In this article, we have presented a static anisotropic solution of stellar compact objects for self-gravitating system by using minimal geometric deformation techniques in the framework of embedding ...class one space-time. For solving of this coupling system, we deform this system into two separate system through the geometric deformation of radial components for the source function
λ
(
r
)
by mapping:
e
-
λ
(
r
)
→
e
-
λ
~
(
r
)
+
β
g
(
r
)
, where
g
(
r
) is deformation function. The first system corresponds to Einstein’s system which is solved by taking a particular generalized form for source function
λ
~
(
r
)
while another system is solved by choosing well-behaved deformation function
g
(
r
). To test the physical viability of this solution, we find complete thermodynamical observable as pressure, density, velocity, and equilibrium condition via. TOV equation etc. In addition to the above, we have also obtained the moment of inertia (
I
), Kepler frequency (
v
), compression modulus (
K
e
) and stability for this coupling system. The
M
–
R
curve has been presented for obtaining the maximum mass and corresponding radius of the compact objects.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We attempt to study a singularity-free model for the spherically symmetric anisotropic strange stars under Einstein’s general theory of relativity by exploiting the Tolman–Kuchowicz (Tolman in Phys ...Rev 55:364,
1939
; Kuchowicz in Acta Phys Pol 33:541,
1968
) metric. Further, we have assumed that the cosmological constant
Λ
is a scalar variable dependent on the spatial coordinate
r
. To describe the strange star candidates we have considered that they are made of strange quark matter distribution, which is assumed to be governed by the MIT bag equation of state. To obtain unknown constants of the stellar system we match the interior Tolman–Kuchowicz metric to the exterior modified Schwarzschild metric with the cosmological constant, at the surface of the system. Following Deb et al. (Ann Phys 387:239,
2017
) we have predicted the exact values of the radii for different strange star candidates based on the observed values of the masses of the stellar objects and the chosen parametric values of the
Λ
as well as the bag constant
B
. The set of solutions satisfies all the physical requirements to represent strange stars. Interestingly, our study reveals that as the values of the
Λ
and
B
increase the anisotropic system become gradually smaller in size turning the whole system into a more compact ultra-dense stellar object.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this article we present a class of relativistic solutions describing spherically symmetric and static anisotropic stars in hydrostatic equilibrium. For this purpose, we consider a particularized ...metric potential, namely, Buchdahl ansatz Phys. Rev. D 116, 1027 (1959). which encompasses almost all the known analytic solutions to the spherically symmetric, static Einstein equations with a perfect fluid source, including, in particular, the Vaidya-Tikekar and Finch-Skea. We developed the model by considering an anisotropic spherically symmetric static general relativistic configuration that has a significant effect on the structure and properties of stellar objects. We have considered eight different cases for generalized Buchdahl dimensionless parameter K and analyzed them in a uniform manner. As a result it turns out that all the considered cases are valid at every point in the interior spacetime. In addition to this, we show that the model satisfies all the energy conditions and maintains the hydrostatic equilibrium equation. In the frame work of anisotropic hypothesis, we consider analogue objects with similar mass and radii, such as LMC X-4, SMC X-1, EXO 1785-248 etc. to restrict the model parameter arbitrariness. Also, establishing a relation between pressure and density in the form of P=P(ρ), we demonstrate that equation of state (EoS) can be approximated to a linear function of density. Despite the simplicity of this model, the obtained results are satisfactory.
In this paper, we consider wormhole geometries in the context of the teleparallel equivalent of general relativity (TEGR) as well as f(T) gravity. The TEGR is an alternative geometrical formulation ...of Einstein's general relativity, where modified teleparallel gravity or f(T) gravity has been invoked as an alternative approach for explaining an accelerated expansion of the universe. We present the analytical solutions under the assumption of spherical symmetry and the existence of a conformal Killing vectors to proceed a more systematic approach in searching for exact wormhole solutions. More preciously, the existence of a conformal symmetry places restrictions on the model. Considering the field equations with a diagonal tetrad and anisotropic distribution of the fluid, we study the properties of traversable wormholes in TEGR that violates the weak and the null energy conditions at the throat and its vicinity. In the second part, wormhole solutions are constructed in the framework of f(T) gravity, where T represents torsion scalar. As a consistency check, we also discuss the behavior of energy conditions with a viable power-law f(T) model and the corresponding shape functions. In addition, a wide variety of solutions are deduced by considering a linear equation of state relating the density and pressure, for the isotropic and anisotropic pressure, independently of the shape functions, and various phantom wormhole geometries are explored.
