User Greg Stevenson

81 votes

Accepted

How do I check if a functor has a (left/right) adjoint?

answered Nov 17, 2009 at 6:31

50 votes

Accepted

How do I know the derived category is NOT abelian?

answered Feb 18, 2010 at 2:43

49 votes

Accepted

Order of an automorphism of a finite group

answered Oct 18, 2009 at 21:24

28 votes

Accepted

What is the "right" definition of a ring?

answered Oct 27, 2009 at 2:44

27 votes

Pushouts in the Category of Schemes

answered Nov 12, 2009 at 5:54

25 votes

Accepted

What is the opposite category of the category of modules (or Hopf algebra representations)?

answered Jun 25, 2010 at 0:35

22 votes

Accepted

Why do people "forget" Verdier abelianization functor?(Looking for application)

answered Feb 11, 2010 at 21:27

22 votes

Accepted

triangulated vs. dg/A-infinity

answered Oct 17, 2009 at 1:27

20 votes

Accepted

Noetherian local ring and the growth of $\dim_k \operatorname{Ext}^i(k,k)$

answered Oct 31, 2018 at 8:42

19 votes

Accepted

Nonprojective Surface

answered Nov 1, 2009 at 0:21

18 votes

Accepted

Splitting in triangulated categories

answered Nov 9, 2009 at 23:00

17 votes

Accepted

What is the relationship between t-structure and Torsion pair?

answered Feb 8, 2010 at 11:32

15 votes

Why is it a good idea to study a ring by studying its modules?

answered Nov 12, 2009 at 20:29

14 votes

Accepted

Characterization of schemes whose dualizing complex is perfect

answered Sep 15, 2012 at 8:05

13 votes

When does sheaf cohomology commute with arbitrary direct sums?

answered Feb 5, 2013 at 4:20

13 votes

Some intuition behind the five lemma?

answered Oct 26, 2009 at 22:46

12 votes

Accepted

Intuitive Example of a Jacobson Radical

answered Oct 30, 2009 at 23:27

12 votes

Categories which are not compactly generated

answered Nov 11, 2009 at 2:56

11 votes

What is an intuitive view of adjoints? (version 1: category theory)

answered Nov 23, 2009 at 10:41

11 votes

Accepted

Is the chain homotopy category, K(Ab), an Abelian category? By Ab, I mean the category of Abelian groups.

answered Apr 29, 2010 at 0:54

10 votes

Abelian category which is not well-powered

answered Apr 12, 2012 at 11:35

10 votes

Accepted

Classifying triangulated structures on a graded category

answered Nov 8, 2009 at 20:24

10 votes

Presheaves as limits of representable functors?

answered Oct 28, 2009 at 23:24

10 votes

Accepted

Does the fiber product of two normal varieties remain normal?

answered Oct 23, 2009 at 9:08

9 votes

Accepted

Freyd-Mitchell for triangulated categories?

answered Oct 20, 2009 at 19:55

9 votes

distinguished triangles and cohomology

answered Oct 31, 2009 at 21:01

9 votes

Accepted

Verdier duality via Brown representability?

answered Feb 17, 2010 at 11:13

9 votes

Accepted

Matrix factorization categories beyond the isolated singularity case

answered Aug 28, 2010 at 0:32

8 votes

Accepted

Can one extend a morphism of commutative triangles to a morphism of octahedral diagrams?

answered May 13, 2010 at 23:38

8 votes

Accepted

Is the tensorproduct of a triangulated category with a ring again triangulated?

answered Jun 2, 2010 at 2:03

Stack Exchange Network

86 Answers

How do I check if a functor has a (left/right) adjoint?

How do I know the derived category is NOT abelian?

Order of an automorphism of a finite group

What is the "right" definition of a ring?

Pushouts in the Category of Schemes

What is the opposite category of the category of modules (or Hopf algebra representations)?

Why do people "forget" Verdier abelianization functor?(Looking for application)

triangulated vs. dg/A-infinity

Noetherian local ring and the growth of $\dim_k \operatorname{Ext}^i(k,k)$

Nonprojective Surface

Splitting in triangulated categories

What is the relationship between t-structure and Torsion pair?

Why is it a good idea to study a ring by studying its modules?

Characterization of schemes whose dualizing complex is perfect

When does sheaf cohomology commute with arbitrary direct sums?

Some intuition behind the five lemma?

Intuitive Example of a Jacobson Radical

Categories which are not compactly generated

What is an intuitive view of adjoints? (version 1: category theory)

Is the chain homotopy category, K(Ab), an Abelian category? By Ab, I mean the category of Abelian groups.

Abelian category which is not well-powered

Classifying triangulated structures on a graded category

Presheaves as limits of representable functors?

Does the fiber product of two normal varieties remain normal?

Freyd-Mitchell for triangulated categories?

distinguished triangles and cohomology

Verdier duality via Brown representability?

Matrix factorization categories beyond the isolated singularity case

Can one extend a morphism of commutative triangles to a morphism of octahedral diagrams?

Is the tensorproduct of a triangulated category with a ring again triangulated?