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Related papers: Cellularity of hermitian K-theory and Witt theory

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An object in motivic homotopy theory is called cellular if it can be built out of motivic spheres using homotopy colimit constructions. We explore some examples and consequences of cellularity. We explain why the algebraic K-theory and…

Algebraic Topology · Mathematics 2014-10-01 Daniel Dugger , Daniel C. Isaksen

In the Morel-Voevodsky motivic stable homotopy category of a quasi-compact quasi-separated scheme S, several candidates exist for a motivic spectrum representing hermitian K-theory. This note shows that the cellular absolute motivic…

K-Theory and Homology · Mathematics 2025-07-16 K. Arun Kumar , Oliver Röndigs

We argue that the very effective cover of hermitian $K$-theory in the sense of motivic homotopy theory is a convenient algebro-geometric generalization of the connective real topological $K$-theory spectrum. This means the very effective…

K-Theory and Homology · Mathematics 2017-12-06 Alexey Ananyevskiy , Oliver Röndigs , Paul Arne Østvær

The theme of this paper is to compute hermitian $K$-groups in terms of the recently developed theory of Milnor-Witt motivic cohomology. Our approach makes use of the very effective slice spectral sequence within the motivic stable homotopy…

Algebraic Geometry · Mathematics 2025-09-23 Håkon Kolderup , Oliver Röndigs , Paul Arne Østvær

In this paper we define a notion of Witt group for sesquilinear forms in hermitian categories, which in turn provides a notion of Witt group for sesquilinear forms over rings with involution. We also study the extension of scalars for…

Representation Theory · Mathematics 2013-01-01 Eva Bayer-Fluckiger , Daniel Moldovan

We use descent theoretic methods to solve the homotopy limit problem for Hermitian $K$-theory over quasi-compact and quasi-separated base schemes. As another application of these descent theoretic methods, we compute the cellular Picard…

Algebraic Topology · Mathematics 2021-07-14 Drew Heard

We develop the theory of Milnor-Witt motives and motivic cohomology. Compared to Voevodsky's theory of motives and his motivic cohomology, the first difference appears in our definition of Milnor-Witt finite correspondences, where our…

Algebraic Geometry · Mathematics 2022-04-05 Tom Bachmann , Baptiste Calmès , Frédéric Déglise , Jean Fasel , Paul Arne Østvær

We advance the understanding of K-theory of quadratic forms by computing the slices of the motivic spectra representing hermitian K-groups and Witt-groups. By an explicit computation of the slice spectral sequence for higher Witt-theory, we…

K-Theory and Homology · Mathematics 2017-05-31 Oliver Röndigs , Paul Arne Østvær

We show that the Grothendieck-Witt and Witt groups of smooth complex cellular varieties can be identified with their topological KO-groups. As an application, we deduce the values of the Witt groups of all irreducible hermitian symmetric…

K-Theory and Homology · Mathematics 2011-06-28 Marcus Zibrowius

Over any field of characteristic not 2, we establish a 2-term resolution of the $\eta$-periodic, 2-local motivic sphere spectrum by shifts of the connective 2-local Witt K-theory spectrum. This is curiously similar to the resolution of the…

K-Theory and Homology · Mathematics 2021-05-05 Tom Bachmann , Michael J. Hopkins

We compute the $\mathbb{G}W$-spectrum (Karoubi--Grothendieck--Witt spectrum) of Grassmannians over divisorial schemes defined over fields of characteristic zero, and, as a corollary, determine their stabilized $\mathbb{L}$-theory spectrum.…

K-Theory and Homology · Mathematics 2026-03-24 Sunny Sood , Chunkai Xu

We use recent results proved by Berrick and the author (math.KT/0509404) to improve the periodicity theorem in hermitian K-theory. We define also a new filtration of the classical Witt ring W(A), built from non degenerate quadratic forms…

K-Theory and Homology · Mathematics 2007-05-23 Max Karoubi

Let $k$ be a perfect field and $X$ be a smooth projective surface over $k$ with a rational point, we discuss the condition of splitting off the top cell for the motivic stable homotopy type of $X$. We also study some outlying examples, such…

Algebraic Geometry · Mathematics 2025-07-09 Haoyang Liu

Let X be a noetherian scheme of finite Krull dimension, having 2 invertible in its ring of regular functions, an ample family of line bundles, and a global bound on the virtual mod-2 cohomological dimensions of its residue fields. We prove…

K-Theory and Homology · Mathematics 2015-02-20 A. J. Berrick , M. Karoubi , M. Schlichting , P. A. Østvær

We give a set of foundations for cellular $E_k$-algebras which are especially convenient for applications to homological stability. We provide conceptual and computational tools in this setting, such as filtrations, a homology theory for…

Algebraic Topology · Mathematics 2024-01-01 Soren Galatius , Alexander Kupers , Oscar Randal-Williams

We prove a duality statement on modules over KH-theory in the stable motivic homotopy category whose dualizing object is given by G-theory, over any quasi-excellent scheme of characteristic zero.

K-Theory and Homology · Mathematics 2025-08-04 Christian Dahlhausen , Jeroen Hekking , Storm Wolters

We study the cohomology theory and the canonical Milnor-Witt cycle module associated to a motivic spectrum. We prove that the heart of Morel-Voevodsky stable homotopy category over a perfect field (equipped with its homotopy t-structure) is…

Algebraic Geometry · Mathematics 2021-02-18 Niels Feld

Algebraic K-theory is the stable homotopy theory of homotopy theories, and it interacts with algebraic structures accordingly. In particular, we prove the Deligne Conjecture for algebraic K-theory.

K-Theory and Homology · Mathematics 2014-07-17 C. Barwick

We compute the 2-line of stable homotopy groups of motivic spheres over fields of characteristic not two in terms of motivic cohomology and hermitian K-groups.

Algebraic Geometry · Mathematics 2021-04-01 Oliver Röndigs , Markus Spitzweck , Paul Arne Østvær

We establish fundamental motivic results about hermitian K-theory without assuming that 2 is invertible on the base scheme. In particular, we prove that both quadratic and symmetric Grothendieck-Witt theory satisfy Nisnevich descent, and…

K-Theory and Homology · Mathematics 2025-01-27 Baptiste Calmès , Yonatan Harpaz , Denis Nardin
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