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For a finite abelian group action on a linear category, we study the dual action given by the character group acting on the category of equivariant objects. We prove that the groups of equivariant autoequivalences on these two categories…

Representation Theory · Mathematics 2021-09-27 Jianmin Chen , Xiao-Wu Chen , Shiquan Ruan

Let G denote a compact connected Lie group with torsion-free fundamental group acting on a compact space X such that all the isotropy subgroups are connected subgroups of maximal rank. Let $T\subset G$ be a maximal torus with Weyl group W.…

Algebraic Topology · Mathematics 2014-02-26 Alejandro Adem , José Manuel Gómez

It is well known that the Euler characteristic of the cohomology of a complex algebraic variety coincides with the Euler characteristic of its cohomology with compact support. An old result of G. Laumon asserts that a relative version of…

Algebraic Geometry · Mathematics 2014-10-09 Rahbar Virk

Consider a Hamiltonian action of a compact Lie group on a symplectic manifold which has the strong Lefschetz property. We establish an equivariant version of the Merkulov-Guillemin $d\delta$-lemma and an improved version of the…

Symplectic Geometry · Mathematics 2007-05-23 Yi Lin , Reyer Sjamaar

For a Hamiltonian action of a compact group $U$ of isometries on a compact K\"ahler manifold $Z$ and a compatible subgroup $G$ of $U^{\mathbb{C}}$, we prove that for any closed $G$--invariant subset $Y\subset Z$ the image of the gradient…

Complex Variables · Mathematics 2014-02-11 Leonardo Biliotti , Alessandro Ghigi , Peter Heinzner

We provide a natural interpretation of the secondary Euler characteristic and introduce higher Euler characteristics. For a compact oriented manifold of odd dimension, the secondary Euler characteristic recovers the Kervaire…

K-Theory and Homology · Mathematics 2015-09-18 Niranjan Ramachandran

We introduce the notion of equivariant basic cohomology for singular Riemannian foliations with transverse infinitesimal actions, and prove some elementary properties such as its invariance under homotopies. For the particular case of…

Differential Geometry · Mathematics 2023-06-21 Francisco C. Caramello

In this paper we study the asymptotic behaviour of the equivariant holomorphic analytic torsion forms associated with increasing powers of a fibrewise positive line bundle. The result is an equivariant extension of a result of Puchol.

Differential Geometry · Mathematics 2024-08-23 Pascal Tessmer

Motivated by representation theory and geometry, we introduce and develop an equivariant generalization of Ehrhart theory, the study of lattice points in dilations of lattice polytopes. We prove representation-theoretic analogues of…

Combinatorics · Mathematics 2014-12-05 Alan Stapledon

Let X be a compact manifold with a smooth action of a compact connected Lie group G. Let $L\to X$ be a complex line bundle. Using the Cartan complex for equivariant cohomology, we give a new proof of a theorem of Hattori and Yoshida which…

Differential Geometry · Mathematics 2007-05-23 Ignasi Mundet i Riera

Let $U$ be a graded unipotent group over the complex numbers, in the sense that it has an extension $\hat{U}$ by the multiplicative group such that the action of the multiplicative group by conjugation on the Lie algebra of $U$ has all its…

Algebraic Geometry · Mathematics 2020-01-22 Gergely Bérczi , Brent Doran , Thomas Hawes , Frances Kirwan

Starting from any proper action of any locally compact quantum group on any discrete quantum space, we show that its equivariant representation theory yields a concrete unitary 2-category of finite type Hilbert bimodules over the discrete…

Operator Algebras · Mathematics 2025-08-27 Lukas Rollier

Ehrhart theory is the study of the enumeration of lattice points in lattice polytopes. Equivariant Ehrhart theory is a generalization of Ehrhart theory that takes into account the action of a finite group acting via affine transformations…

Combinatorics · Mathematics 2025-09-26 Alan Stapledon

The smooth action of a compact Lie group on a compact manifold can be resolved to an iterated space, as made explicit by Pierre Albin and the second author. On the resolution the lifted action has fixed isotropy type corresponding to the…

K-Theory and Homology · Mathematics 2021-01-05 Panagiotis Dimakis , Richard Melrose

Given certain intersection cohomology sheaves on a projective variety with a torus action, we relate the cohomology groups of their tensor product to the cohomology groups of the individual sheaves. We also prove a similar result in the…

Representation Theory · Mathematics 2016-01-20 Asilata Bapat

Following an outline of Rezk, we give a construction of complex-analytic $G$-equivariant elliptic cohomology for an arbitrary compact Lie group $G$ and we prove some of its fundamental properties. The construction is parametrised over the…

Algebraic Topology · Mathematics 2024-08-06 Matthew Spong

Consider a degeneration of projective algebraic manifolds equipped with a compact group action over a curve. Suppose that the total space carries a Nakano semi-positive vector bundle, which is equivariant with respect to this action. We…

Algebraic Geometry · Mathematics 2026-02-17 Ken-Ichi Yoshikawa

For T an abelian compact Lie group, we give a description of T-equivariant K-theory with complex coefficients in terms of equivariant cohomology. In the appendix we give applications of this by extending results of Chang-Skjelbred and…

Algebraic Topology · Mathematics 2009-03-10 Ioanid Rosu , Allen Knutson

We introduce a torsor-theoretic obstruction to equivariant unirationality and show that it is also sufficient for actions of finite groups on toric varieties arising from automorphisms of the torus.

Algebraic Geometry · Mathematics 2025-06-10 Andrew Kresch , Yuri Tschinkel

We investigate group actions on the category of coherent sheaves over weighted projective lines. We show that the equivariant category with respect to certain finite group action is equivalent to the category of coherent sheaves over a…

Representation Theory · Mathematics 2021-04-20 Qiang Dong , Shiquan Ruan , Hongxia Zhang