Density fluctuations in granular piles traversing the glass transition: A grain-scale characterization via the internal energy

The grain-scale dynamics of the internal energy inside a tapped granular pile is studied, advancing on a kinetic theory of grains.

Jeans analysis with κ-deformed Kaniadakis distribution in f (R) gravity

The influence of the κ-deformed Kaniadakis distribution on Jeans instability in the background of f(R) gravity is investigated, the dispersion relation considering the κ-deformed Kaniadakis distribution is derived by exploiting the kinetic theory. The cases of high and low frequency perturbations are analyzed, respectively, it is found that the range of the unstable modes and the growth rates decrease with the increased distribution index κ in both of high and low frequency regime. Finally, based on the derivation of effective temperature, the relation between Jeans mass and temperature is studied, it is found that lower Jeans mass means that the system is more likely to collapse due to gravitational instability, the system is unstable for lower distribution index κ.

On the derivation of the Landau-Lifshitz frame in relativistic kinetic theory

The Landau-Lifshitz frame has been widely used to represent the macroscopic quantities of relativistic hydrodynamics in the presence of the dissipative process. In this paper, we derive the Landau-Lifshitz frame in the near-equilibrium regime under self-contained assumptions that do not require comparison with the Eckart frame. And then we revisit the relativistic BGK model proposed by Anderson and Witting to provide an application example of the Landau-Lifshitz frame.

Longitudinal remagnetization of uniaxial antiferromagnetic nanoparticles: the role of spontaneous magnetic moment

A kinetic theory of magnetic response of uniaxial antiferromagnetic nanoparticles is presented. Within the developed framework, a particular case when an external field is applied strictly along the anisotropy axis is considered in detail. Analysis of the relaxation spectrum of an antiferromagnetic particle with a spontaneous magnetic moment is performed. It is shown that in a wide frequency range the magnetic response of such particle is determined entirely by the relaxation mode with the longest time. An analytical expression for this time that explicitly contains a value of the decompensation magnetic moment is derived. Also, simple formulae for both static and dynamic longitudinal magnetic susceptibility of an antiferromagnetic nanoparticle are obtained. According to them, longitudinal susceptibility grows quadratically with the value of the spontaneous magnetic moment. Besides, if the latter is not zero, the change of the static susceptibility with temperature turns out to be non-monotonic. The influence of the spontaneous magnetic moment of the particle on the magnetization curves in strong fields is analysed using both energy approach and kinetic theory. The calculated dependences of the dynamic coercivity on the amplitude and variation rate of the applied field are qualitatively compared with experimental data. This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.

Profile of Guided Discovery Learning Implementation Assisted by Virtual Lab and Students’ Problem-Solving Skills on Gas Kinetic Theory

This research was conducted to obtain a guided discovery learning implementation profile with virtual lab assistance and problem-solving skills for high school students on gas kinetic theory. The type of research was descriptive preliminary research, without hypothesis testing. The research subjects consisted of 106 students in senior high school. This study used qualitative descriptive analysis from questionnaires and online tests. This study revealed that the level of students’ problem-solving skills was low. This case was proven by 102 students (27 male; 75 female) in the low category with a score range of 0 to 45, and four students in the moderate category with a score range of 46 to 75, while there were no students in the high category with a score range of 76 to 100. This research implies that there is a need for a guided discovery learning model with the help of a virtual lab to analyze the problem-solving skills of high school students, especially on gas kinetic theory.

A kinetic theory model for rain out and wash out of soluble gaseous air pollutants

A new theory, using kinetic theory of gases, for dissolution of gaseous air pollutants and applicable both for wash out and rain out processes has been proposed. It has been shown that the current theory of wash out of gases given by Hales (1972) is a special case of the general theory proposed here.

Cutting rules on a cylinder: a simplified diagrammatic approach to quantum kinetic theory

Nonequilibrium quantum field theory is often used to derive an approximation for the evolution of number densities and asymmetries in astroparticle models when a more precise treatment of quantum thermal effects is required. This work presents an alternative framework using the zero-temperature quantum field theory, S-matrix unitarity, and classical Boltzmann equation as starting points leading to a set of rules for calculations of thermal corrections to reaction rates. Statistical factors due to on-shell intermediate states are obtained from the cuts of forward diagrams with multiple spectator lines. It turns out that it is equivalent to cutting closed diagrams on a cylindrical surface.