scholarly journals Neutron stars in $$f(\mathtt {R,L_m})$$ gravity with realistic equations of state: joint-constrains with GW170817, massive pulsars, and the PSR J0030+0451 mass-radius from NICER data

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
R. V. Lobato ◽  
G. A. Carvalho ◽  
C. A. Bertulani
Keyword(s):  
Neutron Stars ◽  
Equations Of State ◽  
Matter Density ◽  
Hydrostatic Equilibrium ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Equilibrium Equations ◽  
Wave Event ◽  
Theory Of Gravity ◽  
First Time

AbstractIn this work, we investigate neutron stars (NS) in $$f(\mathtt {R,L_m})$$ f ( R , L m ) theory of gravity for the case $$f(\mathtt {R,L_m})= \mathtt {R}+ \mathtt {L_m}+ \sigma \mathtt {R}\mathtt {L_m}$$ f ( R , L m ) = R + L m + σ R L m , where $$\mathtt {R}$$ R is the Ricci scalar and $$\mathtt {L_m}$$ L m the Lagrangian matter density. In the term $$\sigma \mathtt {R}\mathtt {L_m}$$ σ R L m , $$\sigma $$ σ represents the coupling between the gravitational and particles fields. For the first time the hydrostatic equilibrium equations in the theory are solved considering realistic equations of state and NS masses and radii obtained are subject to joint constrains from massive pulsars, the gravitational wave event GW170817 and from the PSR J0030+0451 mass-radius from NASA’s Neutron Star Interior Composition Explorer (NICER) data. We show that in this theory of gravity, the mass-radius results can accommodate massive pulsars, while the general theory of relativity can hardly do it. The theory also can explain the observed NS within the radius region constrained by the GW170817 and PSR J0030+0451 observations for masses around $$1.4~M_{\odot }$$ 1.4 M ⊙ .

Mass, radius, and moment of inertia for neutron stars

1991 ◽  
Vol 69 (1) ◽  
pp. 8-15 ◽  
Author(s):  
Tommy Øvergård ◽  
Erlend Østgaard
Keyword(s):  
Total Mass ◽  
Nuclear Energy ◽  
Equations Of State ◽  
Mass Density ◽  
Moment Of Inertia ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Mass Energy ◽  
Energy Calculations ◽  
Models Comparison

Using results from energy calculations of "neutron matter," we construct various equations of state. From these equations of state, together with the Tolman–Oppenheimer–Volkoff equations derived from Einstein's general theory of relativity, we calculate quantities such as pressure, mass density, mass energy density, total mass, radius, and moment of inertia for configurations described in the models. Comparison is made with calculations based on other nuclear potentials and nuclear energy calculations, and our results are in reasonable agreement with results from observational data.

Newtonian quantum gravity

2020 ◽  
Vol 33 (1) ◽  
pp. 99-113 ◽  
Author(s):  
Reiner Georg Ziefle
Keyword(s):  
General Relativity ◽  
Quantum Gravity ◽  
Quantum Physics ◽  
Physical Reality ◽  
Theory Of Relativity ◽  
General Relativistic ◽  
Physical Effects ◽  
Theory Of Gravity ◽  
Physical Phenomena ◽  
First Time

Newtonian Quantum Gravity (NQG) unifies quantum physics with Newton's theory of gravity and calculates the so-called “general relativistic” phenomena more precisely and in a much simpler way than General Relativity, whose complicated theoretical construct is no longer needed. Newton's theory of gravity is less accurate than Albert Einstein's theory of general relativity. Famous examples are the precise predictions of General Relativity at binary pulsars. This is the reason why relativistic physicists claim that there can be no doubt that Einstein's theory of relativity correctly describes our physical reality. With the example of the famous “Hulse-Taylor binary” (also known as PSR 1913 + 16 or PSR B1913 + 16), the author proves that the so-called “general relativistic phenomena” observed at this binary solar system can be calculated without having any knowledge on relativistic physics. According to philosophical and epistemological criteria, this should not be possible, if Einstein's theory of relativity indeed described our physical reality. Einstein obviously merely developed an alternative method to calculate these phenomena without quantum physics. The reason was that in those days quantum physics was not yet generally taken into account. It is not the first time that a lack of knowledge of the underlying physical phenomena has to be compensated by complicated mathematics. Einstein's theory of general relativity indirectly already includes additional quantum physical effects of gravitation. This is the reason why it cannot be possible to unite Einstein's theory of general relativity with quantum physics, unless one uses “mathematical tricks” that make the additional quantum physical effects disappear again in the end.

