We obtain a class of new anisotropic relativistic solution in Einstein Gauss-Bonnet (EGB) gravity with Finch-Skea metric in hydrostatic equilibrium. The relativistic solutions are employed to construct anisotropic stellar models for strange star with MIT Bag equation of state $ p_{r}= \frac{1}{3} \left( ρ- 4 B_{g}\right)$, where $B_{g}$ is the Bag constants. Considering the mass and radius of a known star PSR J0348+0432 we construct stellar models in the framework of higher dimensions. We also predict the mass and radius of stars for different model parameters. The Gauss-Bonnet coupling term ($α$) plays an important role in determining the density, pressure, anisotropy profiles and other features. The stability of the stellar models are probed analyzing the different energy conditions, variation of sound speed and adiabatic stability conditions inside the star. The central density and pressure of a star in EGB gravity are found to have higher values compared to that one obtains in Einstein gravity ($α=0$). We also explore the effect of extra dimensions for the physical features of a compact object. For this we consider $D=5$ and $D=6$ to obtain a realistic stellar model and found that in the formal case both positive and negative values of $α$ are allowed. But in the later case, only $α<0$ permits compact object in the Finch-Skea metric. We determine the best fit values of the model parameters for a number of observed stars for acceptable stellar models.
The static, charged, spherically symmetric matter distribution have been studied by considering polytropic equation of state. Two polytropic indices have been considered for study. The plots of density, radial pressure, tangential pressure, anisotropy and causality condition indicates the models are suitable to describe the relativistic polytropes.
In this paper a compact charged stellar model in the Finch and Skea background spacetime [{\it Class. Quantum Gravity} {\bf6}, 467 (1989)] is presented. The model has been developed by assuming a particular charge distribution within the stellar interior. The model is well behaved and can describe a large class of compact stars. Physical features of the model are studied and in particular we show how the presence of charge can have a non-negligible impact on the mass-radius ($M-R$) relationship of such class of stars.
The Bañados, Teitelboim and Zanelli\cite{BTZ} solution corresponding to the exterior space-time of a black hole in $(2+1)$ dimensions has been found to be very useful to understand various aspects relating to the gravitational field of a black hole. We present here a class of interior solutions corresponding to the BTZ exterior by making use of a model presented by Finch and Skea\cite{Finch} which was earlier found to be relevant for the description realistic stars in $(3+1)$ dimensions. We show physical viability of the model in lower dimensions as well.
Several new families of exact solution to the Einstein-Maxwell system of differential equations are found for anisotropic charged matter. The spacetime geometry is that of Finch and Skea which satisfies all criteria for physical acceptability. The exact solutions can be expressed in terms of elementary functions, Bessel functions and modified Bessel functions. When a parameter is restricted to be an integer then the special functions reduce to simple elementary functions. The uncharged model of Finch and Skea (Class. Quantum Grav. 6, 467 (1989)) and the charged model of Hansraj and Maharaj (In…
We present solutions to the Einstein-Maxwell system of equations in spherically symmetric gravitational fields for static interior spacetimes with a specified form of the electric field intensity. The condition of pressure isotropy yields three category of solutions. The first category is expressible in terms of elementary functions and does not have an uncharged limit. The second category is given in terms of Bessel functions of half-integer order. These charged solutions satisfy a barotropic equation of state and contain Finch-Skea uncharged stars. The third category is obtained in terms of …
In this paper we obtained some spherically stellar configurations that represent new models of dark energy stars specifying particular forms for gravitational potential and the electric field intensity which allows solve the Einstein-Maxwell field equations. We have chosen the metric potential proposed by Finch and Skea (1989). We found that the radial pressure, the anisotropy factor, energy density, metric coefficients, mass function, charge density are regular and well behaved in the stellar interior but the causality conditions and of strong energy are not satisfied. These models have great…
The popularity of the Finch-Skea ansatz to describe relativistic stellar model have encouraged us to study the analytic solutions of the Einstein field equation. We have presented a class of exact solutions to the field equations after considering the corresponding two cases: (i) positive value of anisotropic parameter, and (ii) absence of any anisotropy. Smooth matching of the interior solutions with the Schwarzschild exterior solution helped us to determine constants. The physical features of the solutions thus obtained have been studied both graphically and numerically with the specific pul…
