The global period-index conjecture for orbifolds

Let XX be a smooth, proper, connected orbifold, that is, a Deligne–Mumford stack of finite type with trivial generic stabilizers, of dimension dd over an algebraically closed field kk. Let αHeˊt2(X,Gm)\alpha\in \mathrm{H}^2_{\mathrm{\acute et}}(X,\mathbf G_m), with period and index defined as in the source.

Global period-index conjecture. For any such Brauer class α\alpha,

ind(α)\dividesper(α)d1.\operatorname{ind}(\alpha)\divides\operatorname{per}(\alpha)^{d-1}.

This is a global orbifold formulation of the period-index problem. For smooth connected orbifolds, the index agrees with the index of the restriction to the function field, linking this conjecture to the field-theoretic period-index conjecture. The source gives no resolution status.

Sources & referencesView supporting material

Primary source

James Hotchkiss, “Hodge theory of twisted derived categories and the period-index problem”, arXiv:2212.10638 (2022).

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