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If a closed 3-manifold M supports a closed, nonsingular, irrational 1-form which linearly deforms into contact forms, then M supports a K-contact form. On the 3-torus, a closed nonsingular 1-form deforms linearly into contact forms if and…

Differential Geometry · Mathematics 2008-12-18 Hamidou Dathe , Philippe Rukimbira

In this paper, we deal with a strongly pseudoconvex almost CR manifold with a CR contraction. We will prove that the stable manifold of the CR contaction is CR equivalent to the Heisenberg group model.

Complex Variables · Mathematics 2022-08-04 Jae-Cheon Joo , Kang-Hyurk Lee

We investigate the line between tight and overtwisted for surgeries on fibred transverse knots in contact 3-manifolds. When the contact structure $\xi_K$ is supported by the fibred knot $K \subset M$, we obtain a characterisation of when…

Geometric Topology · Mathematics 2016-12-28 James Conway

Motivated by the moduli theory of taut contact circles on spherical 3-manifolds, we relate taut contact circles to transversely holomorphic flows. We give an elementary survey of such 1-dimensional foliations from a topological viewpoint.…

Differential Geometry · Mathematics 2017-09-01 Hansjörg Geiges , Jesús Gonzalo

Cosymplectic and normal almost contact structures are analogues of symplectic and complex structures that can be defined on 3-manifolds. Their existence imposes strong topological constraints. Generalized geometry offers a natural common…

Differential Geometry · Mathematics 2026-05-21 Joan Porti , Roberto Rubio

The notion of \emph{contact triad connection} on contact triads $(Q,\lambda,J_\xi)$ was introduced by Wang and the present author in early 2010's from scratch as the contact analog to the canonical connection of an almost K\"ahler…

Differential Geometry · Mathematics 2026-01-01 Yong-Geun Oh

We study the Riemann curvature tensor of (\kappa,\mu,\nu)-spaces when they have almost cosymplectic and almost Kenmotsu structures, giving its writing explicitly. This leads to the definition and study of a natural generalisation of the…

Differential Geometry · Mathematics 2013-08-06 Alfonso Carriazo , Verónica Martín-Molina

We continue the study of compact holomorphic $p$-contact manifolds $X$ that we introduced recently by expanding the discussion to include non-K\"ahler hyperbolicity issues and a differential calculus based on what we call the Lie derivative…

Differential Geometry · Mathematics 2025-11-17 Hisashi Kasuya , Dan Popovici , Luis Ugarte

We prove that every strong symplectic filling of a planar contact manifold admits a symplectic Lefschetz fibration over the disk, and every strong filling of the 3-torus similarly admits a Lefschetz fibration over the annulus. It follows…

Symplectic Geometry · Mathematics 2019-12-19 Chris Wendl

We classify all contact structures with contact surgery number one on the Brieskorn sphere Sigma(2,3,11) with both orientations. We conclude that there exist infinitely many non-isotopic contact structures on each of the above manifolds…

Symplectic Geometry · Mathematics 2024-04-30 Rima Chatterjee , Marc Kegel

We show that every closed toroidal irreducible orientable 3-manifold carries infinitely many universally tight contact structures.

Geometric Topology · Mathematics 2016-09-07 Vincent Colin

Almost Riemann solitons are introduced and studied on an almost contact complex Riemannian manifold, i.e. an almost contact B-metric manifold, obtained from a cosymplectic manifold of the considered type by a contact conformal…

Differential Geometry · Mathematics 2023-09-06 Mancho Manev

We classify all smooth compact connected K\"ahler threefolds that admit the structure of a $C^\infty$-fiber bundle over the circle. This generalizes the work of Hao and Schreieder in the projective case. In contrast to the projective case,…

Algebraic Geometry · Mathematics 2025-06-30 Simon Pietig

We study almost contact metric structures induced by 2-fold vector cross products on manifolds with $G_2$ structures. We get some results on possible classes of almost contact metric structures. Finally we give examples.

Differential Geometry · Mathematics 2016-01-08 Nülifer Özdemir , Mehmet Solgun , Şirin Aktay

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

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

Homogeneous compatible almost complex structures on symplectic manifolds are studied, focusing on those which are special, meaning that their Chern-Ricci form is a multiple of the symplectic form. Non Chern-Ricci flat ones are proven to be…

Symplectic Geometry · Mathematics 2019-12-02 Alberto Della Vedova

Starting from a cubic form, we give a general construction of a quasi-complete homogeneous manifold endowed with a natural contact structure. We show that it can be compactified into a projective contact manifold if and only if the cubic…

Algebraic Geometry · Mathematics 2008-12-22 Jun-Muk Hwang , Laurent Manivel

To give an almost quaternionic structure on a 4n-manifold $M$ is equivalent to give its bundle of twistors $Z(Q)\longrightarrow M$. When $Q$ is invariant under a torsion free connection, $Z(Q) $ can be provided with an almost complex…

Differential Geometry · Mathematics 2016-01-18 Guillaume Deschamps

In this work, we revisit quasi-Sasakian geometry in dimension three and examine how these structures interact with the foliation generated by the Reeb vector field and its basic cohomology. Through a deformation-based approach, we show that…

Differential Geometry · Mathematics 2025-12-29 Emmanuel Gnandi , Fortuné Massamba