Anisotropic compact stars: Constraining model parameters to account for physical features of tidal Love numbers

This work is to introduce a new kind of modified gravitational theory, named as [Formula: see text] (also [Formula: see text]) gravity, where [Formula: see text] is the Ricci scalar, [Formula: see text] is Gauss–Bonnet invariant and [Formula: see text] is the trace of the energy–momentum tensor. With the help of different models in this gravity, we investigate some physical features of different relativistic compact stars. For this purpose, we develop the effectively modified field equations, conservation equation, and the equation of motion for test particle. Then, we check the impact of additional force (massive test particle followed by a nongeodesic line of geometry) on compact objects. Furthermore, we took three notable stars named as [Formula: see text], [Formula: see text] and [Formula: see text]. The physical behavior of the energy density, anisotropic pressures, different energy conditions, stability, anisotropy, and the equilibrium scenario of these strange compact stars are analyzed through various plots. Finally, we conclude that the energy conditions hold, and the core of these stars is so dense.

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Simple Linear Modeling Approach for Linking Hydrological Model Parameters to the Physical Features of a River Basin

Water Resources Management ◽

10.1007/s11269-015-0996-9 ◽

2015 ◽

Vol 29 (9) ◽

pp. 3265-3289 ◽

Cited By ~ 4

Author(s):

Chengcheng Huang ◽

Guoqiang Wang ◽

Xiaogu Zheng ◽

Jingshan Yu ◽

Xinyi Xu

Keyword(s):

River Basin ◽

Hydrological Model ◽

Model Parameters ◽

Linear Modeling ◽

Modeling Approach ◽

Physical Features

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A study on charged compact stars

International Journal of Modern Physics D ◽

10.1142/s0218271819500536 ◽

2019 ◽

Vol 28 (03) ◽

pp. 1950053 ◽

Cited By ~ 3

Author(s):

S. K. Maurya ◽

Saibal Ray ◽

Abdul Aziz ◽

M. Khlopov ◽

P. Chardonnet

Keyword(s):

Maxwell Equations ◽

Stellar System ◽

Compact Stars ◽

Physical Analysis ◽

Field Equations ◽

Electromagnetic Mass ◽

Regular Solutions ◽

Mass Model ◽

Class 1 ◽

Physical Features

In this paper, the Einstein–Maxwell spacetime is considered for compact stellar system. To find out solutions of the field equations, we adopt a finite and positive well-behaved metric potential. Under this particular choice, we therefore develop the expressions of the physical features, such as mass, charge, density and pressure, for stellar system in embedding class 1 spacetime. It is observed that all these features are physically viable. In the model, some known compact stars, viz. [Formula: see text] 1820–30, [Formula: see text] 1608–52 and [Formula: see text] 1745–248 [Formula: see text] are studied successfully through physical analysis. It is also interesting to note that the obtained set of regular solutions to the Einstein–Maxwell equations represents an electromagnetic mass model for isotropic fluid without invoking any negative pressure.

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Dynamics of an Anisotropic Universe inf(R,T)Theory

Advances in High Energy Physics ◽

10.1155/2016/8543560 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

B. Mishra ◽

Sankarsan Tarai ◽

S. K. Tripathy

Keyword(s):

Power Law ◽

Modified Gravity ◽

Bianchi Type ◽

Energy Momentum Tensor ◽

Momentum Tensor ◽

Model Parameters ◽

Anisotropic Universe ◽

Expansion Of The Universe ◽

Physical Features ◽

The Universe

Dynamics of an anisotropic universe is studied inf(R,T)gravity using a rescaled functionalf(R,T), whereRis the Ricci Scalar andTis the trace of energy-momentum tensor. Three models have been constructed assuming a power law expansion of the universe. Physical features of the models are discussed. The model parameters are constrained from a dimensional analysis. It is found from the work that the anisotropic Bianchi typeVIh(BVIh) model in the modified gravity generally favours a quintessence phase when the parameterhis either-1or0. We may not get viable models in conformity with the present day observation forh=1.

