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In this paper we study the groups of contactomorphisms of a closed contact manifold from a topological viewpoint. First we construct examples of contact forms on spheres whose Reeb flow has a dense orbit. Then we show that the unitary group…

Symplectic Geometry · Mathematics 2015-05-04 Roger Casals , Oldřich Spáčil

We investigate the local geometry of a pair of independent contact structures on 3-manifolds under maps that independently preserve each contact structure. We discover that such maps are homotheties on the contact 1-forms and we discover…

Differential Geometry · Mathematics 2024-05-22 Taylor J. Klotz , George R. Wilkens

A curvature-type tensor invariant called para contact (pc) conformal curvature is defined on a paracontact manifold. It is shown that a paracontact manifold is locally paracontact conformal to the hyperbolic Heisenberg group or to a…

Differential Geometry · Mathematics 2010-03-12 Stefan Ivanov , Dimiter Vassilev , Simeon Zamkovoy

We investigate 3-dimensional almost Kenmotsu manifolds satisfying special types of nullity conditions depending on two smooth functions $\kappa,\mu$. When either $\kappa<-1$ and $\mu=0$ or $h=0$, such conditions coincide with the…

Differential Geometry · Mathematics 2013-01-29 Vincenzo Saltarelli

In this paper, we prove that evry 3-dimensional manifold M is a ?- recurrent N(k)-contact metric manifold if and only if it is flat. Then we classify the ?-recurrent contact metric manifolds of constant curvature. This implies that there…

Differential Geometry · Mathematics 2013-02-20 E. Peyghan , H. Nasrabadi , A. Tayebi

We present a classification of the complete, simply connected, contact metric $(\kappa,\mu)$-spaces as homogeneous contact metric manifolds, by studying the base space of their canonical fibration. According to the value of the Boeckx…

Differential Geometry · Mathematics 2019-07-24 Eugenia Loiudice , Antonio Lotta

Let M be a closed simply connected n-manifold of positive sectional curvature. We determine its homeomorphism or homotopic type if M also admits an isometric elementary p-group action of large rank. Our main results are: There exists a…

Differential Geometry · Mathematics 2007-05-23 Fuquan Fang , Xiaochun Rong

The defining property of every three-dimensional $\varepsilon$-contact manifold is shown to be equivalent to requiring the fulfillment of London's equation in 2+1 electromagnetism. To illustrate this point, we show that every such manifold…

General Relativity and Quantum Cosmology · Physics 2021-02-23 D. Flores-Alfonso , C. S. Lopez-Monsalvo , M. Maceda

We consider compact complex surfaces with Hermitian metrics which are Einstein but not Kaehler. It is shown that the manifold must be CP2 blown up at 1,2, or 3 points, and the isometry group of the metric must contain a 2-torus. Thus the…

dg-ga · Mathematics 2008-02-03 Claude LeBrun

It is provided an overview of existed results concerning classification of contact metric, almost cosymplectic and almost Kenmotsu $(\kappa,\mu)$-manifolds. In the case of dimension three it is described in full details structure of contact…

Differential Geometry · Mathematics 2020-09-23 Piotr Dacko

It is well known that a unit sphere admits Sasakian 3-structure. Also, Sasakian manifolds are locally isometric to a unit sphere under several curvature and critical conditions. So, a natural question is: Does there exist any curvature or…

Differential Geometry · Mathematics 2021-09-10 Dibakar Dey

We study paracontact metric $(\kappa,\mu)$-spaces with $\kappa=-1$, equivalent to $h^2=0$ but not $h=0$. In particular, we will give an alternative proof of Theorem 3.2 of [11] and present examples of paracontact metric $(-1,2)$-spaces and…

Differential Geometry · Mathematics 2015-07-28 Verónica Martín-Molina

We study low-dimensional problems in topology and geometry via a study of contact and Cauchy-Riemann ($CR$) structures. A contact structure is called spherical if it admits a compatible spherical $CR$ structure. We will talk about spherical…

Symplectic Geometry · Mathematics 2007-05-23 Jih-Hsin Cheng

In this paper, we investigate the geometry of Einstein-type equation on a Riemannian manifold, unifying various particular geometric structures recently studied in the literature, such as critical point equation and vacuum static equation.…

Differential Geometry · Mathematics 2022-03-31 Gabjin Yun , Seungsu Hwang

We prove some contact analogs of smooth embedding theorems for closed $\pi$-manifolds. We show that a closed, $k$-connected, $\pi$-manifold of dimension (2n + 1) that bounds a $\pi$-manifold, contact embeds in the $(4n-2k+3)$-dimensional…

Symplectic Geometry · Mathematics 2020-05-21 Kuldeep Saha

We prove that any compact complex surface with positive first Chern class admits an Einstein metric which is conformally related to a Kaehler metric. The key new ingredient is the existence of such a metric on the blow-up of the complex…

Differential Geometry · Mathematics 2007-06-13 Xiuxiong Chen , Claude LeBrun , Brian Weber

We prove that a 2n-dimensional compact homogeneous nearly Kahler manifold with strictly positive sectional curvature is isometric to CP^{n}, equipped with the symmetric Fubini-Study metric or with the standard Sp(m)-homogeneous metric, n…

Differential Geometry · Mathematics 2009-04-06 J. C. Gonzalez Davila , F. Martin Cabrera

On a compact $n$-dimensional manifold, it is well known that a critical metric of the total scalar curvature, restricted to the space of metrics with unit volume is Einstein. It has been conjectured that a critical metric of the total…

Differential Geometry · Mathematics 2018-09-05 Gabjin Yun , Seungsu Hwang

We show that every K-contact Einstein manifold is Sasakian-Einstein and discuss several corollaries of this result.

Differential Geometry · Mathematics 2007-05-23 Charles P. Boyer , Krzysztof Galicki

We study the geometry of almost contact pseudo-metric manifolds in terms of tensor fields $h:=\frac{1}{2}\pounds _\xi \varphi$ and $\ell := R(\cdot,\xi)\xi$, emphasizing analogies and differences with respect to the contact metric case.…

Differential Geometry · Mathematics 2018-06-01 Venkatesha , Devaraja Mallesha Naik , Mukut Mani Tripathi