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In this article, using gravitational decoupling by means of minimal geometric deformation approach, we obtain a new spherically symmetric and static black hole solution. To progress, we close the system by assuming that the average pressure of the θ -sector is vanishing. Also, we tackle the problem regarding how, for a given minimally deformed black hole solution, one can connect it to a wormhole space–time. [ABSTRACT FROM AUTHOR]

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 article, new wormhole solutions in the framework of General Relativity are presented. Taking advantage of gravitational decoupling by means of minimal geometric deformation approach and, the so–called noncommutative geometry Gaussian and Lorentzian density profiles, the seminal Morris–Thorne space–time is minimally deformed providing new asymptotically wormhole solutions. Constraining the signature of some parameters, the dimensionless constant α is bounded using the flare–out and energy conditions. In both cases, this results in an energy–momentum tensor that violates energy conditions, thus the space–time is threading by an exotic matter distribution. However, it is possible to obtain a positive defined density at the wormhole throat and its neighborhood. To further support the study a thoroughly graphical analysis has been performed. [ABSTRACT FROM AUTHOR]

In this paper, we studied the bouncing behavior of the cosmological models formulated in the background of the Hubble function in the F (R , G) theory of gravity, where R and G , respectively, denote the Ricci scalar and Gauss–Bonnet invariant. The actions of the bouncing cosmology are studied with a consideration of the different viable models that can resolve the difficulty of singularity in standard Big Bang cosmology. Both models show bouncing behavior and satisfy the bouncing cosmological properties. Models based on dynamical, deceleration, and energy conditions indicate the accelerating behavior at the late evolution time. The phantom at the bounce epoch is analogous to quintessence behavior. Finally, we formulate the perturbed evolution equations and investigate the stability of the two bouncing solutions. [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]

In this paper we present two new classes of solutions describing compact objects within the framework of five‐dimensional Einstein‐Gauss‐Bonnet (EGB) gravity. We employ the Complete Geometric Deformation (CGD) formalism which extends the Minimal Geometric Deformation (MGD) technique adopted in earlier investigations to generate anisotropic models from known isotropic solutions. The two solutions presented arise from mimicking the constraint for the pressure and density respectively which generate independent deformation functions. Rigorous physical tests show that contributions from CDG suppress the effective pressure but enhances the effective density and mass of the compact object, with the suppression/enhancement being modified by the EGB coupling constant. One of the highlights in our findings is that the deformation function along the radial component in CDG is nonzero at the boundary when we mimic both the pressure and density while in MGD we observe a vanishing of this deformation function at the boundary of the fluid configuration only for the pressure constraint. The difference in behavior of the deformation function at the surface predicts different stellar characteristics such as mass‐to‐radius and surface redshifts. In this paper two new classes of solutions are presented describing compact objects within the framework of five‐dimensional Einstein‐Gauss‐Bonnet (EGB) gravity. The Complete Geometric Deformation (CGD) formalism will be employed which extends the Minimal Geometric Deformation (MGD) technique adopted in earlier investigations to generate anisotropic models from known isotropic solutions. The two solutions presented arise from mimicking the constraint for the pressure and density respectively which generate independent deformation functions. Rigorous physical tests show that contributions from CDG suppress the effective pressure but enhances the effective density and mass of the compact object, with the suppression/enhancement being modified by the EGB coupling constant. One of the highlights in the findings is that the deformation function along the radial component in CDG is nonzero at the boundary when one mimics both the pressure and density while in MGD one observes a vanishing of this deformation function at the boundary of the fluid configuration only for the pressure constraint. The difference in behavior of the deformation function at the surface predicts different stellar characteristics such as mass‐to‐radius and surface redshifts. [ABSTRACT FROM AUTHOR]

A spherically symmetric solution of the field equations of the Hořava–Lifshitz gravity–gauge vector interaction theory is obtained and analyzed. It describes a charged throat. The solution exists provided a restriction on the relation between the mass and charge is satisfied. The restriction reduces to the Reissner–Nordström one in the limit in which the coupling constants tend to the relativistic values of General Relativity. We introduce the correct charts to describe the solution across the entire manifold, including the throat connecting an asymptotic Minkowski space-time with a singular 3+1 dimensional manifold. The solution external to the throat on the asymptotically flat side tends to the Reissner–Nordström space-time at the limit when the coupling parameter, associated with the term in the low energy Hamiltonian that manifestly breaks the relativistic symmetry, tends to zero. Also, when the electric charge is taken to be zero the solution becomes the spherically symmetric and static solution of the Hořava–Lifshitz gravity. [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]

