The Contribution of Degenerate Electron Pressure to The Stability of The Outer Region of Thin Keplerian Accretion Disks Around a Neutron Star

2015 ◽  
Vol 11 (1) ◽  
pp. 2886-2891
Author(s):  
Abbi Seyoum Demissie
Keyword(s):  
Neutron Star ◽  
Accretion Disks ◽  
Outer Region ◽  
Thin Disk ◽  
Gas Pressure ◽  
Degenerate Electron ◽  
Small Temperature ◽  
Radial Perturbation ◽  
The Stability ◽  
Definite Temperature

The stability analysis of a geometrically thin, gas-pressure dominated accretion disk around a neutron star is presented. In purely radial perturbation case, thin disk is stable to thermal modes. The stability is analyzed at a small temperature, that is temperature approaching zero and at definite temperature. The contribution of both fully and partially degenerate electrons pressure for the stability of the disk in its outer region is investigated. We find that the disk is stable in this region, where the gas pressure is more dominant than radiation pressure.

The radial–azimuthal instability of accretion disk with anomalous viscosity

2014 ◽  
Vol 92 (5) ◽  
pp. 395-400
Author(s):  
Yue Qi Chen ◽  
Wei Qun Jiang
Keyword(s):  
Numerical Simulations ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Radiation Pressure ◽  
Gas Pressure ◽  
Thermal Mode ◽  
Acoustic Modes ◽  
Anomalous Viscosity ◽  
The Stability ◽  
Inner Region

The stability of the accretion disk is solved by numerical simulations when the radial and azimuthal perturbations are considered, where we adopt the anomalous viscosity model, which is close to real accretion disks. The results are discussed in the inner, intermediate, and outer regions of the accretion disk, respectively. With the increase of viscosity, α, the thermal mode and the viscous mode, as well as the acoustic modes, become more unstable in the disk dominated by radiation pressure (inner region). The instability is also influenced by the azimuthal perturbation wavenumber, n. With the increase of n, the thermal mode becomes more unstable, while the in-mode and out-mode become more stable no matter if the disk is dominated by radiation pressure or by gas pressure (intermediate and outer regions). There are many differences between our results and others’ results, especially in the inner region of the disk, when the anomalous viscosity is considered.

scholarly journals Warped Accretion Disks and Longterm X-Ray Periodicities

2004 ◽  
Vol 194 ◽  
pp. 136-137
Author(s):  
W. I. Clarkson ◽  
P. A. Charles ◽  
S. Laycock ◽  
M. J. Coe ◽  
C. Wilson-Hodge ◽  
...  
Keyword(s):  
Neutron Star ◽  
Accretion Disks ◽  
Theoretical Work ◽  
Mass Ratio ◽  
X Ray ◽  
Physical Mechanisms ◽  
Recent Theoretical Work ◽  
The Stability ◽  
X Ray Binaries

AbstractA significant number of X-ray binaries are now known to exhibit long-term periodicities on timescales of ~10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, one of which is radiation-driven warping and precession of the accretion disk. Recent theoretical work predicts the stability to disk warping as a, function of the mass ratio, binary radius, viscosity and accretion efficiency. We investigate the stability of the superorbital periodicities in the neutron star X-ray binaries Cyg X-2, LMC X-4, SMC X-l and Her X-l, and thereby confront stability predictions with observation. We find that the period and nature of the superorbital variations in these sources is consistent with the predictions of warping theory.

scholarly journals Numerical Investigation on Shape Optimization of Small-Spacing Twin-Well for Salt Cavern Gas Storage in Ultra-Deep Formation

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2859
Author(s):  
Haitao Li ◽  
Jingen Deng ◽  
Qiqi Wanyan ◽  
Yongcun Feng ◽  
Arnaud Regis Kamgue Lenwoue ◽  
...  
Keyword(s):  
Safety Evaluation ◽  
Gas Storage ◽  
Gas Pressure ◽  
Salt Cavern ◽  
Well Spacing ◽  
3D Geomechanical Model ◽  
The Stability ◽  
Bedded Rock Salt ◽  
Salt Cavern Gas Storage ◽  
Small Spacing

Small-spacing twin-well (SSTW) salt caverns have an extensive application prospect in thin or bedded rock salt formations due to their good performance, while they are rarely used in ultra-deep formations. The target strata depth of Pingdingshan salt mine is over 1700 m, and it is planned to apply an SSTW cavern to construct the underground gas storage (UGS). A 3D geomechanical model considering the viscoelastic plasticity of the rock mass is introduced into Flac3D to numerically study the influence of internal gas pressure, cavern upper shape and well spacing on the stability of an SSTW salt cavern for Pingdingshan UGS. A set of assessment indices is summarized for the stability of gas storage. The results show that the minimum internal gas pressure is no less than 14 MPa, and the cavern should not be operated under constant low gas pressure for a long time. The cavern with an upper height of 70 m is recommended for Pingdingshan gas storage based on the safety evaluation and maximum volume. The well spacing has a limited influence on the stability of the salt cavern in view of the volume shrinkage and safety factor. Among the values of 10 m, 20 m and 30 m, the well spacing of 20 m is recommended for Pingdingshan gas storage. In addition, when the cavern groups are constructed, the pillar width on the short axis should be larger than that on the long axis due to its greater deformation in this direction. This study provides a design reference for the construction of salt cavern gas storage in ultra-deep formations with the technology of SSTW.

