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We characterize the $2$-Killing vector fields on a multiply twisted product manifold, with a special view towards generalized spacetimes. More precisely, we determine the nonlinear differential equations that completely describe them and…

Differential Geometry · Mathematics 2025-08-04 Adara M. Blaga

We show necessary conditions for the existence of transversal Killing spinors on a spin manifold endowed with a Riemannian flow.

Differential Geometry · Mathematics 2008-09-17 Nicolas Ginoux , Georges Habib

Using examples of compact complex 3-manifolds which arise as twistor spaces, we show that the class of compact complex manifolds bimeromorphic to K\"ahler manifolds is not stable under small deformations of complex structure.

alg-geom · Mathematics 2008-02-03 Claude LeBrun , Yat-Sun Poon

A smooth foliation is Riemannian when its leaves are locally equidistant. The closures of the leaves of a Riemannian foliation on a simply connected manifold, or more generally of a Killing foliation, are described by flows of transverse…

Differential Geometry · Mathematics 2022-10-05 Marcos M. Alexandrino , Francisco C. Caramello

For Kaehler manifolds we explicitly determine the solution to the conformal Killing form equation in middle degree. In particular, we complete the classification of conformal Killing forms on compact Kaehler manifolds. We give the first…

Differential Geometry · Mathematics 2023-05-15 Paul-Andi Nagy , Uwe Semmelmann

We study Riemannian foliations with complex leaves on Kaehler manifolds. The tensor T, the obstruction to the foliation be totally geodesic, is interpreted as a holomorphic section of a certain vector bundle. This enables us to give…

Differential Geometry · Mathematics 2012-07-02 Paul-Andi Nagy

We study left-invariant Killing $k$-forms on simply connected $2$-step nilpotent Lie groups endowed with a left-invariant Riemannian metric. For $k=2,3$, we show that every left-invariant Killing $k$-form is a sum of Killing forms on the…

Differential Geometry · Mathematics 2021-06-15 Viviana del Barco , Andrei Moroianu

We characterize Osserman and conformally Osserman Riemannian manifolds with the local structure of a warped product. By means of this approach we analyze the twisted product structure and obtain, as a consequence, that the only Osserman…

Differential Geometry · Mathematics 2008-07-22 M. Brozos-Vazquez , E. Garcia-Rio , R. Vazquez-Lorenzo

Generalization of twistor spinors to K\"ahler manifolds which are called K\"ahlerian twistor spinors are considered. We find the differential equation satisfied by the bilinear forms of K\"ahlerian twistor spinors. We show that the bilinear…

Differential Geometry · Mathematics 2018-11-27 Ümit Ertem

In this paper we review some results on the Riemannian and almost Hermitian geometry of twistor spaces of oriented Riemannian $4$-manifolds with emphasis on their curvature properties.

Differential Geometry · Mathematics 2021-02-09 Johann Davidov , Oleg Mushkarov

For the twistor spaces of the Bochner-K\"ahler manifold $M = H^l \times P^n$, systems of holomorphic coordinates are constructed. As an application of them, an explicit description of the moduli space of relative deformations of fibers of…

dg-ga · Mathematics 2008-02-03 Yoshinari Inoue

The twistor construction for Riemannian manifolds is extended to the case of manifolds endowed with generalized metrics (in the sense of generalized geometry \`a la Hitchin). The generalized twistor space associated to such a manifold is…

Differential Geometry · Mathematics 2018-07-03 Johann Davidov

We study invariant systems of PDEs defining Killing vector-valued forms, and then we specialize to Killing spinor-valued forms. We give a detailed treatment of their prolongation and integrability conditions by relating the point-wise…

Differential Geometry · Mathematics 2020-09-22 Petr Somberg , Petr Zima

In this paper, we compute the index form of the multiply twisted products. We study the Killing vector fields on the multiply twisted product manifolds and determine the Killing vector fields in some cases. We compute the curvature of the…

Differential Geometry · Mathematics 2014-07-29 Yong Wang

In this article, we study the L2-transverse conformal Killing forms on complete foliated Riemannian manifolds and prove some vanishing theorems. Also, we study the same problems on Kahler foliations with a complete bundle-like metric.

Differential Geometry · Mathematics 2020-03-16 Seoung Dal Jung , Huili Liu

Hano's theorem states that the space of Killing vector fields of a complete simply connected Riemannian manifold is isomorphic to the direct sum of the Killing vector fields of the factors in its de Rham decomposition. We prove a…

Differential Geometry · Mathematics 2023-12-04 Federico Costanza , Thomas Leistner

We present a rough classification of differential forms on a Riemannian manifold, we consider definitions and properties of conformal Killing forms on a compact Riemannian manifold and define Tachibana numbers as an analog of the well known…

Differential Geometry · Mathematics 2013-07-01 S. E. Stepanov , J. Mikeš

We study the geometry of compact Lorentzian manifolds that admit a somewhere timelike Killing vector field, and whose isometry group has infinitely many connected components. Up to a finite cover, such manifolds are products (or amalgamated…

Differential Geometry · Mathematics 2010-02-04 Paolo Piccione , Abdelghani Zeghib

Valence two Killing tensors in the Euclidean and Minkowski planes are classified under the action of the group which preserves the type of the corresponding Killing web. The classification is based on an analysis of the system of…

Differential Geometry · Mathematics 2009-09-29 C. Chanu , L. Degiovanni , R. G. McLenaghan

We present definitions and properties of conformal Killing, Killing and planarity forms on a Riemannian manifold and determine Tachibana, Killing and planarity numbers as an analog of the well known Betti numbers. We state some set of…

Differential Geometry · Mathematics 2013-01-04 Sergey E. Stepanov , Josef Mikeš