Browsing by Author "Kahil, Magd E"

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Motion of Spinning and Spinning De- viation Density Tensors in Riemannian Geometry
(2022-09) Kahil, Magd E; Ammar, Samah A; Refaey, Shymaa A
Equations of motion of spinning density for extended objects, and corresponding deviation equations are derived. The problem of motion for a variable mass to a spinning extended object is obtained. Spinning fluids may be considered as a special case to express the motion of spinning density for extended objects. Meanwhile, spinning density tensor can be expressed in terms of tetrad formalism of General Relativity to be regarded as a gauge theory of gravity. Equations of spinning and spinning deviation density tensors have been derived using a specific type of Bazanski Lagrangian is performed.
Motion of Spinning and Spinning Deviation in Riemannian Geometry
(Pleiades Publishing, 2023-06) Kahil, Magd E; Ammar, Samah A; Refaey, Shymaa A
Equations of motion of spinning density for extended objects and tthe corresponding deviation equations are derived. The problem of motion for a variable mass of a spinning extended object is obtained. Spinning fluids may be considered as a special case to express the motion of spinning density for extended objects. Meanwhile, the spinning density tensor can be expressed in terms of the tetrad formalism of general relativity to be regarded as a gauge theory of gravity. The equations of spinning and spinning deviation density tensors have been derived using a specific type of Bazanski Lagrangian.
Self-Creation Gravity Versus General Relativity: a Cosmological Comparison
(Pleiades Publishing, 2024-09) Hegazy, E. A; Kahil, Magd E
Abstract: In the context of the self-creation theory of gravitation and its counterpart, the relativity theory, we examine their associated Bianchi-type cosmological models by considering the existence of electromagnetic fields. The solution of the Einstein equations is presented by assuming that the cosmological model leads to a constant deceleration parameter (). There is no restriction on the pressure and density for the solution derived (i.e., the equation of state is not used). The technique of obtaining the scalar field is different from that used in the previous investigation. A law that shows the effect of the electromagnetic field on the entropy of the universe is derived. The entropy introduced in the two theories is a consequence of the second law of thermodynamics. Consequently, the well-known thermodynamic functions of the universe are revisited. The scalar field introduced in the self-creation theory give a good explanation for the entropy and other thermodynamics functions of the universe as compared to general relativity. Moreover, in the absence of the electromagnetic field, the solution obtained in the self-creation theory and in general relativity indicate a radiation model, provided that the obtained models, whether expressed geometrically or physically are displayed.
Spinning and spinning deviation equations of bi-metric type theories
(Springer, 7/15/2020) Kahil, Magd E
Spinning equations of bi-metric type theories of gravity, the counterpart of the Papapetrou equations of motion are derived as well as their corresponding spinning deviation equations, by means of introducing different types of bi-metric theories. The influence of different curvatures based on different connections is illustrated. A specific Lagrangian function for each type theory is proposed, in order to derive the set of spinning motion and their corresponding spinning deviation equations.