scholarly journals Possible maximum mass of dark matter existing in compact stars based on the self-interacting fermionic model

2019 ◽  
Vol 28 (11) ◽  
pp. 1950148
Author(s):  
Xu Dong Wang ◽  
Bin Qi ◽  
Gao Le Yang ◽  
Nai Bo Zhang ◽  
Shou Yu Wang
Keyword(s):  
Dark Matter ◽  
Energy Density ◽  
Strong Interaction ◽  
Milky Way ◽  
Compact Star ◽  
Compact Stars ◽  
Maximum Mass ◽  
Obvious Effect ◽  
Milky Way Galaxy ◽  
Fermionic Model

The dark matter admixed neutron stars (DANSs) are studied using the two-fluid TOV equations separately, in which the normal matter (NM) and dark matter (DM) are simulated by the relativistic mean field theory and self-interacting fermionic model, respectively. A universal relationship [Formula: see text] is suggested, where [Formula: see text] is the maximum mass of DM existing in DANSs, [Formula: see text] is the particle mass of DM ranging from 5[Formula: see text]GeV to 1[Formula: see text]TeV, [Formula: see text] is the interaction mass scale with the value 300[Formula: see text]GeV (0.1[Formula: see text]GeV) for weak (strong) interaction DM model. This simple formula connects directly the microcosmic nature of DM particle with its macrocosmic mass existing in DANSs. Meanwhile, such a formula exhibits that the existence of NM has little effect on [Formula: see text]. It is found that the ratio of radius of DM in DANSs over [Formula: see text] is a constant with the value about 12[Formula: see text] (7[Formula: see text]) for weak (strong) interaction DM cases. According to the calculated results, only for the strong interaction DM cases with [Formula: see text] to [Formula: see text][Formula: see text]GeV and central energy density [Formula: see text][Formula: see text]MeV/fm3, DM has obvious effect on the mass of compact star. Compared with the energy density of DM in the Milky Way galaxy, [Formula: see text][Formula: see text]MeV/fm3, the existence of DM might hardly affect the mass of compact stars in the Milky Way galaxy.

Dark matter with chiral symmetry admixed hadronic matter in compact stars

2021 ◽  
Author(s):  
SiNa Wei ◽  
Zhaoqing Feng
Keyword(s):  
Dark Matter ◽  
Energy Density ◽  
Chiral Symmetry ◽  
Density Ratio ◽  
Compact Stars ◽  
Hadronic Matter ◽  
Meson Exchange ◽  
Maximum Mass ◽  
Central Energy ◽  
Two Fluid

Abstract With the two-fluid TOV equation, the properties of dark matter (DM) admixed NSs (DANSs) have been studied. Different from previous studies, we found that increase of the maximum mass and decrease of the radius of 1.4 $M_\odot$ can occur simultaneously in DANS. This stems from the fact that the equation of state (EOS) of DM can be very soft at low density but very stiff at high density. It is well known that the IU-FSU and XS models can not reproduce the neutron star (NS) with a maximum mass greater than 2.0 $M_\odot$. However, considering IU-FSU and XS models in DANS, there are always mass and interactions of DM that can reproduce a maximum mass greater than 2.0 $M_\odot$ and the radius of 1.4 $M_\odot$ below 13.7km. The difference of DANS between the DM with chiral symmetry (DMC) and the DM with meson exchange (DMM) becomes obvious when the central energy density ratio of the DM is greater than one of the NM. When the central energy density ratio of the DM is greater than one of the NM, the DMC model with the DM mass of 1000 MeV still can reproduce a maximum mass greater than 2.0 $M_\odot$ and the radius of 1.4 $M_\odot$ below 13.7km. In the same case, although the maximum mass of DANS with the DMM model is greater than 2.0 $M_\odot$ , the radius of 1.4 $M_\odot$ with the DMM model will surpass 13.7km obviously. \com{In two-fluid system, it is worth noting that the maximum mass of DANS can be larger than 3.0 $M_\odot$. As a consequence, the dimensionless tidal deformability $\Lambda_{CP}$ of DANS with 1.4 $M_\odot$, which increase with increasing the maximum mass of DANS, could be larger than 800 when the radius of DANS with 1.4 $M_\odot$ is about 13.0km.}

scholarly journals Upper limit on the central density of dark matter in the Eddington-inspired Born–Infeld (EiBI) gravity

