scholarly journals A Generic Embedding Class-I Model via Karmarkar Condition in f ℛ , T Gravity

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
M. Zubair ◽  
Saira Waheed ◽  
Hina Javaid
Keyword(s):  
Coupling Parameter ◽  
Compact Star ◽  
Momentum Tensor ◽  
Class I ◽  
Physical Parameters ◽  
Star Model ◽  
Anisotropic Matter ◽  
Symmetric Geometry ◽  
Suitable Form ◽  
Relationship Of

In the present work, we investigate the existence of compact star model in the background of f ℛ , T gravity theory, where ℛ represents the Ricci scalar and T refers to the energy-momentum tensor trace. Here, we use Karmarkar condition for the interior stellar setup so that a complete and precise model following the embedding class-I strategy can be obtained. For this purpose, we assume anisotropic matter contents along with static and spherically symmetric geometry of compact star. As Karmarkar embedding condition yields a relationship of metric potentials, therefore we assume a suitable form for one of the metric components as e ϕ = a r 2 + b n − 1 r n + 1 , where a and b represent constants and n is a free parameter, and evaluate the other. We approximate the values of physical parameters like a , A , and B by utilizing the known values of mass and radius for the compact star Vela X-1. The validity of the acquired model is then explored for different values of coupling parameter λ graphically. It is found that the resulting solution is physically interesting and well-behaved.

scholarly journals A new class of relativistic model of compact stars of embedding class I

2017 ◽  
Vol 26 (09) ◽  
pp. 1750090 ◽  
Author(s):  
Piyali Bhar ◽  
Ksh. Newton Singh ◽  
Tuhina Manna
Keyword(s):  
Compact Star ◽  
Mass Function ◽  
Static Stability ◽  
Compact Stars ◽  
Stable Region ◽  
Energy Conditions ◽  
Arbitrary Form ◽  
Star Model ◽  
Field Equations ◽  
Anisotropic Matter

In the present paper, we have constructed a new relativistic anisotropic compact star model having a spherically symmetric metric of embedding class one. Here we have assumed an arbitrary form of metric function [Formula: see text] and solved the Einstein’s relativistic field equations with the help of Karmarkar condition for an anisotropic matter distribution. The physical properties of our model such as pressure, density, mass function, surface red-shift, gravitational redshift are investigated and the stability of the stellar configuration is discussed in details. Our model is free from central singularities and satisfies all energy conditions. The model we present here satisfy the static stability criterion, i.e. [Formula: see text] for [Formula: see text][Formula: see text]g/cm3(stable region) and for [Formula: see text][Formula: see text]g/cm3, the region is unstable i.e. [Formula: see text].

Physical properties of class I compact star model for linear and Starobinsky−f(R,T) functions

2020 ◽  
Vol 30 ◽  
pp. 100620 ◽  
Author(s):  
Ksh. Newton Singh ◽  
S.K. Maurya ◽  
Abdelghani Errehymy ◽  
Farook Rahaman ◽  
Mohammed Daoud
Keyword(s):  
Physical Properties ◽  
Compact Star ◽  
Class I ◽  
Star Model

Embedding class I spherically symmetric charged compact star model

2020 ◽  
Vol 365 (2) ◽  
Author(s):  
B. Dayanandan ◽  
Smitha T.T. ◽  
S. K. Maurya
Keyword(s):  
Compact Star ◽  
Class I ◽  
Spherically Symmetric ◽  
Star Model

Extended gravitational decoupling approach in f(𝒢) gravity

2020 ◽  
Vol 29 (06) ◽  
pp. 2050041 ◽  
Author(s):  
M. Sharif ◽  
Saadia Saba
Keyword(s):  
Compact Star ◽  
Spherical Geometry ◽  
Physical Parameters ◽  
Coupling Constant ◽  
Star Model ◽  
Anisotropic Models ◽  
Physical Constraints ◽  
Energy Bounds ◽  
Decoupling Approach ◽  
Static Sphere

