PreprintCC BY-NC-ND 4.0arXiv
On the measure of definable sets in profinite groups
Abstract
We study the (Haar) measure of verbal sets in profinite groups, and especially in free profinite groups. Relating the measure of a verbal set with the width of the corresponding word, we find verbal sets of positive measure different from one. We prove a sufficient condition for the measure of a verbal set to be zero in a free profinite group of finite rank, from which we deduce that certain existentially definable sets in free profinite groups of finite rank can only have measure zero or one. Finally, we compute the measure of definable sets in torsion-free finitely generated abelian groups.
Related
- Polycyclic groups and profinite isomorphism
- An algebro-geometric approach to profinite iterated monodromy groups
- Hilbertian Fields and Profinite Iterated Monodromy Groups Over Transcendental Elements with Specializations of Infinite Index
- Profinite groups whose closed subgroups are subnormal of defect at most two
- Large profinite genus and extensions in Bestvina-Brady groups
BibTeX
@misc{conte2026measure,
title = {{On the measure of definable sets in profinite groups}},
author = {Martina Conte and Matteo Vannacci},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25448},
eprint = {2609.25448},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25448},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - On the measure of definable sets in profinite groups
AU - Martina Conte
AU - Matteo Vannacci
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25448
UR - https://arxiv.org/abs/2609.25448
AB - We study the (Haar) measure of verbal sets in profinite groups, and especially in free profinite groups. Relating the measure of a verbal set with the width of the corresponding word, we find verbal sets of positive measure different from one. We prove a sufficient condition for the measure of a verbal set to be zero in a free profinite group of finite rank, from which we deduce that certain existentially definable sets in free profinite groups of finite rank can only have measure zero or one. Finally, we compute the measure of definable sets in torsion-free finitely generated abelian groups.
ER -