Homological Milnor-Witt modules and Chow-Witt groups over general bases

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Auteurs principaux: Déglise, Frédéric, Feld, Niels, Jin, Fangzhou
Format: Preprint
Publié: 2025
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author Déglise, Frédéric
Feld, Niels
Jin, Fangzhou
author_facet Déglise, Frédéric
Feld, Niels
Jin, Fangzhou
contents We introduce a general theory of homological Milnor-Witt cycle modules over an excellent base scheme equipped with a dimension function, extending both Rost's cycle modules and Feld's theory over fields. To any such module we associate a Rost-Schmid type complex whose homology defines a Borel-Moore intersection theory with quadratic coefficients, satisfying homotopy invariance, localization, proper pushforwards, smooth pullbacks, and Gysin morphisms for essentially smoothable lci morphisms. Using duality data induced by pinning structures, we define cohomological Milnor-Witt modules and establish a duality equivalence between homological and cohomological theories. As applications, we extend Chow-Witt groups to schemes over general (possibly singular or arithmetic) bases, prove generalized Bloch formulas and representability results, and compute graded Chow-Witt groups over Dedekind schemes of finite type over the integers. In particular, we obtain finiteness results for Chow-Witt and related Milnor-Witt invariants in dimension at most one.
format Preprint
id arxiv_https___arxiv_org_abs_2512_09876
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Homological Milnor-Witt modules and Chow-Witt groups over general bases
Déglise, Frédéric
Feld, Niels
Jin, Fangzhou
Algebraic Geometry
Algebraic Topology
K-Theory and Homology
14C25, 14F42, 19E15, 14F05, 14C15, 19G12
We introduce a general theory of homological Milnor-Witt cycle modules over an excellent base scheme equipped with a dimension function, extending both Rost's cycle modules and Feld's theory over fields. To any such module we associate a Rost-Schmid type complex whose homology defines a Borel-Moore intersection theory with quadratic coefficients, satisfying homotopy invariance, localization, proper pushforwards, smooth pullbacks, and Gysin morphisms for essentially smoothable lci morphisms. Using duality data induced by pinning structures, we define cohomological Milnor-Witt modules and establish a duality equivalence between homological and cohomological theories. As applications, we extend Chow-Witt groups to schemes over general (possibly singular or arithmetic) bases, prove generalized Bloch formulas and representability results, and compute graded Chow-Witt groups over Dedekind schemes of finite type over the integers. In particular, we obtain finiteness results for Chow-Witt and related Milnor-Witt invariants in dimension at most one.
title Homological Milnor-Witt modules and Chow-Witt groups over general bases
topic Algebraic Geometry
Algebraic Topology
K-Theory and Homology
14C25, 14F42, 19E15, 14F05, 14C15, 19G12
url https://arxiv.org/abs/2512.09876