arXiv subjects

Michael Cerchia

Publications and source records attributed to Michael Cerchia.

4 recordsLinked to original sources

arXiv2025

Modular curves of prime-power level with infinitely many quadratic points

We completely determine the $1085$ open subgroups $H$ of $\operatorname{GL}_2(\widehat{\mathbb{Z}})$ of prime-power level that satisfy $-I \in H$ and $\operatorname{det}(H)=\widehat{\mathbb{Z}}^{\times}$ for which the corresponding modular curve $X_H$ has infinitely many quadratic points. When $g(X_H)\geq 2$ this is equivalent to determining all the hyperelliptic modular curves of prime-power level and all the bielliptic modular curves of prime-power level that admit a degree two map to a positive rank elliptic curve. From the moduli perspective, this means that there are exactly 1085 subgroups $H$ of $\operatorname{GL}_2(\widehat{\mathbb{Z}})$ of prime-power level for which there are infinitely many elliptic curves $E/K$ over quadratic extensions such that $\rho_E(G_k)$ is conjugate to a subgroup of $H$.

math.NT↗

arXiv2025

Weil polynomials of abelian varieties over finite fields

In this paper, we investigate Weil polynomials and their relationship with isogeny classes of abelian varieties over finite fields. We give a necessary condition for a degree 12 polynomial with integer coefficients to be a Weil polynomial. Moreover, we provide explicit criteria that determine when a Weil polynomial of degree 14 occurs as the characteristic polynomial of a Frobenius endomorphism acting on an abelian variety.

math.NT↗

arXiv2024

Section Rings of $\mathbb{Q}$-Divisors on Genus $1$ Curves

We compute generators and relations for the section ring of a rational divisor on an elliptic curve. Our technique generalizes the work of O'Dorney (in genus zero) and Voight--Zureick-Brown (for specific divisors arising from the study of stacky curves). For effective divisors supported on at most two points, we give explicit descriptions of the generators and the leading terms of the relations for a minimal presentation. As in the genus zero case, the generators are parametrized by best lower approximations to the coefficients, but there are added wrinkles. Following Landesman, Ruhm and Zhang we can bound the degrees of generators for the section ring of an effective divisor supported at any finite number of points.

math.NT↗

arXiv2020

Uniform bounds on the image of the arboreal Galois representations attached to non-CM elliptic curves

Let $\ell$ be a prime number and let $F$ be a number field and $E/F$ a non-CM elliptic curve with a point $α\in E(F)$ of infinite order. Attached to the pair $(E,α)$ is the $\ell$-adic arboreal Galois representation $ω_{E,α,\ell^{\infty}} : {\rm Gal}(\overline{F}/F) \to \mathbb{Z}_{\ell}^{2} \rtimes {\rm GL}_{2}(\mathbb{Z}_{\ell})$ describing the action of ${\rm Gal}(\overline{F}/F)$ on points $β_{n}$ so that $\ell^{n} β_{n} = α$. We give an explicit bound on the index of the image of $ω_{E,α,\ell^{\infty}}$ depending on how $\ell$-divisible the point $α$ is, and the image of the ordinary $\ell$-adic Galois representation. The image of $ω_{E,α,\ell^{\infty}}$ is connected with the density of primes $\mathfrak{p}$ for which $α\in E(\mathbb{F}_{\mathfrak{p}})$ has order coprime to $\ell$.

math.NT↗