Browsing by Author "Syied, Noha"

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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.
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.