Neutron star mass-radius relation with gravitational field shielding by a scalar field

Zhang, Bojun; Zhang, Tian-Xi; Guggilla, Padmaja; Dokhanian, Mostafa

doi:10.1088/1674-4527/13/5/008

Cited by 3 publications

(2 citation statements)

References 28 publications

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“…The scalar field in the 5D gravity plays the role of dark energy for the acceleration of the universe expansion [71,72]. Recently, we have also, in accord with the 5D fully-covariant KKΦ theory, developed a new mass-radius relation that perfectly explained the new observations of neutron stars, especially those with greater masses and/or smaller radii [73][74][75][76][77]. From this 5D fully-covariant KKΦ theory, we can have a modified Friedmann equation for cosmology, as well as a modified Tolman-Oppenheimer-Volkoff (TOV) equation for neutron star.…”

Section: Discussionmentioning

confidence: 90%

The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications

Zhang¹

2014

Galaxies

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In this paper, we comprehensively review the five-dimensional (5D) fully-covariant theory of gravitation developed by Zhang two decades ago and its recent applications in astrophysics and cosmology. This 5D gravity describes not only the fields, but also the matter and its motion in a 5D spacetime. The greatest advantage of this theory is that there does not exist any unknown parameter, so that we can apply it to explain astrophysical and cosmological issues by quantitatively comparing the results obtained from it with observations and to predict new effects that could not be derived from any other gravitational theories. First, the 5D covariant description of matter and its motion enabled Zhang to analytically derive the fifteenth component of the 5D energy-momentum tensor of matter (T 44 ), which significantly distinguishes this 5D gravity from other 5D gravitational theories that usually assumed aT 44 with an unknown parameter, called the scalar charge s, and, thus, to split the 5D covariant field equation into (4 + 1) splitting form as the gravitational, electromagnetic, and scalar field equations. The gravitational field equation turns into the 4D Einstein's field equation of general relativity if the scalar field is equal to unity. Then, Zhang solved the field equations and obtained an exact static spherically-symmetric external solution of the gravitational, electromagnetic and scalar fields, in which all integral constants were completely determined with a perfect set of simple numbers and parameters that only depend on the mass and electric charge of the matter, by comparing with the obtained weak internal solution of the fields at a large radial distance. In the Einstein frame, the exact field solution obtained from the 5D fully-covariant theory of gravitation reduces to the Schwarzschild solution when the matter is electrically neutral and the fields are weak in strength. This guarantees that the four fundamental tests (light deflection, gravitational redshift, perihelion advance and radar echo delay) of the 4D Einstein's general relativity in the case of weak fields are also the tests of the 5D fully-covariant theory of gravitation. In19 the case of strong fields, especially when the matter is highly charged, however, the results from the 5D fully-covariant theory of gravitation are significantly different from the 4D Einstein's general relativity. Applying this 5D gravity and its exact field solution, Zhang has recently developed a new redshift mechanism, called electric redshift, a new supernova explosion mechanism with gravitational field shielding, a new gravitationless black hole model, a modified neutron star mass-radius relation, a modified Friedmann equation for the accelerating universe, and so on. This paper provides an overview of this 5D fully-covariant theory of gravitation, including also its solution properties and astrophysical applications.

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Section: Discussionmentioning

confidence: 90%

The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications

Zhang¹

2014

Galaxies

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“…Amongst the first few attempts to solve this issue after the work of Demorest et al, Refs. [158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176] put forward the idea that this puzzle is not a crisis of the nuclear equation of state physics, but rather of gravitation. Alternative theories to Einstein's General Relativity (GR) or, modified gravity, are alternative hypothesis to dark matter in solving open cosmological questions.…”

Section: Modified Gravity As a Solutionmentioning

confidence: 99%

The Role of Baryon Structure in Neutron Stars

Motta,

Thomas

2022

Preprint

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The current state of neutron star mass measurements is depicted in Fig. 1. We see that the only measurements of heavy neutron stars with reasonably small errors are those of PSR J1614-2230 [29] and PSR J0348+0432 [2], along with PSR J0740+6620 [30] which is the newest member of the heavy neutron star club. Nevertheless, the uncertainties on the aforementioned pulsars still make them all comparable with each other within two standard deviations. Therefore, a conservative lower estimate for the maximum mass of neutron stars is that of PSR J1614-2230, namely, 1.908±0.016M . RadiiOther than their masses, the radii of neutron stars are extremely sensitive to different models for the equations of state. However, the experimental constraints on radii are less numerous and until recently the systematic errors were quite large. The first new source of a constraint came on August 17th 2017, with the first gravitational wave measurement [4] of the merger of two neutron stars. This yielded the result that the radii of the neutron stars involved in the merger both lie within R = 11.9 +1.4 −1.4 , at the 90% confidence level.More recently, the NICER mission, with its X-ray telescope on the space station, obtained results [5,37] for PSR J0030+0451. The collaboration applied different analyses on the data and obtained values of (all at 68% credibility) 12.71 +1.14 −1.19 km and mass 1.34 +0.15 −0.16 M in Ref.[5] and 13.02 +1.24 −1.06 km in Ref.[37] with the mass estimated at 1.44 +0.15 −0.14 M . Another recent measurement by the NICER collaboration was that of pulsar PSR J0740+6620 which by virtue of being much heavier, is of considerable interest to nuclear physicists. They measured a radius of 12.39 +1.3 −0.98 km for a mass of 2.07 ± 0.06M [38]. Modelling Dense MatterHistorically, studies of the properties of nuclear matter were primarily aimed at understanding finite nuclei. They were based primarily on using two-body and three-body potentials with standard techniques in quantum many-body theory, such as Brueckner-Hartree-Fock (BHF) [39], Bethe-Brueckner-Goldstone (BBG) [40]. The two-body potentials were derived from phenomenological fits to nucleonnucleon scattering [41]. The quantum Monte Carlo variational approach has had considerable success with light nuclei [42], with parameters of the phenomenological three-body force tuned to nuclear data. In recent years there has been a great deal of activity using chiral effective field theory [43,44,45,46,47,48], with its systematic expansion in powers of momentum. This approach builds in the constraints of chiral symmetry within a Lagrangian theory built upon pion and nucleon degrees of freedom, plus counterterms. With a similar number of parameters to those needed for phenomenological potentials (typically 25-30), it yields a good description of nucleon-nucleon scattering data. Within the same framework, one also has a systematic expansion of a three-nucleon force, with counterterms again tuned to nuclear data. Once again one finds excellent agreement with data for light nuc...

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The role of baryon structure in neutron stars

Motta

Thomas

2022

Mod. Phys. Lett. A

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Understanding the equation of state of dense nuclear matter is a fundamental challenge for nuclear physics. It is an especially timely and interesting challenge as we have reached a period where neutron stars, which contain the most dense nuclear matter in the Universe, are now being studied in completely new ways, from gravitational waves to satellite-based telescopes. We review the theoretical approaches to calculating this equation of state which involve a change in the structure of the baryons, along with their predictions for neutron star properties.

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Neutron star mass-radius relation with gravitational field shielding by a scalar field

Cited by 3 publications

References 28 publications

The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications

The 5D Fully-Covariant Theory of Gravitation and Its Astrophysical Applications

The Role of Baryon Structure in Neutron Stars

The role of baryon structure in neutron stars

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