scholarly journals Gamma Ray Bursts and Stellar Evolution

2017 ◽  
Vol 45 ◽  
pp. 1760008
Author(s):  
Kauan D. Marquez ◽  
Débora P. Menezes
Keyword(s):  
Stellar Evolution ◽  
Gamma Ray ◽  
Equations Of State ◽  
Hydrostatic Equilibrium ◽  
Gamma Ray Bursts ◽  
Compact Stars ◽  
Quark Star ◽  
Equilibrium Equations ◽  
Order Of Magnitude ◽  
Effective Models

The phenomenon that originates gamma ray bursts (GRBs) remains undefined. In this work the conversion of a hadronic star into a quark star is discussed as one of the possible causes of GRBs. Effective models are used to describe the compact stars and to obtain their equations of state. Macroscopic properties, such baryonic and gravitational masses, of both types of stars are then obtained from the solution of the hydrostatic equilibrium equations. The relation between this values allows to calculate the amount of energy possibly released in this process. The obtained results are then compared to actual GRB observational data, and are within the observational order of magnitude.

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 Measuring quantum gravity

2018 ◽  
Vol 96 (4) ◽  
pp. 366-378
Author(s):  
Arundhati Dasgupta
Keyword(s):  
General Relativity ◽  
Quantum Theory ◽  
General Theory ◽  
Quantum Gravity ◽  
Gravity Waves ◽  
Experimental Tests ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Theory Of Gravity

Einstein’s theory of gravity, known as the general theory of relativity was established in 1915. The theory has survived many experimental tests, and the recent discovery of gravity waves announced in 2016 confirms yet another success. In this article we examine some results from quantum general relativity, and ask whether the new quantum theory can survive tests in the same way as its classical origins.

The general theory of relativity is correct!

1988 ◽  
Vol 155 (7) ◽  
pp. 517-527 ◽  
Author(s):  
Ya.B. Zel'dovich ◽  
Leonid P. Grishchuk
Keyword(s):  
General Theory ◽  
Theory Of Relativity ◽  
General Theory Of Relativity

Dualism QM and GR

2019 ◽  
Author(s):  
Vitaly Kuyukov
Keyword(s):  
Quantum Mechanics ◽  
General Theory ◽  
Noncommutative Geometry ◽  
Quantum Tunneling ◽  
Closed Surface ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Surface Integral ◽  
Definition Of

Quantum tunneling of noncommutative geometry gives the definition of time in the form of holography, that is, in the form of a closed surface integral. Ultimately, the holography of time shows the dualism between quantum mechanics and the general theory of relativity.

Gravity as the curvature of the wave function of the universe.

2019 ◽  
Author(s):  
Vitaly Kuyukov
Keyword(s):  
Wave Function ◽  
Wave Functions ◽  
Main Task ◽  
Reference Systems ◽  
Theory Of Relativity ◽  
General Theory Of Relativity ◽  
Principle Of Equivalence ◽  
Relative Wave Function ◽  
New Equation ◽  
The Universe

Modern general theory of relativity considers gravity as the curvature of space-time. The theory is based on the principle of equivalence. All bodies fall with the same acceleration in the gravitational field, which is equivalent to locally accelerated reference systems. In this article, we will affirm the concept of gravity as the curvature of the relative wave function of the Universe. That is, a change in the phase of the universal wave function of the Universe near a massive body leads to a change in all other wave functions of bodies. The main task is to find the form of the relative wave function of the Universe, as well as a new equation of gravity for connecting the curvature of the wave function and the density of matter.

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