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We show that a singular Riemannian foliation of codimension two on a compact simply-connected Riemannian $(n+2)$-manifold, with regular leaves homeomorphic to the $n$-torus, is given by a smooth effective $n$-torus action. This solves in…

Differential Geometry · Mathematics 2025-12-25 Diego Corro

Demushkin's Theorem says that any two toric structures on an affine variety X are conjugate in the automorphism group of X. We provide the following extension: Let an (n-1)-dimensional torus T act effectively on an n-dimensional affine…

Algebraic Geometry · Mathematics 2007-05-23 Florian Berchtold , Juergen Hausen

We study holomorphic GL(2) and SL(2) geometries on compact complex manifolds. We show that a compact K\"ahler manifold of complex even dimension higher than two admitting a holomorphic GL(2)-geometry is covered by a compact complex torus.…

Differential Geometry · Mathematics 2020-08-12 Indranil Biswas , Sorin Dumitrescu

This is a continuation of arXiv: 2408.03012. We answer affirmatively Question 5.10 posed in the previous article. More precisely, let $(X, \omega)$ be a conical symplectic variety of dimension $2n$ with $wt(\omega) = 2$, which has a…

Algebraic Geometry · Mathematics 2026-04-07 Yoshinori Namikawa

The {\it torus manifolds} have been defined and studied by M. Masuda and T. Panov (arXiv:math.AT/0306100) who in particular describe its cohomology ring structure. In this note we shall describe the topological $K$-ring of a class of torus…

Algebraic Topology · Mathematics 2007-05-23 V. Uma

Let G be a torus and M a G-Hamiltonian manifold with Kostant line bundle L and proper moment map. Let P be the weight lattice of G. We consider a parameter k and the multiplicity $m(\lambda,k)$ of the quantized representation associated to…

Differential Geometry · Mathematics 2016-12-15 Michele Vergne

In the classical theory of toric manifolds polytopes appear in two guises -- as Newton polytopes of line bundles on the complex, and as moment polytopes on the symplectic side, the link between the two being established by the…

Differential Geometry · Mathematics 2018-07-03 Thomas Baier , José M. Mourão , João P. Nunes

Let $\overline G$ be the wonderful compactification of a simple affine algebraic group $G$ defined over $\mathbb C$ such that its center is trivial and $G\not= {\rm PSL}(2,\mathbb{C})$. Take a maximal torus $T \subset G$, and denote by…

Algebraic Geometry · Mathematics 2015-07-01 Indranil Biswas , S. Senthamarai Kannan , D. S. Nagaraj

Toric orbifolds are a topological generalization of projective toric varieties associated to simplicial fans. We introduce some sufficient conditions on the combinatorial data associated to a toric orbifold to ensure the existence of an…

Algebraic Geometry · Mathematics 2021-06-29 Soumen Sarkar , V. Uma

The CSM class of a very affine manifold $U$ is represented by the rank drop locus of a general tuple of torus invariant 1-forms on it. This equality holds in the homology of any toric compactification $X\supset U$. It was proved for sch\"on…

Algebraic Geometry · Mathematics 2024-08-13 Alexander Esterov

Every cohomology ring isomorphism between two non-singular complete toric varieties and quasitoric manifolds, respectively, with second Betti number $2$ is realizable by a diffeomorphism and homeomorphism, respectively.

Algebraic Topology · Mathematics 2018-07-24 Suyoung Choi , Seonjeong Park

We classify projective toric manifolds whose dual variety is not a hypersurface in the dual projective space. Under the standard dictionary between toric geometry and convex geometry, they correspond to certain convex Delzant integer…

Algebraic Geometry · Mathematics 2007-05-23 Sandra Di Rocco

A fundamental idea in toric topology is that classes of manifolds with well-behaved torus actions (simply, toric spaces) are classified by pairs of simplicial complexes and (non-singular) characteristic maps. The authors in their previous…

Algebraic Topology · Mathematics 2019-08-15 Suyoung Choi , Hanchul Park

We prove that any compact K\"ahler 3-dimensional manifold which has no non-trivial complex subvarieties is a torus. This is a very special case of a general conjecture on the structure of 'simple manifolds', central in the bimeromorphic…

Algebraic Geometry · Mathematics 2014-01-16 Frédéric Campana , Jean-Pierre Demailly , Misha Verbitsky

This paper attempts to provide an analogue of the Novikov conjecture for algebraic (or K\"{a}hler) manifolds. Inter alia, we prove a conjecture of Rosenberg's on the birational invariance of higher Todd genera. We argue that in the…

Algebraic Geometry · Mathematics 2007-05-23 Jonathan Block , Shmuel Weinberger

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

We generalized the construction of deformations of affine toric varieties of K. Altmann and our previous construction of deformations of weak Fano toric varieties to the case of arbitrary toric varieties by introducing the notion of…

Algebraic Geometry · Mathematics 2011-02-25 Anvar Mavlyutov

An almost complex torus manifold is a $2n$-dimensional compact connected almost complex manifold equipped with an effective action of a real $n$-dimensional torus $T^n \simeq (S^1)^n$ that has fixed points. For an almost complex torus…

Algebraic Topology · Mathematics 2024-04-30 Donghoon Jang , Jiyun Park

We formulate a quantum generalization of the notion of the group of Riemannian isometries for a compact Riemannian manifold, by introducing a natural notion of smooth and isometric action by a compact quantum group on a classical or…

Quantum Algebra · Mathematics 2009-11-13 Debashish Goswami

Our aim is to bring the theory of analogous polytopes to bear on the study of quasitoric manifolds, in the context of stably complex manifolds with compatible torus action. By way of application, we give an explicit construction of a…

Algebraic Topology · Mathematics 2011-11-09 Victor M. Buchstaber , Taras E. Panov , Nigel Ray