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We use quantum and Floer homology to construct (partial) quasi-morphisms on the universal cover of the group of compactly supported Hamiltonian diffeomorphisms for a certain class of non-closed strongly semi-positive symplectic manifolds…

Symplectic Geometry · Mathematics 2016-05-10 Sergei Lanzat

The structure of nearly K\"ahler manifolds was studied by Gray in several papers. More recently, a relevant progress on the subject has been done by Nagy. Among other results, he proved that a strict and complete nearly K\"ahler manifold is…

Differential Geometry · Mathematics 2010-11-29 J. C. González Dávila , F. Martín Cabrera

We generalize the notions of the Futaki invariant and extremal vector field of a compact K\"ahler manifold to the general almost-Kahler case and show the periodicity of the extremal vector field when the symplectic form represents an…

Differential Geometry · Mathematics 2010-04-22 Mehdi Lejmi

This is an expository paper, which provides a first approach to nearly Kenmotsu manifolds. The purpose of this paper is to focus on nearly Kenmotsu manifolds and get some new results from it. We prove that for a nearly Kenmotsu manifold is…

Differential Geometry · Mathematics 2015-05-21 Irem Kupeli Erken , Piotr Dacko , Cengizhan Murathan

The covariant derivative of the K\"ahler form of an almost pseudo-Hermitian or of an almost para-Hermitian manifold satisfies certain algebraic relations. We show, conversely, that any 3-tensor which satisfies these algebraic relations can…

Differential Geometry · Mathematics 2010-12-23 Miguel Brozos-Vázquez , Eduardo García-Río , Peter Gilkey , Luis Hervella

In this paper we study almost complex manifolds admitting a quasi-K\"ahler Chern-flat metric (Chern-flat means that the holonomy of the Chern connection is trivial). We prove that in the compact case such manifolds are all nilmanifolds.…

Differential Geometry · Mathematics 2014-05-26 Antonio J. Di Scala , Luigi Vezzoni

We study almost Kaehler manifolds whose curvature tensor satisfies the third curvature condition of Gray. We show that the study of manifolds within this class reduces to the study of a subclass having the property that the torsion of the…

Differential Geometry · Mathematics 2007-05-23 Paul-Andi Nagy

In the present paper, we characterize a class of almost Kenmotsu manifolds admitting quasi Yamabe soliton. It is shown that if a $(k,\mu)'$-almost Kenmotsu manifold admits a quasi Yamabe soliton $(g,V,\lambda,\alpha)$ with $V$ pointwise…

Differential Geometry · Mathematics 2020-05-05 Dibakar Dey , Pradip Majhi

In Kaehler manifolds are investigated conformally flat totally real submanifolds, which are semiparallel or have semiparallel mean curvature vector.

Differential Geometry · Mathematics 2010-01-26 Ognian Kassabov

Let $M$ be a closed symplectic manifold of dimension $2n$ with non-ellipticity. We can define an almost K\"ahler structure on $M$ by using the given symplectic form. Hence, we have a $\G=\pi_1(M)$-invariant almost K\"ahler structure on the…

Symplectic Geometry · Mathematics 2024-07-08 Shouwen Fang , Hongyu Wang

The object of the present paper is to study $\beta$-almost Yamabe solitons and $\beta$-almost Ricci solitons on almost co-K\"{a}hler manifolds. In this paper, we prove that if an almost co-K\"{a}hler manifold $M$ with the Reeb vector field…

General Mathematics · Mathematics 2020-04-07 Shahroud Azami

In this paper we introduce the concept of $(\varepsilon)$-almost paracontact manifolds, and in particular, of $(\varepsilon)$-para Sasakian manifolds. Several examples are presented. Some typical identities for curvature tensor and Ricci…

Differential Geometry · Mathematics 2009-08-20 Mukut Mani Tripathi , Erol Kilic , Selcen Yuksel Perktas , Sadik Keles

We consider almost Riemann and almost Ricci solitons in a $D$-homothetically deformed Kenmotsu manifold having as potential vector field a gradient vector field, a solenoidal vector field or the Reeb vector field of the deformed structure,…

Differential Geometry · Mathematics 2025-08-04 Adara M. Blaga

We study the question of integrability of a compatible almost complex structure on a compact symplectic 4-manifold, under various natural assumptions on the curvature of the associated almost Kahler metric.

Differential Geometry · Mathematics 2007-05-23 Vestislav Apostolov , Tedi Draghici

For a finite family of 3-dimensional almost contact metric manifolds with closed the structure form $\eta$ is described a construction of an almost contact metric manifold, where the members of the family are building blocks - cells.…

Differential Geometry · Mathematics 2012-04-02 Piotr Dacko

For a closed smooth manifold $M$ admitting a symplectic structure, we define a smooth topological invariant $Z(M)$ using almost-K\"ahler metrics, i.e. Riemannian metrics compatible with symplectic structures. We also introduce $Z(M,…

Differential Geometry · Mathematics 2014-09-19 Jongsu Kim , Chanyoung Sung

In the paper we develop a framework for the alternative way of the study of a local geometry of almost cosymplectic manifolds with Kahlerian leaves. The main idea is to apply the concept of a geometry and analysis of CR manifolds. Locally…

Differential Geometry · Mathematics 2012-10-08 Piotr Dacko

We show that a compact almost-K\"ahler four manifold $(M, g, \omega)$ with harmonic self-dual Weyl curvature and constant scalar curvature is K\"ahler if $c_{1}\cdot\omega\geq 0$. We also prove an integral curvature inequality for compact…

Differential Geometry · Mathematics 2023-11-29 Inyoung Kim

A compact symplectic manifold $(M, \omega)$ is said to satisfy the hard-Lefschetz condition if it is possible to develop an analogue of Hodge theory for $(M, \omega)$. This loosely means that there is a notion of harmonicity of differential…

Differential Geometry · Mathematics 2024-11-25 Adrián Andrada , Agustín Garrone

We classify six-dimensional homogeneous nearly K\"{a}hler manifolds and give a positive answer to Gray and Wolf's conjecture: every homogeneous nearly K\"{a}hler manifold is a Riemannian 3-symmetric space equipped with its canonical almost…

Differential Geometry · Mathematics 2007-05-23 Jean-Baptiste Butruille