scholarly journals Non-Newtonian gravity in strange stars and constraints from the observations of compact stars

New Astronomy ◽  
2021 ◽  
pp. 101670
Author(s):  
Chun-Mei Pi ◽  
Shu-Hua Yang
Keyword(s):  
Compact Stars ◽  
Newtonian Gravity ◽  
Strange Stars

scholarly journals Quadrupole moments of rotating compact stars

2012 ◽  
Vol 8 (S291) ◽  
pp. 536-536
Author(s):  
Martin Urbanec ◽  
John Miller ◽  
Zdenek Stuchlik
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Strange Star ◽  
Compact Stars ◽  
Quadrupole Moments ◽  
Strange Stars

AbstractWe present quadrupole moments of rotating neutron and strange stars calculated using standard Hartle Thorne approach. We demonstrate differences between neutron and strange star parameters connected with quadrupole moments and how this parameters could be, in the case of neutron stars, approximated almost independently on neutron star equation of state.

scholarly journals Some New Models of Strange Stars in 5-D Einstein-Gauss-Bonnet Gravity

2021 ◽  
Author(s):  
Manuel Malaver ◽  
Hamed Daei Kasmaei
Keyword(s):  
Equation Of State ◽  
Energy Density ◽  
Nonlinear Equation ◽  
Radial Pressure ◽  
Compact Stars ◽  
Coupling Constant ◽  
Strange Stars ◽  
Bonnet Gravity ◽  
New Models ◽  
Linear And Nonlinear

In this paper, we present some new models for anisotropic compact stars within the framework of 5-dimensional Einstein-Gauss-Bonnet (EGB) gravity with a linear and nonlinear equation of state considering a metric potential proposed for Thirukkanesh and Ragel (2012) and generalized for Malaver (2014). The new obtained models satisfy all physical requirements of a physically reasonable stellar object. Variables as energy density, radial pressure and the anisotropy are dependent of the values of the Gauss-Bonnet coupling constant

CENTRIFUGAL FORCE INDUCED COLLAPSE OF STRANGE STARS INTO BLACK HOLES

2007 ◽  
Vol 16 (05) ◽  
pp. 827-831 ◽  
Author(s):  
F. DE PAOLIS ◽  
G. INGROSSO ◽  
A. A. NUCITA ◽  
ASGHAR QADIR
Keyword(s):  
Black Hole ◽  
Centrifugal Force ◽  
Gamma Ray ◽  
Compact Stars ◽  
Stationary Black Hole ◽  
Strange Stars ◽  
New Class ◽  
Particle Orbit ◽  
S Quarks ◽  
Schwarzschild Radius

It has been suggested that there could be objects even more compact than neutron stars, like the so-called strange stars, P-stars, and magnetars. Strange stars are collapsed stars consisting of u, d, and s quarks. P-stars are a new class of compact stars made of u and d quarks in β-equilibrium with electrons in an Abelian chromomagnetic condensate. It has also been shown that a particle in a circular orbit around a stationary black hole is subject to a centrifugal force that turns out to be directed inwards if the particle orbit radius is between the Schwarzschild radius rs and 3rs/2. Here it is proposed that rotation of a sufficiently compact collapsed object may lead to a centrifugal force induced collapse to a black hole that could emit short gamma-ray bursts.

scholarly journals Relativistic Cowling approximation for fluid oscillation modes of color superconducting self-bound stars

2012 ◽  
Vol 8 (S291) ◽  
pp. 451-451
Author(s):  
German Lugones ◽  
Cesar Vasquez Flores
Keyword(s):  
Equation Of State ◽  
Gravitational Waves ◽  
Internal Structure ◽  
Quark Matter ◽  
Normal Modes ◽  
Pressure Oscillation ◽  
Compact Stars ◽  
Color Superconductivity ◽  
Strange Stars ◽  
Oscillation Modes

AbstractThe investigation of the quasi-normal modes of oscillation of compact stars can reveal much information about their equation of state and internal structure mainly through the analysis of the expected emission of gravitational waves. In this work we study non-radial oscillation modes of strange stars consisting of color superconducting quark matter. We focus on the fundamental and pressure oscillation modes within the frame of the Cowling approximation. We discuss the observable features that may allow a differentiation among hadronic stars, strange stars, and strange stars with color superconductivity.

scholarly journals Stellar hydrostatic equilibrium compact structures in f(𝒢,T) gravity

2019 ◽  
Vol 34 (05) ◽  
pp. 1950038 ◽  
Author(s):  
M. Farasat Shamir ◽  
Mushtaq Ahmad
Keyword(s):  
Energy Density ◽  
Neutron Stars ◽  
Gravity Model ◽  
Fluid Pressure ◽  
Stellar Mass ◽  
Hydrostatic Equilibrium ◽  
Compact Stars ◽  
Equilibrium Equations ◽  
Strange Stars ◽  
State Models

