Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 39304

for questions about etale cohomology of schemes, including foundational material and applications.

1 vote
Accepted

Analytic and algebraic torsor of abelian scheme

Here is an example when $\gamma $ is not injective. In general, if $A=A_0\times M$ is a constant abelian scheme, choose a presentation for $(A_0)_{an}$ as $\mathbb{C}^g/\mathbb{Z}^{2g}$. This induces …
SashaP's user avatar
  • 7,377
4 votes
1 answer
240 views

$l$-dependence of the group of homologically zero cycles

Consider the class map $$cl:CH^i(X)\to H^{2i}_{cont}(X,\mathbb{Z}_l(i))$$ where the RHS is the continuous etale cohomology(defined by Jannsen in his paper "Continuous etale cohomology"). In this paper …
SashaP's user avatar
  • 7,377
8 votes
0 answers
283 views

Functorial classes in Brauer group

For a smooth variety $X$ over a perfect field of characteristics $p$ the sheaf of differential operators is an Azumaya algebra(etale locally is isomorphic to endomorphisms of its center, which is bigg …
SashaP's user avatar
  • 7,377
9 votes

Is there a version of algebraic de Rham cohomology that can be used to calculate torsion cla...

Let $k$ be a field of characteristics $p$ and $R$ be any ring where $p$ is not invertible. Asuume that $F:Var_{k}\to D(R-mod)$ is a cohomology theory of smooth algebraic varieties over the field $k$ …
SashaP's user avatar
  • 7,377
6 votes
Accepted

Cohomological interpretation of G-equivariant line bundles

See Theorem 4.2.2 in https://www-fourier.ujf-grenoble.fr/~mbrion/lin.pdf In particular, in your example properness of $X=G/B$ simplifies the left part of the sequence, turning it into $$0\to \hat{G} …
SashaP's user avatar
  • 7,377
3 votes
Accepted

Functoriality of crystalline cohomology

Let's first figure out why the definition given in Berthelot-Ogus coincides with the one from the Stacks project. Unraveling the definition 5.8.3 we see that for a sheaf $G$ on $(Y/W)_{cris}$ the in …
SashaP's user avatar
  • 7,377
32 votes
2 answers
2k views

Etale cohomology can not be computed by Cech

It can be proven that if in a quasicompact scheme $X$ any finite subset is contained in an affine open subset then for any sheaf $\mathcal{F}$ on $X$ its Cech cohomology $\hat{H_{et}^{\bullet}}(X,\mat …
SashaP's user avatar
  • 7,377
9 votes
Accepted

Some basic questions on crystalline cohomology

1)Yes, such decomposition follows from the fact that Frobenius on the de Rham-Witt differential forms acts in a way that slopes on $H^i(X, W\Omega^j)[1/p]$ are in the interval $[j,j+1)$. This forces t …
SashaP's user avatar
  • 7,377