This work is devoted to the study of relativistic anisotropic compact objects. To obtain this class of solutions of the Einstein field equations, we have developed a general scheme to generate the metric of the space–time describing the interior of the compact structure. This approach is based on the class I space–time and the extended gravitational decoupling by means of an extended geometric deformation (EGD). The class I condition provides a differential equation relating both metric potential ν and λ , whilst the EGD translates the metric potentials to ν = ξ + β h (r) and λ = - ln [ μ + β f (r) ] , where h(r) and f(r) are the deformation functions and β a dimensionless constant. In this case the pair { ξ , μ } represents the seed solution satisfying the class I condition without any deformation. Once the deformed metric potentials are inserted into the class I, the main task is to obtain h(r) or f(r). So, in this case a particular ansatz for h(r) is considered in conjunction with β = 0.5 to get f(r). In order to check feasibility of our model, we have performed a thoroughly physical, mathematical and graphical analysis. [ABSTRACT FROM AUTHOR]

We implement the gravitational decoupling through the minimal geometric deformation method and explore its effect on exterior solutions by imposing a regularity condition in the Tolman–Oppenheimer–Volkoff equation of the decoupling sector. We obtain that the decoupling function can be expressed formally in terms of an integral involving the gtt component of the metric of the seed solution. As a particular example, we implement the method by using the Schwarzschild exterior as a seed and we obtain that the asymptotic behavior of the extended geometry corresponds to a manifold with constant curvature. [ABSTRACT FROM AUTHOR]

A spherically symmetric wormhole family of solutions, with null red-shift, in the context of f(R)-gravity is presented. The model depends on two parameters: m and β and meets all requirements to be an asymptotically and traversable wormhole. To solve the field equations, an EoS is imposed: p ⊥ = - ρ . It is found that for m = 1 the solution satisfies the null energy condition, although F (R) < 0 everywhere. For m = 0 , the model satisfies the null energy condition away from the throat, where the function F(R) is everywhere positive and together with dF(R)/dR vanish at the throat of the wormhole. This fact is beyond the scope of the non-existence theorem. Furthermore, the cosmological viability of the model, to address the late – time accelerated epoch, is analyzed on the background of a flat FLRW space-time. The model satisfies consistency of local gravity tests, stability under cosmological perturbations, ghosts free and stability of the de Sitter point. [ABSTRACT FROM AUTHOR]

In this work we investigate the extra packing of mass within the framework of gravitational decoupling by means of Minimal Geometric Deformation approach. It is shown that, after a suitable set of the free parameters involved, the like-Tolman IV solution extended by Minimal Geometric Deformation not only acquire extra packing of mass but it corresponds to a stable configuration according to the adiabatic index criteria. Additionally, it is shown that the extra packing condition induce a lower bound on the compactness parameter of the seed isotropic solution and a stringent restriction on the decoupling parameter. [ABSTRACT FROM AUTHOR]

In this work an analytic fluid sphere built on the well-known Tolman IV space–time is obtained. This toy model is sourced by an imperfect fluid distribution with a dark matter component. The anisotropic behavior is introduced into the system via gravitational decoupling by means of minimal geometric deformation. In this regard, the temporal component of the θ -sector has been interpreted as the dark side of the matter distribution. To validate the feasibility of the salient model a detailed graphical analysis is performed, supported by real observational data corresponding to some strange star candidates. Besides, the impacts of minimal geometric deformation approach on the main macro physical observables ı.e, the total mass M, compactness factor u and surface gravitational red-shift z s are discussed. [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 build a relativistic anisotropic admissible compact structures. To do so we combine the class I approach with gravitational decoupling in order to generate the deformation function f(r). As an example we have re-anisotropized two anisotropic matter distributions previously obtained by the class I procedure. To produce all the graphical study supporting this analysis, we have considered the data corresponding to the compact object 4U 1538-52, SMC X-1 and LMC X-4 for model 1 and Cen X-3 for model 2. In considering the last one, we have taken the constant parameter α to be { - 0.3 ; 0.1 ; 0.3 } . It is found that the resulting models satisfy all the general requirement in order to represent or describe realistic compact structures such as neutron or quark stars. [ABSTRACT FROM AUTHOR]

