Kinetics of relativistic axionically active plasma in the field of dynamic aether. Part II: Particle dynamics and symptoms of plasma instability

TL;DR

This work develops a collisionless kinetic theory for a relativistic multi-component plasma coupled to an axion field and dynamic aether in a cosmological FLRW background, presenting exact distribution functions $f_{(a)}(K_0,\ldots, K_6)\,\delta(K_0-m^2_{(a)}c^2)$. By analyzing five background evolutions and the axion–aether induced forces, it shows that curvature couplings can split the plasma into hot and cold sub-populations and drive diverse particle-dynamics regimes, including ultra-relativistic growth or cooling depending on the balance of Stokes and tidal terms. The results lay a concrete groundwork for instability analysis in axion-aether plasmas and anticipate gravitational-wave–driven currents as a route to plasma instabilities, to be explored in Part III. The framework integrates an aether vector, axion dark matter, electromagnetism, and gravity within a unified kinetic description.

Abstract

In the paper [I], the first part of our work, we established the model of interaction of five elements: first, a unit time-like vector field, associated with the velocity of dynamic aether, second, the pseudoscalar field describing an axionic component of the dark matter, third, the electromagnetic field, fourth, the relativistic multi-component plasma and, fifth, the gravitational field. The initial step of analysis of this model was the reconstruction of the equilibrium states of the axionically-aetherically active plasma, which are characterized by frequent inter-particle collisions. In the second part of the work, presented here, in the framework of isotropic homogeneous cosmological model we consider the collisionless limit of the theory, and thus, we focus on the analysis of the particle dynamics under the influence of axionically-aetherically induced forces. The complete distribution functions, as exact solutions to the kinetic equations, are presented. Based on five examples of the background solutions of the model, we discuss the symptoms of plasma instability provoked by the influence of forces of the friction and tidal types.

Figures (8)

• Figure 2: Illustration of the behavior of the particle momentum for the quasi-periodic space-time platform. For illustration we put $\rho {=} 1$.
• Figure 3: Illustration of the formula (\ref{['A11']}) for the case (\ref{['SPS1']}), when only one parameter $\Theta$ is varying. On the panel a) the third curve with $\Theta {=} \Theta_* {\approx} 15.72$ plays the role of some separatrix: when $\Theta {<} \Theta_*$, extrema do not appear. On the panel b) we present the illustrations with $\Theta{>}\Theta_*$; clearly, these curves have minima and maxima.
• Figure 4: Illustration of the formula (\ref{['A11']}) for the case (\ref{['SPS1']}), when only one parameter $\lambda_{(G)}$ is varying and the value of $\Theta$ is fixed by $\Theta{=}1{<}\Theta_*$. On the panel a) the upper curve with $\lambda_{(G)}{=} \lambda_{(G)}^{*} {\approx} -6.21$ plays the role of separatrix: when $\lambda_{(G)} {>} \lambda_{(G)}^{*}$, extrema do not appear. On the panel b) we present the illustrations with $\lambda_{(G)} {<} \lambda_{(G)}^{*}$; these curves have maxima.
• Figure 5: Illustration of the behavior of the particle momentum: the panel a) corresponds to the formula (\ref{['SPS2']}) and panel (b) to the formula (\ref{['SPS3']}).
• Figure 6: The panel a) illustrates the behavior of the particle momentum for the axion field described by the formula (\ref{['SPS5']}) with $\phi(t_0){=}0$ and $m_A t_0 {=} 1$. The panel (b) visualizes the case related to the formula (\ref{['SPS71']}) with $\phi(t_0){=}0$ and $\nu {=} 1$. Here $\Xi {=} \frac{\dot{\phi}(t_0)}{m_{A}}$ and $\Theta {=} \frac{\dot{\phi}(t_0)}{H_0}.$