Transport Coefficients of Hyperonic Neutron Star Cores

We consider transport properties of the hypernuclear matter in neutron star cores. In particular, we calculate the thermal conductivity, the shear viscosity, and the momentum transfer rates for npΣ−Λeμ composition of dense matter in β–equilibrium for baryon number densities in the range 0.1–1 fm−3. The calculations are based on baryon interactions treated within the framework of the non-relativistic Brueckner-Hartree-Fock theory. Bare nucleon-nucleon (NN) interactions are described by the Argonne v18 phenomenological potential supplemented with the Urbana IX three-nucleon force. Nucleon-hyperon (NY) and hyperon-hyperon (YY) interactions are based on the NSC97e and NSC97a models of the Nijmegen group. We find that the baryon contribution to transport coefficients is dominated by the neutron one as in the case of neutron star cores containing only nucleons. In particular, we find that neutrons dominate the total thermal conductivity over the whole range of densities explored and that, due to the onset of Σ− which leads to the deleptonization of the neutron star core, they dominate also the shear viscosity in the high density region, in contrast with the pure nucleonic case where the lepton contribution is always the dominant one.

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Recalculation of the friction constant and transport coefficients of liquid argon from the Rice-Allnatt theory

Australian Journal of Chemistry ◽

10.1071/ch9710225 ◽

1971 ◽

Vol 24 (2) ◽

pp. 225 ◽

Cited By ~ 5

Author(s):

AF Collings ◽

LA Woolf

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Distribution Function ◽

Shear Viscosity ◽

Transport Coefficients ◽

Liquid Argon ◽

Viscosity Data ◽

Liquid Region ◽

Linear Trajectory ◽

Momentum And Heat Transfer

The linear trajectory approximation of the ?soft? friction constant in the Rice-Allnatt theory of transport has been computed with specific attention to the lower limit of the integral. The results are significantly different from the Palyvos-Davis values for ζS in the dense gas region but agree within 2% in the liquid region. The Rice- Allnatt expressions for the coefficients of shear viscosity and thermal conductivity have been simplified and a correction of a numerical error in the collisional contributions to momentum and heat transfer is made. The coefficients D, η, and λ have been calculated for the corrected ζS and related expressions. No significant change in D is obtained, but a worsening of agreement with experimental viscosities and thermal conductivities occurs. Conversely, a better prediction of the ratio mλ/kη is obtained. More recent viscosity data for liquid argon indicate the theory is less satisfactory than has previously been considered. These results suggest that any improvement of this class of theory can only come through the use of a better representation of the radial distribution function.

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On the transport properties of a Van der Waals gas near the critical point

Canadian Journal of Physics ◽

10.1139/p68-653 ◽

1968 ◽

Vol 46 (24) ◽

pp. 2821-2841 ◽

Cited By ~ 2

Author(s):

Luis de Sobrino

Keyword(s):

Thermal Conductivity ◽

Time Dependence ◽

Critical Point ◽

Bulk Viscosity ◽

Shear Viscosity ◽

Van Der Waals ◽

Transport Coefficients ◽

Hydrodynamic Equations ◽

Van Der Waals Gas ◽

Critical Fluctuations

A calculation of the critical anomalies of the transport coefficients of a simple fluid based on a microscopic model of a nonequilibrium Van der Waals gas is presented. It is found that, in the gas region, the anomalous bulk viscosity behaves as (T – Tc)−2. Both the anomalous thermal conductivity and shear viscosity behave as In (T – Tc)−1, but the anomaly in the shear viscosity is much smaller than the anomaly in the thermal conductivity. The results appear to indicate that previous calculations, in which the time dependence of the critical fluctuations is obtained from hydrodynamic equations, are not valid.

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Transport coefficients of the Lennard–Jones fluid by molecular dynamics

Canadian Journal of Physics ◽

10.1139/p86-139 ◽

1986 ◽

Vol 64 (7) ◽

pp. 773-781 ◽

Cited By ~ 21

Author(s):

D. M. Heyes

Keyword(s):

Thermal Conductivity ◽

Molecular Dynamics ◽

Bulk Viscosity ◽

Shear Viscosity ◽

Diffusion Coefficients ◽

Transport Coefficients ◽

The Self ◽

Nonequilibrium Molecular Dynamics ◽

Self Diffusion ◽

Lennard Jones

New nonequilibrium molecular dynamics (MD) calculations of the shear viscosity, bulk viscosity, and thermal conductivity are presented. Together with the self-diffusion coefficients obtained from equilibrium MD, the success of the Dymond–Batchinski expressions for the density and temperature dependence of these transport coefficients is demonstrated.The shear viscosity and self-diffusion coefficients are very good probes for the approach point of the solid-to-liquid phase change. The bulk viscosity and thermal conductivity are less useful in this respect.

