Lubotzky–Weiss conjecture on amenable and property (T) dense subgroups

Let KK be a compact group, and let Λ1\Lambda_1 and Λ2\Lambda_2 be finitely generated subgroups dense in KK. Lubotzky–Weiss conjecture. If Λ1\Lambda_1 is amenable and Λ2\Lambda_2 has Kazhdan's property (T)(\mathrm{T}), then KK is finite.

The conjecture asks whether these opposing properties of two finitely generated dense subgroups force the ambient compact group to be finite. It was resolved in the negative by Ershov and Jaikin-Zapirain, and independently by Kassabov around 2010; the paper constructs further extreme counterexamples.

Sources & referencesView supporting material

Primary source

Masato Mimura, “An extreme counterexample to the Lubotzky–Weiss conjecture”, arXiv:1809.08918 (2019).

Additional references

3 papers in this index state this conjecture (2005–2018). The statement above is taken from the most recent of them; the others are arXiv:0809.4095, arXiv:math/0502237.

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