In this paper, stellar hydrostatic equilibrium configuration of the compact stars (neutron stars and strange stars) has been studied for [Formula: see text] gravity model, with [Formula: see text] and [Formula: see text] being the Gauss–Bonnet invariant and the trace of energy–momentum tensor, respectively. After deriving the hydrostatic equilibrium equations for [Formula: see text] gravity, the fluid pressure for the neutron stars and the strange stars has been computed by implying two equation of state models corresponding to two different compact stars. For the [Formula: see text] gravity model, with [Formula: see text], [Formula: see text], and [Formula: see text] being some specific parameters, substantial change in the behavior of the physical attributes of the compact stars like the energy density, pressure, stellar mass, and total radius has been noted with the corresponding change in [Formula: see text] values. Meanwhile, it has been shown that for some fixed central energy density and with increasing values of [Formula: see text], the stellar mass both for the neutron stars and the strange stars increases, while the total stellar radius [Formula: see text] exhibits the opposite behavior for both of the compact stars. It is concluded that for this [Formula: see text] stellar model, the maximum stellar mass can be boosted above the observational limits.

scholarly journals Strange stars with a mirror-dark-matter core confronting with the observations of compact stars

2021 ◽  
Vol 104 (8) ◽  
Author(s):  
Shu-Hua Yang ◽  
Chun-Mei Pi ◽  
Xiao-Ping Zheng
Keyword(s):  
Dark Matter ◽  
Compact Stars ◽  
Strange Stars

SELF-LENSING EFFECTS FOR COMPACT STARS AND THEIR MASS–RADIUS RELATION

2004 ◽  
Vol 19 (32) ◽  
pp. 2431-2435
Author(s):  
A. R. PRASANNA ◽  
SUBHARTHI RAY
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Equation Of State ◽  
Quark Matter ◽  
Strange Quark ◽  
Strange Quark Matter ◽  
Compact Stars ◽  
Strange Stars ◽  
Lensing Effect ◽  
R Relation

During the last couple of years astronomers and astrophysicists have been debating on the fact whether the so-called "strange stars" — stars made up of strange quark matter, have been discovered with the candidates like SAX J1808.4–3658, 4U 1728–34, RX J1856.5–3754, etc. The main contention has been the estimation of radius of the star for an assumed mass of ~ 1.4 M⊙ and to see whether the point overlaps with the graphs for the neutron star equation of state or whether it goes to the region of stars made of strange matter equation of state. Using the well-established formulae from general relativity for the gravitational redshift and the "lensing effect" due to bending of photon trajectories, we, in this letter, relate the parameters M and R with the observable parameters, the redshift z and the radiation radius R∞, thus constraining both M and R for specific ranges, without any other arbitrariness. With the required inputs from observations, one ought to incorporate the effects of self-lensing of the compact stars which has been otherwise ignored in all of the estimations done so far. Nonetheless, these effects of self-lensing make a marked difference for constraints on the M–R relation.

Effects of non-Newtonian gravity on the properties of strange stars

2017 ◽  
Vol 17 (2) ◽  
pp. 11 ◽  
Author(s):  
Zhen-Yan Lu ◽  
Guang-Xiong Peng ◽  
Kai Zhou
Keyword(s):  
Newtonian Gravity ◽  
Strange Stars

Quantum 20/20

2019 ◽  
Author(s):  
Ian R. Kenyon
Keyword(s):  
Quantum Mechanics ◽  
Hall Effect ◽  
Particle Physics ◽  
Quantum Spin ◽  
Lessons Learned ◽  
Compact Stars ◽  
Einstein Condensation ◽  
Local Conservation ◽  
Variable Theory ◽  
Quantum Gauge Theory

This text reviews fundametals and incorporates key themes of quantum physics. One theme contrasts boson condensation and fermion exclusivity. Bose–Einstein condensation is basic to superconductivity, superfluidity and gaseous BEC. Fermion exclusivity leads to compact stars and to atomic structure, and thence to the band structure of metals and semiconductors with applications in material science, modern optics and electronics. A second theme is that a wavefunction at a point, and in particular its phase is unique (ignoring a global phase change). If there are symmetries, conservation laws follow and quantum states which are eigenfunctions of the conserved quantities. By contrast with no particular symmetry topological effects occur such as the Bohm–Aharonov effect: also stable vortex formation in superfluids, superconductors and BEC, all these having quantized circulation of some sort. The quantum Hall effect and quantum spin Hall effect are ab initio topological. A third theme is entanglement: a feature that distinguishes the quantum world from the classical world. This property led Einstein, Podolsky and Rosen to the view that quantum mechanics is an incomplete physical theory. Bell proposed the way that any underlying local hidden variable theory could be, and was experimentally rejected. Powerful tools in quantum optics, including near-term secure communications, rely on entanglement. It was exploited in the the measurement of CP violation in the decay of beauty mesons. A fourth theme is the limitations on measurement precision set by quantum mechanics. These can be circumvented by quantum non-demolition techniques and by squeezing phase space so that the uncertainty is moved to a variable conjugate to that being measured. The boundaries of precision are explored in the measurement of g-2 for the electron, and in the detection of gravitational waves by LIGO; the latter achievement has opened a new window on the Universe. The fifth and last theme is quantum field theory. This is based on local conservation of charges. It reaches its most impressive form in the quantum gauge theories of the strong, electromagnetic and weak interactions, culminating in the discovery of the Higgs. Where particle physics has particles condensed matter has a galaxy of pseudoparticles that exist only in matter and are always in some sense special to particular states of matter. Emergent phenomena in matter are successfully modelled and analysed using quasiparticles and quantum theory. Lessons learned in that way on spontaneous symmetry breaking in superconductivity were the key to constructing a consistent quantum gauge theory of electroweak processes in particle physics.

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