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We classify $7$-dimensional Riemannian manifolds carrying a metric connection with parallel skew-symmetric torsion whose holonomy is contained in $\mathrm{G}_2$, up to naturally reductive homogeneous spaces and nearly parallel…

Differential Geometry · Mathematics 2026-04-08 Andrei Moroianu , Uwe Semmelmann

We construct new examples of non-formal simply connected compact Sasaki-Einstein 7-manifolds. We determine the minimal model of the total space of any fibre bundle over $CP^2$ with fibre $S^1\times S^2$ or $S^3/Z_p$ ($p>0$), and we apply…

Differential Geometry · Mathematics 2023-04-19 Marisa Fernández , Anna Fino , Alexei Kovalev , Vicente Muñoz

A nearly K\"ahler manifold is an almost Hermitian manifold with the weakened K\"ahler condition, that is, instead of being zero, the covariant derivative of the almost complex structure is skew-symmetric. We give the explicit…

Differential Geometry · Mathematics 2019-11-15 Miloš Djorić , Mirjana Djorić , Marilena Moruz

We consider principal fibre bundles with a given connection and construct almost complex structures on the total space if the adjoint bundle is isomorphic to the tangent bundle of the base. We derive the integrability condition. If the…

Differential Geometry · Mathematics 2017-02-15 Raphael Zentner

The differential geometry of almost Grassmann structures defined on a differentiable manifold of dimension n = pq by a fibration of Segre cones SC (p, q) is studied. The peculiarities in the structure of almost Grassmann structures for the…

Differential Geometry · Mathematics 2007-05-23 Maks A. Akivis , Vladislav V. Goldberg

The class of the hypercomplex pseudo-Hermitian manifolds is considered. The flatness of the considered manifolds with the 3 parallel complex structures is proved. Conformal transformations of the metrics are introduced. The conformal…

Differential Geometry · Mathematics 2012-03-27 Kostadin Gribachev , Mancho Manev , Stancho Dimiev

The space ${\mathcal A}$ of almost complex structures on a closed manifold $M$ is studied. A natural parametrization of the space ${\mathcal A}$ is defined. It is shown, that ${\mathcal A}$ is a infinite dimensional complex weak…

Differential Geometry · Mathematics 2007-05-23 N. A. Daurtseva , N. K. Smolentsev

We prove that any totally geodesic hypersurface $N^5$ of a 6-dimensional nearly K\"ahler manifold $M^6$ is a Sasaki-Einstein manifold, and so it has a hypo structure in the sense of \cite{ConS}. We show that any Sasaki-Einstein 5-manifold…

Differential Geometry · Mathematics 2014-02-26 Marisa Fernández , Stefan Ivanov , Vicente Muñoz , Luis Ugarte

In a previous paper, the authors together with L. Vrancken initiated the study of $3$-dimensional CR submanifolds of the nearly K\" ahler homogeneous $\mathbb S^3\times \mathbb S^3$. As is shown by Butruille this is one of only four…

Differential Geometry · Mathematics 2019-11-15 Miroslava Anti\' c , Nataša Djurdjevi\' c , Marilena Moruz

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

We give a method to obtain new 7-dimensional Lie algebras endowed with closed and coclosed G2-structures starting from 6-dimensional Lie algebras with symplectic half- at SU(3)-structures and half- at SU(3)- structures, respectively.…

Differential Geometry · Mathematics 2016-02-16 Victor Manero

The present article investigates Sp(3) structures on 14-dimensional Riemannian manifolds, a continuation of the recent study of manifolds modeled on rank two symmetric spaces (here: SU(6)/Sp(3)). We derive topological criteria for the…

Differential Geometry · Mathematics 2013-11-05 Ilka Agricola , Thomas Friedrich , Jos Höll

We consider the Laplacian coflow of a $\mathrm{G}_2$-structure on warped products of the form $M^7= M^6 \times_f S^1$ with $M^6$ a compact 6-manifold endowed with an $\mathrm{SU}(3)$-structure. We give an explicit reinterpretation of this…

Differential Geometry · Mathematics 2019-04-15 Victor Manero , Antonio Otal , Raquel Villacampa

In this paper we study invariant almost Hermitian geometry on generalized flag manifolds which the isotropy representation decompose into two or three irreducible components. We will provide a classification of such flag manifolds admitting…

Differential Geometry · Mathematics 2022-11-10 Lino Grama , Ailton R. Oliveira

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

Local SU(3)-structures on an oriented submanifold of Spin(7)-manifold are determined and their types are characterized in terms of the shape operator and the type of the Spin(7)-structure. An application to Bryant \cite{MR89b:53084} and…

Differential Geometry · Mathematics 2008-11-26 Stefan Ivanov , Francisco Martín Cabrera

We consider higher dimensional generalisations of normal almost contact structures, the so called f.pk-structures where parallelism spans a Lie algebra g (f.pk-g-structures). Two types of these structures are discussed. In the first case,…

Differential Geometry · Mathematics 2016-11-15 Andrzej Czarnecki , Marcin Sroka , Robert Wolak

In the present paper we study locally semiflat (we also call them semiintegrable) almost Grassmann structures. We establish necessary and sufficient conditions for an almost Grassmann structure to be alpha- or beta-semiintegrable. These…

Differential Geometry · Mathematics 2007-05-23 Maks A. Akivis , Vladislav V. Goldberg

We study and classify almost complex totally geodesic submanifolds of the nearly Kaehler flag manifold $F_{1,2}(\mathbb C^3)$, and of its semi-Riemannian counterpart. We also develop a structural approach to the nearly Kaehler flag manifold…

Differential Geometry · Mathematics 2021-07-05 Kamil Cwilinski , Luc Vrancken

Reflection in a line in Euclidean 3-space defines an almost paracomplex structure on the space of all oriented lines, isometric with respect to the canonical neutral Kaehler metric. Beyond Euclidean 3-space, the space of oriented geodesics…

Differential Geometry · Mathematics 2022-05-11 Nikos Georgiou , Brendan Guilfoyle