English

Galois deformation spaces with a sparsity of automorphic points

Number Theory 2020-01-15 v1

Abstract

Let k/Fpk/\mathbb F_p denote a finite field. For any split connected reductive group G/W(k)G/W(k) and certain CM number fields FF, we deform certain Galois representations ρ:Gal(F/F)G(k)\overline\rho:Gal(\overline F/F) \to G(k) to continuous families XρX_{\overline\rho} of Galois representations Gal(F/F)G(Qp)Gal(\overline F/F) \to G(\overline{\mathbb Q_p}) lifting ρ\overline\rho such that the space of points of XρX_{\overline\rho} which are geometric (in the sense of the Fontaine-Mazur conjecture) with parallel Hodge-Tate weights has positive codimension in XρX_{\overline\rho}. Thus the set of points in XρX_{\overline\rho} which could (conjecturally) be associated to automorphic forms is sparse. This generalizes a result of Calegari and Mazur for F/QF/\mathbb Q quadratic imaginary and G=GL2G = GL_2. The sparsity of automorphic points for FF a CM field contrasts with the situation when FF is a totally real field, where automorphic points are often provably dense.

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Cite

@article{arxiv.2001.04956,
  title  = {Galois deformation spaces with a sparsity of automorphic points},
  author = {Kevin Childers},
  journal= {arXiv preprint arXiv:2001.04956},
  year   = {2020}
}

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39 pages