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A generalized moment map is proposed for arbitrary symplectic actions of compact connected Lie groups on closed symplectic manifolds, in the spirit of the circle -valued maps introduced by D. McDuff in the case of non-Hamiltonian circle…

Symplectic Geometry · Mathematics 2016-09-07 Pierre Sleewaegen

We develop a set of sufficient conditions for guaranteeing that an integrable system with a symmetry group $K$ on a manifold $M$ descends to an integrable system on a dense open subset of the quotient Poisson space $M/K$. The higher…

Mathematical Physics · Physics 2026-05-21 L. Feher , M. Fairon

Given a symplectic manifold, we ask in how many different ways can a torus act on it. Classification theorems in equivariant symplectic geometry can sometimes tell that two Hamiltonian torus actions are inequivalent, but often they do not…

Symplectic Geometry · Mathematics 2014-09-23 Yael Karshon , Liat Kessler , Martin Pinsonnault

In this article we introduce flag Bott manifolds of general Lie type as the total spaces of iterated flag bundles. They generalize the notion of flag Bott manifolds and generalized Bott manifolds, and admit nice torus actions. We calculate…

Algebraic Topology · Mathematics 2020-06-09 Shizuo Kaji , Shintarô Kuroki , Eunjeong Lee , Dong Youp Suh

We prove that the GKM graphs of GKM$_4$ manifolds that are either Hamiltonian or of complexity one extend to torus graphs. The arguments are based on a reformulation of the extension problem in terms of a natural representation of the…

Algebraic Topology · Mathematics 2026-03-18 Oliver Goertsches , Grigory Solomadin

We show that for any cohomogeneity one continuous action of a compact connected Lie group $G$ on a closed topological manifold the equivariant cohomology equipped with its canonical $H^*(BG)$-module structure is Cohen-Macaulay. The proof…

Algebraic Topology · Mathematics 2018-03-16 Oliver Goertsches , Augustin-Liviu Mare

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

We show that symplectic forms taming complex structures on compact manifolds are related to special types of almost generalized K\"ahler structures. By considering the commutator $Q$ of the two associated almost complex structures…

Differential Geometry · Mathematics 2011-12-13 Nicola Enrietti , Anna Fino , Gueo Grantcharov

In this paper, we do the two things. 1. We present a formula to compute the rational cohomology ring of a real topological toric manifold, and thus that of a small cover or a real toric manifold, which implies the formula of Suciu and…

Algebraic Topology · Mathematics 2013-11-28 Suyoung Choi , Hanchul Park

Using the language of T-varieties, we study torus invariant curves on a complete normal variety $X$ with an effective codimension-one torus action. In the same way that the $T$-invariant Weil divisors on $X$ are sums of "vertical" divisors…

Algebraic Geometry · Mathematics 2013-07-31 Geoffrey Scott

We show that the cohomology algebra of the complement of a coordinate subspace arrangement in m-dimensional complex space is isomorphic to the cohomology algebra of Stanley-Reisner face ring of a certain simplicial complex on m vertices.…

Algebraic Topology · Mathematics 2016-09-07 Victor M. Buchstaber , Taras E. Panov

We study fixed points of smooth torus actions on closed manifolds using fixed point formulas and equivariant elliptic genera. We also give applications to positively curved Riemannian manifolds with symmetry.

Geometric Topology · Mathematics 2016-08-19 Anand Dessai

The Chow quotient of a projective variety by the action of a complex torus is known to have a very complicated geometry, even in the case of simple varieties, such as rational homogeneous varieties. In this paper we propose an approach in…

Algebraic Geometry · Mathematics 2026-05-08 Luis E. Solá Conde , Gianluca Occhetta

An action of a complex reductive group $\mathrm G$ on a smooth projective variety $X$ is regular when all regular unipotent elements in $\mathrm G$ act with finitely many fixed points. Then the complex $\mathrm G$-equivariant cohomology…

Algebraic Geometry · Mathematics 2026-05-27 Tamás Hausel , Kamil Rychlewicz

We explore the consequences of curvature and torsion on the topology of quaternionic contact manifolds with integrable vertical distribution. We prove a general Myers theorem and establish a Cartan-Hadamard result for almost qc-Einstein…

Differential Geometry · Mathematics 2014-02-11 Robert K. Hladky

Let $S$ and $T$ be smooth projective varieties over an algebraically closed field. Suppose that $S$ is a surface admitting a decomposition of the diagonal. We show that, away from the characteristic of $k$, if an algebraic correspondence $T…

Algebraic Geometry · Mathematics 2026-01-14 Kanetomo Sato , Takao Yamazaki

Let $M^{2d}$ be a compact symplectic manifold and $T$ a compact $n$-dimensional torus. A Hamiltonian action, $\tau$, of $T$ on $M$ is a GKM action if, for every $p \in M^T$, the isotropy representation of $T$ on $T_pM$ has pair-wise…

Symplectic Geometry · Mathematics 2007-05-23 Victor Guillemin , Tara S. Holm

We show that the theory of stable complex $G$-cobordisms, for a torus $G$, is embedded into the theory of stable complex $G$-cobordisms of not necessarily compact manifolds equipped with proper abstract moment maps. Thus the introduction of…

Differential Geometry · Mathematics 2007-05-23 Viktor L. Ginzburg , Victor L. Guillemin , Yael Karshon

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

GKM theory is a powerful tool in equivariant topology and geometry that can be used to generalize classical ideas from (quasi)toric manifolds to more general torus actions. After an introduction to the topic this survey focuses on recent…

Algebraic Topology · Mathematics 2022-10-13 Oliver Goertsches , Panagiotis Konstantis , Leopold Zoller