Relative push-forward conjecture for characteristic classes

Let SS be a smooth connected scheme over a perfect field kk of characteristic pp. Let f ⁣:XSf\colon X\to S and g ⁣:YSg\colon Y\to S be smooth morphisms of relative dimensions nn and mm, respectively. Let Dcb(X/S,Λ)D_c^b(X/S,\Lambda) be the thick subcategory of objects FDcb(X,Λ)\mathcal F\in D_c^b(X,\Lambda) for which ff is SS(F,X/k)SS(\mathcal F,X/k)-transversal, and define K0(X/S,Λ)K_0(X/S,\Lambda) as its Grothendieck group; define Dcb(Y/S,Λ)D_c^b(Y/S,\Lambda) and K0(Y/S,Λ)K_0(Y/S,\Lambda) analogously. For a proper morphism h ⁣:XYh\colon X\to Y over SS, relative push-forward conjecture. The diagram

K0(X/S,Λ)ccXnCHn(X)hhK0(Y/S,Λ)ccYmCHm(Y)\begin{CD} K_0(X/S,\Lambda) @>{cc_X^n}>> CH^n(X)\\ @V{h_\ast}VV @VV{h_*}V\\ K_0(Y/S,\Lambda) @>{cc_Y^m}>> CH^m(Y) \end{CD}

commutes; equivalently, for every FDcb(X,Λ)\mathcal F\in D_c^b(X,\Lambda) such that ff is SS(F,X/k)SS(\mathcal F,X/k)-transversal, h(ccXn(F))=ccYm(RhF)h_\ast(cc_X^n(\mathcal F))=cc_Y^m(Rh_\ast\mathcal F) in CHm(Y)CH^m(Y). This extends the known degree-zero compatibility over finite fields; its validity in the stated relative setting is open.

Sources & referencesView supporting material

Primary source

Enlin Yang and Yigeng Zhao, “On the relative twist formula of -adic sheaves”, arXiv:1807.06930 (2018).

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