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Object of investigation are almost hypercomplex manifolds with Hermitian-Norden metrics of the lowest dimension. The considered manifolds are constructed on 4-dimensional Lie groups. It is established a relation between the classes of a…

Differential Geometry · Mathematics 2021-03-16 Hristo Manev

This note is concerned in so called harmonic complex structures introduced by the author previously. I will recall some previous results and emphasize the motivation: Provide an attempt to a fundamental problem in geometry--determining the…

Differential Geometry · Mathematics 2016-10-27 Jianming Wan

Through the means of an alternative and less algebraic method, an explicit expression for the isometry groups of the six-dimensional homogeneous nearly K\"ahler manifolds is provided.

Differential Geometry · Mathematics 2024-11-11 Mateo Anarella , Michaël Liefsoens

We find a new class of invariant metrics existing on the tangent bundle of any given almost-Hermitian manifold. We focus here on the case of Riemannian surfaces, which yield new examples of K\"ahlerian Ricci-flat manifolds in four real…

Differential Geometry · Mathematics 2021-09-06 Rui Albuquerque

Here, we classify Lie groups acting isometrically on compact Lorentz manifolds, and in particular we describe the geometric structure of compact homogeneous Lorentz manifolds.

Differential Geometry · Mathematics 2009-09-25 Abdelghani Zeghib

This (quasi-)survey addresses the quasi-isometry classification of locally compact groups, with an emphasis on amenable hyperbolic locally compact groups. This encompasses the problem of quasi-isometry classification of homogeneous…

Group Theory · Mathematics 2020-05-05 Yves Cornulier

We study almost Hermitian 4-manifolds with holonomy algebra, for the canonical Hermitian connection, of dimension at most one. We show how Riemannian 4-manifolds admitting five orthonormal symplectic forms fit therein and classify them. In…

Differential Geometry · Mathematics 2013-07-10 SImon G. Chiossi , Paul-Andi Nagy

We study some basic properties and examples of Hermitian metrics on complex manifolds whose traces of the curvature of the Chern connection are proportional to the metric itself.

Differential Geometry · Mathematics 2020-07-22 Daniele Angella , Simone Calamai , Cristiano Spotti

We introduce holomorphic Riemannian maps between almost Hermitian manifolds as a generalization of holomorphic submanifolds and holomorphic submersions, give examples and obtain a geometric characterization of harmonic holomorphic…

Differential Geometry · Mathematics 2014-02-25 Bayram Sahin

We complete the classification of six-dimensional strongly unimodular almost nilpotent Lie algebras admitting complex structures. For several cases we describe the space of complex structures up to isomorphism. As a consequence we determine…

Differential Geometry · Mathematics 2023-06-19 Anna Fino , Fabio Paradiso

We find geometric conditions on a four-dimensional Hermitian manifold endowed with a metric connection with totally skew-symmetric torsion under which the complex structure is a harmonic map from the manifold into its twistor space…

Differential Geometry · Mathematics 2021-07-05 Johann Davidov

We find geometric conditions on a four-dimensional almost Hermitian manifold under which the almost complex structure is a harmonic map or a minimal isometric imbedding of the manifold into its twistor space.

Differential Geometry · Mathematics 2017-11-15 Johann Davidov , Absar Ul Haq , Oleg Mushkarov

Almost para-Hermitian manifold it is manifold equipped with almost para-complex structure and compatible pseudo-metric of neutral signature. It is considered a class of immersions of almost para-Hermitian manifolds into almost…

Differential Geometry · Mathematics 2017-10-27 Piotr Dacko

Integrable hypercomplex structures with Hermitian and Norden metrics on Lie groups of dimension 4 are considered. The corresponding five types of invariant hypercomplex structures with hyper-Hermitian metric, studied by M.L. Barberis, are…

Differential Geometry · Mathematics 2014-04-15 Mancho Manev

In this paper we discuss the geometry of homogeneous spaces witch are almost Hermitian submanifolds of flag manifolds. We prove that such spaces are necessarily minimal submanifolds and in the case where these submanifolds are also flag…

Differential Geometry · Mathematics 2024-06-19 Neiton Pereira da Silva

There is a well developed theory of weakly symmetric Riemannian manifolds. Here it is shown that several results in the Riemannian case are also valid for weakly symmetric pseudo-Riemannian manifolds, but some require additional hypotheses.…

Differential Geometry · Mathematics 2011-07-26 Zhiqi Chen , Joseph A. Wolf

We study the integrability of a (almost) complex structure calibrated by a symplectic form. We find new sufficent conditions.

Symplectic Geometry · Mathematics 2014-05-26 Luigi Vezzoni

Notions of compatible and almost compatible pseudo-Riemannian metrics, which are motivated by the theory of compatible (local and nonlocal) Poisson structures of hydrodynamic type and generalize the notion of flat pencil of metrics, are…

Differential Geometry · Mathematics 2007-05-23 O. I. Mokhov

The notion of $\Gamma$-symmetric space is a natural generalization of the classical notion of symmetric space based on $\z_2$-grading of Lie algebras. In our case, we consider homogeneous spaces $G/H$ such that the Lie algebra $\g$ of $G$…

Differential Geometry · Mathematics 2012-01-04 Michel Goze , Paola Piu

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