English

Lifting residual Galois representations with the same semi-simplification

Number Theory 2025-06-17 v1

Abstract

If a pp-adic Galois representation ρf,ν:ΓQ\GL2(Ef,ν)\rho_{f,\nu}:\Gamma_{\mathbb Q} \to \GL_2(E_{f,\nu}) attached to some eigenform ff is residually reducible it will have 2 non-isomorphic reductions, which have the same semi-simplification. In this paper, we answer a version of the inverse question, first brought up by Toby Gee and Alice Pozzi. Starting with two modulo pp non-semi-simple representations ρ1,ρ2:ΓQ\GL2(k)\overline{\rho_1},\overline{\rho_2}:\Gamma_{\mathbb Q} \to \GL_2(k), which have the same semi-simplification we show that under some mild conditions that they are reductions of representations attached to newforms of the same weight r2r \ge 2, the same level N1N \ge 1, and the same Neben character ε\varepsilon.

Keywords

Cite

@article{arxiv.2506.12644,
  title  = {Lifting residual Galois representations with the same semi-simplification},
  author = {Stefan Nikoloski},
  journal= {arXiv preprint arXiv:2506.12644},
  year   = {2025}
}

Comments

50 pages. Comments are welcomed!

R2 v1 2026-07-01T03:18:02.947Z