A physically reasonable anisotropic stellar model is constructed with the help of the gravitational decoupling via complete geometric deformation (CGD) technique under the condition of vanishing ...complexity factor Contreras and Stuchlik in Eur Phys J C 82:706 2022; Herrera, in Phys Rev D 97:044010, 2018. The source splits into a perfect fluid and an anisotropic distribution. The Finch Skea metric proves a useful seed solution to solve the Einstein sector while the condition of vanishing complexity is invoked to solve the remaining anisotropic system of equations. A comprehensive battery of tests for physical significance is imposed on the model. Through a careful choice of parameter space, it is demonstrated that the model is regular, stable, and contains a surface of vanishing pressure establishing its boundary. Matching with the exterior metric is also achieved. Finally, the energy flows between the two sectors of the source fluid are studied graphically.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, we attempt to find an anisotropic solution for a compact star generated by gravitational decoupling in
f
(
Q
)-gravity theory having a null complexity factor. To do this, we initially ...derive the complexity factor condition in
f
(
Q
) gravity theory using the definition given by Herrera (Phys Rev D 97:044010, 2018) and then derived a bridge equation between gravitational potentials by assuming complexity factor to be zero (Contreras and Stuchlik in Eur Phys J C 82:706, 2022). Next, we obtain two systems of equations using the complete geometric deformation (CGD) approach. The first system of equations is assumed to be an isotropic system in
f
(
Q
)-gravity whose isotropic condition is similar to GR while the second system is dependent on deformation functions. The solution of the first system is obtained by Buchdahl’s spacetime geometry while the governing equations for the second system are solved through the mimic constraint approach along with vanishing complexity condition. The novelty of our work is to generalize the perfect fluid solution into an anisotropic domain in
f
(
Q
)-gravity theory with zero complexity for the first time. We present the solution’s analysis to test its physical viability. We exhibit that the existence of pressure anisotropy due to gravitational within the self-gravitating bounded object plays a vital role to stabilize the
f
(
Q
) gravity system. In addition, we show that the constant involved in the solution controls the direction of energy flow between the perfect fluid and generic fluid matter distributions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recently it has been proposed that the Gauss-Bonnet coupling parameter of Lovelock gravity may suitably be rescaled in order to admit physically viable models of celestial phenomena such that higher ...curvature effects are active in standard four dimensions as opposed to the usual higher dimensions. We investigate the consequences of this modification in the context of stellar modelling. The evolution of perfect fluid distributions is governed by the pressure isotropy condition and through stipulation of one of the metric potentials complete models emerge from solutions of the master differential equation. New classes of exact solution with this approach have been reported. One particular model is analysed in detail and shown to comport with elementary physical requirements demanded of realistic compact stars suggesting that the modified theory is not inconsistent with observations.
We consider the f(R,T) theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy–momentum tensor, to study static ...spherically symmetric wormhole geometries sustained by matter sources with isotropic pressure. According to restrictions on the wormhole geometries, we carefully adopt different strategies to construct solutions with the properties and characteristics of wormholes. Using an utterly general procedure, we provide several examples of wormholes in which the matter threading the wormhole throat satisfies all of the energy conditions and discuss general mechanisms for finding them. Finally, we postulate a smooth transformation for simplifying the nonlinear field equations and have more consistent results than the other ones to conclude that the results can be viewed as specific exact wormhole solutions without exotic matter.
•Wormhole geometries in the framework of f(R, T) theory of gravity.•Wormhole solutions have been found for a specific shape function.•These solutions are supported by a matter content that satisfies the NEC.
In the present paper, we focused on exploring the possibility of providing a new class of exact solutions for viable anisotropic stellar systems by means of the massive Brans–Dicke (BD) theory of ...gravity. In this respect, we used the decoupling of gravitational sources by minimal geometric deformation (MGD) (e−η=Ψ+βh) for compact stellar objects in the realm of embedding class-one space-time to study anisotropic solutions for matter sources through the modified Einstein field equations. For this purpose, we used the ansatz for Ψ relating to the prominent, well-known and well-behaved Finch–Skea model via Karmarkar condition, and the determination scheme for deformation function h(r) was proposed via mimic requirement on radial pressure component: θ11(r)=pr(r) and matter density: θ00(r)=ρ(r) for the anisotropic sector. Moreover, we analyzed the main physical highlights of the anisotropic celestial object by executing several physical tests for the case θ11(r)=pr(r). We have clearly shown how the parameters α, β and ωBD introduced by massive BD gravity via the MGD approach incorporating the anisotropic profile of the matter distribution have an immense effect on many physical parameters of compact bodies such as LMC X-4, LMC X-4, Her X-1, 4U 1820-30, 4U 1608-52, SAX J1808.4–658 and many others that can be fitted.
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