Abelian varieties over Q and modular forms

This paper gives a conjectural characterization of those elliptic curves over the field of complex numbers which "should" be covered by standard modular curves. The elliptic curves in question all have algebraic j-invariant, so they can be viewed as curves over Q-bar, the field of algebraic numbers. The condition that they satisfy is that they must be isogenous to all their Galois conjugates. Borrowing a term from B.H. Gross, "Arithmetic on elliptic curves with complex multiplication," we say that the elliptic curves in question are "Q-curves." Since all complex multiplication elliptic curves are Q-curves (with this definition), and since they are all uniformized by modular forms (Shimura), we consider only non-CM curves for the remainder of this abstract. We prove: 1. Let C be an elliptic curve over Q-bar. Then C is a Q-curve if and only if C is a Q-bar simple factor of an abelian variety A over Q whose algebra of Q-endomorphisms is a number field of degree dim(A). (We say that abelian varieties A/Q with this property are of "GL(2) type.") 2. Suppose that Serre's conjecture on mod p modular forms are correct (Ref: Duke Journal, 1987). Then an abelian variety A over Q is of GL(2)-type if and only if it is a simple factor (over Q) of the Jacobian J_1(N) for some integer N\ge1. (The abelian variety J_1(N) is the Jacobian of the standard modularComment: 19 pages, AMS-TeX 2.

Galois theory and torsion points on curves

In this paper, we survey some Galois-theoretic techniques for studying torsion points on curves. In particular, we give new proofs of some results of A. Tamagawa and the present authors for studying torsion points on curves with "ordinary good" or "ordinary semistable" reduction at a given prime. We also give new proofs of: (1) The Manin-Mumford conjecture: There are only finitely many torsion points lying on a curve of genus at least 2 embedded in its Jacobian by an Albanese map; and (2) The Coleman-Kaskel-Ribet conjecture: If p is a prime number which is at least 23, then the only torsion points lying on the curve X_0(p), embedded in its Jacobian by a cuspidal embedding, are the cusps (together with the hyperelliptic branch points when X_0(p) is hyperelliptic and p is not 37). In an effort to make the exposition as useful as possible, we provide references for all of the facts about modular curves which are needed for our discussion.Comment: 18 page

On the modularity level of modular abelian varieties over number fields

Let f be a weight two newform for Gamma_1(N) without complex multiplication. In this article we study the conductor of the absolutely simple factors B of the variety A_f over certain number fields L. The strategy we follow is to compute the restriction of scalars Res_{L/\Q}(B), and then to apply Milne's formula for the conductor of the restriction of scalars. In this way we obtain an expression for the local exponents of the conductor N_L(B). Under some hypothesis it is possible to give global formulas relating this conductor with N. For instance, if N is squarefree we find that N_L(B) belongs to Z and N_L(B)*f_L^{dim B}=N^{dim B}, where f_L is the conductor of L

Documento elaborado en el marco del Seminario Virtual 2004

Este documento es producto de un seminario virtual realizado durante el primer semestre de 2004, con el objetivo de consolidar federalmente una mirada sobre los problemas que afectan a la educación en establecimientos penitenciarios

How will the pandemic change urban life?

The after-effects of lockdown will carry on for months. What will this mean for our cities? How will this pandemic shape our future urban interactions and the way we perceive life in cities? LSE alumna Louise Ribet says it is never too early to start thinking about the new normal

Emergent Disability and the Limits of Equality: A Critical Reading of the UN Convention on the Rights of Persons with Disabilities

The UN Convention on the Rights of Persons with Disabilities marks a shift in international legal relationships to, and conceptions of, disability. The Convention is the first binding international instrument of its kind related to disability. Its premises differ from the earlier World Programme on Disability, and more closely integrate the frameworks of U.S. domestic equal protection and disability civil rights law. Drawing on critical race and feminist theory, this Article critically examines the implications of internationalizing a U.S. disability law framework, with particular attention to the problem of emergent disability, or disability which is specifically produced as a consequence of social inequity or state violence