User Heer

14 votes

4 answers

4k views

group of Yoneda extensions and the EXT groups defined via derived category

asked Sep 24, 2010 at 23:23

7 votes

2 answers

773 views

Is an algebraic space over a DVR, whose special fibre and generic fibre are schemes, actually a scheme?

asked Jul 4, 2013 at 13:21

7 votes

1 answer

636 views

How to compute the group cohomology of $\mathbb{Z}/n\mathbb{Z}\times \mathbb{Z}/n\mathbb{Z}$ with coefficient in a trivial module?

asked Apr 4, 2018 at 21:05

6 votes

0 answers

151 views

Does an fppf cohomological class annihilated by an etale cover come from etale cohomological group?

asked Jan 1, 2019 at 16:42

6 votes

1 answer

2k views

Does a section of a morphism of schemes give a subscheme?

asked Sep 14, 2013 at 0:05

6 votes

1 answer

418 views

Representability of sheaf of Ext^1 of a Néron model by $\mathbb{G}_m$

asked Nov 24, 2012 at 14:31

5 votes

0 answers

239 views

Semiabelian actions appearing in the toroidal campactification of a degenearting abelian varieties

asked Jul 25, 2013 at 12:26

4 votes

0 answers

247 views

How to compute the first etale cohomology of a constructible torsion-free sheaf?

asked Nov 22, 2015 at 17:11

4 votes

1 answer

568 views

How to construct cup-product in a general site?

asked Jun 12, 2019 at 10:14

3 votes

1 answer

1k views

what is the first Galois cohomology group of the Galois module End(T_l(A)) for some abelian variety A over a finite field k and l some prime number different from the characteristic of the base field?

asked May 17, 2010 at 9:57

2 votes

1 answer

329 views

What is the projective dimension of the ring $\mathbb{Z}_l[T,T^{-1}]$ ? l is a prime number

asked May 1, 2011 at 0:02

2 votes

0 answers

297 views

about the fppf-hom sheaf $\mathscr{H}om(X,\mathbb{G}_a)$

asked Sep 16, 2011 at 13:32

2 votes

1 answer

283 views

about the local ring of $\mathbb{Z}_p[T]/(pT^2+T+1)$ at the prime p

asked May 16, 2012 at 20:49

2 votes

2 answers

571 views

How to compute the first derived direct image along an open immersion, for the fppf sheaf represented by a multiplicative group?

asked Jul 16, 2012 at 22:06

2 votes

0 answers

209 views

About Alexeev and Nakamura's paper "on Mumford's construction of degenerating abelian varieites"

asked Apr 11, 2013 at 15:12

2 votes

0 answers

171 views

How to determine a functor (natrually arising from geometry or homological algebra) to be locally of finite presentation?

asked Jan 2, 2015 at 10:34

2 votes

0 answers

499 views

Reference for cdh topology

asked Jan 24, 2015 at 16:57

2 votes

0 answers

207 views

How far is it to extend the results of SGA III Exp. VIB from group schemes to group spaces?

asked Mar 26, 2015 at 16:08

2 votes

0 answers

198 views

Is surjectivity for morphisms of schemes local on the domain?

asked Mar 27, 2015 at 15:30

2 votes

1 answer

88 views

Is the integral closure of a $\mathbb{Z}/n\mathbb{Z}$-graded noetherian domain in a bigger $\mathbb{Z}/n\mathbb{Z}$-graded domain also graded?

asked Mar 19, 2023 at 17:16

1 vote

0 answers

256 views

How does the line bundles look like on a proper model (or Néron model) of an abelian variety?

asked Dec 15, 2012 at 16:35

1 vote

1 answer

1k views

what is the tensor product of two anti-commutative DG-algebras?

asked Aug 30, 2010 at 22:59

0 votes

0 answers

808 views

restriction and pullback of representable etale sheaf along closed immersion

asked Dec 5, 2012 at 10:40

0 votes

1 answer

562 views

Obstruction and 1st order infinitesimal deformations of Generalized Elliptic Curves (Deligne-Rapoport)

asked Aug 15, 2014 at 12:58

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24 Questions

group of Yoneda extensions and the EXT groups defined via derived category

Is an algebraic space over a DVR, whose special fibre and generic fibre are schemes, actually a scheme?

How to compute the group cohomology of $\mathbb{Z}/n\mathbb{Z}\times \mathbb{Z}/n\mathbb{Z}$ with coefficient in a trivial module?

Does an fppf cohomological class annihilated by an etale cover come from etale cohomological group?

Does a section of a morphism of schemes give a subscheme?

Representability of sheaf of Ext^1 of a Néron model by $\mathbb{G}_m$

Semiabelian actions appearing in the toroidal campactification of a degenearting abelian varieties

How to compute the first etale cohomology of a constructible torsion-free sheaf?

How to construct cup-product in a general site?

what is the first Galois cohomology group of the Galois module End(T_l(A)) for some abelian variety A over a finite field k and l some prime number different from the characteristic of the base field?

What is the projective dimension of the ring $\mathbb{Z}_l[T,T^{-1}]$ ? l is a prime number

about the fppf-hom sheaf $\mathscr{H}om(X,\mathbb{G}_a)$

about the local ring of $\mathbb{Z}_p[T]/(pT^2+T+1)$ at the prime p

How to compute the first derived direct image along an open immersion, for the fppf sheaf represented by a multiplicative group?

About Alexeev and Nakamura's paper "on Mumford's construction of degenerating abelian varieites"

How to determine a functor (natrually arising from geometry or homological algebra) to be locally of finite presentation?

Reference for cdh topology

How far is it to extend the results of SGA III Exp. VIB from group schemes to group spaces?

Is surjectivity for morphisms of schemes local on the domain?

Is the integral closure of a $\mathbb{Z}/n\mathbb{Z}$-graded noetherian domain in a bigger $\mathbb{Z}/n\mathbb{Z}$-graded domain also graded?

How does the line bundles look like on a proper model (or Néron model) of an abelian variety?

what is the tensor product of two anti-commutative DG-algebras?

restriction and pullback of representable etale sheaf along closed immersion

Obstruction and 1st order infinitesimal deformations of Generalized Elliptic Curves (Deligne-Rapoport)