Integrality and pullback conjecture for Swan classes

Let UU be a smooth connected scheme of dimension dd over a perfect field FF, and let F\mathcal F be a smooth F\overline{\mathbb F}_\ell-sheaf on UU. Swan class conjecture. (1) The Swan class

Sw(F)CH0(UU)ZQ\operatorname{Sw}(\mathcal F)\in CH_0(\overline U\setminus U)\otimes_{\mathbb Z}\mathbb Q

is in the image of CH0(UU)CH_0(\overline U\setminus U). (2) If f:VUf:V\to U is a finite étale Galois covering trivializing F\mathcal F, if CVsm,0\mathcal C_V^{\mathrm{sm},0} is cofinal in CV\mathcal C_V, and if the conjecture concerning the log Lefschetz class holds as in the definition of the integral Swan class, then

SwV/U(F)ZCH0(VV)\operatorname{Sw}_{V/U}(\mathcal F)_{\mathbb Z}\in CH_0(\overline V\setminus V)

is in the image of

f:CH0(UU)CH0(VV).f^*:CH_0(\overline U\setminus U)\to CH_0(\overline V\setminus V).

The curve case is established in the preceding lemma, and the text says that the analogous assertion is expected in higher dimension; it also notes that the needed assumptions hold when dimU2\dim U\le 2.

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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