Equality of the three-dimensional abelian Cremona group classes

From papers

Let A3\mathcal{A}_3 and B3\mathcal{B}_3 be the classes of finite abelian groups arising in the paper, and let

A3=PA3=A1×A2,\mathcal{A}'_3=\mathcal{PA}_3=\mathcal{A}_1\times\mathcal{A}_2,

while

B3=A3+{G1,G2,G3,G4},\mathcal{B}'_3=\mathcal{A}_3+\{G_1,G_2,G_3,G_4\},

where G1=(Z/4)4G_1=(\mathbb{Z}/4)^4, G2=(Z/8)2×(Z/4)×Z/2G_2=(\mathbb{Z}/8)^2\times(\mathbb{Z}/4)\times\mathbb{Z}/2, G3=(Z/6)2×(Z/3)2G_3=(\mathbb{Z}/6)^2\times(\mathbb{Z}/3)^2, and G4=(Z/6)3×Z/2G_4=(\mathbb{Z}/6)^3\times\mathbb{Z}/2. The inclusions A3A3\mathcal{A}'_3\subseteq\mathcal{A}_3 and B3B3\mathcal{B}'_3\subseteq\mathcal{B}_3 hold. Three-dimensional class conjecture. One has

A3=A3,B3=B3.\mathcal{A}_3=\mathcal{A}'_3,\qquad \mathcal{B}_3=\mathcal{B}'_3.

The conjecture would classify the relevant finite abelian groups in dimension three by showing that no groups beyond the explicitly listed candidates occur. The supplied context does not state whether these equalities have been proved or disproved.

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Sources & referencesView supporting material

Primary source

Luka Filin, “On abelian extensions of finite abelian subgroups of Cremona groups”, arXiv:2510.13200 (2025).

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