RELATIVISTIC STRANGE STARS WITH ANISOTROPY

2011 ◽  
Vol 26 (08) ◽  
pp. 575-587 ◽  
Author(s):  
B. C. PAUL ◽  
P. K. CHATTOPADHYAY ◽  
S. KARMAKAR ◽  
R. TIKEKAR
Keyword(s):  
Equation Of State ◽  
Compact Star ◽  
Anisotropy Parameter ◽  
Radial Distance ◽  
Matter Content ◽  
Strange Matter ◽  
Effect Of Pressure ◽  
A Value ◽  
Pressure Anisotropy ◽  
Compactness Factor

We study a compact star comprising strange matter content in the presence of pressure anisotropy. Considering strange matter with equation of state p = (ρ-4B)/3, where B is Bag parameter, we analyze the effect of pressure anisotropy on the Bag parameter for a compact star described by Vaidya–Tikekar metric. The values of B inside and on surface of the star are determined for different anisotropy parameter α. It is found that in the vicinity of the center of a compact star, B parameter is almost constant. However, away from the center B varies with the radial distance and finally at the surface B attains a value independent of the anisotropy. It is also noted that for some values of α, B remains constant throughout the star. Given α and spheriodicity a, B is found to be decreasing with the increase in compactness factor. The models admitting B increasing with α for a given spheriodicity parameter (a) and compactness are also found.

scholarly journals Relativistic strange stars with anisotropy and B-parameter in pseudo spheroidal space time

2012 ◽  
Vol 8 (S291) ◽  
pp. 362-364
Author(s):  
P. K. Chattopadhyay ◽  
B. C. Paul
Keyword(s):  
Equation Of State ◽  
Compact Star ◽  
Anisotropy Parameter ◽  
Space Time ◽  
Stable Model ◽  
Strange Stars ◽  
Strange Matter ◽  
Pressure Anisotropy ◽  
Spheroidal Geometry ◽  
Anisotropic Case

AbstractA class of compact cold stars in the presence of strange matter is obtained for a pseudo-spheroidal geometry. Considering the strange matter equation of state $p = \frac{1}{3}(\rho-4B)$ with pressure anisotropy described by Vaidya-Tikekar metric, we determine the parameter B both inside and on the surface of the star for different values of anisotropy parameter α. In the anisotropic case, we note that a stable model of a compact star may be realized.

scholarly journals Traversable wormholes with exponential shape function in modified gravity and general relativity: A comparative study

2020 ◽  
Vol 29 (09) ◽  
pp. 2050068 ◽  
Author(s):  
Gauranga C. Samanta ◽  
Nisha Godani ◽  
Kazuharu Bamba
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Comparative Study ◽  
Modified Gravity ◽  
Shape Function ◽  
Anisotropy Parameter ◽  
Energy Conditions ◽  
Traversable Wormholes

We have proposed a novel shape function on which the metric that models traversable wormholes is dependent. Using this shape function, the energy conditions, equation-of-state and anisotropy parameter are analyzed in [Formula: see text] gravity, [Formula: see text] gravity and general relativity. Furthermore, the consequences obtained with respect to these theories are compared. In addition, the existence of wormhole geometries is investigated.

OF CHARGED STARS AND CHARGED BLACK HOLES

2004 ◽  
Vol 13 (07) ◽  
pp. 1375-1379 ◽  
Author(s):  
MANUEL MALHEIRO ◽  
RODRIGO PICANÇO ◽  
SUBHARTHI RAY ◽  
JOSÉ P. S. LEMOS ◽  
VILSON T. ZANCHIN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Charged Particle ◽  
Equation Of State ◽  
Mass Density ◽  
Compact Star ◽  
Maximum Amount ◽  
Stellar Structure ◽  
Charged Black Holes ◽  
Polytropic Equation

Effect of maximum amount of charge a compact star can hold, is studied here. We analyze the different features in the renewed stellar structure and discuss the reasons why such huge charge is possible inside a compact star. We studied a particular case of a polytropic equation of state (EOS) assuming the charge density is proportional to the mass density. Although the global balance of force allows a huge charge, the electric repulsion faced by each charged particle forces it to leave the star, resulting in the secondary collapse of the system to form a charged black hole.

scholarly journals Analysis of the Quality of Mixed Coconut Shell Waste Briquettes with Various Biomass Additives as Alternative Fuels

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Yusraida Khairani Dalimunthe ◽  
Sugiatmo Kasmungin ◽  
Listiana Satiawati ◽  
Thariq Madani ◽  
Teuku Ananda Rizky
Keyword(s):  
Moisture Content ◽  
Calorific Value ◽  
Volatile Matter ◽  
Matter Content ◽  
Ash Content ◽  
Coconut Shell ◽  
Bamboo Charcoal ◽  
A Value ◽  
Shell Waste