We introduce the electromagnetic-gravitational coupling in the Hořava–Lifshitz framework, in 3 + 1 dimensions, by considering the Hořava–Lifshitz gravity theory in 4 + 1 dimensions at the kinetic conformal point and then performing a Kaluza–Klein reduction to 3 + 1 dimensions. The action of the theory is second order in time derivatives and the potential contains only higher order spacelike derivatives up to z = 4 , z being the critical exponent. These terms include also higher order derivative terms of the electromagnetic field. The propagating degrees of freedom of the theory are exactly the same as in the Einstein–Maxwell theory. We obtain the Hamiltonian, the field equations and show consistency of the constraint system. The conformal kinetic point is protected from quantum corrections by a second class constraint. At low energies the theory depends on two coupling constants, β and α . We show that the anisotropic field equations for the gauge vector is a deviation of the covariant Maxwell equations by a term depending on β - 1 . Consequently, for β = 1 , Maxwell equations arise from the anisotropic theory at low energies. We also prove that the anisotropic electromagnetic-gravitational theory at the IR point β = 1 , α = 0 , is exactly the Einstein–Maxwell theory in a gravitational gauge used in the ADM formulation of General Relativity. [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]

A Correction to this paper has been published: 10.1140/epjc/s10052-021-09179-5 [ABSTRACT FROM AUTHOR]

This article studies the thermodynamics phase transitions and critical phenomena of an FLRW cosmological model under truncated Kaniadakis's statistics. The EoS is derived from the corrected Friedmann field equations and the thermodynamics unified first law. To approach thermodynamics, we use an approximation for K S AH ≪ 1 , on the cosmological equation, and also check the validity of our approximation. Then for different values from Kaniadakis parameter K , order O (10 − 37) for the relic-abundance, O (10 − 84) for 7Li-abundance and O (10 − 125) in the recombination era, the EoS reveals non-trivial critical points where a first-order phase transition occurs a sort of a van der Waals fluid. Interestingly, the numerical values of the critical exponents are the same as those of the van der Waals system. Besides, to obtain more insights into the thermodynamics description, the so-called Ruppeiner's geometry is studied through the normalized scalar curvature, disclosing this invariant zone where the system undergoes repulsive/attractive interactions. Near the critical point, this curvature provides again the same critical exponent and universal constant value as for van der Waals fluid. Despite the similarity, both systems are quite different because the present one considers a relativistic entropy (Kaniadakis entropy) while the Van der Waals gas responds to a classical entropy (Maxwell-Boltzmann). [ABSTRACT FROM AUTHOR]

This work is devoted to the study of analytic wormhole solutions within the framework of f(R)$f(R)$ gravity theory. To check the possibility of having wormhole structures satisfying energy conditions, by means of the class I approach the pair {Φ(r),b(r)}$\lbrace \Phi (r), b(r)\rbrace$ describing the wormhole geometry has been obtained. Then, in conjunction with a remarkably f(R)$f(R)$ gravity model, the satisfaction of the null and weak energy conditions at the wormhole throat and its neighborhood is investigated. To do so, some constant parameters have been bounded restricting the space parameter. In this concern, the f(R)$f(R)$ gravity model and its derivatives are playing a major role, specially in considering the violation of the non–existence theorem. Furthermore, the shape function should be bounded from above by the Gronwall–Bellman shape function, where the red–shift function plays a relevant role. By analyzing the main properties at the spatial stations and tidal accelerations at the wormhole throat, possibilities and conditions for human travel are explored. This work is devoted to the study of analytic wormhole solutions within the framework of f(R) gravity theory. To check the possibility of having wormhole structures satisfying the energy conditions, by means of the class I approach the pair {Φ(r),b(r)}$\lbrace \Phi (r), b(r)\rbrace$ describing the wormhole geometry has been obtained. Then, in conjunction with a remarkably f(R) gravity model, the satisfaction of the null and weak energy conditions at the wormhole throat and its neighborhood is investigated. To do so, some constant parameters have been bounded restricting the space parameter. In this concern, the f(R) gravity model and its derivatives are playing a major role, specially in considering the violation of the non‐existence theorem. Furthermore, the shape function should be bounded from above by the Gronwall‐Bellman shape function, where the red‐shift function plays a relevant role. By analyzing the main properties at the spatial stations and tidal accelerations at the wormhole throat, possibilities and conditions for human travel are explored. [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]