scholarly journals Stability of thin-shell wormholes from noncommutative BTZ black hole

2015 ◽  
Vol 24 (05) ◽  
pp. 1550034 ◽  
Author(s):  
Piyali Bhar ◽  
Ayan Banerjee
Keyword(s):  
Black Hole ◽  
Thin Shell ◽  
Static Solution ◽  
Dynamical Analysis ◽  
Energy Conditions ◽  
Btz Black Hole ◽  
Wormhole Throat ◽  
Radial Perturbation ◽  
Thin Shell Wormholes ◽  
The Stability

In this paper, we construct thin-shell wormholes in (2 + 1)-dimensions from noncommutative BTZ black hole by applying the cut-and-paste procedure implemented by Visser. We calculate the surface stresses localized at the wormhole throat by using the Darmois–Israel formalism and we find that the wormholes are supported by matter violating the energy conditions. In order to explore the dynamical analysis of the wormhole throat, we consider that the matter at the shell is supported by dark energy equation of state (EoS) p = ωρ with ω < 0. The stability analysis is carried out of these wormholes to linearized spherically symmetric perturbations around static solutions. Preserving the symmetry we also consider the linearized radial perturbation around static solution to investigate the stability of wormholes which was explored by the parameter β (speed of sound).

scholarly journals Non-spherical nucleon clusters in the mantle of a neutron star: CLDM based on Skyrme-type forces

2021 ◽  
Vol 2103 (1) ◽  
pp. 012004
Author(s):  
N A Zemlyakov ◽  
A I Chugunov ◽  
N N Shchechilin
Keyword(s):  
Neutron Star ◽  
Nuclear Matter ◽  
Liquid Drop ◽  
Outer Region ◽  
Spherical Shape ◽  
Baryon Number ◽  
Compressible Liquid ◽  
Liquid Drop Model ◽  
The Core ◽  
Nuclear Clusters

Abstract Neutron stars are superdense compact astrophysical objects. The central region of the neuron star (the core) consists of locally homogeneous nuclear matter, while in the outer region (the crust) nucleons are clustered. In the outer crust these nuclear clusters represent neutron-rich atomic nuclei and all nucleons are bound within them. Whereas in the inner crust some neutrons are unbound, but nuclear clusters still keeps generally spherical shape. Here we consider the region between the crust and the core of the star, so-called mantle, where non-spherical nuclear clusters may exist. We apply compressible liquid drop model to calculate the energy density for several shape types of nuclear clusters. It allows us to identify the most energetically favorable configuration as function of baryon number density. Employing four Skyrme-type forces (SLy4 and BSk24, BSk25, BSk26), which are widely used in the neutron star physics, we faced with strong model dependence of the ground state composition. In particular, in agreement with previous works within liquid drop model, mantle is absent for SLy4 (nuclear spheres directly transit into homogeneous nuclear matter; exotic nuclear shapes do not appear).

scholarly journals Gas Pressure Sensor Based on BDK-Doped Polymer Optical Fiber

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 717 ◽  
Author(s):  
Xin Cheng ◽  
Yi Liu ◽  
Changyuan Yu
Keyword(s):  
Optical Fiber ◽  
Pressure Sensor ◽  
Chemical Structure ◽  
High Sensitivity ◽  
Gas Pressure ◽  
Air Pressure ◽  
Response Behavior ◽  
Polymer Optical Fiber ◽  
The Stability ◽  
Doped Polymer

This paper presents a high sensitivity gas pressure sensor with benzyl-dimethylketal (BDK)-doped polymer optical fiber Bragg grating (POFBG), whose sensitivity is up to 8.12 pm/kPa and 12.12 pm/kPa in positive and negative pressure atmosphere, respectively. The high sensitivity can be explained by its porous chemical structure. The stability and response behavior under air pressure atmosphere has also been investigated. The new understanding of the air pressure response principle and sensitivity difference for the presented sensor can be a worthy reference.

scholarly journals Photophoresis in the circumjovian disk and its impact on the orbital configuration of the Galilean satellites

2019 ◽  
Vol 629 ◽  
pp. A106 ◽  
Author(s):  
Sota Arakawa ◽  
Yuhito Shibaike
Keyword(s):  
Density Distribution ◽  
Accretion Disks ◽  
Surface Density ◽  
Outer Region ◽  
Dust Particles ◽  
Magnetorotational Instability ◽  
Galilean Satellites ◽  
Ionization Fraction ◽  
Orbital Configuration ◽  
Inner Region

Jupiter has four large regular satellites called the Galilean satellites: Io, Europa, Ganymede, and Callisto. The inner three of the Galilean satellites orbit in a 4:2:1 mean motion resonance; therefore their orbital configuration may originate from the stopping of the migration of Io near the bump in the surface density distribution and following resonant trapping of Europa and Ganymede. The formation mechanism of the bump near the orbit of the innermost satellite, Io, is not yet understood, however. Here, we show that photophoresis in the circumjovian disk could be the cause of the bump using analytic calculations of steady-state accretion disks. We propose that photophoresis in the circumjovian disk could stop the inward migration of dust particles near the orbit of Io. The resulting dust-depleted inner region would have a higher ionization fraction, and thus admit increased magnetorotational-instability-driven accretion stress in comparison to the outer region. The increase of the accretion stress at the photophoretic dust barrier would form a bump in the surface density distribution, halting the migration of Io.

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