In this paper, we explore decoupled anisotropic interior solutions for static sphere using extended gravitational decoupling technique in [Formula: see text] gravity. We choose Tolman-IV solution as the isotropic interior source describing compact spherical geometry and extend its domains to determine two anisotropic models using some physical constraints. We test physical acceptability of both models for the compact star PSRJ1416-2230 through physical parameters, energy bounds and causality condition. It is observed that both models are physically viable as well as stable. It is also found that the first star model becomes more dense at its core as compared to the second for a small increase in the coupling constant [Formula: see text].

scholarly journals Topology change, emergent symmetries and compact star matter

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Yong-Liang Ma ◽  
Mannque Rho
Keyword(s):  
Nuclear Matter ◽  
Compact Star ◽  
Momentum Tensor ◽  
Effective Field ◽  
Compact Stars ◽  
Strongly Correlated ◽  
Topology Change ◽  
Dense Nuclear Matter ◽  
Skyrmion Matter ◽  
Energy Constants

AbstractTopology effects have being extensively studied and confirmed in strongly correlated condensed matter physics. In the limit of large number of colors, baryons can be regarded as topological objects—skyrmions—and the baryonic matter can be regarded as a skyrmion matter. We review in this paper the generalized effective field theory for dense compact-star matter constructed with the robust inputs obtained from the skyrmion approach to dense nuclear matter, relying on possible “emergent” scale and local flavor symmetries at high density. All nuclear matter properties from the saturation density n0 up to several times n0 can be fairly well described. A uniquely novel—and unorthdox—feature of this theory is the precocious appearance of the pseudo-conformal sound velocity $v^{2}_{s}/c^{2} \approx 1/3$ v s 2 / c 2 ≈ 1 / 3 , with the non-vanishing trace of the energy momentum tensor of the system. The topology change encoded in the density scaling of low energy constants is interpreted as the quark-hadron continuity in the sense of Cheshire Cat Principle (CCP) at density $\gtrsim 2n_{0}$ ≳ 2 n 0 in accessing massive compact stars. We confront the approach with the data from GW170817 and GW190425.

Self-gravitating anisotropic star using gravitational decoupling

2021 ◽  
Author(s):  
Baiju Dayanandan ◽  
T. T. Smitha ◽  
Sunil Maurya
Keyword(s):  
Compact Star ◽  
Radial Component ◽  
Energy Conditions ◽  
Regularity Conditions ◽  
Star Model ◽  
Anisotropic Solution ◽  
Seed System ◽  
The Stability ◽  
Metric Function ◽  
Anisotropic Star

Abstract This paper addresses a new gravitationally decoupled anisotropic solution for the compact star model via the minimal geometric deformation (MGD) approach. We consider a non-singular well-behaved gravitational potential corresponding to the radial component of the seed spacetime and embedding class I condition that determines the temporal metric function to solve the seed system completely. However, two different well-known mimic approaches such as pr = Θ1 1 and ρ = Θ0 0 have been employed to determine the deformation function which gives the solution of the second system corresponding to the extra source. In order to test the physical viability of the solution, we have checked several conditions such as regularity conditions, energy conditions, causality conditions, hydrostatic equilibrium, etc. Moreover, the stability of the solutions has been also discussed by the adiabatic index and its critical value. We find that the solutions set seems viable as far as observational data are concerned.

FRW cosmological models with cosmological constant in f (R,T) theory of gravity

2021 ◽  
Author(s):  
Anirudh Pradhan ◽  
Priyanka Garg ◽  
Archana Dixit
Keyword(s):  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Apparent Magnitude ◽  
Physical Parameters ◽  
Distance Modulus ◽  
Luminosity Distance ◽  
Field Equations ◽  
Eos Parameter ◽  
Accelerating Expansion ◽  
Frw Cosmological Model

In the present paper, we have generalized the behaviors of {\color{blue}transit-decelerating to accelerating} FRW cosmological model in f (R, T) gravity theory, where R, T are Ricci scalar and trace of energy-momentum tensor respectively. The solution of the corresponding field equations is obtained by assuming a linear function of the Hubble parameter H, i.e., q = c<sub>1</sub> + c<sub>2</sub>H which gives a time-dependent DP (deceleration parameter) q(t)=-1+\frac{c_2}{\sqrt{2c_2 t +c_3}}, where c<sub>3</sub> and c<sub>2</sub> are arbitrary integrating constants [Tiwari et al., Eur. Phys. J. Plus: 131, 447 (2016); 132, 126 (2017)]. There are two scenarios in which we explain the particular form of scale factor thus obtained  (i) By using the recent constraints from OHD and JLA data which shows a cosmic deceleration to acceleration and (ii) By using new constraints from supernovae type la union data which shows accelerating expansion universe (q<0) throughout the evolution. We have observed that the EoS parameter, energy density parameters, and important cosmological planes yield the results compatible with the modern observational data. For the derived models, we have calculated various physical parameters as Luminosity distance, Distance modulus, and Apparent magnitude versus redshift for both supporting current observations.

