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Related papers: Equivariant birational types and Burnside volume

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After we have given a survey on the Burnside ring of a finite group, we discuss and analyze various extensions of this notion to infinite (discrete) groups. The first three are the finite-G-set-version, the inverse-limit-version and the…

Algebraic Topology · Mathematics 2007-05-23 Wolfgang Lueck

There are (at least) two different approaches to define equivariant analogue of the Euler charateristic for a space with a finite group action. The first one defines it as an element of the Burnside ring of the group. The second approach…

Algebraic Geometry · Mathematics 2016-05-11 S. M. Gusein-Zade , I. Luengo , A. Melle-Hernández

We complete the classification of regular generically free actions of finite groups on del Pezzo surfaces, up to birational equivalence. As a byproduct, we settle several open problems in equivariant birational geometry, e.g., we classify…

Algebraic Geometry · Mathematics 2026-04-23 Ivan Cheltsov , Yuri Tschinkel , Zhijia Zhang

Fix a finite group $G$. We seek to classify varieties with $G$-action equivariantly birational to a representation of $G$ on affine or projective space. Our focus is odd-dimensional smooth complete intersections of two quadrics, relating…

Algebraic Geometry · Mathematics 2022-02-02 Brendan Hassett , Yuri Tschinkel

Let A be a finite abelian group. We set up an algebraic framework for studying A-equivariant complex-orientable cohomology theories in terms of a suitable kind of equivariant formal groups. We compute the equivariant cohomology of many…

Algebraic Topology · Mathematics 2008-11-14 Neil P. Strickland

We discuss invariants in equivariant birational geometry.

Algebraic Geometry · Mathematics 2026-03-02 Andrew Kresch , Yuri Tschinkel

For a complex analytic variety with an action of a finite group and for an invariant 1-form on it, we give an equivariant version (with values in the Burnside ring of the group) of the local Euler obstruction of the 1-form and describe its…

Algebraic Geometry · Mathematics 2014-07-25 Wolfgang Ebeling , Sabir M. Gusein-Zade

Using equivariant obstruction theory we construct equivariant maps from certain classifying spaces to representation spheres for cyclic groups, product of elementary Abelian groups and dihedral groups. Restricting them to finite skeleta…

Algebraic Topology · Mathematics 2016-07-22 Samik Basu , Surojit Ghosh

We investigate equivariant birational geometry of rational surfaces and threefolds from the perspective of derived categories.

Algebraic Geometry · Mathematics 2023-11-28 Christian Böhning , Hans-Christian Graf von Bothmer , Yuri Tschinkel

We study relations between the classical modular symbols associated with congruence subgroups and Kontsevich-Pestun-Tschinkel groups $\mathcal{M}_n(G)$ associated with finite abelian groups $G$.

Number Theory · Mathematics 2024-07-17 Zhijia Zhang

We survey new results on finite groups of birational transformations of algebraic varieties.

Algebraic Geometry · Mathematics 2021-12-28 Yuri Prokhorov

To any Hamiltonian action of a reductive algebraic group $G$ on a smooth irreducible symplectic variety $X$ we associate certain combinatorial invariants: Cartan space, Weyl group, weight and root lattices. For cotangent bundles our…

Algebraic Geometry · Mathematics 2009-05-30 Ivan V. Losev

A classical set of birational invariants of a variety are its spaces of pluricanonical forms and some of their canonically defined subspaces. Each of these vector spaces admits a typical metric structure which is also birationally…

Algebraic Geometry · Mathematics 2009-11-13 Chen-Yu Chi , Shing-Tung Yau

This paper introduces a novel framework for constructing invariants in $G$-equivariant birational geometry by unifying two recent approaches: the theory of atoms recently developed by Katzarkov, Kontsevich, Pantev, and Yu, and the theory of…

Algebraic Geometry · Mathematics 2026-04-02 Leonardo F. Cavenaghi , Ludmil Katzarkov , Maxim Kontsevich

We introduce the notion of a standard weighted graph and show that every weighted graph has an essentially unique standard model. Moreover we classify birational transformations between such models. Our central result shows that these are…

Algebraic Geometry · Mathematics 2007-05-23 Hubert Flenner , Shulim Kaliman , Mikhail Zaidenberg

In this work the equivariant signature of a manifold with proper action of a discrete group is defined as an invariant of equivariant bordisms. It is shown that the computation of this signature can be reduced to its computation on fixed…

Algebraic Topology · Mathematics 2011-12-12 A. S. Mishchenko , Quitzeh Morales Meléndez

By a $B$-regular variety, we mean a smooth projective variety over $C$ admitting an algebraic action of the upper triangular Borel subgroup $B \subset SL_2(C)$ such that the unipotent radical in $B$ has a unique fixed point. A result of M.…

Algebraic Geometry · Mathematics 2008-09-09 James B. Carrell , Kiumars Kaveh

We construct invariants of birational maps with values in the Kontsevich--Tschinkel group and in the truncated Grothendieck groups of varieties. These invariants are morphisms of groupoids and are well-suited to investigating the structure…

Algebraic Geometry · Mathematics 2023-06-13 Hsueh-Yung Lin , Evgeny Shinder

We introduce the universal Euler characteristic of orbit space definable groupoids, a class of groupoids containing cocompact proper Lie groupoids as well as translation groupoids associated to proper definable group actions. We show that…

Differential Geometry · Mathematics 2025-07-22 Carla Farsi , Emily Proctor , Christopher Seaton

We consider geometric invariant theory for \emph{graded additive groups}, groups of the form $\mathbb{G}_a^r\rtimes_w\mathbb{G}_m$ such that the $\mathbb{G}_m$-action on $\mathbb{G}_a^r$ is a scalar multiplication with weight…

Algebraic Geometry · Mathematics 2025-07-17 Yikun Qiao