Serre's uniformity problem in the split Cartan case

Serre's Uniformity Conjecture for Elliptic Curves with Rational Cyclic Isogenies

Let $E$ be an elliptic curve over $\mathbb{Q}$ such that $\mathrm{End}_{\bar{\mathbb{Q}}}(E)=\mathbb{Z}$ and which admits a non-trivial cyclic $\mathbb{Q}$-isogeny. We prove that, for $p>37$, the residual mod $p$ Galois representation $\barρ_{E,p}:G_{\mathbb{Q}}\rightarrow\mathrm{GL}_2(\mathbb{F}_p)$ is surjective.

Some cases of Serre's uniformity problem

We show that if $E/\mathbb{Q}$ is an elliptic curve without complex multiplication and for which there is a prime $q$ such that the image of $\barρ_{E,q}$ is contained in the normaliser of a split Cartan subgroup of $\rm{GL}_2(\mathbb{F}_q)$, then $\barρ_{E,p}$ surjects onto $\rm{GL}_2(\mathbb{F}_p)$ for every prime $p>37$. This result complements a previous result by the author. We also prove analogue results for certain families of $\mathbb{Q}$-curves, building on results of Ellenberg (2004) and Le Fourn (2016).

塞尔的统一问题与 $C_{ns}^+(p)$ 的 proper subgroups

Serre's uniformity question and proper subgroups of $C_{ns}^+(p)$

研究证明对于大于5的素数，塞尔的统一问题中残余伽罗瓦表示的像不共轭于特定子群，强化了关于非满射情况的结论。

On Serre's uniformity conjecture for semistable elliptic curves over totally real fields

Let $K$ be a totally real field, and let $S$ be a finite set of non-archimedean places of $K$. It follows from the work of Merel, Momose and David that there is a constant $B_{K,S}$ so that if $E$ is an elliptic curve defined over $K$, semistable outside $S$, then for all $p>B_{K,S}$, the representation $\barρ_{E,p}$ is irreducible. We combine this with modularity and level lowering to show the existence of an effectively computable constant $C_{K,S}$, and an effectively computable set of elliptic curves over $K$ with CM $E_1,\dotsc,E_n$ such that the following holds. If $E$ is an elliptic cur…

An explicit bound on reducibility of mod $\mathfrak{l}$ Galois image for Drinfeld modules of arbitrary rank and its application on the uniformity problem

Suppose we are given a Drinfeld Module $ϕ$ over $\mathbb{F}_q(t)$ of rank $r$ and a prime ideal $\mathfrak{l}$ of $\mathbb{F}_q[T]$. In this paper, we prove that the reducibility of mod $\mathfrak{l}$ Galois representation $${\rm{Gal}}(\mathbb{F}_q(T)^{\rm{sep}}/\mathbb{F}_q(T))\rightarrow {\rm{Aut}}(ϕ[\mathfrak{l}])\cong {\rm{GL}}_r(\mathbb{F}_\mathfrak{l})$$ gives a bound on the degree of $\mathfrak{l}$ which depends only on the rank $r$ of Drinfeld module $ϕ$ and the minimal degree of place $\mathcal{P}$ where $ϕ$ has good reduction at $\mathcal{P}$. Then, we apply this reducibility bound t…

A moduli interpretation for the non-split Cartan modular curve

Modular curves like X_0(N) and X_1(N) appear very frequently in arithmetic geometry. While their complex points are obtained as a quotient of the upper half plane by some subgroups of SL_2(Z), they allow for a more arithmetic description as a solution to a moduli problem. This description turns out to be very useful in many applications. We wish to give such a moduli description for two modular curves: those associated to non-split Cartan subgroups and their normaliser in GL_2(F_p). These modular curves appear for instance in Serre's problem of classifying all possible Galois structures of p-t…