Computing the multiplicative group of residue class rings

  • Authors:
  • Florian Heß;Sebastian Pauli;Michael E. Pohst

  • Affiliations:
  • Department of Computer Science, University of Bristol, BS8 1UB, England;Institut für Mathematik, MA 8-1, Technische Universität Berlin, Strasse des 17. Juni 136, 10623 Berlin, Germany;Institut für Mathematik, MA 8-1, Technische Universität Berlin, Strasse des 17. Juni 136, 10623 Berlin, Germany

  • Venue:
  • Mathematics of Computation
  • Year:
  • 2003

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Abstract

Let k be a global field with maximal order 0k and let m0 be an ideal of 0k. We present algorithms for the computation of the multiplicative group (0k/m0)* of the residue class ring 0k/m0 and the discrete logarithm therein based on the explicit representation of the group of principal units. We show how these algorithms can be combined with other methods in order to obtain more efficient algorithms. They are applied to the computation of the ray class group Clkm modulo m = m0m∞, where m∞ denotes a formal product of real infinite places, and also to the computation of conductors of ideal class groups and of discriminants and genera of class fields.