Geometric Jordan conjecture for the Cremona group

Let nn be a positive integer, let XX be an nn-dimensional rational variety, and let GG be a finite group acting on XX. Geometric Jordan conjecture. There exists a constant c(n)c(n) depending only on nn such that GG contains a normal abelian subgroup AA of index at most c(n)c(n) and

AGmkBir(X)A\leqslant \mathbb{G}_m^k\leqslant \operatorname{Bir}(X)

for some kk. The conjecture asks whether the finite-group Jordan property can always be realized by a subgroup contained in an algebraic torus of the birational automorphism group. The conjecture remains open in dimension three and higher.

Sources & referencesView supporting material

Primary source

Joaquín Moraga, “Cluster type varieties”, arXiv:2602.23584 (2026).

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