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This article studies left-invariant Hermitian structures on Lie groups with two-dimensional commutator subgroups. We provide an explicit classification for two specific types of such structures, which we designate as Type I and Type II.…

Differential Geometry · Mathematics 2026-02-17 Hamid Reza Salimi Moghaddam

A discussion of torsion of Riemannian G-structures leads to a survey of contributions of Alfred Gray and others on almost Hermitian manifolds, G_2-manifolds, curvature identities, volume expansions, plotting geodesics, and the geometry of…

Differential Geometry · Mathematics 2007-05-23 Simon Salamon

It is introduced a differentiable manifold with almost contact 3-structure which consists of an almost contact metric structure and two almost contact B-metric structures. The product of this manifold and a real line is an almost…

Differential Geometry · Mathematics 2017-11-21 Mancho Manev

Generically an almost complex structure has no symmetries at all, but there exist symmetric structures. In this paper we describe how to guarantee that the pseudogroup of local symmetries is small (finite-dimensional). It will be indicated…

Differential Geometry · Mathematics 2013-11-19 Boris Kruglikov

A natural metric on the space of all almost hermitian structures on a given manifold is investigated.

Differential Geometry · Mathematics 2008-02-03 Olga Gil-Medrano , Peter W. Michor

This note is about the interplay between the almost-hermitian and Riemannian geometries of a manifold. These geometries can be seen to interact through curvature. The main result is an obstruction equation to the integrability of…

Differential Geometry · Mathematics 2023-01-31 Gabriella Clemente

The axiom of {\theta}-holomorphic 2-planes is introduced. It is proved, that if an almost Hermitian manifold satisfies this axiom for a fixed {\theta}, 0< {\theta}< {\pi}/2, then it is a real space form.

Differential Geometry · Mathematics 2010-04-26 Grozjo Stanilov , Ognian Kassabov

This article deals with 3-forms on 6-dimensional manifodls, the first dimension where the classification of 3-forms is not trivial. There are three classes of multisymplectic 3-forms there. We study the class which is closely related to…

Differential Geometry · Mathematics 2007-05-23 Martin Panak , Jiri Vanzura

We explicitly describe all SO(7)-invariant almost quaternion-Hermitian structures on the twistor space of the six sphere and determine the types of their intrinsic torsion.

Differential Geometry · Mathematics 2013-02-27 Francisco Martin Cabrera , Andrew Swann

We classify nilmanifolds with an invariant symplectic half-flat structure. We solve the half-flat evolution equations in one example, writing down the resulting Ricci-flat metric. We study the geometry of the orbit space of 6-manifolds with…

Differential Geometry · Mathematics 2007-05-23 Diego Conti , Adriano Tomassini

Hitchin shows that half-flat SU(3)-structures on a 6-dimensional manifold M can be lifted to parallel G_{2}-structure on the product $M\times\mathbb{R}$. We show that Hitchin's approach can also be used to construct nearly parallel…

Differential Geometry · Mathematics 2007-07-16 Sebastian Stock

It is proved, that if an almost Hermitian manifold satisfies the axiom of coholomorphic spheres, it is conformal flat.

Differential Geometry · Mathematics 2010-04-23 Ognian Kassabov

We study the $\rm{SU}(3)$-structure induced on an oriented hypersurface of a 7-dimensional manifold with a nearly parallel $\rm{G}_2$-structure. We call such $\rm{SU}(3)$-structures nearly half-flat. We characterise the left invariant…

Differential Geometry · Mathematics 2024-09-05 Ragini Singhal

A unitary representation of a, possibly infinite dimensional, Lie group $G$ is called semibounded if the corresponding operators $i\dd\pi(x)$ from the derived representation are uniformly bounded from above on some non-empty open subset of…

Representation Theory · Mathematics 2011-05-23 Karl-Hermann Neeb

We prove that any left-invariant symplectic almost complex structure on a Thurston manifold which is compatible with its canonical left-invariant Riemannian metric has holomorphic type 1.

Complex Variables · Mathematics 2016-11-11 Oleg Mushkarov , Christian L. Yankov

Almost paracontact almost paracomplex Riemannian manifolds of the lowest dimension are studied. Such structures are constructed on hyperspheres in 4-dimensional spaces, Euclidean and pseudo-Euclidean, respectively. The obtained manifolds…

Differential Geometry · Mathematics 2021-01-22 Mancho Manev , Veselina Tavkova

In this paper we study invariant almost Hermitian geometry on generalized flag manifolds. We will focus on providing examples of K\"ahler like scalar curvature metric, that is, almost Hermitian structures $(g,J)$ satisfying $s=2s_{\rm C}$,…

Differential Geometry · Mathematics 2021-12-22 Lino Grama , Ailton R. Oliveira

It is first shown that the nilpotent or the solvable approximation of an almost-Riemannian structure at a singular point is always a linear almost-Riemannian structure on a Lie group or a homogeneous space. The generic properties of…

Optimization and Control · Mathematics 2022-04-25 Yacine Chitour , Philippe Jouan , Ronald Manríquez

In this paper the notion of the intrinsic geometry of an almost contact metric manifold is introduced. Description of some classes of spaces with almost contact metric structures in terms of the intrinsic geometry is given. A new type of…

Differential Geometry · Mathematics 2011-07-28 Sergey V. Galaev

In this paper, we study the existence of constant holomorphic d-scalar curvature and the prescribing holomorphic d-scalar curvature problem on closed, connected almost Hermitian manifolds of dimension $n\geq6$. In addition, we obtain an…

Differential Geometry · Mathematics 2023-02-27 Jianquan Ge , Yi Zhou