Articles written in Pramana – Journal of Physics

    • Electromagnetic field and spherically symmetric dissipative fluid models


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      This paper studies a few properties of Lemaître–Tolman–Bondi (LTB) space–time to the dissipative cases that may lead to its extension in Maxwell- f (R, T ) gravity, where R is the Ricci scalar and T is the trace of energy–momentum tensor. Using Misner and Sharp mass formalism, we have first established a relationship between the Weyl tensor and other physical variables. The role of electric charge in the development of the Bianchi identities was also investigated. The physical importance of the effective form of structure scalars was then analysedin view of some realistic backgrounds.We also discussed the generalisations of LTB and the extension of LTB based on structure scalars and a few symmetry properties under constant curvature conditions.

    • Matter–curvature gravity modification and the formation of cylindrical isotropic systems


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      In this paper,we constructed the three-layered gravastar model in cylindrical space–time.We considered one of the modified gravity theories to investigate the structural progression of the celestial object. The matter we considered in this model is effective, which further constituted the perfect fluid and extra degrees of freedom due to the modification of Einstein gravity. For the modelling of the three regions of gravastar, we used a specific barotropic equation of state. We then evaluated the subsequent field equations, hydrostatic equilibrium condition and gravitational mass. Furthermore, the metric coefficients for the three regions of the system were determined.Eventually, we discussed the important features of the gravastar and deduced its physical significance along with its graphical representations.

    • Gravastars with cylindrical space–time in f (G, T) gravity


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      The aim of this paper is to investigate the formation and evolution of the celestial object, known as gravastar. The idea of this gravitationally vacuum star is suggested by Mazur and Mottola. In general, the gravatar is assumed to be composed of three distinct regions. These regions are explained thoroughly with the help of certain equations of states and the values of metric coefficients corresponding to these sectors are also determined. The perfect fluid and cylindrically symmetric metric are assumed to derive Bianchi identities and modified field equations. The internal and external geometries are combined with each other at intermediate thin shell and specific conditions are used for this purpose. In the framework of an alternative gravitational theory, i.e., f (G, T) theory, we calculate a regular solution for gravastar along with the elaboration of specific substantial attributes of the model. The significance of f (G, T) theory for attaining gravastar model is also studied.

    • Causes of energy density inhomogenisation with f ($\mathcal{G} $) formalism


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      Here, we analyse the distribution of self-gravitating collapsing fluid to identify the factors accountable for the energy–density in homogeneity with the systematic construction in modified Gauss–Bonnet (GB) gravity, by taking the space–time which is spherically symmetric. The modified Einstein’s equations help us to observe the variation in the mass function due to different quantities. The dynamical equations and two differential equations for Weyl curvature are formulated and used to explore the quantities responsible for the inhomogeneity. Irregularity in the fluid is analysed by taking various cases of fluid, under the effects of f ($\mathcal{G} $) theory, where $\mathscr{G} $ is a Gauss–Bonnet term.

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