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We decompose linear $\mathrm{G}_2$-structure in canonical ways adapted to 3-dimensional subspaces, in terms of certain natural 1-forms and definite triple of 2-forms, and apply the decompositions to the study of $\mathrm{G}_2$-structure…

Differential Geometry · Mathematics 2026-05-13 Chengjian Yao , Ziyi Zhou

We introduce the notion of a multi-fan. It is a generalization of that of a fan in the theory of toric variety in algebraic geometry. Roughly speaking a toric variety is an algebraic variety with an action of algebraic torus of the same…

Symplectic Geometry · Mathematics 2007-05-23 Akio Hattori , Mikiya Masuda

We study certain foliated complex manifolds that behave similarly to complete nonsingular toric varieties. We classify them by combinatorial objects that we call marked fans. We describe the basic cohomology algebras of them in terms of…

Algebraic Geometry · Mathematics 2018-08-15 Hiroaki Ishida

Let X be a complete toric variety of dimension n and \del the fan in a lattice N associated to X. For each cone \sigma of \del there corresponds an orbit closure V(\sigma) of the action of complex torus on X. The homology classes…

Algebraic Topology · Mathematics 2013-08-13 Akio Hattori

Let $V$ be a complex linear space, $G\subset\GL(V)$ be a compact group. We consider the problem of description of polynomial hulls $\wh{Gv}$ for orbits $Gv$, $v\in V$, assuming that the identity component of $G$ is a torus $T$. The paper…

Complex Variables · Mathematics 2009-07-14 V. M. Gichev

Let $G$ be a complex semi-simple Lie group and form its maximal flag manifold $\mathbb{F}=G/P=U/T$ where $P$ is a minimal parabolic subgroup, $U$ a compact real form and $T=U\cap P$ a maximal torus of $U$. The aim of this paper is to study…

Differential Geometry · Mathematics 2020-04-01 Carlos A. B. Varea , Luiz A. B. San Martin

A horospherical variety is a normal algebraic variety where a reductive algebraic group acts with an open orbit which is a torus bundle over a flag variety. For example, toric varieties and flag varieties are horospherical. In this paper,…

Algebraic Geometry · Mathematics 2007-05-23 Boris Pasquier

Let T be a maximal torus in a classical linear group G. In this paper we find all simple rational G-modules V such that for each vector v in V the closure of its T-orbit is a normal affine variety. For every other G-module we present a…

Algebraic Geometry · Mathematics 2011-10-18 Karine Kuyumzhiyan

We show that each orbit of a Borel subgroup $B_{n-1}$ of GL(n-1) (respectively SO(n-1)) on the flag variety of GL(n) (respectively of SO(n)) is a bundle over a $B_{n-1}$-orbit on a generalized flag variety of GL(n-1) (respectively SO(n-1)),…

Representation Theory · Mathematics 2021-07-23 Mark Colarusso , Sam Evens

A complex flag manifold F= G /Q decomposes into finitely many real orbits under the action of a real form of G. Their embedding into F define on them CR manifold structures. We characterize the closed real orbits which are finitely…

Differential Geometry · Mathematics 2023-01-02 Stefano Marini , Costantino Medori , Mauro Nacinovich

A toric origami manifold is a generalization of a symplectic toric manifold (or a toric symplectic manifold). The origami symplectic form is allowed to degenerate in a good controllable way in contrast to the usual symplectic form. It is…

Algebraic Topology · Mathematics 2017-09-15 Anton Ayzenberg , Mikiya Masuda , Seonjeong Park , Haozhi Zeng

We characterize those real flag manifolds that can be endowed with invariant generalized almost complex structures. We show that no $GM_2$-maximal real flag manifolds admit integrable invariant generalized almost complex structures. We give…

Differential Geometry · Mathematics 2023-04-20 Fabricio Valencia , Carlos Varea

Let G be an exceptional simple algebraic group, and let T be a maximal torus in G. In this paper, for every such G, we find all simple rational G-modules V with the following property: for every vector v in V, the closure of its T-orbit is…

Algebraic Geometry · Mathematics 2011-05-24 Ilya I. Bogdanov , Karine G. Kuyumzhiyan

In this paper, we give a necessary and sufficient condition for a generalized real Bott manifold to have a Spin structure in terms of column vectors of the associated matrix. We also give an interpretation of this result to the associated…

Algebraic Topology · Mathematics 2023-03-21 Aslı Güçlükan İlhan , S. Kaan Gürbüzer , Semra Pamuk

This work is concerned with the calculation of the fundamental group of torus knots. Torus knots are special types of knots which wind around a torus a number of times in the longitudinal and meridional directions. We compute and describe…

Geometric Topology · Mathematics 2022-04-20 Ilyas Aderogba Mustapha , Paul Arnaud Songhafouo , Donald Stanley

In this article, we investigate the orbit configuration spaces of some equivariant closed manifolds over simple convex polytopes in toric topology, such as small covers, quasi-toric manifolds and (real) moment-angle manifolds; especially…

Algebraic Topology · Mathematics 2012-11-06 Junda Chen , Zhi Lü , Jie Wu

The main aim of this article is to study the topology of real Bott towers as special and interesting examples of real toric varieties. We first give a presentation of the fundamental group of a real Bott tower and show that the fundamental…

Algebraic Topology · Mathematics 2016-09-20 Raisa Dsouza , V. Uma

We study a class of smooth torus manifolds whose orbit space has the combinatorial structure of a simple polytope with holes. We construct moment angle manifolds for such polytopes with holes and use them to prove that the associated torus…

Symplectic Geometry · Mathematics 2024-12-05 Mainak Poddar , Soumen Sarkar

The aim of this paper is to describe the equivariant and ordinary Grothendieck ring and the equivariant and ordinary topological $K$-ring of flag Bott manifolds of general Lie type. This will generalize the results on the equivariant and…

Algebraic Topology · Mathematics 2024-06-18 Bidhan Paul , Vikraman Uma

We develop the geometric theory of equivariant quasisymmetry via a new ``quasisymmetric flag variety''. This is a toric complex in the flag variety whose fixed point set is the set of noncrossing partitions, and whose cohomology ring is the…

Algebraic Geometry · Mathematics 2025-08-19 Nantel Bergeron , Lucas Gagnon , Philippe Nadeau , Hunter Spink , Vasu Tewari