Profinite groups with many elements of bounded order
Abstract
Lévai and Pyber proposed the following as a conjecture: Let $G$ be a profinite group such that the set of solutions of the equation $x^n=1$ has positive Haar measure. Then $G$ has an open subgroup $H$ and an element $t$ such that all elements of the coset $tH$ have order dividing $n$ (see Problem 14.53 of [The Kourovka Notebook, No. 19, 2019]). \\ We define a constant $c_n$ for all finite groups and prove that the latter conjecture is equivalent with a conjecture saying $c_n<1$. Using the latter equivalence we observe that correctness of Lévai and Pyber conjecture implies the existence of the universal upper bound $\frac{1}{1c_n}$ on the index of generalized HughesThompson subgroup $H_n$ of finite groups whenever it is nontrivial. It is known that the latter is widely open even for all primes $n=p\geq 5$. For odd $n$ we also prove that Lévai and Pyber conjecture is equivalent to show that $c_n$ is less than $1$ whenever $c_n$ is only computed on finite solvable groups. \\ The validity of the conjecture has been proved in [Arch. Math. (Basel) 75 (2000) 17] for $n=2$. Here we confirm the conjecture for $n=3$.
 Publication:

arXiv eprints
 Pub Date:
 December 2020
 arXiv:
 arXiv:2012.13886
 Bibcode:
 2020arXiv201213886A
 Keywords:

 Mathematics  Group Theory;
 20E18;
 20P05;
 43A05