Displaying similar documents to “On ϕ -conformally flat contact metric manifolds.”

An Osserman-type condition on g.f.f-manifolds with Lorentz metric

Letizia Brunetti (2014)

Annales Polonici Mathematici

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A condition of Osserman type, called the φ-null Osserman condition, is introduced and studied in the context of Lorentz globally framed f-manifolds. An explicit example shows the naturality of this condition in the setting of Lorentz 𝓢-manifolds. We prove that a Lorentz 𝓢-manifold with constant φ-sectional curvature is φ-null Osserman, extending a well-known result in the case of Lorentz Sasaki space forms. Then we state a characterization of a particular class of φ-null Osserman 𝓢-manifolds....

Metric polynomial structures

Barbara Opozda

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CONTENTSIntroduction.................................................................................................................................................51. Preliminaries...........................................................................................................................................62. f-Kählerian manifolds............................................................................................................................113. The f-sectional...

A short introduction to shadows of 4-manifolds

Francesco Costantino (2005)

Fundamenta Mathematicae

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We give a self-contained introduction to the theory of shadows as a tool to study smooth 3-manifolds and 4-manifolds. The goal of the present paper is twofold: on the one hand, it is intended to be a shortcut to a basic use of the theory of shadows, on the other hand it gives a sketchy overview of some of the most recent results on shadows. No original result is proved here and most of the details of the proofs are left out.

On the asymptotic geometry of gravitational instantons

Vincent Minerbe (2010)

Annales scientifiques de l'École Normale Supérieure

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We investigate the geometry at infinity of the so-called “gravitational instantons”, i.e. asymptotically flat hyperkähler four-manifolds, in relation with their volume growth. In particular, we prove that gravitational instantons with cubic volume growth are ALF, namely asymptotic to a circle fibration over a Euclidean three-space, with fibers of asymptotically constant length.