Arithmetic geometry & number theory

Research

I study Galois covers of curves in characteristic p, with an emphasis on wild ramification, deformation, and liftability to characteristic zero. More recently, I have been exploring p-adic differential equations as a way to understand degenerations of wildly ramified covers.

Published work and papers to appear, newest first.

01

Algebraic Geometry 13 (2026), 305–370 · DOI: 10.14231/AG-2026-010

Deforming cyclic covers in towers

A deformation of a cyclic subcover in positive characteristic can be extended through the entire tower after a finite base extension.

02

Annales de l’Institut Fourier · to appear

Hurwitz trees and deformations of Artin–Schreier covers

Generalized Hurwitz trees classify deformation types and give new information about connectedness in moduli.

03

With S. Groen · Journal of Number Theory 279 (2026), 78–116 · DOI: 10.1016/j.jnt.2025.05.016

a-numbers of ℤ/p²-covers of the projective line

We identify a family of ℤ/9-covers whose a-numbers are determined by the ramification data.

04

With Matthias Hippold · IMRN 2024, 10169–10188 · DOI: 10.1093/imrn/rnae060

The moduli space of cyclic covers in positive characteristic

We identify the irreducible components of the moduli space, determine their dimensions, and study deformations varying p-rank and branch points.

05

With S. Das, K. Karagiannis, A. Obus, and V. Thatte · JTNB 34 (2022), 251–269 · DOI: 10.5802/jtnb.1200

Local Oort groups and the isolated differential data criterion

The isolated differential data criterion proves new lifting results for covers with specified dihedral inertia groups.

06

Journal of Algebra 547 (2020), 398–429 · DOI: 10.1016/j.jalgebra.2019.11.034

Connectedness of the moduli space of Artin–Schreier curves of fixed genus

The moduli space of Artin–Schreier covers of the projective line of genus g is connected when g is sufficiently large.

Preprints

01

With Adrian Vasiu · Preprint, 2026

On lifting representations and actions on curves of the metacyclic groups Cₚˢ ⋊ Cₘ

We give criteria for lifting representations of metacyclic groups and apply them to actions on curves, including an obstruction to lifting in mixed characteristic.

02

With Nguyen-Dang Khai-Hoan · submitted, 2024

Kummer–Artin–Schreier–Witt theory

An algebrization of Matsuda’s morphism connecting the Kummer and Artin–Schreier–Witt exact sequences of group schemes.

03

Preprint, 2024

The vanishing of the Hurwitz tree obstruction for the refined local lifting problem

We introduce Hurwitz-tree obstructions for the refined local lifting problem and determine when they vanish for cyclic groups.

04

Preprint, 2021

The refined lifting problem for cyclic coverings of order 4

We show that ℤ/4-covers in characteristic 2 lift in towers when the first-level lift satisfies a suitable condition.