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We start with a curve over an algebraically closed ground field of positive characteristic $p>0$. By using specialization techniques, under suitable natural coprimality conditions, we prove a cohomological Simpson Correspondence between the…

Algebraic Geometry · Mathematics 2022-03-01 Mark Andrea A. de Cataldo , Siqing Zhang

We prove that the ideal in complex cobordism ring $\MU^*$ generated by the polynomial generators $S=(x_1, x_k, k\geq 3)$ of $c_1$-spherical cobordism ring $W^*$, viewed as elements in $\MU^*$ by forgetful map is prime. Using the…

Algebraic Topology · Mathematics 2023-10-31 Malkhaz Bakuradze

For the cyclic group $C_2$ we give a complete description of the derived category of perfect complexes of modules over the constant Mackey ring $\underline{\mathbb{Z}/\ell}$, for $\ell$ a prime. This is fairly simple for $\ell$ odd, but for…

Algebraic Topology · Mathematics 2023-07-03 Daniel Dugger , Christy Hazel , Clover May

The goal of this paper is to develop the theory of Deligne-Beilinson cohomology of affine groups with a mixed Hodge structure. The motivation comes from Hodge theory and the study of motives, where such groups appear. Several of Francis…

Algebraic Geometry · Mathematics 2016-02-23 Richard Hain

Let $C_2$ denote the cyclic group of order 2. We compute the $RO(C_2)$-graded cohomology of all $C_2$-surfaces with constant integral coefficients. We show when the action is nonfree, the answer depends only on the genus, the orientability…

Algebraic Topology · Mathematics 2021-12-10 Christy Hazel

We extend results of Colliot-Th\'el\`ene and Raskind on the $\mathcal{K}_2$-cohomology of smooth projective varieties over a separably closed field $k$ to the \'etale motivic cohomology of smooth, not necessarily projective, varieties over…

Algebraic Geometry · Mathematics 2019-11-22 Bruno Kahn

This paper determines the RO(G)-graded Eilenberg-MacLane cohomology of the real, infinite, equivariant Grassmannians in the case G=Z/2. Possible connections with motivic characteristic classes for quadratic bundles are briefly discussed.

Algebraic Topology · Mathematics 2015-05-27 Daniel Dugger

We use the action of the Bockstein homomorphism on the cohomology ring $H^*(X,\mathbb{Z}_2)$ of a finite-type CW-complex $X$ in order to define the resonance varieties of $X$ in characteristic 2. Much of the theory is done in the more…

Algebraic Topology · Mathematics 2023-11-20 Alexander I. Suciu

We compute the integer cohomology rings of the ``polygon spaces'' introduced in [Hausmann,Klyachko,Kapovich-Millson]. This is done by embedding them in certain toric varieties; the restriction map on cohomology is surjective and we…

dg-ga · Mathematics 2008-02-03 Jean-Claude Hausmann , Allen Knutson

We construct a motivic Eilenberg-MacLane spectrum with a highly structured multiplication over smooth schemes over Dedekind domains which represents Levine's motivic cohomology. The latter is defined via Bloch's cycle complexes. Our method…

Algebraic Geometry · Mathematics 2013-11-20 Markus Spitzweck

Let $k$ be a perfect field of characteristic $p > 0$, $W_n = W_n(k)$. For separated $k$-schemes of finite type, we explain how rigid cohomology with compact supports can be computed as the cohomology of certain de Rham-Witt complexes with…

Algebraic Geometry · Mathematics 2012-05-22 Pierre Berthelot

The motivic version of the $c_1$-spherical cobordism spectrum is constructed. A connection of this spectrum with other motivic Thom spectra is established. Using this connection, we compute the $\mathbb{P}^1$-diagonal of the homotopy groups…

Algebraic Topology · Mathematics 2026-04-10 Egor Zolotarev

We introduce equivariant twisted cohomology of a simplicial set equipped with simplicial action of a discrete group and prove that for suitable twisting function induced from a given equivariant local coefficients, the simplicial version of…

Algebraic Topology · Mathematics 2010-05-11 Goutam Mukherjee , Debasis Sen

In this, the second of three papers about $C_2$-equivariant complex quadrics, we calculate the equivariant ordinary cohomology of smooth symmetric quadrics graded on the representation ring of $\Pi BU(1)$ and with coefficients in the…

Algebraic Topology · Mathematics 2025-11-19 Steven R. Costenoble , Thomas Hudson

We introduce a theory of motivic cohomology for quasi-compact quasi-separated schemes, which generalises the construction of Elmanto--Morrow in the case of schemes over a field. Our construction is non-$\mathbb{A}^1$-invariant in general,…

Algebraic Geometry · Mathematics 2025-07-22 Tess Bouis

We present an overview of computational methods for Bredon cohomology with a special focus on infinite groups

Algebraic Topology · Mathematics 2023-04-06 Noe Barcenas

In this paper we present algorithms that compute certain local cohomology modules associated to a ring of polynomials containing the rational numbers. In particular we are able to compute the local cohomological dimension of algebraic…

alg-geom · Mathematics 2007-05-23 Uli Walther

B\'ezout's theorem, nonequivariantly, can be interpreted as a calculation of the Euler class of a sum of line bundles over complex projective space, expressing it in terms of the rank of the bundle and its degree. We give here a…

Algebraic Topology · Mathematics 2024-07-24 Steven R. Costenoble , Thomas Hudson , Sean Tilson

We obtain a characterization of Maximal and Galois-Maximal $C_2$-spaces (including real algebraic varieties) in terms of $\operatorname{RO}(C_2)$-graded cohomology with coefficients in the constant Mackey functor $\underline{\mathbf{F}}_2$,…

Algebraic Geometry · Mathematics 2023-10-27 Pedro F. dos Santos , Carlos Florentino , Javier Orts

We give algorithms for the computation of the algebraic de Rham cohomology of open and closed algebraic sets inside projective space or other smooth complex toric varieties. The methods, which are based on Gr\"obner basis computations in…

Algebraic Geometry · Mathematics 2009-09-25 Uli Walther