterization of schemes whose dualizing complex is perfect

Reverse Engineering to find deformation problem (from cohomology groups)?

Figure out the roots from the Dynkin diagram

obstruction to smooth lifting of smooth schemes

Is it possible to do intersection theory in the derived category of a scheme?

Can irreducibility of polynomials be figured out in polynomial time?

How many commuting nilpotent matrices are there?

Why are the following varieties symplectomorphic?

What is an example of a function on M_g?

Is there a cohomological criterion of nefness?