Functorial cyclic-homology decomposition for quotient schemes

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Let XX be a quasiprojective scheme over a field kk, let GG be a finite group acting on XX, and assume that char⁡k\operatorname{char} k does not divide ∣G∣|G|. Let Coh⁡(X)\operatorname{Coh}(X) be the exact category of coherent sheaves on XX, and let Coh⁡G(X)\operatorname{Coh}_G(X) be the exact category of GG-equivariant sheaves. For each g∈Gg\in G, write XgX^g for the fixed-point subscheme. The cyclic-homology decomposition conjecture. For every WW of finite projective dimension over k[u]k[u], there exists an isomorphism

ϕX:(⨁g∈GHC∙(Coh⁡(Xg),W))G⟶HC∙(Coh⁡G(X),W)\phi_X:\left(\bigoplus_{g\in G}HC_\bullet(\operatorname{Coh}(X^g),W)\right)_G\longrightarrow HC_\bullet(\operatorname{Coh}_G(X),W)

that is functorial with respect to derived pushforwards under GG-equivariant proper maps. This conjecture is motivated by the corresponding decomposition for smooth varieties and by the relation between equivariant cyclic homology and orbifold cohomology. The source gives no resolution status.

References

Primary source

Vladimir Baranovsky, “Orbifold Cohomology as Periodic Cyclic Homology”, arXiv:math/0206256 (2002).

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