Relaxation-time approximation for a Boltzmann gas in Robertson-Walker universe models

1995 ◽  
Vol 34 (5) ◽  
pp. 761-777 ◽  
Author(s):  
Zbigniew Banach ◽  
Hanna Makaruk
Keyword(s):  
Relaxation Time ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Boltzmann Gas ◽  
Universe Models

scholarly journals Bulk viscosity of strongly interacting matter in the relaxation time approximation

2018 ◽  
Vol 97 (4) ◽  
Author(s):  
Alina Czajka ◽  
Sigtryggur Hauksson ◽  
Chun Shen ◽  
Sangyong Jeon ◽  
Charles Gale
Keyword(s):  
Relaxation Time ◽  
Bulk Viscosity ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Strongly Interacting

scholarly journals Calculations of the thermal conductivity of Si1-xGex films with nonuniform composition

2018 ◽  
Vol 19 (1) ◽  
pp. 48-52
Author(s):  
V. V. Kuryliuk ◽  
O. M. Krit
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Boltzmann Equation ◽  
Temperature Interval ◽  
Thermoelectric Properties ◽  
Bulk Material ◽  
Nonuniform Distribution ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Available Information

SiGe films have attracted much attention recently due to experimental demonstrations of improved thermoelectric properties over those of the corresponding bulk material. However, despite this increasing attention, available information on the thermoelectric properties of Si1-xGex films is quite limited, especially for nonuniform composition in wide temperature interval. In this paper we have used the Boltzmann equation under the relaxation-time approximation to calculate the thermal conductivity of Si1-xGex films with nonuniform composition. It is confirmed that SiGe films with nonuniform composition has significantly lower thermal conductivity than its uniform counterpart. This suggests that an improvement in thermoelectric properties is possible by using the SiGe films with nonuniform distribution of germanium.

Longitudinal magnetoresistance in silver and copper between 4.2 and 35 °K

1967 ◽  
Vol 302 (1468) ◽  
pp. 83-98 ◽  
Keyword(s):  
Relaxation Time ◽  
Electron Scattering ◽  
Small Angle ◽  
Time Approximation ◽  
Long Wavelength ◽  
Relaxation Time Approximation ◽  
Angle Scattering ◽  
Different Types ◽  
Pure Single Crystal ◽  
Longitudinal Magnetoresistance

Longitudinal magnetoresistance has been measured in a number of single crystals of silver and one very pure single crystal of copper in fields up to 65 kG and at temperatures between 4.2 and 35 °K. The purpose of the work has been to investigate the effects of different types of electron scattering, in particular small angle scattering. It has been found that at 4.2 °K impure crystals obey the relaxation time approximation fairly well, whereas crystals that have been purified (by oxidation at 800 °C) do not. Above 4.2 °K, the addition of long wavelength phonons has caused the magnetoresistance to increase substantially, as predicted by Pippard (1964), but agreement with Pippard’s theory is only qualitative. To account for the results a more detailed treatment of the scattering is required.

LATTICE THERMAL CONDUCTIVITY IN A HOLLOW SILICON NANOWIRE

2005 ◽  
Vol 19 (06) ◽  
pp. 1017-1027 ◽  
Author(s):  
WEI-QING HUANG ◽  
KE-QIU CHEN ◽  
Z. SHUAI ◽  
LINGLING WANG ◽  
WANGYU HU
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Silicon Nanowire ◽  
Boundary Scattering ◽  
Phonon Confinement ◽  
Time Approximation ◽  
Si Nanowire ◽  
Scattering Mechanisms ◽  
Relaxation Time Approximation

We theoretically investigate the lattice thermal conductivity of a hollow Si nanowire under the relaxation time approximation. The results show that the thermal conductivity in such structure is decreased markedly below the bulk value due to phonon confinement and boundary scattering. The thermal conductivities under different scattering mechanisms are given, and it is found that the boundary scattering is dominant resistive process for the decrease of the thermal conductivity.

scholarly journals Kinetic equations and anisotropic hydrodynamics for quark and gluon fluids

2018 ◽  
Vol 182 ◽  
pp. 02079
Author(s):  
Ewa Maksymiuk
Keyword(s):  
Relaxation Time ◽  
Kinetic Theory ◽  
Quark Mass ◽  
Kinetic Equations ◽  
Baryon Number ◽  
Number Density ◽  
Time Approximation ◽  
One Dimensional ◽  
Relaxation Time Approximation ◽  
Good Agreement

The mixture of quark and gluon fluids is studied in a one-dimensional boostinvariant setup using the set of relativistic kinetic equations treated in the relaxation time approximation. Effects of a finite quark mass, non-zero baryon number density, and quantum statistics are discussed. Comparisons between the exact kinetic-theory results and anisotropic hydrodynamics predictions are performed and a very good agreement between the two are found.

A Non-Quasi-Static Model for Tunneling FETs Based on the Relaxation Time Approximation

2019 ◽  
Vol 40 (12) ◽  
pp. 1996-1999
Author(s):  
Bin Lu ◽  
Zhijun Lv ◽  
Hongliang Lu ◽  
Yan Cui
Keyword(s):  
Relaxation Time ◽  
Static Model ◽  
Time Approximation ◽  
Relaxation Time Approximation
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