Separating measurable recurrence from strong recurrence via rigidity sequences
Abstract
If is an abelian group, we say is a set of recurrence if for every probability measure preserving -system and every having , there is a such that . We say is a set of strong recurrence if for every set having there is a such that for infinitely many . We call measure expanding if for all , the translate is a set of recurrence. A rigidity sequence for is a sequence of elements satisfying for all measurable . For all but countably many countable abelian groups , we prove that if is measure expanding, there is a sequence of elements such that is also measure expanding and every translate of is a rigidity sequence for some free weak mixing measure preserving -system. The special case where proves a conjecture of Ackelsberg. As a consequence, we prove that for every countably infinite abelian group and every measure expanding set there is a subset such that is measure expanding and no translate of is a set of strong recurrence.
Cite
@article{arxiv.1808.05609,
title = {Separating measurable recurrence from strong recurrence via rigidity sequences},
author = {John T. Griesmer},
journal= {arXiv preprint arXiv:1808.05609},
year = {2024}
}
Comments
30 pages. v4 incorporates referee comments