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We study 5-dimensional Riemannian manifolds that admit an almost contact metric structure. In particular, we generalize the class of quasi-Sasaki manifolds and characterize these structures by their intrinsic torsion. Among other things, we…

Differential Geometry · Mathematics 2012-11-14 Christof Puhle

A four-parametric family of linear connections preserving the almost complex structure is defined on an almost complex manifold with Norden metric. Necessary and sufficient conditions for these connections to be natural are obtained. A…

Differential Geometry · Mathematics 2011-05-02 Marta Teofilova

We review the theory of quaternionic Kahler and hyperkahler structures. Then we consider the tangent bundle of a Riemannian manifold M with a metric connection D (with torsion) and with its well estabilished canonical complex structure.…

Differential Geometry · Mathematics 2011-12-15 Rui Albuquerque

We introduce new metric structures on a smooth manifold (called "weak" structures) that generalize the almost contact, Sasakian, cosymplectic, etc. metric structures $(\varphi,\xi,\eta,g)$ and allow us to take a fresh look at the classical…

Differential Geometry · Mathematics 2022-03-29 Vladimir Rovenski , Dhriti Sundar Patra

Isotropic almost complex structures induce a class of Riemannian metrics on tangent bundle of a Riemannian manifold. In this paper the curvature tensors of these metrics will be calculated.

Differential Geometry · Mathematics 2017-04-24 Amir Baghban , Esmaeil Abedi

We consider a pair of smooth manifolds, which are the counterparts in the even-dimensional and odd-dimensional cases. They are separately an almost complex manifold with Norden metric and an almost contact manifolds with B-metric,…

Differential Geometry · Mathematics 2015-05-06 Mancho Manev

We define, on smooth manifolds, the notions of almost twistorial structure and twistorial map, thus providing a unified framework for all known examples of twistor spaces. The condition of being harmonic morphisms naturally appears among…

Differential Geometry · Mathematics 2007-06-06 Eric Loubeau , Radu Pantilie

In this note, we propose an approach to the study of the analogue for unipotent harmonic bundles of Schmid's Nilpotent Orbit Theorem. Using this approach, we construct harmonic metrics on unipotent bundles over quasi-compact K\"ahler…

Differential Geometry · Mathematics 2010-01-17 Juergen Jost , Yi-Hu Yang , Kang Zuo

We study the Schouten-van Kampen connection associated to an almost contact or paracontact metric structure. With the help of such a connection, some classes of almost (para) contact metric manifolds are characterized. Certain curvature…

Differential Geometry · Mathematics 2014-02-25 Zbigniew Olszak

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

We develop a spinorial description of CR structures of arbitrary codimension. More precisely, we characterize almost CR structures of arbitrary codimension on (Riemannian) manifolds by the existence of a Spin$^{c, r}$ structure carrying a…

Differential Geometry · Mathematics 2016-10-17 Rafael Herrera , Roger Nakad , Ivan Tellez

Let $X$ be a quasi-projective curve, compactified to $(Y,D)$ with $X=Y-D$. We construct a Deligne-Hitchin twistor space out of moduli spaces of framed $\lambda$-connections of rank $2$ over $Y$ with logarithmic singularities and…

Algebraic Geometry · Mathematics 2021-11-02 Carlos Simpson

We construct a one-parameter family of Lorentzian conformal structures on the canonical circle bundle of a partially integrable contact almost Cauchy-Riemann manifold. This builds on previous work by Leitner, who generalised Fefferman's…

Differential Geometry · Mathematics 2025-06-11 Arman Taghavi-Chabert

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

Differential Geometry · Mathematics 2007-05-23 Marian Ioan Munteanu

For an almost contact metric manifold $N$, we find conditions for which either the total space of an $S^1$-bundle over $N$ or the Riemannian cone over $N$ admits a strong K\"ahler with torsion (SKT) structure. In this way we construct new…

Differential Geometry · Mathematics 2010-11-19 Marisa Fernandez , Anna Fino , Luis Ugarte , Raquel Villacampa

In this work, almost product and almost golden structures are studied. Conditions for those structures being Integrable and parallel are investigated. Also harmonicity of a map between almost pruduct or almost golden manifolds with pure or…

Differential Geometry · Mathematics 2016-12-23 S. Erdem

For complete complex connections on almost complex manifolds we introduce a natural definition of compactification. This is based on almost c--projective geometry, which is the almost complex analogue of projective differential geometry.…

Differential Geometry · Mathematics 2019-10-31 Andreas Cap , A. Rod Gover

We interpret the property of having an infinitesimal symmetry as a variational property in certain geometric structures. This is achieved by establishing a one-to-one correspondence between a class of cone structures with an infinitesimal…

Differential Geometry · Mathematics 2026-04-03 Omid Makhmali , Katja Sagerschnig

We investigate the integrability of almost complex structures on the twistor space of an almost quaternionic manifold constructed with the help of a quaternionic connection. We show that if there is an integrable structure it is independent…

Differential Geometry · Mathematics 2007-05-23 Stefan Ivanov , Ivan Minchev , Simeon Zamkovoy

We provide models that are as close as possible to being formal for a large class of compact manifolds that admit a transversely Kaehler structure, including Vaisman and quasi-Sasakian manifolds. As an application we are able to classify…

Differential Geometry · Mathematics 2022-03-18 Beniamino Cappelletti-Montano , Antonio De Nicola , Juan Carlos Marrero , Ivan Yudin