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An analytical anisotropic compact stellar model of embedding class I

Modern Physics Letters A ◽

10.1142/s0217732321500280 ◽

2021 ◽

Vol 36 (05) ◽

pp. 2150028

Author(s):

Lipi Baskey ◽

Shyam Das ◽

Farook Rahaman

Keyword(s):

Radial Pressure ◽

Stellar Model ◽

Compact Objects ◽

Compact Stars ◽

Model Parameters ◽

Field Equations ◽

Principal Stresses ◽

Schwarzschild Solution ◽

Spherical Fluid ◽

Physical Profile

A class of solutions of Einstein field equations satisfying Karmarkar embedding condition is presented which could describe static, spherical fluid configurations, and could serve as models for compact stars. The fluid under consideration has unequal principal stresses i.e. fluid is locally anisotropic. A certain physically motivated geometry of metric potential has been chosen and codependency of the metric potentials outlines the formation of the model. The exterior spacetime is assumed as described by the exterior Schwarzschild solution. The smooth matching of the interior to the exterior Schwarzschild spacetime metric across the boundary and the condition that radial pressure is zero across the boundary lead us to determine the model parameters. Physical requirements and stability analysis of the model demanded for a physically realistic star are satisfied. The developed model has been investigated graphically by exploring data from some of the known compact objects. The mass-radius (M-R) relationship that shows the maximum mass admissible for observed pulsars for a given surface density has also been investigated. Moreover, the physical profile of the moment of inertia (I) thus obtained from the solutions is confirmed by the Bejger–Haensel concept.

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The possibility of twin star solutions in a model based on lattice QCD thermodynamics

The European Physical Journal C ◽

10.1140/epjc/s10052-020-08779-x ◽

2021 ◽

Vol 81 (1) ◽

Author(s):

P. Jakobus ◽

A. Motornenko ◽

R. O. Gomes ◽

J. Steinheimer ◽

H. Stoecker

Keyword(s):

Neutron Stars ◽

Lattice Qcd ◽

Model Equation ◽

Compact Stars ◽

Model Parameters ◽

Bag Model ◽

First Order ◽

Stellar Masses ◽

First Order Phase

AbstractThe properties of compact stars and in particular the existence of twin star solutions are investigated within an effective model that is constrained by lattice QCD thermodynamics. The model is modified at large baryon densities to incorporate a large variety of scenarios of first order phase transitions to a phase of deconfined quarks. This is achieved by matching two different variants of the bag model equation of state, in order to estimate the role of the Bag model parameters on the appearance of a second family of neutron stars. The produced sequences of neutron stars are compared with modern constrains on stellar masses, radii, and tidal deformability from astrophysical observations and gravitational wave analyses. It is found that those scenarios in our analysis, in which a third family of stars appeared due to the deconfinement transition, are disfavored from astrophysical constraints.

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Charged stars in 4D Einstein–Gauss–Bonnet gravity

The European Physical Journal C ◽

10.1140/epjc/s10052-021-09585-9 ◽

2021 ◽

Vol 81 (9) ◽

Author(s):

Ayan Banerjee ◽

Sudan Hansraj ◽

Lushen Moodly

Keyword(s):

Graphical Analysis ◽

Compact Objects ◽

Gravity Theory ◽

Compact Stars ◽

Model Parameters ◽

The Novel ◽

Coupling Constant ◽

Curvature Effects ◽

New Exact Solutions ◽

Local Gravity

AbstractAn alternative gravity theory that has attracted considerable attention recently is the novel four-dimensional Einstein–Gauss–Bonnet (4EGB) gravity. This idea was proposed to bypass the Lovelock’s theorem and to permit nontrivial higher curvature effects on the four-dimensional local gravity. In this approach, the Gauss–Bonnet (GB) coupling constant $$\alpha $$ α is rescaled by a factor of $$\alpha /(D -4)$$ α / ( D - 4 ) in D dimensions and taking the limit $$D \rightarrow 4$$ D → 4 . In this article, we analyze the effects of charge on static compact stars in the regularized 4D EGB gravity theory. Two classes of new exact solutions are found for a particular choice of the gravitational potential and assuming a relationship between the electric field intensity and the spatial potential. A graphical analysis indicates that the matter and electromagnetic variables are well behaved for specific values of the parameter space. Finally, based on physical grounds appropriate bounds on the model parameters we show that compact objects with the value of adiabatic index $$\gamma $$ γ is consistent with expectations.

