Let $X$ be a curve over a field $k$ with a rational point $e$. We define a canonical cycle ${\Delta }_e\in Z^2(X^3{)}_{\mathrm{hom}}$. Suppose that $k$ is a number field and that $X$ has semi-stable reduction over the integers of $k$ with fiber components non-singular. We construct a regular model of $X^3$ and show that the height pairing $⟨{\tau }_{*}\left({\Delta }_e\right),{\tau }_{*}^{\text{'}}\left({\Delta }_e\right)⟩$ is well defined where $\tau$ and ${\tau }^{\text{'}}$ are correspondences. The paper ends with a brief discussion of heights and $L$-functions in the case that $X$ is a modular curve.

The Mordell–Lang conjecture describes the intersection of a finitely generated subgroup with a closed subvariety of a semiabelian variety. Equivalently, this conjecture describes the intersection of closed subvarieties with the set of images of the origin under a finitely generated semigroup of translations. We study the analogous question in which the translations are replaced by algebraic group endomorphisms (and the origin is replaced by another point). We show that the conclusion of the Mordell–Lang...

Let $D_m$ be an elliptic curve over $\mathbb{Q}$ of the form $y^2=x^3-m^{2}x+m^2$, where $m$ is an integer. In this paper we prove that the two points $P_{-1}=(-m,m)$ and $P_0=(0,m)$ on $D_m$ can be extended to a basis for $D_m\left(\mathbb{Q}\right)$ under certain conditions described explicitly.

In this paper we study the structure and the degeneracies of the Mumford-Tate group $MT\left(M\right)$ of a 1-motive $M$ defined over $ℂ$. This group is an algebraic $\mathbb{Q}$- group acting on the Hodge realization of $M$ and endowed with an increasing filtration $W_{•}$. We prove that the unipotent radical of $MT\left(M\right)$, which is $W_{-1}\left(MT\left(M\right)\right)$, injects into a “generalized” Heisenberg group. We then explain how to reduce to the study of the Mumford-Tate group of a direct sum of 1-motives whose torus’character group and whose lattice are both of rank 1....

In this article we show that the Bounded Height Conjecture is optimal in the sense that, if $V$ is an irreducible subvariety with empty deprived set in a power of an elliptic curve, then every open subset of $V$ does not have bounded height. The Bounded Height Conjecture is known to hold. We also present some examples and remarks.

In this paper we show that for every prime $p\ge 5$ the dimension of the $p$-torsion in the Tate-Shafarevich group of $E/K$ can be arbitrarily large, where $E$ is an elliptic curve defined over a number field $K$, with $[K:\mathbb{Q}]$ bounded by a constant depending only on $p$. From this we deduce that the dimension of the $p$-torsion in the Tate-Shafarevich group of $A/\mathbb{Q}$ can be arbitrarily large, where $A$ is an abelian variety, with $dimA$ bounded by a constant depending only on $p$.

We study a moduli space ${\mathrm{𝒜𝒮}}_g$ for Artin-Schreier curves of genus $g$ over an algebraically closed field $k$ of characteristic $p$. We study the stratification of ${\mathrm{𝒜𝒮}}_g$ by $p$-rank into strata ${\mathrm{𝒜𝒮}}_{g.s}$ of Artin-Schreier curves of genus $g$ with $p$-rank exactly $s$. We enumerate the irreducible components of ${\mathrm{𝒜𝒮}}_{g,s}$ and find their dimensions. As an application, when $p=2$, we prove that every irreducible component of the moduli space of hyperelliptic $k$-curves with genus $g$ and $2$-rank $s$ has dimension $g-1+s$. We also determine all pairs $(p,g)$ for...

Let $K$ be a complete discretely valued field with perfect residue field $k$. Assuming upper bounds on the relation between period and index for WC-groups over $k$, we deduce corresponding upper bounds on the relation between period and index for WC-groups over $K$. Up to a constant depending only on the dimension of the torsor, we recover theorems of Lichtenbaum and Milne in a “duality free” context. Our techniques include the use of LLR models of torsors under abelian varieties with good reduction and...

The variation of the rank of elliptic curves over $\mathbb{Q}$ in families of quadratic twists has been extensively studied by Gouvêa, Mazur, Stewart, Top, Rubin and Silverberg. It is known, for example, that any elliptic curve over $\mathbb{Q}$ admits infinitely many quadratic twists of rank $\ge 1$. Most elliptic curves have even infinitely many twists of rank $\ge 2$ and examples of elliptic curves with infinitely many twists of rank $\ge 4$ are known. There are also certain density results. This paper studies the variation of the...