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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.

15 votes

Which curves can be found on Abelian varieties?

For any $g >0$ there exists an abelian surface $A$ containing a smooth curve $C$ of genus $g$; the surface can be assumed to be simple if $g > 1$: For $g=1$, one can just consider $C \times C$. For …
naf's user avatar
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10 votes
1 answer
537 views

Orders of reductions of rational points on elliptic curves

I am looking for references where the following (or similar questions) have been studied: Let $K$ be a number field or a function field in one variable over a finite field and let $E$ be an elliptic …
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8 votes
Accepted

Reference for a theorem of Tate on the endomorphism rings of AVs over finite fields

I think the result appears in: Waterhouse, W. C.; Milne, J. S.: Abelian varieties over finite fields. 1969 Number Theory Institute (Proc. Sympos. Pure Math., Vol. XX, State Univ. New York, Stony Broo …
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8 votes

Canonical liftings of endomorphisms of ordinary abelian varieties

A reference which proves a more general result is Theorem 1 of the appendix to the paper by Mehta and Srinivas "Varieties in positive characteristic with trivial tangent bundle." With an appendix by S …
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5 votes
Accepted

Nef divisors on abelian varieties

I think it is probably easier to prove that $L$ is ample when all the inequalities are strict: The assumption for $i=n$ implies that $K(L)$ is finite, i.e., $L$ is non-degenerate, by the second stat …
4 votes
Accepted

Essential dimension and the moduli space of abelian varieties

The two notions are related using Theorems 4.1 and 6.1 of the paper of Brosnan, Reichstein and Vistoli: Theorem 6.1 reduces the computation of the essential dimension of the stack to that of the gen …
4 votes
Accepted

Kuga-Satake with p-adic methods

A good place to look is the paper "Kuga-Satake abelian varieties of K3 surfaces in mixed characteristic". J. Reine Angew. Math. 648 (2010), 13–67, by Jordan Rizov. There are also related results by Yv …
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4 votes

CM abelian varieties and potential good reduction

Potential good reduction everywhere is quite far from having complex multiplication. For elliptic curves, the condition is equivalent to the $j$-invariant being an algebraic integer. For $F = \mathbb …
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4 votes
Accepted

Mumford-Tate groups of abelian varieties with potentially good reduction everywhere

An elliptic curve with integral $j$-invariant has potential good reduction everywhere. If it does not have CM then its Mumford-Tate group is $GL_{2,\mathbb{Q}}$ which is not anisotropic modulo its cen …
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4 votes
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Nef classes on abelian varieties in positive characteristic

Here is a sketch of a purely algebraic proof based on the theory developed in Chapter 3 of Mumford's "Abelian Varieties". Let $L$ be a nef line bundle on the abelian variety $A$ of dimension $g$. If …
3 votes
Accepted

Intersection multiplicity in abelian varieties

The following answer expands on my comment. We use Fulton's definition of the intersection product. Consider the diagonal embedding $\Delta$ of $A$ in $A \times A$ (which is regular) and intersect t …
3 votes
Accepted

$p$-divisibility of Picard groups

$\newcommand{\wt}{\widetilde}$ $\newcommand{\mr}{\mathrm}$ The question has a positive answer, in fact, regularity of $C$ is not needed. The proof as written below works under the assumption that $C$ …
2 votes

Algebraic cycles of dimension 2 on the square of a generic abelian surface

As far as I know, there is no smooth projective variety over $\mathbb{C}$ of dimension $n>2$ with all possible Hodge numbers nonzero (i.e. $h^{p,q} \neq 0$ for all $p+q = n$) for which the Griffiths g …
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1 vote

Examples of rational families of abelian varieties.

One can construct some families over rational bases which are not Jacobians by taking quotients: For example, let $A$ be a fixed abelian variety of dimension $> 1$ and let $S$ be the space of all smo …
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