The torsion conjecture for discrete CAT(0)-space isometry groups

Let XX be a proper, CAT(0)\operatorname{CAT}(0)-space and let Γ\Gamma be a discrete group of isometries of XX, not necessarily cocompact. A group is torsion if it contains only finite-order elements.

Torsion conjecture. If Γ\Gamma is torsion, then Γ\Gamma is finite. An easier version is that if Γ\Gamma is almost-cocompact, then it contains an infinite-order element.

The conjecture concerns whether properness and discreteness impose finiteness on torsion isometry groups; the paper presents the almost-cocompact assertion as the version needed for its application. No resolution is given in the supplied context.

Sources & referencesView supporting material

Primary source

Nicola Cavallucci and Andrea Sambusetti, “Thin actions on CAT(0) spaces”, arXiv:2210.01085 (2022).

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