# On Serre’s conjecture for 2-dimensional mod p representations of $\mathrm{Gal}(\bar{\mathbb{Q}}/\mathbb{Q})$

### Abstract

We prove the existence in many cases of minimally ramified $p$-adic lifts of 2-dimensional continuous, odd, absolutely irreducible, mod $p$ representations $\overline{\rho}$ of the absolute Galois group of $\mathbb{Q}$. It is predicted by Serre’s conjecture that such representations arise from newforms of optimal level and weight.

Using these minimal lifts, and arguments using compatible systems, we prove some cases of Serre’s conjectures in low levels and weights. For instance we prove that there are no irreducible $(p, p)$ type group schemes over $\mathbb{Z}$. We prove that a $\overline{\rho}$ as above of Artin conductor $1$ and Serre weight $12$ arises from the Ramanujan Delta-function.

In the last part of the paper we present arguments that reduce Serre’s conjecture to proving generalisations of modularity lifting theorems of the type pioneered by Wiles.

## Authors

Chandrashekhar Khare

Department of Mathematics
UCLA
Los Angeles, CA 90095
United States

Jean-Pierre Wintenberger

Université Louis Pasteur
Département de Mathématique
7, rue Renée Descartes
67084 Strasbourg Cedex
France