2015 ◽  
Vol 30 (11) ◽  
pp. 1550056 ◽  
Author(s):  
Ramil Izmailov ◽  
Alexander A. Potapov ◽  
Alexander I. Filippov ◽  
Mithun Ghosh ◽  
Kamal K. Nandi
Keyword(s):  
Dark Matter ◽  
Alternative Model ◽  
Milky Way ◽  
Viable Alternative ◽  
Central Density ◽  
Density Profiles ◽  
Milky Way Galaxy ◽  
Upper Limit ◽  
The Stability ◽  
Individual Galaxy

We investigate the stability of circular material orbits in the analytic galactic metric recently derived by Harko et al., Mod. Phys. Lett. A29, 1450049 (2014). It turns out that stability depends more strongly on the dark matter central density ρ0 than on other parameters of the solution. This property then yields an upper limit on ρ0 for each individual galaxy, which we call here [Formula: see text], such that stable circular orbits are possible only when the constraint [Formula: see text] is satisfied. This is our new result. To approximately quantify the upper limit, we consider as a familiar example our Milky Way galaxy that has a projected dark matter radius R DM ~180 kpc and find that [Formula: see text]. This limit turns out to be about four orders of magnitude larger than the latest data on central density ρ0 arising from the fit to the Navarro–Frenk–White (NFW) and Burkert density profiles. Such consistency indicates that the Eddington-inspired Born–Infeld (EiBI) solution could qualify as yet another viable alternative model for dark matter.

Orbits

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Milky Way ◽  
Extrasolar Planets ◽  
Binary Star ◽  
Milky Way Galaxy ◽  
Newtonian Model ◽  
Theory Of Gravity ◽  
The Masses ◽  
The Universe

Orbits are ubiquitous in the universe: moons orbit planets, planets orbit stars, stars orbit around the center of the Milky Way galaxy, and so on. Any theory of gravity will have to explain the properties of all these orbits. To pave the way for developing the metric theory of gravity (general relativity) this chapter examines the basics of orbits as observed and as explained by the Newtonian model of gravity. We can use our understanding of gravity to infer the masses and other properties of these cosmic systems. Te chapter concludes with four optional sections in this spirit, covering the slingshot maneuver; dark matter; binary star orbits and how they reveal the masses of stars; and extrasolar planets.

Stellar accelerations and the galactic gravitational field

2019 ◽  
Vol 36 ◽  
Author(s):  
Hamish Silverwood ◽  
Richard Easther
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Precision Measurements ◽  
Small Scale ◽  
Milky Way Galaxy ◽  
Newtonian Dynamics ◽  
The Galaxy ◽  
Velocity Changes ◽  
Blind Search ◽  
Stellar Motion

AbstractTypical stars in the Milky Way galaxy have velocities of hundreds of kilometres per second and experience gravitational accelerations of $\sim\!10^{-10}~{\rm m\,s}^{-2}$, resulting in velocity changes of a few centimetres per second over a decade. Measurements of these accelerations would permit direct tests of the applicability of Newtonian dynamics on kiloparsec length scales and could reveal significant small-scale inhomogeneities within the galaxy, as well increasing the sensitivity of measurements of the overall mass distribution of the galaxy. Noting that a reasonable extrapolation of progress in exoplanet hunting spectrographs suggests that centimetre per second level precision will be attainable in the coming decade(s), we explore the possibilities such measurements would create. We consider possible confounding effects, including apparent accelerations induced by stellar motion and reflex velocities from planetary systems, along with possible strategies for their mitigation. If these issues can be satisfactorily addressed, it will be possible to use high-precision measurements of changing stellar velocities to perform a ‘blind search’ for dark matter, make direct tests of theories of non-Newtonian gravitational dynamics, detect local inhomogeneities in the dark matter density, and greatly improve measurements of the overall properties of the galaxy.

scholarly journals Phat ELVIS: The inevitable effect of the Milky Way’s disc on its dark matter subhaloes