The present work discusses about the existence of compact star model in the context of $f(R,T)$ gravity with $R$ as the Ricci scalar and $T$ as the trace of energy-momentum tensor $T_{μν}$. The model has been developed by considering the spherically symmetric spacetime consisting of isotropic fluid with $f(R,T)=R+2 βT$ with $β$ be the coupling parameter. The corresponding field equations are solved by choosing well known Finch-Skea {\em ansatz} [Finch, M.R., Skea, J.E.F.:{\it Class. Quantum Gravity} {\bf 6}, 467 (1989)]. For spacetime continuity we elaborate the boundary conditions by consider…
Present paper deals with the composition and modelling of compact dense astrophysical bodies under the framework of $f(R)$ gravity. The model is employed on various observed strange stars viz., SMC X-1, SAX J1808.4-3658, Swift J1818.0-1607, PSR J1614-2230 and PSR J0348+0432. Upon setting the appropriate value of dimensionless coupling parameter $λ$, the physical parameters such as the density, the radial and tangential pressures were obtained. Mass-Radius relation without presuming any equation of state is capable enough to accommodate all strange stars nearly having solar mass up to 2.5. The …
This manuscript explores the compact geometries by employing Karmarkar condition with the charged anisotropic source of matter distribution. For this purpose, we consider an explicit model by indulging $\mathrm{g}_{rr}$ metric potential obeying the Karmarkar condition. Moreover, we ansatz the time metric co-efficient following the approach by Adler. The crucial aspect of present investigation is the implication of the Bardeen model as an outer spacetime. Implementation of Bardeen approach turns out to be very interesting as this corresponds to the magnetic mono-pole gravitational remnants emer…
In the present article authors investigate the anisotropic stellar solutions admitting Finch-Skea symmetry (viable and non-singular metric potentials) in the presence of some exotic matter fields, such as: Bose-Einstein Condensate (BEC) dark matter, Kalb-Ramond fully anisotropic rank-2 tensor field from the low-energy string theory effective action, gauge field imposing $U(1)$ symmetry. Interior spacetime is matched with both Schwarzchild and Reissner-Nördstrom vacuum spacetimes for BEC, KB and gauge fields respectively. Further, we have studied energy conditions, Equation of State (EoS), radi…
In this article, we demonstrated a stellar model for compact star in presence of strange matter embedded in $D\ge4$ dimensional space-time defind by Finch-Skea metric. To study the relevant physical properties of the interior matter, we consider the equation of state $(henceforth~EOS)$ as proposed in MIT bag model given by $p=\frac{1}{3}(ρ-4B)$, where $B$ is termed as bag constant. The Mass-Radius relationships in four and higher dimensions are determined using the range of values of surface density through the relation $ρ_{s}=4B$ for which bulk strange matter may be a viable issue for compact…
A new model of anisotropic compact star is obtained in our present paper by assuming the pressure anisotropy. The proposed model is singularity free. The model is obtained by considering a physically reasonable choice for the metric potential $g_{rr}$ which depends on a dimensionless parameter `n'. The effect of $n$ is discussed numerically, analytically and through plotting. We have concentrated a wide range for n ($10\leq n \leq 1000$) for drawing the profiles of different physical parameters. The maximum allowable mass for different values of $n$ have been obtained by M-R plot. We have chec…
For a given Lovelock order $N$, it turns out that static fluid solutions of the pure Lovelock equation for a star interior have the universal behavior in all $n\geq 2N+2$ dimensions relative to an appropriately defined variable and the Vaidya-Tikekar parameter $K$, indicating deviation from sphericity of $3$-space geometry. We employ the Buchdahl metric ansatz which encompasses almost all the known physically acceptable models including in particular the Vaidya-Tikekar and Finch-Skea. Further for a given star radius, the constant density star, always described by the Schwarzschild interior sol…
The aim of this work is to obtain new analitical solutions for Einstein equations in the anisotropical domain. This will be done via the minimal geometric deformation (MGD) approach, which is a simple and systematical method that allow us to decouple the Einstein equations. It requires a perfect fluid known solution that we will choose to be Finch-Skeas(FS) solution. Two different constraints were applied, and in each case we found an interval of values for the free parameters, where necesarly other physical solutions shall live.
