Swan trace formula for tensor products over finite fields

From papers

Let UU be a connected separated smooth scheme of dimension dd of finite type over a finite field FF, let XX be a proper normal scheme over FF containing UU as a dense open subscheme, and let FrFGal(F/F)Fr_F\in\operatorname{Gal}(\overline F/F) be geometric Frobenius. Let ρX:CH0(X)π1(X)ab\rho_X:CH_0(X)\to\pi_1(X)^{\mathrm{ab}} be the reciprocity map sending a closed point class [x][x] to geometric Frobenius FrxFr_x. Let \ell be invertible in FF, let F\mathcal F be a smooth F\overline{\mathbb F}_\ell- or Q\overline{\mathbb Q}_\ell-sheaf on UU, and assume the integrality conjecture holds and SwX(F)CH0(XU)\operatorname{Sw}_X(\mathcal F)\in CH_0(X\setminus U) is defined. For a smooth sheaf G\mathcal G on XX, let detG:π1(X)abF×\det\mathcal G:\pi_1(X)^{\mathrm{ab}}\to\overline{\mathbb F}_\ell^\times or Q×\overline{\mathbb Q}_\ell^\times be the character corresponding to its determinant. Define

det(FrF:Hc(UF,F))=q=02ddet(FrF:Hcq(UF,F))(1)q.\det(-Fr_F:H_c^*(U_{\overline F},\mathcal F))=\prod_{q=0}^{2d}\det(-Fr_F:H_c^q(U_{\overline F},\mathcal F))^{(-1)^q}.

Swan trace formula conjecture. Then

det(FrF:Hc(UF,FG))=det(FrF:Hc(UF,F))rankGdetG(ρX(SwX(F))).\det(-Fr_F:H_c^*(U_{\overline F},\mathcal F\otimes\mathcal G)) =\det(-Fr_F:H_c^*(U_{\overline F},\mathcal F))^{\operatorname{rank}\mathcal G}\cdot\det\mathcal G\bigl(\rho_X(\operatorname{Sw}_X(\mathcal F))\bigr).

This is presented as an expected refinement of the theorem cited in the source; the supplied text gives no resolution.

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Sources & referencesView supporting material

Primary source

Kazuya Kato and Takeshi Saito, “Ramification theory for varieties over a perfect field”, arXiv:math/0402010 (2005).

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