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

1 vote
0 answers
79 views

Abelian coverings as pull-backs of isogenies

Fix an algebraically closed field $k$ and a smooth projective (geometrically) integral genus $\geq 2$ curve $C$ over $k$. Denote by $J_C$ the Jacobian variety of $C$. Chapter VI, Proposition 11 of Ser …
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1 vote
0 answers
92 views

Some questions about inclusions of Brauer groups/sets

I have a feeling this question will be left hanging on StackExchange, so I've decided to just post it here, let me know if it's not suitable. First of all, I'm trying to show that given an immersion o …
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  • 895
1 vote
0 answers
49 views

Corresponding morphism of an adèlic point

Let $X$ be a smooth geometrically connected variety over a number field $k$ and let $X(\mathbb{A}_k)$ be the space of adèlic points of $X$, i.e., for some finite set $S$ containing the infinite places …
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  • 895
0 votes
0 answers
185 views

Torsors under non-abelian group schemes

Let $X \rightarrow Y$ be an immersion of smooth geometrically connected varieties over a number field $k$. Let $G$ be a finite étale non-abelian group scheme. Are there known cases where we have an is …
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  • 895
2 votes
1 answer
187 views

Is there a Rosenlicht's lemma for semi-abelian varieties?

In the literature, there are a number of results called Rosenlicht's lemma, but I am talking about the following one: Let $T$ be a torus over a, in my case, number field $k$. Denote by $\bar{k}[T]$ th …
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  • 895
1 vote
0 answers
85 views

Geometric Picard group of a semi-abelian variety

Fix a number field $k$ and consider a smooth projective geometrically connected $k$-curve $C$, with a $k$-rational divisor class of degree one inducing the embedding into its Jacobian $J$. For any den …
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  • 895
4 votes
1 answer
541 views

Curves and semi-abelian varieties

Fix $k$ a number field, and let $C$ be a smooth geometrically integral affine curve over $k$. We can "associate" to $C$ a semi-abelian variety in the following way: One knows that $C$ is a finite numb …
oleout's user avatar
  • 895
3 votes
1 answer
495 views

The notion of abelian covers

I have some doubts about what an abelian covering is, and I'll try my best to articulate them. In Serre's Algebraic groups and class fields Chapter VI.2, he fixed a base field $k$ with algebraic closu …
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  • 895
1 vote
0 answers
198 views

Cohomology of a curve and its Jacobian over an algebraic closure of a number field

In this MathOverflow post, the smooth projective curve $C$ was defined over $\mathbb{C}$ and we have an isomorphism of de Rham cohomology groups $$H^1(C, \mathbb{C}) \cong H^1(J_C, \mathbb{C}),$$ wher …
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  • 895
2 votes
0 answers
90 views

Reconciling two notions of finite descent obstructions

Let $k$ be a number field and $X$ a smooth geometrically connected variety over $k$. We denote by $H(k,X)$ the set of sections $G_k \rightarrow \pi_1(X)$, where $G_k$ is the absolute Galois group of $ …
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  • 895
1 vote
0 answers
83 views

Are there known situations where this weaker form of the section conjecture holds?

Let $k$ be a number field. The section conjecture predicts that for a (smooth geometrically connected) hyperbolic curve over $k$, the profinite Kummer map $\kappa :X(k) \rightarrow \mathscr{J}_{\pi_1( …
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  • 895
1 vote
0 answers
107 views

Does an open immersion "cut out" points surviving finite descent?

Let $X$ be a smooth affine curve over a number field $k$, and let $C$ be its smooth compactification. Let $i:X(\mathbb{A}_k) \rightarrow C(\mathbb{A}_k)$ be the induced morphism of adelic points by th …
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  • 895
2 votes
0 answers
134 views

Results concerning surjectivity of Brauer groups

Are there known cases of a morphism of smooth geometrically connected curves $f: X \rightarrow Y$ over a number field $k$ (to be specific) that would give rise to a surjective restriction map $f^*:\ma …
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  • 895
1 vote
0 answers
158 views

The $H^1$ of a smooth curve and its (generalized) Jacobian variety

Let $C$ be a smooth projective curve of genus $\geq 1$ over a number field $k$ with a $k$-rational divisor of degree $1$ inducing the embedding $C \hookrightarrow J$, where $J$ is the Jacobian variety …
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  • 895
1 vote
0 answers
112 views

Isomorphism of Brauer groups of curves

I asked this question a few days ago on math.stackexchange with no success, and it doesn't seem like there'll be any. So I thought I'll repost it here. A recent big result proved by $\mathrm{\check{C} …
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