Search

In this work, we generate curved Lorentzian manifolds from a flat Minkowskian space–time, through the Gravitational Decoupling by the Minimal Geometric Deformation method interpreting the decoupling sector as a generator of curvature and matter distribution. In particular, we obtain some new wormhole geometries by imposing either physically relevant equations of state or certain physically–motivated geometric constraints. These solutions are analyzed in detail. For all these solutions, we study the associated energy conditions, the geometric behavior and construct their embedding diagrams. [ABSTRACT FROM AUTHOR]

In this paper, we have presented a bouncing cosmological model of the Universe in an extended theory of gravity. The dynamical behaviour of the model obtained from the flat FLRW space‐time along with the violation of null energy condition have been shown. The geometrical parameters show singularity behaviour at the bouncing epoch. The parameters involved in the scale factor play a major role in the bouncing behaviour. In addition, the coupling parameter that resulted in the minimal matter‐geometry coupling in the extended gravity has significant role to avoid the singularity of equation of state parameter at the bouncing epoch. Using a linear homogeneous perturbation calculation, we show the dynamical stability of the model. In this paper, a bouncing cosmological model of the Universe is presented in an extended theory of gravity. The dynamical behaviour of the model obtained from the flat FLRW space‐time along with the violation of null energy condition have been shown. The geometrical parameters show singularity behaviour at the bouncing epoch. The parameters involved in the scale factor play a major role in the bouncing behaviour. In addition, the coupling parameter that resulted in the minimal matter‐geometry coupling in the extended gravity has significant role to avoid the singularity of equation of state parameter at the bouncing epoch. Using a linear homogeneous perturbation calculation the dynamical stability of the model is shown. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of wormhole solutions in the framework of gravitational decoupling by means of the minimal geometric deformation scheme. As an example, to analyze how this methodology works in this scenario, we have minimally deformed the well-known Morris–Thorne model. The decoupler function f(r) and the θ -sector are determined considering the following approaches: (i) the most general linear equation of state relating the θ μ ν components is imposed and (ii) the generalized pseudo-isothermal dark matter density profile is mimicked by the temporal component of the θ -sector. It is found that the first approach leads to a non-asymptotically flat space-time with an unbounded mass function. To address this issue we have matched both the wormhole and the Schwarzschild vacuum solutions, via a thin-shell at the junction surface. Using the second approach, it can be seen that, on one hand, the solution for γ = 1 does not give place to a bounded mass and it presents a topological defect at large distances; on the other hand, the wormhole manifold is asymptotically flat in the γ = 2 case. In order to satisfy the flare-out condition, we have found restrictions on the value of the α parameter, which is related with the amount of exotic matter distribution. Finally, the averaged weak energy condition has been analyzed by using the volume integral quantifier. [ABSTRACT FROM AUTHOR]

In this work, a spherically symmetric and static relativistic anisotropic fluid sphere solution of the Einstein field equations is provided. To build this particular model, we have imposed metric potential e 2 λ (r) and an equation of state. Specifically, the so-called modified generalized Chaplygin equation of state with ω = 1 and depending on two parameters, namely, A and B. These ingredients close the problem, at least mathematically. However, to check the feasibility of the model, a complete physical analysis has been performed. Thus, we analyze the obtained geometry and the main physical observables, such as the density ρ , the radial p r , and tangential p t pressures as well as the anisotropy factor Δ . Besides, the stability of the system has been checked by means of the velocities of the pressure waves and the relativistic adiabatic index. It is found that the configuration is stable in considering the adiabatic index criteria and is under hydrostatic balance. Finally, to mimic a realistic compact object, we have imposed the radius to be R = 9.5 [ k m ] . With this information and taking different values of the parameter A the total mass of the object has been determined. The resulting numerical values for the principal variables of the model established that the structure could represent a quark (strange) star mixed with dark energy. [ABSTRACT FROM AUTHOR]

