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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

The space of smooth sections of a symplectic fiber bundle carries a natural symplectic structure. We provide a general framework to determine the momentum map for the action of the group of bundle automorphism on this space. Since, in…

Differential Geometry · Mathematics 2020-02-05 Tobias Diez , Tudor S. Ratiu

We present a K-theoritic approach to the Guillemin-Sternberg conjecture, about the commutativity of geometric quantization and symplectic reduction, which was proved by Meinrenken and Tian-Zhang. Besides providing a new proof of this…

Differential Geometry · Mathematics 2007-05-23 Paul-Emile Paradan

We extend the definition of Weinstein's Action homomorphism to Hamiltonian actions with equivariant moment maps of (possibly infinite-dimensional) Lie groups on symplectic manifolds, and show that under conditions including a uniform bound…

Symplectic Geometry · Mathematics 2012-02-22 Egor Shelukhin

We provide a model for an open invariant neighborhood of any orbit in a symplectic manifold endowed with a canonical proper symmetry. Our results generalize the constructions of Marle and Guillemin and Sternberg for canonical symmetries…

Symplectic Geometry · Mathematics 2007-05-23 Juan-Pablo Ortega , Tudor S. Ratiu

Atiyah proved that the moment map image of the closure of an orbit of a complex torus action is convex. Brion generalized this result to actions of a complex reductive group. We extend their results to actions of a maximal solvable…

Symplectic Geometry · Mathematics 2010-11-02 Victor Guillemin , Reyer Sjamaar

In the first part of the paper, we build a foundation for further work on Hamiltonian actions on symplectic orbifolds. Most importantly we prove the orbifold versions of the abelian connectedness and convexity theorems. In the second half,…

dg-ga · Mathematics 2008-02-03 Eugene Lerman , Susan Tolman

This is the second of two companion papers. We describe a generalization of the point vortex system on surfaces to a Hamiltonian dynamical system consisting of two or three points on complex projective space CP^2 interacting via a…

Mathematical Physics · Physics 2021-05-18 James Montaldi , Amna Shaddad

The moment map $\mu$ is a central concept in the study of Hamiltonian actions of compact Lie groups $K$ on symplectic manifolds. In this short note, we propose a theory of moment maps coupled with an $\mathrm{Ad}_K$-invariant convex…

Differential Geometry · Mathematics 2022-08-09 King Leung Lee , Jacob Sturm , Xiaowei Wang

We prove that if an (n-1)-dimensional torus acts symplectically on a 2n-dimensional manifold, then the action has a fixed point if and only if the action is Hamiltonian. One may regard it as a symplectic version of Frankel theorem. The case…

Symplectic Geometry · Mathematics 2007-05-23 Min Kyu Kim

We prove that for every proper Hamiltonian action of a Lie group G in finite dimensions the momentum map is locally G-open relative to its image (i.e. images of G-invariant open sets are open). As an application we deduce that in a…

Symplectic Geometry · Mathematics 2016-09-07 James Montaldi , Tadashi Tokieda

In this paper we prove a convexity and fibre-connectedness theorem for proper maps constructed by Thimm's trick on a connected Hamiltonian $G$-space $M$ that generate a Hamiltonian torus action on an open dense submanifold. Since these maps…

Symplectic Geometry · Mathematics 2021-10-06 Jeremy Lane

Let $G_{\P}$ be a compact simple Poisson-Lie group equipped with a Poisson structure $\P$ and $(M, \o)$ be a symplectic manifold. Assume that $M$ carries a Poisson action of $G_{\P}$ and there is an equivariant moment map in the sense of Lu…

dg-ga · Mathematics 2008-02-03 Anton Yu. Alekseev

In this paper we generalize to coisotropic actions of compact Lie groups a theorem of Guillemin on deformations of Hamiltonian structures on compact symplectic manifolds. We show how one can reconstruct from the moment polytope the…

Symplectic Geometry · Mathematics 2008-10-01 Lucio Bedulli , Anna Gori

We introduce the notion of a weak (homotopy) moment map associated to a Lie group action on a multisymplectic manifold. We show that the existence/uniqueness theory governing these maps is a direct generalization from symplectic geometry.…

Symplectic Geometry · Mathematics 2018-07-05 Jonathan Herman

We introduce non-smooth symplectic forms on manifolds and describe corresponding Poisson structures on the algebra of Colombeau generalized functions. This is achieved by establishing an extension of the classical map of smooth functions to…

Differential Geometry · Mathematics 2016-09-15 Guenther Hoermann , Sanja Konjik , Michael Kunzinger

Let $p$ be a prime number. We introduce symplectic actions of $p$-adic analytic Lie groups on $p$-adic symplectic manifolds. Then we show that any $p$-adic symplectic action $G\times(M,\omega)\to(M,\omega)$ has a momentum map…

Symplectic Geometry · Mathematics 2025-12-18 Luis Crespo , Álvaro Pelayo

We extend Noether's theorem to the setting of multisymplectic geometry by exhibiting a correspondence between conserved quantities and continuous symmetries on a multi-Hamiltonian system. We show that a homotopy co-momentum map interacts…

Symplectic Geometry · Mathematics 2017-11-15 Jonathan Herman

We consider symplectic manifolds with Hamiltonian torus actions which are "almost but not quite completely integrable": the dimension of the torus is one less than half the dimension of the manifold. We provide a complete set of invariants…

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

The Local-to-Global-Principle used in the proof of convexity theorems for momentum maps has been extracted as a statement of pure topology enriched with a structure of convexity. We extend this principle to not necessarily closed maps…

Symplectic Geometry · Mathematics 2012-02-14 Wolfgang Rump , Jenny Santoso