Browsing by Author "Shenawy, Sameh"

Now showing 1 - 6 of 6

2-Killing vector fields on warped product manifolds
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2015) Shenawy, Sameh; Unal, Bulent
This paper provides a study of 2-Killing vector fields on warped product manifolds as well as characterization of this structure on standard static and generalized Robertson-Walker space-times. Some conditions for a 2-Killing vector field on a warped product manifold to be parallel are obtained. Moreover, some results on the curvature of a warped product manifolds in terms of 2-Killing vector fields are derived. Finally, we apply our results to describe 2-Killing vector fields of some well-known warped product space-time models.
Conformal Vector Fields on Doubly Warped Product Manifolds and Applications
(HINDAWI LTD, 2016) El-Sayied, H. K.; Shenawy, Sameh; Syied, Noha
This article aimed to study and explore conformal vector fields on doubly warped product manifolds as well as on doubly warped spacetime. Then we derive sufficient conditions for matter and Ricci collineations on doubly warped product manifolds. A special attention is paid to concurrent vector fields. Finally, Ricci solitons on doubly warped product spacetime admitting conformal vector fields are considered.
Einstein-like warped product manifolds
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2017) Mantica, Carlo Alberto; Shenawy, Sameh
In this paper, it is proved that the fiber manifold M-2 of a warped product manifold M = M-1 x(f) M-2 inherits the Einstein-like class type of M whereas the base manifold does under some conditions. Some related results are considered.
Locally symmetric f-associated standard static spacetimes
(WILEY, 2018-10) El‐Sayied, H. K.; Shenawy, Sameh; Syied, Noha
In this note, we study and explore locally symmetric f-associated standard static spacetimes I-f x M. Necessary and sufficient conditions on f-associated standard static spacetimes to be locally symmetric are derived. Some implications for these conditions are considered.
On symmetries of generalized Robertson-Walker spacetimes and applications
(TAYLOR & FRANCIS LTD, 2017) Syied, Noha; Shenawy, Sameh; El-Sayied, H. K
The purpose of the present article is to study and characterize several types of symmetries of generalized Robertson-Walker spacetimes. Conformal vector fields, curvature and Ricci collineations are studied. Many implications for existence of these symmetries on generalized Robertson-Walker spacetimes are obtained. Finally, Ricci solitons on generalized Robertson-Walker spacetimes admitting conformal vector fields are investigated.
The W-2-curvature tensor on warped product manifolds and applications
(WORLD SCIENTIFIC PUBL CO PTE LTD, 2016-08) Unal, Bulent); Shenawy, Sameh
The purpose of this paper is to study the W-2-curvature tensor on (singly) warped product manifolds as well as on generalized Robertson-Walker and standard static space-times. Some different expressions of the W-2-curvature tensor on a warped product manifold in terms of its relation with W-2-curvature tensor on the base and fiber manifolds are obtained. Furthermore, we investigate W-2-curvature flat warped product manifolds. Many interesting results describing the geometry of the base and fiber manifolds of a W-2-curvature flat warped product manifold are derived. Finally, we study the W-2-curvature tensor on generalized Robertson-Walker and standard static space-times; we explore the geometry of the fiber of these warped product space-time models that are W-2-curvature flat.