English

Profinite groups with many elements of bounded order

Group Theory 2021-04-12 v2

Abstract

L\'evai and Pyber proposed the following as a conjecture: Let GG be a profinite group such that the set of solutions of the equation xn=1x^n=1 has positive Haar measure. Then GG has an open subgroup HH and an element tt such that all elements of the coset tHtH have order dividing nn (see Problem 14.53 of [The Kourovka Notebook, No. 19, 2019]). \\ We define a constant cnc_n for all finite groups and prove that the latter conjecture is equivalent with a conjecture saying cn<1c_n<1. Using the latter equivalence we observe that correctness of L\'evai and Pyber conjecture implies the existence of the universal upper bound 11cn\frac{1}{1-c_n} on the index of generalized Hughes-Thompson subgroup HnH_n of finite groups whenever it is non-trivial. It is known that the latter is widely open even for all primes n=p5n=p\geq 5. For odd nn we also prove that L\'evai and Pyber conjecture is equivalent to show that cnc_n is less than 11 whenever cnc_n is only computed on finite solvable groups. \\ The validity of the conjecture has been proved in [Arch. Math. (Basel) 75 (2000) 1-7] for n=2n=2. Here we confirm the conjecture for n=3n=3.

Keywords

Cite

@article{arxiv.2012.13886,
  title  = {Profinite groups with many elements of bounded order},
  author = {Alireza Abdollahi and Meisam Soleimani Malekan},
  journal= {arXiv preprint arXiv:2012.13886},
  year   = {2021}
}
R2 v1 2026-06-23T21:27:06.257Z