2019 ◽  
Vol 487 (3) ◽  
pp. 4409-4423 ◽  
Author(s):  
Tyler Kelley ◽  
James S Bullock ◽  
Shea Garrison-Kimmel ◽  
Michael Boylan-Kolchin ◽  
Marcel S Pawlowski ◽  
...  
Keyword(s):  
Dark Matter ◽  
High Resolution ◽  
Milky Way ◽  
Milky Way Galaxy ◽  
Central Galaxy ◽  
The Galaxy ◽  
Satellite Galaxies ◽  
Atomic Cooling

ABSTRACT We introduce an extension of the ELVIS project to account for the effects of the Milky Way galaxy on its subhalo population. Our simulation suite, Phat ELVIS, consists of 12 high-resolution cosmological dark matter-only (DMO) zoom simulations of Milky Way-size ΛCDM haloes [Mv = (0.7−2) × 1012 M⊙] along with 12 re-runs with embedded galaxy potentials grown to match the observed Milky Way disc and bulge today. The central galaxy potential destroys subhalos on orbits with small pericentres in every halo, regardless of the ratio of galaxy mass to halo mass. This has several important implications. (1) Most of the Disc runs have no subhaloes larger than Vmax = 4.5 km s−1 within 20 kpc and a significant lack of substructure going back ∼8 Gyr, suggesting that local stream-heating signals from dark substructure will be rare. (2) The pericentre distributions of Milky Way satellites derived from Gaia data are remarkably similar to the pericentre distributions of subhaloes in the Disc runs, while the DMO runs drastically overpredict galaxies with pericentres smaller than 20 kpc. (3) The enhanced destruction produces a tension opposite to that of the classic ‘missing satellites’ problem: in order to account for ultra-faint galaxies known within 30 kpc of the Galaxy, we must populate haloes with Vpeak ≃ 7 km s−1 (M ≃ 3 × 107 M⊙ at infall), well below the atomic cooling limit of $V_\mathrm{peak}\simeq 16 \,{\rm km} \, {\rm s}^{-1}$ (M ≃ 5 × 108M⊙ at infall). (4) If such tiny haloes do host ultra-faint dwarfs, this implies the existence of ∼1000 satellite galaxies within 300 kpc of the Milky Way.

scholarly journals Testing a possible way of geometrization of the strong interaction by a Kaluza–Klein star

2016 ◽  
Vol 31 (28n29) ◽  
pp. 1645031
Author(s):  
Szilvia Karsai ◽  
Péter Pósfay ◽  
Gergely Gábor Barnaföldi ◽  
BÉla Lukács
Keyword(s):  
Strong Interaction ◽  
Compact Star ◽  
Mass Difference ◽  
Spatial Dimension ◽  
Gravitational Theory ◽  
Compact Stars ◽  
Star Model ◽  
Fundamental Interactions ◽  
Dimension Formula ◽  
Kaluza Klein

Geometrization of the fundamental interactions has been extensively studied during the century. The idea of introducing compactified spatial dimensions originated by Kaluza and Klein. Following their approach, several model were built representing quantum numbers (e.g. charges) as compactified space-time dimensions. Such geometrized theoretical descriptions of the fundamental interactions might lead us to get closer to the unification of the principle theories. Here, we apply a [Formula: see text] dimensional theory, which contains one extra compactified spatial dimension [Formula: see text] in connection with the flavor quantum number in Quantum Chromodynamics. Within our model the size of the [Formula: see text] dimension is proportional to the inverse mass-difference of the first low-mass baryon states. We used this phenomena to apply in a compact star model — a natural laboratory for testing the theory of strong interaction and the gravitational theory in parallel. Our aim is to test the modification of the measurable macroscopical parameters of a compact Kaluza–Klein star by varying the size of the compactified extra dimension. Since larger the [Formula: see text] the smaller the mass difference between the first spokes of the Kaluza–Klein ladder resulting smaller-mass stars. Using the Tolman–Oppenheimer–Volkov equation, we investigate the [Formula: see text]-[Formula: see text] diagram and the dependence of the maximum mass of compact stars. Besides testing the validity of our model we compare our results to the existing observational data of pulsar properties for constraints.

