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Preprint Number 1330

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1330. Grzegorz Jagiella
The Ellis group conjecture and variants of definable amenability

Submission date: 30 October 2017


We consider definable topological dynamics for NIP groups admitting certain decompositions in terms of specific classes of definably amenable groups. For such a group, we find a description of the Ellis group of its universal definable flow. This description shows that the Ellis group is of bounded size. Under additional assumptions, it is shown to be independent of the model, proving a conjecture proposed by Newelski. Finally we apply the results to new classes of groups definable in o-minimal structures, generalizing all of the previous results for this setting.

Mathematics Subject Classification: 03C99, 54H20, 03C64

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Full text arXiv 1710.11081: pdf, ps.

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