English

The additive group of the rationals does not have an automatic presentation

Logic 2009-05-12 v1 Combinatorics

Abstract

We prove that the additive group of the rationals does not have an automatic presentation. The proof also applies to certain other abelian groups, for example, torsion-free groups that are pp-divisible for infinitely many primes pp, or Q/ZQ/Z. The proof is combinatorial and uses most notably Freiman's theorem on sets with small doubling.

Keywords

Cite

@article{arxiv.0905.1505,
  title  = {The additive group of the rationals does not have an automatic presentation},
  author = {Todor Tsankov},
  journal= {arXiv preprint arXiv:0905.1505},
  year   = {2009}
}

Comments

11 pages

R2 v1 2026-06-21T13:00:19.133Z