Wild Galois representations of elliptic and hyperelliptic curves

  • Nirvana Coppola

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


In this thesis we investigate the Galois representation attached to an algebraic curve over a local field. In particular, we consider elliptic and hyperelliptic curves with very bad reduction, i.e. which acquire good reduction over a wildly ramified extension.
It is a well-known fact that the primes at which an elliptic curve may acquire good reduction over a wildly ramified extension are 2 and 3. For such primes, a classification of the restriction to inertia of the Galois representation is well understood in the literature; in particular the image of inertia is a finite group, which can be either cyclic or non-abelian. However, less is known about the full Galois action. In this work we give an explicit and algorithmic description of the Galois representations which occur in these cases, with a particular focus on the curves with non-abelian inertia image.
For a hyperelliptic curve of genus g, the primes of wild reduction are at most 2g +1. In this work we consider the family of hyperelliptic curves which have potentially good reduction at 2g +1, assuming this is a prime, and the largest possible image of inertia. We will see how the result on the Galois representation attached to one such curve is a direct generalisation of the
corresponding result for elliptic curves.
Date of Award23 Mar 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorNina C Snaith (Supervisor) & Tim Dokchitser (Supervisor)


  • Galois representations
  • Elliptic curves
  • Hyperelliptic curves
  • Local fields

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