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For Hamiltonian circle actions on compact, connected, four-dimensional manifolds, we give a generators and relations description for the even part of the equivariant cohomology, as an algebra over the equivariant cohomology of a point. This…

Symplectic Geometry · Mathematics 2025-08-13 Tara Holm , Liat Kessler

We obtain an equivariant classification for orientable, closed, four-dimensional Alexandrov spaces admitting an isometric torus action. This generalizes the equivariant classification of Orlik and Raymond of closed four-dimensional…

Differential Geometry · Mathematics 2023-06-23 Diego Corro , Jesús Núñez-Zimbrón , Masoumeh Zarei

In the past two decades, extensive research has been conducted on the (co)homology of various models of random simplicial complexes. So far, it has always been examined merely as a list of groups. This paper expands upon this by describing…

Algebraic Topology · Mathematics 2024-08-21 Jon V. Kogan

We introduce the category of {\it locally $k$-standard $T$-manifolds} which includes well-known classes of manifolds such as toric and quasitoric manifolds, good contact toric manifolds and moment-angle manifolds. They are smooth manifolds…

Algebraic Topology · Mathematics 2022-01-05 Soumen Sarkar , Jongbaek Song

We present a new geometric interpretation of equivariant cohomology in which one replaces a smooth, complex $G$-variety $X$ by its associated arc space $J_{\infty} X$, with its induced $G$-action. This not only allows us to obtain geometric…

Algebraic Geometry · Mathematics 2014-02-18 Dave Anderson , Alan Stapledon

In this paper, we introduce the notion of maximal actions of compact tori on smooth manifolds and study compact connected complex manifolds equipped with maximal actions of compact tori. We give a complete classification of such manifolds,…

Complex Variables · Mathematics 2015-05-01 Hiroaki Ishida

Given a real arrangement $A$, the complement $M(A)$ of the complexification of $A$ admits an action of $\mathbb{Z}_2$ by complex conjugation. We define the equivariant Orlik-Solomon algebra of $A$ to be the $\mathbb{Z}_2$-equivariant…

Combinatorics · Mathematics 2007-05-23 Nicholas J. Proudfoot

Let R be a commutative ring containing 1/2. We compute the R-cohomology ring of the configuration space F(m,k) of k ordered points in the m-dimensional real projective space. The method uses the observation that the orbit configuration…

Algebraic Topology · Mathematics 2015-07-16 Jesús González , Aldo Guzmán-Sáenz , Miguel Xicotencatl

Let $G$ be a compact, connected Lie group and $T \subset G$ a maximal torus. Let $(M,\omega)$ be a monotone closed symplectic manifold equipped with a Hamiltonian action of $G$. We construct a module action of the affine nil-Hecke algebra…

Symplectic Geometry · Mathematics 2022-05-02 Eduardo González , Cheuk Yu Mak , Dan Pomerleano

We show that if a holomorphic $n$ dimensional compact torus action on a compact connected complex manifold of complex dimension $n$ has a fixed point then the manifold is equivariantly biholomorphic to a smooth toric variety.

Complex Variables · Mathematics 2012-12-18 Hiroaki Ishida , Yael Karshon

In this paper we use the gradient flow equation introduced in [10] to construct a Morse complex for the Hamiltonian action $\mathbb A_H$ on a mixed regularity space of loops in the cotangent bundle $T^*M$ of a closed manifold $M$.…

Symplectic Geometry · Mathematics 2025-01-28 L. Asselle , M. Starostka

We construct an equivariant version of Ray-Singer analytic torsion for proper, isometric actions by locally compact groups on Riemannian manifolds, with compact quotients. We obtain results on convergence, metric independence, vanishing for…

Differential Geometry · Mathematics 2023-06-30 Peter Hochs , Hemanth Saratchandran

This survey paper describes two geometric representations of the permutation group using the tools of toric topology. These actions are extremely useful for computational problems in Schubert calculus. The (torus) equivariant cohomology of…

Algebraic Topology · Mathematics 2007-06-05 Julianna S. Tymoczko

We study torus actions on symplectic manifolds with proper moment maps in the case that each reduced space is two-dimensional. We provide a complete set of invariants for such spaces. Our proof uses sheaves of groupoids of Hamiltonian…

Symplectic Geometry · Mathematics 2007-05-23 Yael Karshon , Susan Tolman

In this present paper we study geometry of compact complex manifolds equipped with a \emph{maximal} torus $T=(S^1)^k$ action. We give two equivalent constructions providing examples of such manifolds given a simplicial fan $\Sigma$ and a…

Complex Variables · Mathematics 2020-09-04 Yury Ustinovskiy

We determine the action of the Torelli group on the equivariant cohomology of the space of flat SL(2,C) connections on a closed Riemann surface. We show that the trivial part of the action contains the equivariant cohomology of the even…

Geometric Topology · Mathematics 2011-09-02 Georgios D. Daskalopoulos , Richard A. Wentworth , Graeme Wilkin

In this paper, we compute the homotopy type of the group of equivariant symplectomorphisms of $S^2 \times S^2$ and $\mathbb{C}P^2 \# \overline{\mathbb{C}P^2}$ under the presence of Hamiltonian group actions of the circle $S^1$. We prove…

Symplectic Geometry · Mathematics 2025-10-22 Pranav Chakravarthy , Martin Pinsonnault

For any orbifold M, we explicitly construct a simplicial complex S(M) from a given triangulation of the `coarse' underlying space together with the local isotropy groups of M. We prove that, for any local system on M, this complex S(M) has…

q-alg · Mathematics 2008-02-03 Ieke Moerdijk , Dorette A Pronk

moment maps arise as a generalization of genuine moment maps on symplectic manifolds when the symplectic structure is discarded, but the relation between the mapping and the action is kept. Particular examples of abstract moment maps had…

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

A good contact toric manifold $M$ is determined by its moment cone $C$. We compute the equivariant cohomology ring with $\Z$ coefficient of $M$ in terms of the combinatorial data of $C$. Then under a smoothness criterion on the cone $C$, we…

Symplectic Geometry · Mathematics 2012-06-27 Shisen Luo