Metric uniform simplicity of simple metric ultraproducts

From papers

Let (Gmet,)({\mathcal G}_{\mathrm{met}},\|\cdot\|) be a metric ultraproduct of metric groups. A metric group is metrically uniformly simple if, for every r>0r>0, there is NNN\in\mathbb{N} such that CN(g,G)=GC_N(g,G)=G for all gGg\in G with g>r\|g\|>r, where CN(g,G):=(gGg1G)NC_N(g,G):=(g^G\cup g^{-1G})^{\leq N}. The metric uniform simplicity conjecture. If (Gmet,)({\mathcal G}_{\mathrm{met}},\|\cdot\|) is simple, then Gmet{\mathcal G}_{\mathrm{met}} must be metrically uniformly simple. The paper identifies this as a conjecture suggested by the fact that all known simple metric ultraproducts have the stronger property, while the available results establish only bounded simplicity.

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Primary source

Jakub Gismatullin, Krzysztof Majcher and Martin Ziegler, “Metric ultraproducts of groups – simplicity, perfectness and torsion”, arXiv:2010.03394 (2024).

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