Dolgachev's essential-dimension and Cremona-dimension inequality

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Let GG be a finite group over the complex numbers. Write ed⁡(G)\operatorname{ed}(G) for the essential dimension of GG, and Crdim⁡(G)\operatorname{Crdim}(G) for the least integer nn such that GG embeds into the Cremona group Cr⁡(n)\operatorname{Cr}(n).

Dolgachev's inequality.

ed⁡(G)⩾Crdim⁡(G).\operatorname{ed}(G)\geqslant\operatorname{Crdim}(G).

The source attributes this claim to I. Dolgachev as unpublished. It compares the minimal dimension of a versal faithful GG-variety with the minimal dimension of affine space on which GG acts birationally; the source gives no resolution status.

References

Primary source

Alexander Duncan and Zinovy Reichstein, “Versality of algebraic group actions and rational points on twisted varieties”, arXiv:1109.6093 (2013).

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