Abstract
Let χ be a proper CAT(0) cube complex admitting a proper cocompact action by a group G. We give three conditions on the action, any one of which ensures that χ has a factor system in the sense of [BHS17]. We also prove that one of these conditions is necessary. This combines with [BHS17] to show that G is a hierarchically hyperbolic group; this partially answers questions raised in [BHS17, BHS19]. Under any of these conditions, our results also affirm a conjecture of Behrstock-Hagen on boundaries of cube complexes, which implies that χ cannot contain a convex staircase. The necessary conditions on the action are all strictly weaker than virtual cospecialness, and we are not aware of a cocompactly cubulated group that does not satisfy at least one of the conditions.
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Hagen was supported by the Engineering and Physical Sciences Research Council grant of Henry Wilton.
Susse was partially supported by National Science Foundation grant DMS-1313559.
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Hagen, M.F., Susse, T. On hierarchical hyperbolicity of cubical groups. Isr. J. Math. 236, 45–89 (2020). https://doi.org/10.1007/s11856-020-1967-2
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DOI: https://doi.org/10.1007/s11856-020-1967-2