English

Subgroups of minimal index in polynomial time

Group Theory 2018-09-05 v2 Computational Complexity

Abstract

Let GG be a finite group and let HH be a proper subgroup of GG of minimal index. By applying an old result of Y. Berkovich, we provide a polynomial algorithm for computing G:H|G : H| for a permutation group GG. Moreover, we find HH explicitly if GG is given by a Cayley table. As a corollary, we get an algorithm for testing whether a finite permutation group acts on a tree or not.

Keywords

Cite

@article{arxiv.1807.11773,
  title  = {Subgroups of minimal index in polynomial time},
  author = {Saveliy V. Skresanov},
  journal= {arXiv preprint arXiv:1807.11773},
  year   = {2018}
}

Comments

In the second version we gave the reference to Theorem 1, since it was obtained by Y. Berkovich earlier (as communcated by A. Mann), and added Theorem 3