Color-flavor locked compact stars: An exact solution approach

2021 ◽  
Author(s):  
Ksh. Newton Singh ◽  
Shyam Das ◽  
Piyali Bhar ◽  
Monsur Rahaman ◽  
Farook Rahaman
Keyword(s):  
Exact Solution ◽  
Compact Star ◽  
Density Perturbation ◽  
Compact Stars ◽  
Stable Configuration ◽  
Physical Parameters ◽  
Superconducting Gap ◽  
Field Equations ◽  
Critical Limit ◽  
Solution Approach

We present an exact solution that could describe compact star composed of color-flavor locked (CFL) phase. Einstein’s field equations were solved through CFL equation of state (EoS) along with a specific form of [Formula: see text] metric potential. Further, to explore a generalized solution we have also included pressure anisotropy. The solution is then analyzed by varying the color superconducting gap [Formula: see text] and its effects on the physical parameters. The stability of the solution through various criteria is also analyzed. To show the physical validity of the obtained solution we have generated the [Formula: see text] curve and fitted three well-known compact stars. This work shows that the anisotropy of the pressure at the interior increases with the color superconducting gap leading to decrease in adiabatic index closer to the critical limit. Further, the fluctuating range of mass due to the density perturbation is larger for lower color superconducting gap leading to more stable configuration.

Stability of generalized polytropic models

2019 ◽  
Vol 16 (04) ◽  
pp. 1950056
Author(s):  
I. Nazir ◽  
M. Azam
Keyword(s):  
Equation Of State ◽  
Local Density ◽  
Hydrostatic Equilibrium ◽  
Physical Parameters ◽  
Spherically Symmetric ◽  
Anisotropic Matter ◽  
Polytropic Equation ◽  
Density Perturbations ◽  
Radial Forces ◽  
The Stability

In this paper, we have investigated the stability of a spherically symmetric object with charged anisotropic matter by using the concept of cracking. The cracking is a very intuitive technique to check the stability which is based on the analysis of the radial forces that appear on the system due to perturbations taking it out of its equilibrium state. For this, we have applied and studied the effect of local density perturbations to the hydrostatic equilibrium equation and on all the physical parameters with generalized polytropic equation of state. It is found that some of the generalized polytropic models exhibit cracking.

Exact wormholes solutions without exotic matter in f(R,T) gravity

2019 ◽  
Vol 16 (03) ◽  
pp. 1950046 ◽  
Author(s):  
M. Zubair ◽  
Rabia Saleem ◽  
Yasir Ahmad ◽  
G. Abbas
Keyword(s):  
Momentum Tensor ◽  
Exotic Matter ◽  
Gravity Models ◽  
Energy Conditions ◽  
Anisotropic Fluid ◽  
Energy Tensor ◽  
Field Equations ◽  
Stress Energy ◽  
Symmetric Geometry ◽  
The Stability

This paper is aimed to evaluate the existence of wormholes in viable [Formula: see text] gravity models (where [Formula: see text] is the scalar curvature and [Formula: see text] is the trace of stress–energy tensor of matter). The exact solutions for energy–momentum tensor components depending on different shapes and redshift functions are calculated without some additional constraints. To investigate this, we consider static spherically symmetric geometry with matter contents as anisotropic fluid and formulate the Einstein field equations for three different [Formula: see text] models. For each model, we derive expression for weak and null energy conditions and graphically analyzed its violation near the throat. It is really interesting that wormhole solutions do not require the presence of exotic matter — like that in general relativity. Finally, the stability of the solutions for each model is presented using equilibrium condition.

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