Genericity conjecture for essential dimension of objects of amenable stacks

From papers

Let X\mathcal{X} be an amenable stack over kk. Let LL be an extension of kk, and let ξ\xi be an object of X(SpecL)\mathcal{X}(\operatorname{Spec} L). Here edkξ\operatorname{ed}_k\xi denotes the essential dimension of ξ\xi, g\mspace2muedkX\operatorname{g\mspace{2mu}ed}_k\mathcal{X} denotes the generic essential dimension of X\mathcal{X}, and \operatorname{R_{u}}(\mathop{\underline{\mathrm{Aut}}\nolimits}_{L}\xi) is the unipotent radical of the automorphism group of ξ\xi over LL. Genericity conjecture. One has

\operatorname{ed}_{k}\xi \leq \operatorname{g\mspace{2mu}ed}_{k} \mathcal{X} + \dim\operatorname{R_{u}}(\mathop{\underline{\mathrm{Aut}}\nolimits_{L}\xi}).

This proposed generalization of the paper's genericity theorem would bound the essential dimension of every object by the generic essential dimension of the ambient amenable stack, together with the dimension of the unipotent radical of its automorphism group. The source presents it as plausible on the basis of examples and does not give evidence that it has been proved or refuted.

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Sources & referencesView supporting material

Primary source

Zinovy Reichstein and Angelo Vistoli, “A genericity theorem for algebraic stacks and essential dimension of hypersurfaces”, arXiv:1103.1611 (2011).

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