Abstract
Ge (2003) asked the question whether LF∞ can be embedded in to LF2 as a maximal subfactor. We answer it affirmatively in three different approaches, all containing the same key ingredient: the existence of maximal subgroups with infinite index. We also show that point stabilizer subgroups for every faithful, 4-transitive action on an infinite set give rise to maximal von Neumann subalgebras. By combining this with the known results on constructing faithful, highly transitive actions, we get many maximal von Neumann subalgebras arising from maximal subgroups with infinite index.
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Acknowledgements
The author was supported by the National Science Center (NCN) (Grant No. 2014/14/E/ST1/00525), Institute of Mathematics, Polish Academy of Sciences (IMPAN) from the Simons Foundation (Grant No. 346300) and the Matching 2015–2019 Polish Ministry of Science and Higher Education (MNiSW) Fund, and the Research Foundation-Flanders-Polish Academy of Sciences (FWO-PAN). The author thanks Professors Alejandra Garrido, Liming Ge, Adam Skalski, Yuhei Suzuki and Stefaan Vaes for helpful discussions. The author is also very grateful to Professors Adam Skalski and Yuhei Suzuki for reading the draft carefully, pointing out inaccuracies and providing many helpful comments.
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Jiang, Y. Maximal von Neumann subalgebras arising from maximal subgroups. Sci. China Math. 64, 2295–2312 (2021). https://doi.org/10.1007/s11425-020-1671-9
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DOI: https://doi.org/10.1007/s11425-020-1671-9
Keywords
- maximal von Neumann subalgebra
- maximal subfactor
- maximal subgroup
- highly transitive action
- rigid subalgebra