English

Galois representations over function fields that are ramified at one prime

Number Theory 2025-02-14 v2

Abstract

Let Fq\mathbb{F}_q be the finite field with qq elements, F:=Fq(T)F:=\mathbb{F}_q(T) and FsepF^{\operatorname{sep}} a separable closure of FF. Set AA to denote the polynomial ring Fq[T]\mathbb{F}_q[T]. Let p\mathfrak{p} be a non-zero prime ideal of AA, and O\mathscr{O} be the completion of AA at p\mathfrak{p}. Given any integer r2r\geq 2, I construct a Galois representation ρ:Gal(Fsep/F)GLr(O)\rho:\operatorname{Gal}(F^{\operatorname{sep}}/F)\rightarrow \operatorname{GL}_r(\mathscr{O}) which is unramified at all non-zero primes lp\mathfrak{l}\neq \mathfrak{p} of AA, and whose image is a finite index subgroup of GLr(O)\operatorname{GL}_r(\mathscr{O}). Moreover, if the degree of p\mathfrak{p} is 11, then ρ\rho is also unramified at \infty.

Keywords

Cite

@article{arxiv.2406.05524,
  title  = {Galois representations over function fields that are ramified at one prime},
  author = {Anwesh Ray},
  journal= {arXiv preprint arXiv:2406.05524},
  year   = {2025}
}

Comments

Accepted for publication in the Ramanujan Journal

R2 v1 2026-06-28T16:58:19.021Z