In this work, we employ the class I approach to obtain wormhole solutions in the framework of general relativity in two different ways. Firstly, we propose a suitable red-shift function in order to find its associated shape function. Afterwards, we solve the inverse problem, namely, we impose the well known Morris–Thorne shape function to obtain the corresponding red-shift. It is found that, on one hand, the first model satisfies all the general requirements of a traversable wormhole. On the other hand, although the second solution violates the null energy condition at the throat as expected, the solution is not asymptotically flat. The study is complemented by analyzing the hydrostatic balance of the system by means of the modified relativistic hydrostatic equilibrium equation. • Analytical wormhole solutions by embedding class I in general relativity. • Morris–Thorne wormhole space–time with a non null red-shift function. • The solutions fulfill the geometrical requirements to represent traversable wormholes. [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]

In this article, we develop a theoretical framework to study compact stars in Einstein gravity with the Gauss–Bonnet (GB) combination of quadratic curvature terms. We mainly analyzed the dependence of the physical properties of these compact stars on the Gauss–Bonnet coupling strength. This work is motivated by the relations that appear in the framework of the minimal geometric deformation approach to gravitational decoupling (MGD-decoupling), we establish an exact anisotropic version of the interior solution in Einstein–Gauss–Bonnet gravity. In fact, we specify a particular form for gravitational potentials in the MGD approach that helps us to determine the decoupling sector completely and ensure regularity in interior space-time. The interior solutions have been (smoothly) joined with the Boulware–Deser exterior solution for 5D space-time. In particular, two different solutions have been reported which comply with the physically acceptable criteria: one is the mimic constraint for the pressure and the other approach is the mimic constraint for density. We present our solution both analytically and graphically in detail. [ABSTRACT FROM AUTHOR]

In this work we have extended the Maurya-Gupta isotropic fluid solution to Einstein field equations to an aniso-tropic domain. To do so, we have employed the gravitational decoupling via the minimal geometric deformation approach. The present model is representing the strange star candidate LMC X-4. A mathematical, physical and graphical analysis, shown that the obtained model fulfills all the criteria to be an admissible solution of the Einstein field equations. Specifically, we have analyzed the regularity of the metric potentials and the effective density, radial and tangential pressures within the object, causality condition, energy conditions, equilibrium via Tolman-Oppenheimer-Volkoff equation and the stability of the model by means of the adiabatic index and the square of subliminal sound speeds. [ABSTRACT FROM AUTHOR]

The present paper provides a new exact and analytic solution of the Einstein-Maxwell field equations describing compact anisotropic charged stars satisfying the MIT bag model equation of state for quark matter. The model is obtained by assuming the Tolman-Kuchowicz spacetime geometry (Tolman, in Phys Rev 55:364, 1939; Kuchowicz, in Acta Phys Pol 33:541, 1968). Our stellar model is free from central singularity and obeys all the conditions for a realistic stellar object. The solution is smoothly matched with the exterior Reissner-Nordstrom spacetime in order to obtain the physical parameters of the system. An interesting phenomenon which arises in this model is the fact that the force due to the pressure anisotropy initially dominates the Coulomb repulsive force, nevertheless as the radius increases the electric force dominates the anisotropic one. This may be an additional mechanism required for stability and equilibrium against the gravitational collapse of the stellar object. Detailed analyses of the obtained model are also given with the help of graphical representations. [ABSTRACT FROM AUTHOR]

Durgapal’s fifth isotropic solution describing spherically symmetric and static matter distribution is extended to an anisotropic scenario. To do so we employ the gravitational decoupling through the minimal geometric deformation scheme. This approach allows to split Einstein’s field equations in two simply set of equations, one corresponding to the isotropic sector and other to the anisotropic sector described by an extra gravitational source. The isotropic sector is solved by the Durgapal’s model and the anisotropic sector is solved once a suitable election on the minimal geometric deformation is imposes. The obtained model is representing some strange stars candidates and fulfill all the requirements in order to be a well behaved physical solution to the Einstein’s field equations. [ABSTRACT FROM AUTHOR]

