scholarly journals Stellar structure of quark stars in a modified Starobinsky gravity

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Arun Mathew ◽  
Muhammed Shafeeque ◽  
Malay K. Nandy
Keyword(s):  
Compact Stars ◽  
Stellar Structure ◽  
Spherically Symmetric ◽  
Matter Coupling ◽  
Binary Pulsars ◽  
Quark Stars ◽  
Equilibrium Configurations ◽  
Matter Interaction ◽  
Maximal Mass ◽  
Stellar Properties

Abstract We propose a form of gravity–matter interaction given by $$\omega RT$$ωRT in the framework of f(R, T) gravity and examine the effect of such interaction in spherically symmetric compact stars. Treating the gravity–matter coupling as a perturbative term on the background of Starobinsky gravity, we develop a perturbation theory for equilibrium configurations. For illustration, we take the case of quark stars and explore their various stellar properties. We find that the gravity–matter coupling causes an increase in the stable maximal mass which is relevant for recent observations on binary pulsars.

scholarly journals Study of charged compact stars with class 1 metric under general relativity

2019 ◽  
Vol 97 (12) ◽  
pp. 1323-1331 ◽  
Author(s):  
S.K. Maurya ◽  
S. Roy Chowdhury ◽  
Saibal Ray ◽  
B. Dayanandan
Keyword(s):  
General Relativity ◽  
Compact Star ◽  
Space Time ◽  
Electron Cloud ◽  
Compact Stars ◽  
Stellar Structure ◽  
Spherically Symmetric ◽  
Class 1 ◽  
Maxwell Space ◽  
Physical Tests

In the present paper we study compact stars under the background of Einstein–Maxwell space–time, where the 4-dimensional spherically symmetric space–time of class 1 along with the Karmarkar condition has been adopted. The investigations, via the set of exact solutions, show several important results, such as (i) the value of density on the surface is finite; (ii) due to the presence of the electric field, the outer surface or the crust region can be considered to be made of electron cloud; (iii) the charge increases rapidly after crossing a certain cutoff region (r/R ≈ 0.3); and (iv) the avalanche of charge has a possible interaction with the particles that are away from the center. As the stellar structure supports all the physical tests performed on it, therefore the overall observation is that the model provides a physically viable and stable compact star.

THE EQUILIBRIUM STRUCTURE OF CHARGED ROTATING RELATIVISTIC STARS

2008 ◽  
Vol 17 (12) ◽  
pp. 2291-2304 ◽  
Author(s):  
BABUR M. MIRZA
Keyword(s):  
Numerical Study ◽  
Mass Density ◽  
Compact Star ◽  
Coulomb Repulsion ◽  
Electrical Energy ◽  
Compact Stars ◽  
Stellar Structure ◽  
Critical Conditions ◽  
Additional Energy ◽  
Equilibrium Configurations

General relativistic equilibrium conditions imply that an electrically charged compact star, in a spherically symmetric configuration, can sustain a huge amount of electric charge (up to 1020 C). The equilibrium, however, is reached under very critical conditions such that a perturbation to the stellar structure can cause these systems to collapse. We study the effects of rotation in charged compact stars and obtain conditions, the modified Tolman–Oppenheimer–Volkoff (TOV) equations, under which such stars form a stable gravitational system against Coulomb repulsion. We assume the star to be rotating slowly. We also assume that the charge density is proportional to the mass density everywhere inside the star. The modified TOV equations for hydrostatic equilibrium are integrated numerically for the general equation of state for a polytrope. The detailed numerical study shows that the centrifugal force adds to the Coulomb pressure in the star. In the stable equilibrium configurations, therefore, a loss in stellar mass (energy) density occurs for higher values of the angular frequency. The additional energy is radiated in the form of electrical energy. The stellar radius is also decreased so that the star does not necessarily becomes more compact.

RADIAL OSCILLATIONS OF COLOR SUPERCONDUCTING QUARK STARS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1499-1504 ◽  
Author(s):  
C. VASQUEZ FLORES ◽  
G. LUGONES
Keyword(s):  
Quark Matter ◽  
Stellar Structure ◽  
Color Superconductivity ◽  
Quark Stars ◽  
Equilibrium Configurations ◽  
Oscillation Modes

In this work, we investigate the effect of color superconductivity in adiabatic radial oscillations of stars consisting of quark matter. We calculate the equilibrium configurations by integrating the Tolman–Oppenheimer–Volkoff equations of relativistic stellar structure and then we integrate the equations of relativistic radial oscillations to determine the oscillation modes.