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Stationary and axisymmetric configurations of compact stars with extremely strong and highly localized magnetic fields

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311007009 ◽

2010 ◽

Vol 6 (S274) ◽

pp. 232-235

Author(s):

Kotaro Fujisawa ◽

Shin'ichiro Yoshida ◽

Yoshiharu Eriguchi

Keyword(s):

Magnetic Fields ◽

Current Density ◽

Compact Stars ◽

Model Parameters ◽

Flux Function ◽

Narrow Region ◽

Deep Interior ◽

Equilibrium Configurations ◽

Basic Equations ◽

New Formulation

AbstractUsing a new formulation to compute structures of stationary and axisymmetric magnetized barotropic stars in Newtonian gravity, we have succeeded in obtaining numerically exact models of stars with extremely high interior magnetic fields. In this formulation, there appear four arbitrary functions of the magnetic flux function from the integrability conditions among the basic equations. Since in our new formulation these arbitrary functions appear in the expression of the current density, configurations with different current distributions can be specified by choosing the forms of the arbitrary functions.By choosing appropriate forms for the four arbitrary functions, we have solved many kinds of equilibrium configurations both with poloidal and toroidal magnetic fields. Among them, by choosing special form for the toroidal current density, we have been able to obtain magnetized stars which have extremely strong poloidal magnetic fields deep inside the core region near the symmetric axis. By adopting the appropriate model parameters for the neutron stars, the magnetic fields could be 1014 ~ 1015 G on the surfaces and be about 1017 G in the deep interior regions. For other model parameters appropriate for white dwarfs, the magnetic fields could be around 107 ~ 108 G (surface regions) and 109 ~ 1010 G (core regions). It is remarkable that the regions with very strong interior magnetic fields are confined to a very narrow region around the symmetric axis in the central part of the stars. The issues of stability of these configurations and of evolutionary paths to reach such configurations need to be investigated in the future work.

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Relating BTOPMC model parameters to physical features of MOPEX basins

Journal of Hydrology ◽

10.1016/j.jhydrol.2005.07.006 ◽

2006 ◽

Vol 320 (1-2) ◽

pp. 84-102 ◽

Cited By ~ 27

Author(s):

Tianqi Ao ◽

Hiroshi Ishidaira ◽

Kuniyoshi Takeuchi ◽

Anthony S. Kiem ◽

Junich Yoshitari ◽

...

Keyword(s):

Model Parameters ◽

Physical Features

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Relativistic compact stars in Tolman spacetime via an anisotropic approach

The European Physical Journal C ◽

10.1140/epjc/s10052-021-09340-0 ◽

2021 ◽

Vol 81 (6) ◽

Author(s):

Piyali Bhar ◽

Pramit Rej ◽

P. Mafa Takisa ◽

M. Zubair

Keyword(s):

Graphical Representation ◽

Dimensional Space ◽

Compact Star ◽

Compact Stars ◽

Stellar Structure ◽

Energy Conditions ◽

Anisotropic Pressure ◽

Model Parameters ◽

Theory Of Relativity ◽

Field Equations

AbstractIn this present work, we have obtained a singularity-free spherically symmetric stellar model with anisotropic pressure in the background of Einstein’s general theory of relativity. The Einstein’s field equations have been solved by exploiting Tolman ansatz [Richard C Tolman, Phys. Rev. 55:364, 1939] in $$(3+1)$$ ( 3 + 1 ) -dimensional space-time. Using observed values of mass and radius of the compact star PSR J1903+327, we have calculated the numerical values of all the constants from the boundary conditions. All the physical characteristics of the proposed model have been discussed both analytically and graphically. The new exact solution satisfies all the physical criteria for a realistic compact star. The matter variables are regular and well behaved throughout the stellar structure. Constraints on model parameters have been obtained. All the energy conditions are verified with the help of graphical representation. The stability condition of the present model has been described through different testings.

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