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Algebraic varieties, stacks, sheaves, schemes, moduli spaces, complex geometry, quantum cohomology.

1 vote
0 answers
137 views

Representablility of maps between classifying spaces

Assume that $G,H$ are two sheaves of groups (say in fpqc topology on the scheme $X$) and there is a map $G\to H$ which is representable by a closed immersion. Let us also assume that the quotient is r …
ali's user avatar
  • 1,093
1 vote
0 answers
87 views

Image of higher displays in isocrystals

There is a functor from the category of higher displays over $k$ of type $\mu$ to the category of isocrystals over $k$ where $k$ is an algebraically closed field where you forget about the filtration …
ali's user avatar
  • 1,093
2 votes
0 answers
498 views

Relative homology in Fargues-Scholze paper

if $f:X\to Y$ is a map of small v-stacks, Scholze and Fargues define relative homology as the left adjoint to the $f^{\star}$. They say the left adjoint exist because $f$ is a slice in $v$-site (they …
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  • 1,093
4 votes
1 answer
261 views

Relation between rational Tate module and universal cover of a p-divisible group

We can associate two $\mathbb Q_p$ vector spaces to a $p$-divisible group, and I'm a little confused about the relation between these two groups. First of all, I think part of my problem is that when …
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  • 1,093
3 votes
0 answers
279 views

Chevalley’s affineness criterion for perfectoid space

Chevalley’s affineness criterion says that if $f: X\to Y$ is surjective and finite, $Y$ is Noetherian and $X$ is affine then $Y$ is also affine. The usual proof uses Serre's criterion and Noetherian i …
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  • 1,093
1 vote

Intuition behind formal neighborhood and local ring and formal power series

First of all $\mathbb{C[[x,y]]}$ is local because it is only depend on $\mathbb{C}[x,y]_{(x,y)}$ because by definition it is $lim \frac{\mathbb{C}[x,y]}{(X,Y)^n}$ and all things outside $(X,Y)$ are in …
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  • 1,093
1 vote
Accepted

Integral models and adelic points

for your first question, the idea is basically what MikhailBorovoi said but of course you have to be careful to get a model outside $S$: add all the prime divisors of dominators of the equations defin …
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  • 1,093
6 votes
Accepted

Motivation for Henselian rings in algebraic geometry

First about the ralation between henselian and formal smoothness property, I think a good idea is to look at what was the first version of Hensel lemma: it says that if $f(\bar{a})=0,f'(\bar{a})\, mo …
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  • 1,093
1 vote
0 answers
282 views

Shimura varieties which are not of abelian type but has a good modular description

Deligne's idea was that Shimura varieties should be understood as moduli space of motives(with extra structures). lot's of Shimura varieties of abelian type can be understood as moduli space of abelia …
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  • 1,093
1 vote
Accepted

Question about valuation and blow up (a lemma in GIT book)

do you know how we cunstruct a blow up? for your first question blow up of affine $A$ at the ideal $I$ is covered by $$Spec(A[\frac{x^{r_0}\cdot y^{s_0}}{x^{r_i}\cdot y^{s_i}},...,\frac{x^{r_n}\cdot y …
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  • 1,093
3 votes
1 answer
270 views

complement of "good reduction" points in p-adic shimura varieties

assume that $X$ is Siegel Shimura variety defined over $\mathbb{Z}_p$, you can take its p-adic formal completion $\mathfrak{X}$,and than take it's adic generic fiber $\mathcal{X}$ and get an adic spa …
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  • 1,093
3 votes
0 answers
129 views

how much information $O_K$ points of a formal scheme over $\mathbb{Z}_p$ contain

assume that $Spf\,A\to Spf\,\mathbb{Z}_p[[t_1,...,t_n]]$ is a closed immersion of flat integral formal schemes over $\mathbb{Z_p}$. I see Kisin several time use that if $Spf\,A(O_K)\subset SPf\,\mathb …
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  • 1,093
4 votes
0 answers
273 views

nearby cycles map for affine formal schemes

Assume that $X=Spf R$ is p-adic formal scheme over $O_{C_p}$ with generic fiber $X_{\eta}$. I want to know why the nearby cycles map $Ru^\star \mathbb{Z/p}$ is equal to $R\Gamma_{et}(spec R[1/p],\math …
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  • 1,093
11 votes
0 answers
874 views

Why diamonds are only defined in characteristic $p$?

I'm trying to read Scholze's article "Etale cohomology of diamonds" (arXiv link) and both in this article and in Berkeley notes, the diamonds are defined as sheaves on the category of characteristic $ …
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  • 1,093
11 votes

What is the cotangent complex good for?

If you want to see the relation between differential forms and deformation theory you can look at the part B of Illusie article in FGA explained which shows that why the obstruction to the problem of …
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  • 1,093

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