A class of solutions describing the interior of a static spherically symmetric compact anisotropic star is reported. The analytic solution has been obtained by utilizing the Finch and Skea ({\it Class. Quant. Grav.} {\bf 6} (1989) 467) ansatz for the metric potential $g_{rr}$ which has a clear geometric interpretation for the associated background space-time. Based on physical grounds appropriate bounds on the model parameters have been obtained and it has been shown that the model admits an equation of state (EOS) which is quadratic in nature.
In the present work we have investigated a new anisotropic solution for polytropic star in the framework of $4D$ Einstein-Gauss-Bonnet (EGB) gravity. The possibility of determining the masses and radii of compact stars which puts some limitations on equation of state (EoS) above the nuclear saturation density. For this purpose, the $4D$ EGB field equations are solved by taking a generalized polytropic equation of state (EoS) with Finch-Skea ansatz. The generalized solution for anisotropic model has been tested for different values of Gauss-Bonnet constant $α$ which satisfies all the physical c…
The field equations for static EGBM gravity are obtained and transformed to an equivalent form through a coordinate redefinition. A form for one of the metric potentials that generalises the spheroidal ansatz of Vaidya--Tikekar superdense stars and additionally prescribing the electric field intensity yields viable solutions. Some special cases of the general solution are considered and analogous classes in the Einstein framework are studied. In particular the Finch--Skea ansatz is examined in detail and found to satisfy the elementary physical requirements. These include positivity of pressur…
We construct an exact anisotropic star model with a linear barotropic equation of state and with Finch-Skea potential within the framework of pure Lovelock gravity. A comparison with the corresponding Einstein model in a suitable limit is easily deduced. Evidently higher curvature effects induced by the Lovelock contributions generate lower densities, pressures, surface tensions and anisotropy factors when compared to its Einstein counterpart. The maximum moment of inertia is attained for the Einstein case and hence it may be inferred that Lovelock effects soften the equation of state. The mod…
In this paper, we have introduced new viable solutions of Einstein-Maxwell field equations by incorporating the features of anisotropic matter distribution in the realm of General theory of Relativity ($GR$). For this procurement, we have employed a Finch-Skea spacetime along with a generalized polytropic equation of state ($EoS$). We have constructed various models of generalized polytropes by assuming the different choices of the polytropic index i.e.,$η=\frac{1}{2}, \frac{2}{3}, 1$ and $2$. The numerous physical characteristics of these considered models have been studied via graphical anal…
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 matric potential, namely, Buchdahl ansatz [Phys. Rev. D \textbf{116}, 1027 (1959).] which encompasses almost all the known analytic solutions to the spherically symmetric, static Einstein field equations(EFEs) with a perfect fluid source, including in particular the Vaidya-Tikekar and Finch-Skea. We here developed the model by considering an anisotropic spherically symmetric static general relativi…
We construct models of static spherical distributions of perfect fluid in trace--free Einstein gravity theory. The equations governing the gravitational field are equivalent to the standard Einstein's equations however, their presentation is manifestly different which motivates the question whether new information would emerge due to the nonlinearity of the field equations. The incompressible fluid assumption does not lead to the well known Schwarzschild interior metric of Einstein gravity and a term denoting the presence of a cosmological constant is present on account of the integration proc…
Hybrid compact stars with finite strange quark mass and dark energy: implications for astrophysical observations
IUCAA Centre for Astronomy Research and Development (ICARD), Department of Physics, Cooch Behar Panchanan Barma University（印度天体物理与宇宙学研究中心（IUCAA）天文研究与发展中心，库奇比哈尔潘查南巴玛大学物理系）
Properties of strange quark stars in $f(Q)$ gravity: A baryon number density-dependent perspective
Cooch Behar Panchanan Barma University（古奇比哈尔潘查南巴尔马大学）；Princess Nourah bint Abdulrahman University（公主诺拉·宾特·阿卜杜勒拉赫曼大学）；Aristotle University of Thessaloniki（塞萨洛尼基亚里士多德大学）；S.M. Nikolskii Mathematical Institute of the Peoples’ Friendship University of Russia (RUDN University)（俄罗斯人民友谊大学S.M.尼科利斯基数学研究所）
