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We study the Sasaki cone of a CR structure of Sasaki type on a given closed manifold. We introduce an energy functional over the cone, and use its critical points to single out the strongly extremal Reeb vectors fields. Should one such…

Differential Geometry · Mathematics 2009-11-23 Charles P. Boyer , Krzysztof Galicki , Santiago R. Simanca

We prove the existence of Sasaki-Einstein metrics on certain simply connected 5-manifolds where until now existence was unknown. All of these manifolds have non-trivial torsion classes. On several of these we show that there are a countable…

Differential Geometry · Mathematics 2011-08-19 Charles P. Boyer , Michael Nakamaye

We investigate some topological properties, in particular formality, of compact Sasakian manifolds. Answering some questions raised by Boyer and Galicki, we prove that all higher (than three) Massey products on any compact Sasakian manifold…

Differential Geometry · Mathematics 2018-08-07 Indranil Biswas , Marisa Fernández , Vicente Muñoz , Aleksy Tralle

The aim of this paper is to study compact 5--manifolds which carry a positive Sasakian structure. Strong restrictions are derived for the integral homology groups. In some cases, all positive Sasakian structures are classified. A key step…

Differential Geometry · Mathematics 2007-05-23 János Kollár

We present a categorical relationship between iterated $S^3$ Sasaki-joins and Bott orbifolds. Then we show how to construct smooth Sasaki-Einstein (SE) structures on the iterated joins. These become increasingly complicated as dimension…

Differential Geometry · Mathematics 2023-03-22 Charles P Boyer , Christina Tønnesen-Friedman

We define a contact metric structure on the manifold corresponding to a second order ordinary differential equation $d^2y/dx^2=f(x,y,y')$ and show that the contact metric structure is Sasakian if and only if the 1-form $\frac{1}{2}(dp-fdx)$…

Differential Geometry · Mathematics 2021-09-01 Tuna Bayrakdar

This paper provides a topological method for filling contact structures on the connected sums of $S^2\times S^3$. Examples of nonsymplectomorphic strong fillings of homotopy equivalent contact structures with vanishing first Chern class on…

Geometric Topology · Mathematics 2015-06-30 Ahmet Beyaz

In this note we give an explicit construction of Sasaki-Einstein metrics on a class of simply connected 7-manifolds with the rational cohomology of the 2-fold connected sum of $S^2\times S^5$. The homotopy types are distinguished by torsion…

Differential Geometry · Mathematics 2019-06-18 Charles P. Boyer , Christina Tønnesen-Friedman

We show certain symmetry of the dimensions of cohomologies of the funda- mental groups of compact Sasakian manifolds by using the Hodge theory of twisted basic cohomology. As applications, we show that the polycyclic fundamental groups of…

Differential Geometry · Mathematics 2015-10-29 Hisashi Kasuya

We study fundamental groups of compact Sasaki manifolds and show that compared to K\"ahler groups, they exhibit rather different behaviour. This class of groups is not closed under taking direct products, and there is often an upper bound…

Differential Geometry · Mathematics 2025-04-08 D. Kotschick , G. Placini

We prove the existence of extremal Sasakian structures occurring on a countably infinite number of distinct contact structures on $T^2\times S^3$ and certain related manifolds. These structures occur in bouquets and exhaust the Sasaki cones…

Differential Geometry · Mathematics 2019-02-20 Charles P. Boyer , Christina W. Tønnesen-Friedman

We study the contact equivalence problem for toric contact structures on $S^3$-bundles over $S^2$. That is, given two toric contact structures, one can ask the question: when are they equivalent as contact structures while inequivalent as…

Symplectic Geometry · Mathematics 2016-01-20 Charles P. Boyer , Justin Pati

We prove that a compact Sasakian manifolds whose first and second basic Chern classes vanish is locally isomorphic to the real Heisenberg group equipped with the standard left invariant Sasakian structure up to deformation associated to a…

Differential Geometry · Mathematics 2023-10-20 Indranil Biswas , Hisashi Kasuya

Two constructions of contact manifolds are presented: (i) products of S^1 with manifolds admitting a suitable decomposition into two exact symplectic pieces and (ii) fibre connected sums along isotropic circles. Baykur has found a…

Symplectic Geometry · Mathematics 2010-06-22 Hansjörg Geiges , András I. Stipsicz

We describe a general procedure for constructing new Sasaki metrics of constant scalar curvature from old ones. Explicitly, we begin with a regular Sasaki metric of constant scalar curvature on a 2n+1-dimensional compact manifold M and…

Differential Geometry · Mathematics 2016-08-23 Charles P. Boyer , Christina W. Tønnesen-Friedman

We prove that every nearly Sasakian manifold of dimension greater than five is Sasakian. This provides a new criterion for an almost contact metric manifold to be Sasakian. Moreover, we classify nearly cosymplectic manifolds of dimension…

Differential Geometry · Mathematics 2019-10-28 Antonio De Nicola , Giulia Dileo , Ivan Yudin

We show that every five-dimensional Sasakian Lie algebra with trivial center is $\varphi$-symmetric. Moreover starting from a particular Sasakian structure on the Lie group $SL(2,\mathbb{R})\times\text{Aff}(\mathbb{R})$ we obtain a family…

Differential Geometry · Mathematics 2016-08-01 E. Loiudice , A. Lotta

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

We give explicit parametrizations for all the homogeneous contact Riemannian structures on $3$-dimensional Sasakian space forms.

Differential Geometry · Mathematics 2025-01-22 Jun-ichi Inoguchi , Yu Ohno

The join construction produces a third Sasaki manifold from two others, and we investigate the algebraic topology of the joins of circle bundles over surfaces of positive genus with weighted three-spheres. Topologically, such a join has the…

Algebraic Topology · Mathematics 2024-04-22 Candelario Castaneda , Ross Staffeldt