Core-envelope model of compact objects in 𝑓(𝑅) gravity
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Date
2025-02-18
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UMT Lahore
Abstract
In this thesis, a relativistic core and envelope model is being developed for spherical symmetry anisotropic compact stars in 𝑓(𝑅) gravity. It is necessary to understand the complex interior structure of these stars to do the study of general relativity and astrophysics. The core area is represented by polytropic equation of state (EOS). This point specifically describes the density-pressure relation. In accordance with physical situation frequently realized for a star interiors. The mathematical handling of the outer layers, where circumstances are often less harsh. It is made simpler using a linear EOS for the envelope area. The smooth matching of the stars core, envelope, and Schwarzschild outer regions is an essential part of the findings. For physical characteristics like density and pressure to be never-changing and clearly-defined in different locations. This smooth changeover is necessary to avoid singularities that would endanger such continuity crucial to the models validity. All of the physical parameters behave well in the core and envelope regions of the specific compact stars SAX J1808.4 3658 and 4U1608-52. The physical properties that characterize the internal structure of these stars, while maintaining non-singularity and continuity at the interface where the core and envelope meet. This comprehensive assessment enhances the robustness of the model. The core and envelope model of compact objects, significantly influence the mass, radius, and compactification factor of a star. The graphical representation is helpful to illustrate these relations and provides a better understanding of the relationship between the inner and the outer features of the star and other such trivial properties that the star might have. These illustrations are useful for the comprehension of structure and equilibrium of stars formed in the limit and all are important for their dynamics. Abstract the adiabatic index and the radial sound speed are important tests to determine the stability of the model. The speed of radial sound is essential in ensuring that sound waves propagate inside the star according to limitations of causality, which state that they cannot travel faster than light. Abstract xiii on the contrary, the adiabatic index explains a relationship between the variations of density and pressure, which is essentially required to evaluate the overall stability arrangements. I observed the core and envelope model stability requirements to verify that the model correctly expresses the physical reality of the compact stars. Moreover, to understand the structures of stars better, this study advances modified gravity theories by shedding light on the underlying reasons that govern the behavior of these interesting celestial bodies.