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Neutron Star Cooling: Criticical Test of Dense Matter Physics

Symposium - International Astronomical Union ◽

10.1017/s007418090016108x ◽

1987 ◽

Vol 125 ◽

pp. 439-446

Author(s):

Naoki Itoh

Keyword(s):

Thermal Conductivity ◽

Neutron Star ◽

Energy Loss ◽

Dense Matter ◽

Neutrino Energy ◽

Standard Theory ◽

Recent Developments ◽

Neutron Star Cooling ◽

Loss Rates

Recent developments in the standard theory of neutron star cooling is critically reviewed. Emphasis is placed on the recent developments in the calculations of thermal conductivity and neutrino energy loss rates.

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Moderately dense gas transport coefficients via time correlation functions. II. Shear viscosity and thermal conductivity

The Journal of Chemical Physics ◽

10.1063/1.479984 ◽

1999 ◽

Vol 111 (15) ◽

pp. 6922-6931 ◽

Cited By ~ 1

Author(s):

Saman Alavi ◽

R. F. Snider

Keyword(s):

Thermal Conductivity ◽

Shear Viscosity ◽

Correlation Functions ◽

Gas Transport ◽

Transport Coefficients ◽

Time Correlation ◽

Time Correlation Functions ◽

Dense Gas

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Effective Thermal Conductivity of Open Cell Polyurethane Foam Based on the Fractal Theory

Advances in Materials Science and Engineering ◽

10.1155/2013/125267 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Kan Ankang ◽

Han Houde

Keyword(s):

Thermal Conductivity ◽

Fractal Dimension ◽

Effective Thermal Conductivity ◽

Polyurethane Foam ◽

Solid Phase ◽

Fractal Theory ◽

Heat Radiation ◽

Total Thermal Conductivity ◽

Equivalent Thermal Conductivity ◽

Open Cell

Based on the fractal theory, the geometric structure inside an open cell polyurethane foam, which is widely used as adiabatic material, is illustrated. A simplified cell fractal model is created. In the model, the method of calculating the equivalent thermal conductivity of the porous foam is described and the fractal dimension is calculated. The mathematical formulas for the fractal equivalent thermal conductivity combined with gas and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity, are deduced. However, the total effective heat flux is the summation of the heat conduction by the solid phase and the gas in pores, the radiation, and the convection between gas and solid phase. Fractal mathematical equation of effective thermal conductivity is derived with fractal dimension and vacancy porosity in the cell body. The calculated results have good agreement with the experimental data, and the difference is less than 5%. The main influencing factors are summarized. The research work is useful for the enhancement of adiabatic performance of foam materials and development of new materials.

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UV and X-ray observations of the neutron star LMXB EXO 0748–676 in its quiescent state

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3734 ◽

2020 ◽

Vol 501 (1) ◽

pp. 1453-1462

Author(s):

A S Parikh ◽

N Degenaar ◽

J V Hernández Santisteban ◽

R Wijnands ◽

I Psaradaki ◽

...

Keyword(s):

Neutron Star ◽

Thermal Emission ◽

Hubble Space Telescope ◽

Dense Matter ◽

Continuum Emission ◽

Quiescent State ◽

X Ray ◽

Low Level ◽

Low Mass ◽

Different Origins

ABSTRACT The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <1034 erg s−1, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here, we examine ultraviolet (UV) and X-ray data obtained when EXO 0748–676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, C iv. The line is relatively broad (≳3500 km s−1), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM–Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of LX/LUV ≳ 100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748–676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.

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Multiscale Simulations of Thermoelectric Properties of PBTE

ASME 2008 3rd Energy Nanotechnology International Conference ◽

10.1115/enic2008-53040 ◽

2008 ◽

Cited By ~ 3

Author(s):

Bo Qiu ◽

Hua Bao ◽

Xiulin Ruan

Keyword(s):

Thermal Conductivity ◽

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Thermoelectric Properties ◽

Transport Coefficients ◽

Multiscale Simulation ◽

Full Potential ◽

Boltzmann Transport ◽

Pair Potentials ◽

Dynamics Simulations

In this paper, thermoelectric properties of bulk PbTe are calculated using first principles calculations and molecular dynamics simulations. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is first employed to calculate the PbTe band structure. The transport coefficients (Seebeck coefficient, electrical conductivity, and electron thermal conductivity) are then computed using Boltzmann transport equation (BTE) under the constant relaxation time approximation. Interatomic pair potentials in the Buckingham form are also derived using ab initio effective charges and total energy data. The effective interatomic pair potentials give excellent results on equilibrium lattice parameters and elastic constants for PbTe. The lattice thermal conductivity of PbTe is then calculated using molecular dynamics simulations with the Green-Kubo method. In the end, the figure of merit of PbTe is computed revealing the thermoelectric capability of this material, and the multiscale simulation approach is shown to have the potential to identify novel thermoelectric materials.

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