The purpose of this study was to see the best quality of briquettes from the main ingredient of coconut shell waste<br />with various biomass additives to see the calorific value, moisture content, ash content, and volatile matter<br />content of the biomass mixture. Furthermore, further research will be carried out specifically to see the quality of<br />briquettes from a mixture of coconut shell waste and sawdust. The method used in this research is to conduct a<br />literature study of various literature related to briquettes from coconut shell waste mixed with various additives<br />specifically and then look at the best quality briquettes produced from these various pieces of literature. As for<br />what is determined as the control variable of this study is coconut shell waste and as an independent variable,<br />namely coffee skin waste, rice husks, water hyacinth, Bintaro fruit, segon wood sawdust, coconut husk, durian<br />skin, bamboo charcoal, areca nut skin, and leather waste. sago with a certain composition. Furthermore, this<br />paper also describes the stages of making briquettes from coconut shell waste and sawdust for further testing of<br />the calorific value, moisture content, ash content, volatile matter content on a laboratory scale for further<br />research. From various literatures, it was found that the highest calorific value was obtained from a mixture of<br />coconut shell waste and bamboo charcoal with a value of 7110.7288 cal / gr and the lowest calorific value was<br />obtained from a mixture of coconut shell waste and sago shell waste with a value of 114 cal / gr, then for the value<br />The highest water content was obtained from a mixture of coconut shell waste and rice husk with a value of<br />37.70% and the lowest water content value was obtained from a mixture of coconut shell waste 3.80%, then for the<br />highest ash content value was obtained from a mixture of coconut shell waste and coffee skin with a value of<br />20.862% and for the lowest ash content value obtained from a mixture of coconut shell and Bintaro fruit waste,<br />namely 2%, and for the highest volatile matter content value obtained from a mixture of coconut shell and coconut<br />husk waste with a value of 33.45% and for the value of volatile matter levels The lowest was obtained from a<br />mixture of coconut shell waste and sago skin waste with a value of 33 , 45%.

Study of conformally flat polytropes with tilted congruence

2018 ◽  
Vol 27 (07) ◽  
pp. 1850063 ◽  
Author(s):  
M. Sharif ◽  
Sobia Sadiq
Keyword(s):  
Equation Of State ◽  
Matter Content ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Conformally Flat ◽  
Flat Condition ◽  
Polytropic Equation ◽  
Dissipative Fluid ◽  
Symmetric Spacetime ◽  
Fluid Configuration

This paper is aimed to study the modeling of spherically symmetric spacetime in the presence of anisotropic dissipative fluid configuration. This is accomplished for an observer moving relative to matter content using two cases of polytropic equation-of-state under conformally flat condition. We formulate the corresponding generalized Tolman–Oppenheimer–Volkoff equation, mass equation, as well as energy conditions for both cases. The conformally flat condition is imposed to find an expression for anisotropy which helps to study spherically symmetric polytropes. Finally, Tolman mass is used to analyze stability of the resulting models.

scholarly journals Anisotropic cosmological dynamics in f(T) gravity in the presence of a perfect fluid

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Maria A. Skugoreva ◽  
Alexey V. Toporensky
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Perfect Fluid ◽  
Matter Content ◽  
Cosmological Evolution ◽  
Anisotropic Universe ◽  
Anisotropic Solution ◽  
Cosmological Singularity ◽  
Hubble Parameters ◽  
The Universe

Abstract We consider the cosmological evolution of a flat anisotropic Universe in f(T) gravity in the presence of a perfect fluid. It is shown that the matter content of the Universe has a significant impact of the nature of a cosmological singularity in the model studied. Depending on the parameters of the f(T) function and the equation of state of the perfect fluid in question the well-known Kasner regime of general relativity can be replaced by a new anisotropic solution, or by an isotropic regime, or the cosmological singularity changes its nature to a non-standard one with a finite values of Hubble parameters. Six possible scenarios of the cosmological evolution for the model studied have been found numerically.

scholarly journals Influence of the equation of state on a compact star made of hidden-sector nucleons

2020 ◽  
Vol 2020 (3) ◽  
Author(s):  
Shinji Maedan
Keyword(s):  
Equation Of State ◽  
Cold Dark Matter ◽  
Compact Star ◽  
Mean Field ◽  
Field Approximation ◽  
Compact Stars ◽  
Mean Field Approximation ◽  
Effective Theory ◽  
Hidden Sector ◽  
Two Parameters

Abstract We study a compact star made of degenerate hidden-sector nucleons which will be a candidate for cold dark matter. A hidden sector like quantum chromodynamics is considered, and as the low-energy effective theory we take the (hidden-sector) $ SU(2) $ chiral sigma model including a hidden-sector vector meson. With the mean field approximation, we find that one can treat the equation of state (EOS) of our model analytically by introducing a variable which depends on the Fermi momentum. The EOS is specified by the two parameters $ C'_{\sigma} $, $ C'_{\omega} $, and we discuss how these parameters affect the mass–radius relation for a compact star as well as the EOS. The dependence of the maximum stable mass of compact stars on the parameter $ C'_{\sigma} $ will also be discussed.

WAVE PROPAGATION IN A PLASMA WITH ANISOTROPIC PRESSURE

1967 ◽  
Vol 45 (10) ◽  
pp. 3189-3198 ◽  
Author(s):  
S. R. Sharma
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Resonant Frequency ◽  
Transverse Wave ◽  
Anisotropy Parameter ◽  
Anisotropic Pressure ◽  
Electrostatic Forces ◽  
Pressure Anisotropy ◽  
Component Plasma ◽  
The Magnetic Field

Wave propagation in an unbounded, magnetoactive, one-component plasma is considered with the help of modified Burgers equations. The pressure is assumed to be anisotropic and the effect of collisions on the wave propagation is examined. New modes of propagation have been reported in which the magnetic field and pressure anisotropy play an important role, while the electrostatic forces are comparatively less important. For the collisionless case, under certain conditions, new resonances appear in the transverse wave propagation, the resonant frequency being dependent upon the anisotropy parameter β. Cases have been pointed out where spatial instabilities may occur for certain values of β and the collision frequencies. It is further shown that the collisions may also offset the velocity–space instabilities which occur in a plasma with anisotropic pressure.

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