Anisotropic solution for compact star in 5D Einstein–Gauss–Bonnet gravity

2021 ◽  
Vol 36 (32) ◽  
Author(s):  
S. K. Maurya ◽  
Anirudh Pradhan ◽  
Ayan Banerjee ◽  
Francisco Tello-Ortiz ◽  
M. K. Jasim
Keyword(s):  
Compact Star ◽  
Compact Objects ◽  
Compact Stars ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Field Equations ◽  
Anisotropic Solution ◽  
Bonnet Gravity ◽  
Spacetime Geometry ◽  
Equilibrium Configurations

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 [Formula: see text] 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.

Theoretical Underpinnings: Stellar Oscillations

2017 ◽  
Author(s):  
Sarbani Basu ◽  
William J. Chaplin
Keyword(s):  
Seismic Data ◽  
Spherical Symmetry ◽  
Three Dimensional ◽  
Stellar Structure ◽  
Spherically Symmetric ◽  
Equilibrium Conditions ◽  
Stellar Oscillations ◽  
Mechanical Disturbance ◽  
Stellar Properties

This chapter shows how the oscillations of a star are related to its structure. It also describes some of the important properties of stellar oscillations that allow us to use seismic data to determine stellar properties. Stellar oscillations are the response of a star to a mechanical disturbance, and thus the equations of stellar oscillations are derived by perturbing the equations of stellar structure. While a star may be spherically symmetric under equilibrium conditions, it need not retain spherical symmetry when it is perturbed, and as a result one can no longer avoid taking into account the three-dimensional nature of a star.

Quantum description of light–matter coupling

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Cavity Mode ◽  
Optical Field ◽  
Level System ◽  
Bloch Equations ◽  
Optical Bloch Equations ◽  
Matter Coupling ◽  
Matter Interaction ◽  
Light Matter Interaction ◽  
Full Quantum ◽  
The Ideal

In this chapter we study with the tools developed in Chapter 3 the basic models that are the foundations of light–matter interaction. We start with Rabi dynamics, then consider the optical Bloch equations that add phenomenologically the lifetime of the populations. As decay and pumping are often important, we cover the Lindblad form, a correct, simple and powerful way to describe various dissipation mechanisms. Then we go to a full quantum picture, quantizing also the optical field. We first investigate the simpler coupling of bosons and then culminate with the Jaynes–Cummings model and its solution to the quantum interaction of a two-level system with a cavity mode. Finally, we investigate a broader family of models where the material excitation operators differ from the ideal limits of a Bose and a Fermi field.

Study of some compact objects in R + 2βT gravity

2019 ◽  
Vol 28 (16) ◽  
pp. 2040005
Author(s):  
Arfa Waseem ◽  
M. Sharif
Keyword(s):  
Stellar System ◽  
Graphical Analysis ◽  
Compact Objects ◽  
Stellar Structure ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Star Models ◽  
Mit Bag Model ◽  
Text Model

The aim of this work is to examine the nature as well as physical characteristics of anisotropic spherically symmetric stellar candidates in the context of [Formula: see text] gravity. We assume that the fluid components such as pressure and energy density are related through MIT bag model equation-of-state in the interior of stellar system. In order to analyze the structure formation of some specific star models, the field equations are constructed using Krori–Barua solution in which the unknown constants are evaluated by employing observed values of radii and masses of the considered stars. We check the consistency of [Formula: see text] model through the graphical analysis of energy conditions as well as stability of stellar structure. It is found that our considered stars show viable as well as stable behavior for this model.

Conversion of neutron stars to 2 + 1 flavor Nambu–Jona-Lasinio quark stars as a mechanism for gamma-ray bursts

2017 ◽  
Vol 32 (37) ◽  
pp. 1750209
Author(s):  
Xiao-Yu Shu ◽  
Yong-Feng Huang ◽  
Hong-Shi Zong
Keyword(s):  
Phase Transition ◽  
Gamma Ray ◽  
Chemical Potential ◽  
Proper Time ◽  
Mean Field ◽  
Gamma Ray Bursts ◽  
Compact Stars ◽  
Relativistic Mean Field ◽  
Quark Stars ◽  
Njl Model

The phase transition from a neutron star to a quark star and its relation to gamma-ray bursts are investigated. A new model: the 2 + 1 flavor Nambu–Jona-Lasinio (NJL) model with the method of proper-time regularization (PTR) is utilized for the quark phase; while the Relativistic Mean Field (RMF) theory is used for the hadronic phase. The process of phase transition is studied by considering the chemical potential, paying special attention to the phase transition point and the emergence of strange quark matter. Characteristics of compact stars are illustrated, and the energy release during the phase transition is found to be [Formula: see text] erg.

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