Classification of $(k,\mu )$-contact manifolds with divergence free Cotton tensor and vanishing Bach tensor

2019 ◽  
Vol 122 (2) ◽  
pp. 153-163
Author(s):  
Amalendu Ghosh ◽  
Ramesh Sharma
Keyword(s):  
Contact Manifolds ◽  
Bach Tensor ◽  
Cotton Tensor ◽  
Divergence Free

Ambitoric geometry I: Einstein metrics and extremal ambikähler structures

2016 ◽  
Vol 2016 (721) ◽  
Author(s):  
Vestislav Apostolov ◽  
David M. J. Calderbank ◽  
Paul Gauduchon
Keyword(s):  
Maxwell Equations ◽  
Einstein Metrics ◽  
Natural Extension ◽  
Torus Action ◽  
Local Geometry ◽  
Kähler Metrics ◽  
Kahler Metrics ◽  
Bach Tensor ◽  
Extremal Kähler Metrics

AbstractWe present a local classification of conformally equivalent but oppositely oriented 4-dimensional Kähler metrics which are toric with respect to a common 2-torus action. In the generic case, these “ambitoric” structures have an intriguing local geometry depending on a quadratic polynomialWe use this description to classify 4-dimensional Einstein metrics which are hermitian with respect to both orientations, as well as a class of solutions to the Einstein–Maxwell equations including riemannian analogues of the Plebański–Demiański metrics. Our classification can be viewed as a riemannian analogue of a result in relativity due to R. Debever, N. Kamran, and R. McLenaghan, and is a natural extension of the classification of selfdual Einstein hermitian 4-manifolds, obtained independently by R. Bryant and the first and third authors.These Einstein metrics are precisely the ambitoric structures with vanishing Bach tensor, and thus have the property that the associated toric Kähler metrics are extremal (in the sense of E. Calabi). Our main results also classify the latter, providing new examples of explicit extremal Kähler metrics. For both the Einstein–Maxwell and the extremal ambitoric structures,

scholarly journals A classification of the torsion tensors on almost contact manifolds with B-metric

2014 ◽  
Vol 12 (10) ◽  
Author(s):  
Mancho Manev ◽  
Miroslava Ivanova
Keyword(s):  
Invariant Subspaces ◽  
Structure Group ◽  
Contact Manifolds ◽  
Linear Connections

AbstractThe space of the torsion (0,3)-tensors of the linear connections on almost contact manifolds with B-metric is decomposed in 15 orthogonal and invariant subspaces with respect to the action of the structure group. Three known connections, preserving the structure, are characterized regarding this classification.

Cotton tensor, Bach tensor and Kenmotsu manifolds

2020 ◽  
Vol 31 (7-8) ◽  
pp. 1193-1205
Author(s):  
Amalendu Ghosh
Keyword(s):  
Bach Tensor ◽  
Kenmotsu Manifolds ◽  
Cotton Tensor

A SELF-LINKING FORMULA FOR CURVES IN THE HEISENBERG SPACE

2002 ◽  
Vol 11 (07) ◽  
pp. 1077-1087
Author(s):  
MARCOS M. DINIZ
Keyword(s):  
Dna Structure ◽  
Contact Structures ◽  
Contact Manifolds ◽  
Linking Number ◽  
Legendrian Curves

The formula Lk = Wr + Tw, which expresses the linking number of two curves that bound a ribbon as a sum of two terms, has particularly interested biologists and was used to understand the DNA structure. The study of Legendrian curves in contact manifolds, and in particular in the Heisenberg space, is attached to some important problems in geometry, as the problem of classification of contact structures. In this work, we show the analogue formula for curves in the Heisenberg space, we relate the writhing number with the Thurston-Benequin invariant of a Legendrian curve and derive some results directly from this formula.

THE BACH TENSOR AND OTHER DIVERGENCE-FREE TENSORS

2005 ◽  
Vol 02 (01) ◽  
pp. 13-21 ◽  
Author(s):  
JONAS BERGMAN ◽  
S. BRIAN EDGAR ◽  
MAGNUS HERBERTHSON
Keyword(s):  
Metric Tensor ◽  
Four Dimensions ◽  
Bach Tensor ◽  
Divergence Free

In four dimensions, we prove that the Bach tensor is the only symmetric divergence-free 2-tensor which is also quadratic in Riemann and has good conformal behavior. In n > 4 dimensions, we prove that there are no symmetric divergence-free 2-tensors which are also quadratic in Riemann and have good conformal behavior, nor are there any symmetric divergence-free 2-tensors which are concomitants of the metric tensor gab together with its first two derivatives, and have good conformal behavior.

scholarly journals A Boothby–Wang Theorem for Besse Contact Manifolds

2020 ◽  
Author(s):  
Marc Kegel ◽  
Christian Lange
Keyword(s):  
Lie Group ◽  
Group Actions ◽  
Contact Manifold ◽  
Complete Classification ◽  
Contact Manifolds ◽  
Lie Group Actions ◽  
Oxford University ◽  
Reeb Flows ◽  
Sasakian Geometry

AbstractA Reeb flow on a contact manifold is called Besse if all its orbits are periodic, possibly with different periods. We characterize contact manifolds whose Reeb flows are Besse as principal $$S^1$$ S 1 -orbibundles over integral symplectic orbifolds satisfying some cohomological condition. Apart from the cohomological condition, this statement appears in the work of Boyer and Galicki in the language of Sasakian geometry (Boyer and Galicki in Sasakian geometry, Oxford Mathematical Monographs, Oxford University Press, Oxford, 2008). We illustrate some non-commonly dealt with perspective on orbifolds in a proof of the above result. More precisely, we work with orbifolds as quotients of manifolds by smooth Lie group actions with finite stabilizer groups. By introducing all relevant orbifold notions in this equivariant way, we avoid patching constructions with orbifold charts. As an application, and building on work by Cristofaro-Gardiner–Mazzucchelli, we deduce a complete classification of closed Besse contact 3-manifolds up to strict contactomorphism.

scholarly journals On Subcritically Stein Fillable 5-manifolds

2018 ◽  
Vol 61 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Fan Ding ◽  
Hansjörg Geiges ◽  
Guangjian Zhang
Keyword(s):  
Fundamental Group ◽  
Contact Structure ◽  
Contact Structures ◽  
Homotopy Classification ◽  
Contact Manifolds ◽  
Almost Contact Structure ◽  
Diffeomorphism Type ◽  
Standard Contact ◽  
Simply Connected

AbstractWe make some elementary observations concerning subcritically Stein fillable contact structures on 5-manifolds. Specifically, we determine the diffeomorphism type of such contact manifolds in the case where the fundamental group is finite cyclic, and we show that on the 5-sphere, the standard contact structure is the unique subcritically ?llable one. More generally, it is shown that subcritically fillable contact structures on simply connected 5-manifolds are determined by their underlying almost contact structure. Along the way, we discuss the homotopy classification of almost contact structures.

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