A remark on $\mathbb{T}$-valued cohomology groups of algebraic group actions
Operator Algebras
2016-06-02 v2 Dynamical Systems
Group Theory
Abstract
We prove that for a weakly mixing algebraic action , the -cohomology group , after quotienting out the natural subgroup , contains as a natural subgroup for . If we further assume the diagonal actions are -cocycle superrigid and is torsion free as an abelian group, then the above also holds true for . Applying it for principal algebraic actions when , we show that is torsion free as an abelian group when has property (T) as a direct corollary of Sorin Popa's cocycle superrigidity theorem; we also use it (when ) to answer, negatively, a question of Sorin Popa on the 2nd cohomology group of Bernoulli shift actions of property (T) groups.
Keywords
Cite
@article{arxiv.1509.08278,
title = {A remark on $\mathbb{T}$-valued cohomology groups of algebraic group actions},
author = {Yongle Jiang},
journal= {arXiv preprint arXiv:1509.08278},
year = {2016}
}
Comments
[v2] minor changes; to appear in the Journal of Functional Analysis