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We consider contact structures on simply-connected 5-manifolds which arise as circle bundles over simply-connected symplectic 4-manifolds and show that invariants from contact homology are related to the divisibility of the canonical class…

Symplectic Geometry · Mathematics 2013-07-18 M. J. D. Hamilton

In this article, we study an almost contact metric structure on a $G_2$-manifold constructed by Arikan, Cho and Salur in via the classification of almost contact metric structures given by Chinea and Gonzalez. In particular, we characterize…

Differential Geometry · Mathematics 2015-01-29 Albert J. Todd

Following T.-J. Li, W. Zhang [Comparing tamed and compatible symplectic cones and cohomological properties of almost complex manifolds, Comm. Anal. Geom.], we continue to study the link between the cohomology of an almost-complex manifold…

Differential Geometry · Mathematics 2012-11-28 Daniele Angella , Adriano Tomassini

In this paper we obtain the structure equation of a contact-complex Riemannian submersion and give some applications of this equation in the study of almost cosymplectic manifolds with Kaehler fibres.

Differential Geometry · Mathematics 2011-06-01 Stere Ianus , Adrian Mihai Ionescu , Raluca Mocanu , Gabriel Eduard Vilcu

In this paper, we define almost paracontact and normal almost paracontact Finsler structures on a vector bundle and find some conditions for integrability of these structures. We define paracontact metric, para- Sasakian and K-paracontact…

Differential Geometry · Mathematics 2013-02-05 E. Peyghan , A. Tayebi , E. Sharahi

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

We consider a 3-dimensional Riemannian manifold V with a metric g and an affinor structure q. The local coordinates of these tensors are circulant matrices. In V we define an almost conformal transformation. Using that definition we…

Differential Geometry · Mathematics 2011-06-15 Georgi Dzhelepov , Dimitar Razpopov , Iva Dokuzova

In this paper we study a Riemanian metric on the tangent bundle $T(M)$ of a Riemannian manifold $M$ which generalizes Sasaki metric and Cheeger Gromoll metric and a compatible almost complex structure which together with the metric confers…

Differential Geometry · Mathematics 2009-07-01 Marian Ioan Munteanu

We obtain conditions on the Lee form under which a holomorphic map between almost Hermitian manifolds is a harmonic map or morphism. Then we discuss under what conditions (i) the image of a holomorphic map from a cosymplectic manifold is…

dg-ga · Mathematics 2008-02-03 S. Gudmundsson , J. C. Wood

We consider compatibility conditions between Poisson and Riemannian structures on smooth manifolds by means of a contravariant partially complex structure, or $f$-structure, introducing the notion of (almost) K\"ahler--Poisson manifolds. In…

Symplectic Geometry · Mathematics 2017-09-11 Nicolás Martínez Alba , Andrés Vargas

Given an integral symplectic manifold, we construct a family of "coherent state" maps into complex projective space. The maps are built from sections of the tensor powers of a hermitian line bundle whose curvature is a multiple of the…

Differential Geometry · Mathematics 2007-05-23 David Borthwick , Alejandro Uribe

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

We introduce the notion of even Clifford structures on Riemannian manifolds, a framework generalizing almost Hermitian and quaternion-Hermitian geometries. We give the complete classification of manifolds carrying parallel even Clifford…

Differential Geometry · Mathematics 2019-01-08 Andrei Moroianu , Uwe Semmelmann

In this article, we study and analyze the \phi-sectional curvature induced by a statistical structure on an almost contact metric manifold. We demonstrate that this sectional curvature is always non-positive. Additionally, we present…

Differential Geometry · Mathematics 2025-07-02 Abbas Heydari , Sadegh Mohammadi

We prove that every homotopy class of almost contact structures on a closed 5-dimensional manifold admits a contact structure.

Symplectic Geometry · Mathematics 2014-11-10 Roger Casals , Dishant M. Pancholi , Francisco Presas

In this article, we consider the almost Hermitian structure on $TM$ induced by a pair of a metric and an affine connection on $M$. We find the conditions under which $TM$ admits almost K\"ahler structures, K\"ahler structures and Einstein…

Differential Geometry · Mathematics 2025-03-24 Hiroyasu Satoh

Two-dimensional almost-Riemannian structures are generalized Riemannian structures on surfaces for which a local orthonormal frame is given by a Lie bracket generating pair of vector fields that can become collinear. We study the relation…

Differential Geometry · Mathematics 2016-11-25 Andrei Agrachev , Ugo Boscain , Grégoire Charlot , Roberta Ghezzi , Mario Sigalotti

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

In this paper, we construct metallic K\"ahler and nearly metallic K\"ahler structures on Riemanian manifolds. For such manifolds with these structures, we study curvature properties. Also we describe linear connections on the manifold,…

General Mathematics · Mathematics 2019-07-02 Sibel Turanli , Aydin Gezer , Hasan Cakicioglu

In this paper we introduce the twistor space of a Riemannian manifold with an even Clifford structure. This notion generalizes the twistor space of quaternion-Hermitian manifolds and weak-Spin(9) structures. We also construct almost complex…

Differential Geometry · Mathematics 2016-02-15 Gerardo Arizmendi , Charles Hadfield