In the present article, we have constructed a static charged anisotropic compact star model of Einstein field equations for a spherically symmetric space-time geometry. Specifically, we have extended the charged isotropic Heintzmann solution to an anisotropic domain. To address this work, we have employed the gravitational decoupling through the so called minimal geometric deformation approach. The charged anisotropic model is representing the realistic compact objects such as RXJ1856-37 and SAXJ1808.4-3658(SS2). We have reported our results in details for the compact star RXJ1856-37 on the ground of physical properties such as pressure, density, velocity of sound, energy conditions, stability conditions, Tolman-Oppenheimer-Volkoff equation and redshift etc. [ABSTRACT FROM AUTHOR]

In the present paper, we analyze the well-known 2+1 dimensional black holes (assuming a non-vanishing cosmological constant) in light of the gravitational decoupling by the minimal geometric deformation approach. To illustrate our results, we consider the BTZ geometry as the seed solution to generate new anisotropic ones. To complement the study, the curvature scalars and the energy conditions are analyzed. [ABSTRACT FROM AUTHOR]

The present work is devoted to the study of anisotropic compact matter distributions within the framework of five-dimensional Einstein–Gauss–Bonnet gravity. To solve the field equations, we have considered that the inner geometry is described by Tolman–Kuchowicz spacetime. The Gauss–Bonnet Lagrangian L GB is coupled to the Einstein–Hilbert action through a coupling constant, namely α . When this coupling tends to zero general relativity results are recovered. We analyze the effect of this parameter on the principal salient features of the model, such as energy density, radial and tangential pressure and anisotropy factor. These effects are contrasted with the corresponding general relativity results. Besides, we have checked the incidence on an important mechanism: equilibrium by means of a generalized Tolman–Oppenheimer–Volkoff equation and stability through relativistic adiabatic index and Abreu's criterion. Additionally, the behavior of the subliminal sound speeds of the pressure waves in the principal directions of the configuration and the conduct of the energy-momentum tensor throughout the star are analyzed employing the causality condition and energy conditions, respectively. All these subjects are illuminated by means of physical, mathematical and graphical surveys. The M–I and the M–R graphs imply that the stiffness of the equation of state increases with α ; however, it is less stiff than GR. [ABSTRACT FROM AUTHOR]

In astronomy, the study of compact stellar remnants — white dwarfs, neutron stars, black holes — has attracted much attention for addressing fundamental principles of physics under extreme conditions in the core of compact objects. In a recent argument, Maurya et al. [Eur. Phys. J. C 77, 45 (2017)] have proposed an exact solution depending on a specific spacetime geometry. Here, we construct equilibrium configurations of compact stars for the same spacetime that make it interesting for modeling high density physical astronomical objects. All calculations are carried out within the framework of the five-dimensional Einstein–Gauss–Bonnet gravity. Our main interest is to explore the dependence of the physical properties of these compact stars depending on the Gauss–Bonnet coupling constant. The interior solutions have been matched to an exterior Boulware–Deser solution for 5 D spacetime. Our finding ensures that all energy conditions hold, and the speed of sound remains causal, everywhere inside the star. Moreover, we study the dynamical stability of stellar structure by taking into account the modified field equations using the theory of adiabatic radial oscillations developed by Chandrasekhar. Based on the observational data for radii and masses coming from different astronomical sources, we show that our model is compatible and physically relevant. [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]

In the present article, we discuss relativistic anisotropic solutions of Einstein field equations for the spherically symmetric line element under the class I condition. To do so we apply the embedding class one technique using Eisland condition. Within this approach, one arrives at a particular differential equation that links the two metric components e ν and e λ . In order to obtain the full space–time description inside the stellar configuration we ansatz the generalized form of metric component g rr corresponding to the Finch–Skea solution. Once the space–time geometry is specified we obtain the complete thermodynamic description i.e. the matter density ρ , the radial, and tangential pressures p r and p t , respectively. Graphical analysis shows that the obtained model respects the physical and mathematical requirements that all ultra-high dense collapsed structures must obey. The M–R diagram suggests that the solution yields stiffer EoS as parameter n increases. The M–I graph is in agreement with the concepts of Bejgar et al. (Mon Not R Astron Soc 364:635, 2005) that the mass at I max is lesser by few percent (for this solution ∼ 3 % ) from M max . This suggests that the EoSs is without any strong high-density softening due to hyperonization or phase transition to an exotic state. [ABSTRACT FROM AUTHOR]