I am an assistant professor at the University of Illinois at Urbana-Champaign. Before that I have been a member at the Institute for Advanced Study, as well as an NSF Postdoctoral Fellow at Columbia and McGill. I completed my PhD in 2016 at Penn State, under the supervision of Winnie Li.

Email: oxeimon[at]gmail[dot]com

CV

My work concerns arithmetic geometry, broadly construed. I am especially interested in studying the relation between group theory, algebraic geometry, and number theory, as mediated by monodromy actions of etale fundamental groups.

Recently I have been interested in the connected components of Hurwitz spaces of Galois covers of curves. While these components are well understood in the regime where the Galois group is fixed and the genus g and number of branch points n are allowed to be large, far less is known if one fixes (g,n) and allows the Galois group to vary over an infinite family. The elliptic curve case (g,n) = (1,1) is particularly interesting, as many of the associated groups — the braid groups B3, B4, and the groups Aut(F2), SL(2,Z) — exhibit exceptional behavior within their respective families. This case is closely related to noncongruence modular curves, the Wiegold conjecture in combinatorial group theory, and Markoff numbers.

 Publications and Preprints

Expository Notes

  • Katz modular forms - Expository notes I wrote to explain the relationship between classical and geometric notions of modular forms (the latter in the sense of Katz) for finite index subgroups of SL(2,Z), including algebraic and integral properties of q-expansions for their modular forms.

  • Two base change results for rings of invariants - A short note explaining two base change results for rings of invariants. The first is a classical theorem in invariant theory, the second is a base change result for character varieties of representations of a free group in a split reductive group.

Computing

  • Given a finite group G, the geometry of the connected components of the moduli stacks of elliptic curves with G-structures can be readily computed from its monodromy as a finite etale cover of the moduli stack of elliptic curves. The results of these computations have led to observations that inspired the papers on Markoff triples and on metabelian groups (joint with Deligne). To facilitate these computations, I have written some code which you can find here (includes documentation and examples. Requires GAP to run). Data from some of these computations can be found below in csv and pdf formats. However, the best way to examine the data is to generate them for yourself in GAP and query the database via the SGD function. The data below took 4 days to generate using a 2021 Macbook Pro.

  • Data for M(G) as G ranges over all finite simple groups of order at most the order of the Janko group |J1| = 175560 can be found here: [csv] [pdf] [README]

  • Data for M(G)/Out(G) can be found here: [csv] [pdf] [README] (readme is the same)

Seminars

  • Fall 2024 - Spring 2025 Reading group on Katz-Mazur’s Arithmetic moduli of elliptic curves

Teaching at University of Illinois Urbana-Champaign

  • Fall 2024 - Math 415 Applied Linear Algebra

Teaching at Rutgers

  • Spring 2023 - Math 356 Theory of Numbers

  • Spring 2023 - Math 135 Calculus I for the life and social sciences

  • Fall 2022 - Math 350 Linear Algebra [course website]

Teaching at Columbia

Teaching at Penn State

  • Spring 2016 - Math 251 Ordinary and partial differential equations [course materials]

  • Fall 2014 - Math 41 Trigonometry and analytic geometry

  • Fall 2013 - Math 21 College Algebra I

  • Fall 2012 - Math 21 College Algebra I

  • Fall 2011 - Math 220 Matrices [course materials]

  • Summer 2011 - Math 220, Matrices [course materials]

  • Spring 2011 - Math 17 Finite Mathematics

Other

I enjoy taking pictures. You can find some of my photography here.