In this work, we present a new class of analytic and well-behaved solution to Einstein's field equations describing anisotropic matter distribution. It's achieved in the embedding class one spacetime framework using Karmarkar's condition. We perform our analysis by proposing a new metric potential g rr which yields us a physically viable performance of all physical variables. The obtained model is representing the physical features of the solution in detail, analytically as well as graphically for strange star candidate SAX J1808.4-3658 ( M a s s = 0.9 M ⊙ , r a d i u s = 7.951 km), with different values of parameter n ranging from 0.5 to 3.4. Our suggested solution is free from physical and geometric singularities, satisfies causality condition, Abreu's criterion and relativistic adiabatic index Γ , and exhibits well-behaved nature, as well as, all energy conditions and equilibrium condition are well-defined, which implies that our model is physically acceptable. The physical sensitivity of the moment of inertia (I) obtained from the solutions is confirmed by the Bejger−Haensel concept, which could provide a precise tool to the matching rigidity of the state equation due to different values of n viz., n = 0.5 , 1.08 , 1.66 , 2.24 , 2.82 and 3.4. [ABSTRACT FROM AUTHOR]

We investigate the existence of high dense compact objects in the light of Rastall gravity theory. The material content is driven by an imperfect fluid distribution and the inner geometry is described by the Tolman–Kuchowicz space–time. The validity of the obtained model is checked by studying the main salient features such as energy–density, radial and tangential pressures and anisotropy factor. Since Einstein gravity theory shares the same vacuum solution with Rastall gravity theory, the interior geometry is joining in a smoothly way with the exterior Schwarzschild's solution. The equilibrium of the model under different gradients is analyzed by using the modified hydrostatic equilibrium equation, containing the so–called Rastall gradient. The compact structure has a positive anisotropy factor which enhances the balance and stability mechanisms. To check the potentially stable behavior, we employ Abreu's and adiabatic index criterion. It was found that the model is completely stable. The incidence of the Rastall's parameter γ on all the physical quantities that characterize the model is described by the help of graphical analysis. Concerning the γ spectrum we have considered 0.3142 ≤ γ ≤ 0.3157 . All the results are compared with the general relativity case. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to obtain analytic relativistic anisotropic spherical solutions in f (R , T) scenario. To do so we use modified Durgapal–Fuloria metric potential and the pressure anisotropy condition is imposed in order to obtain the effective anisotropic factor Δ ̃. Besides, a notable and viable election on f (R , T) gravity formulation is taken. The choice of f (R , T) function modifies the matter sector only, including new ingredients to the physical parameters that characterize the model such as density, pressure, subliminal speeds of sound, surface redshift etc. We analyze all the physical and mathematical general requirements of the configuration taking M = 1. 04 M ⊙ and varying χ from − 0. 1 to 0.1. It is shown by the graphical procedure that χ < 0 yields a more compact object in comparison when χ ≥ 0 (where χ = 0. 0 corresponds to general relativity) and increases the value of the surface redshift. However, negative values of χ introduce in the system an attractive anisotropic force (inward) and the configuration is completely unstable (corroborated employing Abreu's criterion). Furthermore, the model in Einstein gravity theory presents cracking while for χ > 0 the system is fully stable. The relationship between effective radial pressure p ̃ r and effective density ρ ̃ is discussed and obtained. This is achieved by establishing the corresponding equation of state. • We have obtained new analytic relativistic anisotropic spherical solutions for modified Durgapal–Fuloria potential in the framework of f (R , T) gravity theory. • We use pressure anisotropy condition to obtain a physically viable expression for effective anisotropic factor (Δ). • We have shown that the present f (R , T) model is stable while the cracking appears inside the model in case of Einstein's gravity (GR) which shows that the f (R , T) gravity theory could be more useful to discover the stable model than the Einstein theory. • We established the relationship between pressure and density as p = f (ρ) and discovered an approximate equation of state for the present model. [ABSTRACT FROM AUTHOR]

This article is devoted to the study of new exact analytical solutions in the background of Reissner–Nordström space-time by using gravitational decoupling via minimal geometric deformation approach. To do so, we impose the most general equation of state, relating the components of the θ -sector in order to obtain the new material contributions and the decoupler function f(r). Besides, we obtain the bounds on the free parameters of the extended solution to avoid new singularities. Furthermore, we show the finitude of all thermodynamic parameters of the solution such as the effective density ρ ~ , radial p ~ r and tangential p ~ t pressure for different values of parameter α and the total electric charge Q. Finally, the behavior of some scalar invariants, namely the Ricci R and Kretshmann R μ ν ω ϵ R μ ν ω ϵ scalars are analyzed. It is also remarkable that, after an appropriate limit, the deformed Schwarzschild black hole solution always can be recovered. [ABSTRACT FROM AUTHOR]