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Abelian varieties are projective algebraic varieties endowed with an Abelian group structure. Over the complex numbers, they can be described as quotients of a vector space by a lattice of full rank. They are analogs in higher dimensions of elliptic curves, and play an important role in algebraic geometry and number theory.

2 votes
0 answers
273 views

Which endomorphisms of the Tate module of an abelian variety are "algebraic"?

For an abelian variety $A$ over a field $k$ with characteristic different from $\ell$ and Galois group $G = Gal(\overline k/k)$, there is always an injective map of the form: $$\mathbb Q_\ell\otimes E …
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6 votes
0 answers
188 views

Abelian varieties with rank 0 over each global field

For each global field $K$, can we always find an Abelian variety $A$ with $A(K)$ rank $0$? By Lang-Neron, Mordell Weil is also true for finite type fields (fields finitely generated over their prime …
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1 vote
0 answers
144 views

A map on Jacobians coming from a correspondence explicitly

From this question, we know that every map of the form $J(C) \to J(C)$ for a curve $C$ and it's jacobian $J(C)$ comes from a correspondence between $C\times C$ and in fact we can take this corresponde …
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3 votes
0 answers
408 views

The final step in the proof of Neron-Ogg-Shafarevich as in the paper of Serre-Tate

I have been reading the paper "Good Reduction of Abelian Varieties" of Serre-Tate and in particular the part where they show that the Tate module being unramified implies good reduction. As in the p …
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4 votes
0 answers
181 views

Weil Pairing and Galois descent

One way the Weil pairing for an Abelian Variety $A/k$ is phrased is the following (for simplicity, let me only deal with the multiplication by $m$ map ($[m]: A\to A$) instead of arbitrary isogenies): …
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2 votes
0 answers
122 views

A Lefschetz style formula for the $\ell^\infty$ torsion of an Abelian variety over a finite ...

Let $A/\mathbb F_q$ be an abelian variety over a finite field. Define $A_\ell = A[\ell^\infty](\mathbb F_q)$, the $\ell^n$ ($n\geq 0)$ torsion points defined over the base field. I can assume $\ell \n …
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4 votes
0 answers
100 views

The profinite topology on the Mordell Weil group

In this lecture of Serre on his open image theorem, around 6 minutes, Serre mentions the following theorem of Tate: Let $A/k$ be an abelian variety over a number field and consider the Mordell-Weil gr …
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2 votes
0 answers
157 views

Faltings' height theorem for isogenies over finite fields

For an Abelian scheme over a ring of integers in a number field, Faltings has a theorem that describes how the Faltings' height changes through an isogeny. There are multiple references for this state …
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13 votes
2 answers
578 views

A geometric definition of the addition law on abelian surfaces

Most people will have see a geometric "explanation" of the addition law on elliptic curves given by embedding it as a cubic in the projective plane and cutting it with lines. Is there a similar explic …
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4 votes
1 answer
331 views

What is the involution on the moduli space of genus 3 curves induced by the Torelli map

Let $M_g$ be the moduli space of genus $g$ curves, $A_g$ be the moduli space of principally polarized dimension $g$ abelian varieties. They have dimensions $3g-3,g(g+1)/2$ respectively. The Torelli ma …
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5 votes
0 answers
459 views

A functor on Abelian varieties corresponding to this operation on Weil numbers

Let $A/\mathbb F_q$ be an abelian variety over a finite field with Weil numbers $q^{1/2}\alpha_1,\dots,q^{1/2}\alpha_n$. Consider the numbers $q^{d/2}\alpha_1,\dots,q^{d/2}\alpha_n$. These are stil …
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11 votes
1 answer
336 views

Lifting a splitting of an Abelian variety to characteristic 0

Let $R$ be the ring of integers in a (complete) algebraic closure of $\mathbb Q_p$ with maximal ideal $\mathfrak p$. Suppose I have an Abelian surface $\mathcal A/R$ such that over every $R/\mathfrak …
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6 votes
0 answers
126 views

For which (g,q) does there exist a supersingular curve?

We say a curve over a finite field $\mathbb F_q$ is supersingular if it's Frobenius eigenvalues (on $H^1(X,\mathbb Z_\ell)$) are of the form $q^{1/2}\alpha$ for $\alpha$ a root of unity. As far as I …
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6 votes
1 answer
675 views

On the moduli stack of abelian varieties without polarization

(I am especially interested in abelian surfaces and characteristic 0). How bad is the moduli stack of abelian varieties (with no polarization or level structure)? Is it an Artin stack? DM (Deligne-M …
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2 votes
1 answer
288 views

The size of endomorphism rings and the relation to ordinariness of Abelian surfaces

For Elliptic curves over a finite field, there is a very useful characterization of ordinary elliptic as those with commutative, quadratic endomorphism rings and of supersingular curves as those with …
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