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In the theory of algebraic group actions on affine varieties, the concept of a Kempf-Ness set is used to replace the categorical quotient by the quotient with respect to a maximal compact subgroup. By making use of the recent achievements…

Algebraic Geometry · Mathematics 2008-10-08 Taras Panov

This is a survey on natural local torus actions which arise in integrable dynamical systems, and their relations with other subjects, including: reduced integrability, local normal forms, affine structures, monodromy, global invariants,…

Dynamical Systems · Mathematics 2007-05-23 Nguyen Tien Zung

Using Galois descent tools, we extend the Altmann-Hausen presentation of normal affine algebraic varieties endowed with an effective torus action over an algebraically closed field of characteristic zero to the case where the ground field…

Algebraic Geometry · Mathematics 2022-08-03 Pierre-Alexandre Gillard

We present a general vertex operator construction based on the Fock space for an affine Lie algebras of type $A$. This construction allows us to give a unified treatment for both the homogeneous and principle realizations of the affine Lie…

Quantum Algebra · Mathematics 2007-05-23 Stephen Berman , Yun Gao , Shaobin Tan

In this paper we study a specific class of actions of a $2$-torus $\mathbb{Z}_2^k$ on manifolds, namely, the actions of complexity one in general position. We describe the orbit space of equivariantly formal $2$-torus actions of complexity…

Algebraic Topology · Mathematics 2023-04-04 Vladimir Gorchakov

We investigate flexibility of affine varieties with an action of a linear algebraic group. Flexibility of a smooth affine variety with only constant invertible functions and a locally transitive action of a reductive group is proved. Also…

Algebraic Geometry · Mathematics 2019-07-16 Sergey Gaifullin , Anton Shafarevich

We write the equivariant Todd class of a general complete toric variety as an explicit combination of the orbit closures, the coefficients being analytic functions on the Lie algebra of the torus which satisfy Danilov's requirement.

Algebraic Geometry · Mathematics 2007-05-23 Nicole Berline , Michele Vergne

We express the total space of a principal circle bundle over a connected sum of two manifolds in terms of the total spaces of circle bundles over each summand, provided certain conditions hold. We then apply this result to provide…

Geometric Topology · Mathematics 2025-01-29 Fernando Galaz-García , Philipp Reiser

Let a compact torus $T=T^{n-1}$ act on an orientable smooth compact manifold $X=X^{2n}$ effectively, with nonempty finite set of fixed points, and suppose that stabilizers of all points are connected. If $H^{odd}(X)=0$ and the weights of…

Algebraic Topology · Mathematics 2026-02-10 Anton Ayzenberg , Mikiya Masuda

We study the C*-algebra of an affine map on a compact abelian group and give necessary and sufficient conditions for strong transitivity when the group is a torus. The structure of the C*-algebra is completely determined for all strongly…

Operator Algebras · Mathematics 2012-04-03 Kasper K. S. Andersen , Klaus Thomsen

We prove that any embedded Maslov index two analytic disc attached to a totally real torus in the complex two-dimensional affine space extends to an analytic filling provided that the torus is contained in a regular level set of a strictly…

Complex Variables · Mathematics 2016-09-20 Kai Zehmisch

In this work we obtain sufficient conditions for a variety with a torus action of complexity one to have a finite number of automorphism group orbits.

Algebraic Geometry · Mathematics 2023-11-07 Sergey Gaifullin , Dmitriy Chunaev

We generalize to the super context, the known fact that if an affine algebraic group $G$ over a commutative ring $k$ acts freely (in an appropriate sense) on an affine scheme $X$ over $k$, then the dur sheaf $X\tilde{\tilde{/}}G$ of…

Algebraic Geometry · Mathematics 2021-08-10 Akira Masuoka , Taiki Shibata , Yuta Shimada

We construct all possible Hamiltonian torus actions for which all the non-empty reduced spaces are two dimensional (and not single points) and the manifold is connected and compact, or, more generally, the moment map is proper as a map to a…

Symplectic Geometry · Mathematics 2014-11-11 Yael Karshon , Susan Tolman

A rational pseudo-rotation $f$ of the torus is a homeomorphism homotopic to the identity with a rotation set consisting of a single vector $v$ of rational coordinates. We give a classification for rational pseudo-rotations with an invariant…

Dynamical Systems · Mathematics 2021-02-22 Andres Koropecki , Fabio Armando Tal

We study affine toric varieties with an action of group $SL_n$ with a dense orbit. A characterisation in terms of $SL_n \times Q$-modules is given where $Q$ is a quasitorus. This characterisation is more explicitly expanded in case $n=3$.…

Algebraic Geometry · Mathematics 2018-12-27 Nikita Medved

For an action of a compact torus $T$ on a smooth compact manifold~$X$ with isolated fixed points the number $\frac{1}{2}\dim X-\dim T$ is called the complexity of the action. In this paper we study certain examples of torus actions of…

Algebraic Topology · Mathematics 2023-02-20 Anton Ayzenberg

Let A be a finitely generated associative algebra over an algebraically closed field. We characterize the finite dimensional modules over A whose orbit closures are regular varieties.

Algebraic Geometry · Mathematics 2007-05-23 Nguyen Quang Loc , Grzegorz Zwara

Let the compact torus $T^{n-1}$ act on a smooth compact manifold $X^{2n}$ effectively with nonempty finite set of fixed points. We pose the question: what can be said about the orbit space $X^{2n}/T^{n-1}$ if the action is cohomologically…

Algebraic Topology · Mathematics 2023-02-20 Anton Ayzenberg , Vladislav Cherepanov

A two-orbit variety is a normal complete complex algebraic variety on which a reductive complex algebraic group acts with exactly two orbits. The aim of this paper is to give the classification of all two-orbit varieties and to prove Luna's…

Representation Theory · Mathematics 2007-05-23 S. Cupit-Foutou