User BCnrd

74 votes

Classification of (compact) Lie groups

answered Feb 24, 2010 at 15:31

61 votes

Does "finitely presented" mean "always finitely presented"? (Answered: Yes!)

answered Feb 25, 2010 at 22:41

51 votes

Accepted

The algebraic fundamental group of a reductive algebraic group

answered Dec 14, 2010 at 2:24

48 votes

Example of connected-etale sequence for group schemes over a Henselian field?

answered Feb 23, 2010 at 7:02

41 votes

Accepted

Does formally etale imply flat for noetherian schemes?

answered Feb 13, 2010 at 18:13

38 votes

Accepted

fpqc covers of stacks

answered Feb 14, 2010 at 16:55

35 votes

Accepted

Flatness and local freeness

answered Jul 27, 2010 at 20:43

34 votes

Moduli stack of principally polarized abelian varieties

answered Feb 16, 2010 at 3:43

30 votes

What is the difference between PSL_2 and PGL_2?

answered Feb 23, 2010 at 16:30

30 votes

Is projectiveness a Zariski-local property of modules? (Answered: Yes!)

answered Feb 25, 2010 at 21:03

29 votes

Accepted

Standard reduction to the artinian local case?

answered Sep 2, 2010 at 1:30

28 votes

Accepted

Is the fixed locus of a group action always a scheme?

answered Feb 10, 2010 at 8:38

26 votes

Why are Tamagawa numbers equal to Pic/Sha?

answered Oct 29, 2010 at 22:30

25 votes

Are Jacobians principally polarized over non-algebraically closed fields?

answered Feb 13, 2010 at 9:14

25 votes

Why do automorphism groups of algebraic varieties have natural algebraic group structure?

answered Feb 25, 2010 at 14:50

24 votes

Why does non-abelian group cohomology exist?

answered Feb 21, 2010 at 13:12

23 votes

Accepted

To prove the Nullstellensatz, how can the general case of an arbitrary algebraically closed field be reduced to the easily-proved case of an uncountable algebraically closed field?

answered Feb 18, 2010 at 5:52

22 votes

non principally polarized complex abelian varieties

answered Mar 3, 2010 at 20:51

22 votes

Accepted

How do we study the theory of reductive groups?

answered Mar 9, 2010 at 20:11

21 votes

Accepted

When is an irreducible scheme quasi-compact?

answered Aug 5, 2010 at 17:01

21 votes

Accepted

Extra principal Cartier divisors on non-Noetherian rings? (answered: no!)

answered Jun 18, 2010 at 2:08

21 votes

Accepted

The central role of varieties (a comment from Mumford's Red Book)

answered Feb 24, 2010 at 23:37

21 votes

What is a good introductory text for moduli theory?

answered Oct 29, 2010 at 13:34

20 votes

Can Hom_gp(G,H) fail to be representable for affine algebraic groups?

answered Feb 10, 2010 at 8:44

19 votes

Is a quotient of a reductive group reductive?

answered Feb 15, 2010 at 21:46

18 votes

Accepted

Non-representable functor, representable on locally Noetherian schemes?

answered Nov 2, 2010 at 4:51

18 votes

Universal definition of tangent spaces (for schemes and manifolds)

answered Mar 6, 2010 at 21:20

18 votes

Comparing algebraic group orbits over big and small algebraically closed fields

answered Dec 19, 2010 at 18:58

17 votes

Accepted

Realizations and pinnings (épinglages) of reductive groups

answered Mar 9, 2010 at 23:34

17 votes

Accepted

Complete intersections and flat families

answered Mar 4, 2010 at 19:23

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75 Answers

Classification of (compact) Lie groups

Does "finitely presented" mean "always finitely presented"? (Answered: Yes!)

The algebraic fundamental group of a reductive algebraic group

Example of connected-etale sequence for group schemes over a Henselian field?

Does formally etale imply flat for noetherian schemes?

fpqc covers of stacks

Flatness and local freeness

Moduli stack of principally polarized abelian varieties

What is the difference between PSL_2 and PGL_2?

Is projectiveness a Zariski-local property of modules? (Answered: Yes!)

Standard reduction to the artinian local case?

Is the fixed locus of a group action always a scheme?

Why are Tamagawa numbers equal to Pic/Sha?

Are Jacobians principally polarized over non-algebraically closed fields?

Why do automorphism groups of algebraic varieties have natural algebraic group structure?

Why does non-abelian group cohomology exist?

To prove the Nullstellensatz, how can the general case of an arbitrary algebraically closed field be reduced to the easily-proved case of an uncountable algebraically closed field?

non principally polarized complex abelian varieties

How do we study the theory of reductive groups?

When is an irreducible scheme quasi-compact?

Extra principal Cartier divisors on non-Noetherian rings? (answered: no!)

The central role of varieties (a comment from Mumford's Red Book)

What is a good introductory text for moduli theory?

Can Hom_gp(G,H) fail to be representable for affine algebraic groups?

Is a quotient of a reductive group reductive?

Non-representable functor, representable on locally Noetherian schemes?

Universal definition of tangent spaces (for schemes and manifolds)

Comparing algebraic group orbits over big and small algebraically closed fields

Realizations and pinnings (épinglages) of reductive groups

Complete intersections and flat families