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We define and study bivariant equivariant periodic cyclic homology for actions of ample groupoids. In analogy to the group case, we show that the theory satisfies homotopy invariance, stability, and excision in both variables. We also prove…

K-Theory and Homology · Mathematics 2026-02-20 Francesco Pagliuca , Christian Voigt

We extend the notion of the $J$-invariant to arbitrary semisimple linear algebraic groups and provide complete decompositions for the normed Chow motives of all generically quasi-split twisted flag varieties. Besides, we establish some…

Algebraic Geometry · Mathematics 2025-10-29 Nikita Geldhauser , Maksim Zhykhovich

We prove a restriction isomorphism for Chow groups of zero-cycles with coefficients in Milnor K-theory for smooth projective schemes over excellent henselian discrete valuation rings. Furthermore, we study torsion subgroups of these groups…

Algebraic Geometry · Mathematics 2019-10-29 Morten Lüders

We introduce a notion of integration on the category of proper birational maps to a given variety $X$, with value in an associated Chow group. Applications include new birational invariants; comparison results for Chern classes and numbers…

Algebraic Geometry · Mathematics 2012-04-10 Paolo Aluffi

The focus of this note is on the Chow group problem over ramified regular local rings $(R, m)$. Our goal is threefold: i) to introduce a characterization of a ramified regular local ring essentially of finite type over a dvr, ii) to address…

Commutative Algebra · Mathematics 2024-06-17 S. P. Dutta

In this article we show how Gr\"un's results in group theory can be used for studying the structure of class groups in normal extensions.

Number Theory · Mathematics 2011-08-30 Franz Lemmermeyer

This note is about cycle-theoretic properties of the Fano variety of lines on a smooth cubic fivefold. The arguments are based on the fact that this Fano variety has finite-dimensional motive. We also present some results concerning Chow…

Algebraic Geometry · Mathematics 2017-06-20 Robert Laterveer

We obtain examples of smooth projective varieties over $\mathbb{C}$ that violate the integral Hodge conjecture and for which the total Chow group is of finite rank. Moreover, we show that there exist such examples defined over number…

Algebraic Geometry · Mathematics 2023-08-16 Humberto A. Diaz

Let $k$ be a field of arbitrary characteristic. Let $S$ be a singular surface defined over $k$ with multiple rational curve singularities and suppose that the Chow group of zero cycles of its normalisation $\tilde{S}$ is finite dimensional.…

Algebraic Geometry · Mathematics 2007-05-23 G V Ravindra

We study unirationality of actions of finite groups on Fano threefolds.

Algebraic Geometry · Mathematics 2025-02-28 Ivan Cheltsov , Yuri Tschinkel , Zhijia Zhang

Cyclically ordered graphs, or cogs, sit between abstract graphs and cellularly embedded graphs. They arise naturally in topological graph theory, knot theory, and mathematical biology. We develop a formal theory of cogs and establish a…

Combinatorics · Mathematics 2025-11-18 Paul Bratch , M. N. Ellingham , Joanna A. Ellis-Monaghan , Iain Moffatt , Wout Moltmaker

We study rational double Hurwitz cycles, i.e. loci of marked rational stable curves admitting a map to the projective line with assigned ramification profiles over two fixed branch points. Generalizing the phenomenon observed for double…

Algebraic Geometry · Mathematics 2013-05-21 Aaron Bertram , Renzo Cavalieri , Hannah Markwig

We provide new examples of integrable rational maps in four dimensions with two rational invariants, which have unexpected geometric properties, as for example orbits confined to non algebraic varieties, and fall outside classes studied by…

Exactly Solvable and Integrable Systems · Physics 2018-11-06 N. Joshi , CM. Viallet

We briefly indicate some implications of [1] for the second Lie algebra cohomology of equivariant map algebras and (twisted multi) loop algebras.

Differential Geometry · Mathematics 2021-08-10 Bas Janssens

We explain how to exploit Rost's theory of Chow groups with coefficients to carry some computations of cohomological invariants (i.e. characteristic classes for G-torsors in Galois cohomology, for an algebraic group G). In particular, we…

Algebraic Geometry · Mathematics 2007-11-14 Pierre Guillot

Many moduli spaces are constructed as quotients of group actions; this paper surveys the classical theory, as well as recent progress and applications. We review geometric invariant theory for reductive groups and how it is used to…

Algebraic Geometry · Mathematics 2023-03-01 Victoria Hoskins

This note is about the Chow groups of a certain family of smooth cubic fourfolds. This family is characterized by the property that each cubic fourfold $X$ in the family has an involution such that the induced involution on the Fano variety…

Algebraic Geometry · Mathematics 2017-03-14 Robert Laterveer

We investigate the surjectivity of the real cycle class map from $I$-cohomology to classical intergral cohomology for some real smooth varieties, in particular surfaces. This might be considered as one of several possible incarnations of…

K-Theory and Homology · Mathematics 2024-05-24 Jens Hornbostel

Let G be a compact Lie-group, X a compact G-CW-complex. We define equivariant geometric K-homology groups K^G_*(X), using an obvious equivariant version of the (M,E,f)-picture of Baum-Douglas for K-homology. We define explicit natural…

K-Theory and Homology · Mathematics 2012-10-12 Paul Baum , Herve Oyono-Oyono , Thomas Schick , Michael Walter

We study zero-cycles in families of rationally connected varieties. We show that for a smooth projective scheme over a henselian discrete valuation ring the restriction of relative zero cycles to the special fiber induces an isomorphism on…

Algebraic Geometry · Mathematics 2024-07-11 Morten Lüders