scholarly journals On the oscillation spectra of ultra compact stars

1995 ◽  
Vol 451 (1942) ◽  
pp. 341-348 ◽  
Keyword(s):  
Energy Density ◽  
Spherical Harmonic ◽  
Compact Star ◽  
Normal Modes ◽  
Compact Stars ◽  
Real Difference ◽  
Characteristic Frequencies ◽  
Polar Mode ◽  
Uniform Energy Density ◽  
Oscillation Frequencies

Quasi-normal modes of ultra compact stars with uniform energy density have been calculated. For less compact stars, there is only one very slowly damped polar mode (corresponding to the Kelvin f-mode) for each spherical harmonic index l . Further long-lived modes become possible for a sufficiently compact star (roughly when M/R ≥ 1/3). We compare the characteristic frequencies of these resonant polar modes to the axial modes first found by Chandrasekhar & Ferrari ( Proc. R. Soc. Lond . A 434, 449 (1991)). We find that the two spectra approach each other as the star is made more compact. The oscillation frequencies of the corresponding polar and axial modes agree to within a percent for stars more compact than M/R = 0.42. At the same time, the damping times are slightly different. The results illustrate that there is no real difference between the origin of these axial and polar modes: They are essentially spacetime modes.

Physical behavior of anisotropic compact stars in f(R, T, RμνTμν) gravity

2016 ◽  
Vol 94 (10) ◽  
pp. 1024-1039 ◽  
Author(s):  
M. Sharif ◽  
Arfa Waseem
Keyword(s):  
Energy Density ◽  
Compact Star ◽  
Compact Stars ◽  
Energy Conditions ◽  
Effective Energy ◽  
Stability Criteria ◽  
Physical Behavior ◽  
Regular Behavior ◽  
Star Models ◽  
Anisotropic Factor

This paper investigates the behavior of anisotropic compact stars in the background of R + αRμνTμν gravity model. For this purpose, we use Krori–Barua metric solutions where constants are calculated using masses and radii of compact stars like Her X-1, SAX J 1808.4–3658, and 4U1820–30. We analyze regular behavior of effective energy density, and radial and transverse pressures in the interior of compact stars. We also discuss energy conditions, effect of anisotropic factor, and stability criteria of these stars. It is concluded that the considered compact star models satisfy all the energy conditions and remain stable against the anisotropic effect in this gravity.

Charged anisotropic compact stars in Logarithmic-Corrected R2 gravity

2020 ◽  
Vol 35 (04) ◽  
pp. 2050013 ◽  
Author(s):  
M. Farasat Shamir ◽  
I. Fayyaz
Keyword(s):  
Energy Density ◽  
Electric Charge ◽  
Graphical Representation ◽  
Strong Electric Field ◽  
Compact Star ◽  
Compact Stars ◽  
Fluid Distribution ◽  
Anisotropic Fluid ◽  
Distribution Factor ◽  
Field Equations

We consider [Formula: see text] corrected model, i.e. [Formula: see text], where [Formula: see text] is the Ricci scalar and [Formula: see text], [Formula: see text] are arbitrary constant values, to investigate some of the interior configurations of static anisotropic spherical charged stellar structures. The existence of electric charge and a strong electric field confirms due to the higher values of pressure distribution and energy density of the matter inside the stars. Furthermore, for compact star configurations, we also consider the simplified MIT bag model equation of state (EoS) given by [Formula: see text], where [Formula: see text] is radial pressure, [Formula: see text] is energy density and [Formula: see text] is bag constant. This approach allows to find electric charge from the Einstein–Maxwell field equations. We have extensively discussed the behavior of the electric charge and anisotropic fluid distribution factor for five different values of [Formula: see text]. Interestingly, it is noticed during this study, for smaller values of [Formula: see text] we get intensity in electric charge. The Tolman–Oppenheimer–Volkoff equation (TOV), is modified in order to carry electric charge. In particular, we model the compact star candidates SAXJ 1808.4–3658 and Vela X-1 and give graphical representation of some important properties such as equilibrium condition, mass-radius ratio and surface redshift. In the end, our calculated solutions provide strong evidences for more realistic and viable charged stellar model.

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