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I construct the real counterparts (which I call Borel-Bott classes) of the R/Z classes constructed in "Characteristic classes in symplectic topology", to appear, in the cohomology of volume-preserving and symplectomorhisms of a compact…

dg-ga · Mathematics 2008-02-03 Alexander Reznikov

One of the main themes of this long article is the study of projective varieties which are K(H,1)'s, i.e. classifying spaces BH for some discrete group H. After recalling the basic properties of such classifying spaces, an important class…

Algebraic Geometry · Mathematics 2015-07-03 Fabrizio Catanese

Given a small simplicial category $\C$ whose underlying ordinary category is equipped with a Grothendieck topology $\tau$, we construct a model structure on the category of simplicially enriched presheaves on $\C$ where the weak…

Algebraic Topology · Mathematics 2018-11-20 Georgios Raptis , Florian Strunk

In this paper we express certain multiplicities in modular representation-theoretic categories of type A in terms of affine p-Kazhdan-Lusztig polynomials. The representation-theoretic categories we deal with include the categories of…

Representation Theory · Mathematics 2017-01-04 Ben Elias , Ivan Losev

We construct a theory of motivic cohomology for quasi-compact, quasi-separated schemes of equal characteristic, which is related to non-connective algebraic $K$-theory via an Atiyah--Hirzebruch spectral sequence, and to \'etale cohomology…

K-Theory and Homology · Mathematics 2026-03-30 Elden Elmanto , Matthew Morrow

We present a definition of {\em twisted motivic Chern classes} for singular pairs $(X,\Delta)$ consisting of a singular space $X$ and a $\mathbb Q$-Cartier divisor containing the singularities of $X$. The definition is a mixture of the…

Algebraic Geometry · Mathematics 2022-03-31 Jakub Koncki , Andrzej Weber

We study the structure of the rational motivic stable homotopy category over general base schemes. Our first class of results concerns the six operations: we prove absolute purity, stability of constructible objects, and…

Algebraic Geometry · Mathematics 2021-03-15 Frédéric Déglise , Jean Fasel , Adeel A. Khan , Fangzhou Jin

By defining and studying functorial properties of the Borel-Moore motivic homology, we identify the heart of Bondarko-H\'ebert's weight structure on Beilinson motives with Corti-Hanamura's category of Chow motives over a base, therefore…

Algebraic Geometry · Mathematics 2020-10-20 Fangzhou Jin

We generalize a construction of Barthel-Brasselet-Fieseler-Gabber-Kaup in the setting of complex varieties to the setting of finite type, complex algebraic stacks. Given two such stacks $\mathcal{X},\mathcal{Y}$ with affine stabilizers, and…

Algebraic Geometry · Mathematics 2025-04-08 Matthew Huynh

The de Rham stack construction of Simpson shows that D-modules are quasicoherent sheaves on a modified geometry. Drinfeld furthermore introduced the ring stack perspective (aka transmutation), which asserts that a coefficient theory is…

Algebraic Geometry · Mathematics 2026-03-03 Ko Aoki

We study the asymptotical behaviour of the moduli space of morphisms of given anticanonical degree from a rational curve to a split toric variety, when the degree goes to infinity. We obtain in this case a geometric analogue of Manin's…

Number Theory · Mathematics 2014-01-14 David Bourqui

We first recall the construction of the Chow motive modelling intersection cohomology of a proper surface and study its fundamental properties. Using Voevodsky's category of effective geometrical motives, we then study the motive of the…

K-Theory and Homology · Mathematics 2017-06-23 J. Wildeshaus

Let A be a commutative ring with 1/2 in A. In this paper, we define new characteristic classes for finitely generated projective A-modules V provided with a non degenerate quadratic form. These classes belong to the usual K-theory of A.…

K-Theory and Homology · Mathematics 2010-12-20 Max Karoubi

We extend results of Kass--Wickelgren to define an Euler class for a non-orientable (or non-relatively orientable) vector bundle on a smooth scheme, valued in the Grothendieck--Witt group of the ground field. We use a root stack…

Algebraic Geometry · Mathematics 2024-08-19 Andrew Kobin , Libby Taylor

We apply our earlier work on the higher-dimensional analogue of the Mumford conjecture to two questions. Inspired by work of Ebert we prove non-triviality of certain characteristic classes of bundles of smooth closed manifolds. Inspired by…

Algebraic Topology · Mathematics 2013-04-23 Soren Galatius , Oscar Randal-Williams

We show how to make the additive Chow groups of Bloch-Esnault, Ruelling and Park into a graded module for Bloch's higher Chow groups, in the case of a smooth projective variety over a field. This yields a a projective bundle formula as well…

Algebraic Geometry · Mathematics 2007-05-23 Amalendu Krishna , Marc Levine

We give necessary conditions for a category fibred in pseudo-abelian additive categories over the classifying topos of a profinite group to be a stack; these conditions are sufficient when the coefficients are $\mathbf{Q}$-linear. This…

Algebraic Geometry · Mathematics 2025-06-27 Bruno Kahn

We consider some conditions under which a smooth projective variety X is actually the projective space. We also extend to the case of positive characteristic some results in the theory of vector bundle adjunction. We use methods and…

Algebraic Geometry · Mathematics 2007-05-23 Marco Andreatta

Let $k$ be a number field. We describe the category of Laumon 1-isomotives over $k$ as the universal category in the sense of Nori associated with a quiver representation built out of smooth proper $k$-curves with two disjoint effective…

Algebraic Geometry · Mathematics 2019-08-15 Florian Ivorra , Takao Yamazaki

We prove that the symmetric monoidal category of mixed motives generated by an abelian variety (more generally, an abelian scheme) can be described as a certain module category. More precisely, we describe it as the category of…

Algebraic Geometry · Mathematics 2016-05-31 Isamu Iwanari