Conductance Theory of Nonideal Plasmas

The conductivity of nonideal plasmas is investigated by using the kinetic theory as well as the Kubo-type correlation function theory. The effects of dynamical screening, short range forces and the Debye-Onsager relaxation effect on the conductance problem are considered without and with quantum mechanical corrections. For some special plasmas it is found that deviations from Coulomb's law and quantum effects have only a small effect on the conductivity, whereas the numerically most important effects are connected with the dynamical screening and with the Debye-Onsager relaxation force.     

Quantum kinetic theory of trapped particles in a strong electromagnetic field

The idea of treating quantum systems by semiclassical representations using effective quantum potentials (forces) has been successfully applied in equilibrium by many authors, see e.g. [D. Bohm, Phys. Rev. 85 (1986) 166 and 180; D.K. Ferry, J.R. Zhou, Phys. Rev. B 48 (1993) 7944; A.V. Filinov, M. Bonitz, W. Ebeling, J. Phys. A 36 (2003) 5957 and references cited therein]. Here, this idea is extended to nonequilibrium quantum systems in an external field. A gauge-invariant quantum kinetic theory for weakly inhomogeneous charged particle systems in a strong electromagnetic field is developed within the framework of nonequilibrium Green’s functions. The equation for the spectral density is simplified by introducing a classical (local) form for the kinetics. Nonlocal quantum effects are accounted for in this way by replacing the bare external confinement potential with an effective quantum potential. The equation for this effective potential is identified and solved for weak inhomogeneity in the collisionless limit. The resulting nonequilibrium spectral function is used to determine the density of states and the modification of the Born collision operator in the kinetic equation for the Wigner function due to quantum confinement effects.     

Motions of particles in an oscillating plasma

An alternative consideration of oscillations and waves in plasma is suggested based on equations for small deflections of particles from their equilibrium trajectories instead of equations for perturbations of distribution functions and fields, so that average values are calculated with equilibrium distribution functions. Instead of the Maxwell equations for an electromagnetic field their solutions in the Lienard-Wiechert form are used. All the known results of the linear kinetic theory of plasma oscillations are shown to be derivable in this way, and small correlations for dispersion relations of the first order in the plasma parameter due to the Debye screening have been obtained. A simplified consideration of a rarefield plasma in a strong magnetic field is given showing a non-cyclotron character of the motion of the particles. Such a combination of statistical and dynamical approaches may be useful in many problems of plasma physics.     

Investigation of the particle spin properties on the velocity space instability in high‐density plasmas

The nonresonant electromagnetic instabilities of the anisotropic velocity space (Weibel‐like) have always been one of the interesting subjects for researchers. These electromagnetic instabilities play an important role in generating strong magnetic fields in laboratory plasmas for applications such as inertial confinement fusion and space plasmas. In this paper, we investigate the quantum effects of the particle spin on the electromagnetic instabilities. In the case of the presence of a magnetic dipole force and an electron precession frequency like the Vlasov equation, we derive the full quantum equation. This study shows that, in the presence of the spin‐polarized effects, the growth rate of the instabilities is reduced compared to the classical cases and will not arise for low fractions of the temperature anisotropy for different values of the magnetic field. Indeed, it is expected that the probability of electron capture in the background magnetic fields and the effective collision with the particle increase because of the spin effect, so that a high portion of the electron energy is transmitted to the background plasma, and the temperature anisotropy governing the electron distribution is reduced.     

Quantum processes in short and intensive electromagnetic fields

This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g. laser) wave field or generalized Breit–Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is non-linear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields.     

Quantum effects on magnetization due to ponderomotive force in cold quantum plasmas

The quantum effects on the magnetization due to the ponderomotive force are investigated in cold quantum plasmas. It is shown that the ponderomotive force of the electromagnetic wave induces the magnetization and cyclotron motion in quantum plasmas. We also show that the magnetic field would not be induced without the quantum effects in plasmas. It is also found that the quantum effect enhances the cyclotron frequency due to the ponderomotive force related to the time variation of the field intensity. In addition, it is shown that the magnetization diminishes with an increase of the frequency of the electromagnetic field.     

Fluid description of particle transport in HF heated magnetized plasma

Particle fluxes averaged over the high frequency oscillations are analyzed. Collisional effects and kinetic mechanisms of energy absorption are included. Spatial dependences of both the high frequency and the (quasi-)steady electromagnetic fields are arbitrary. Equations governing the fluxes are deduced from moments of the averaged kinetic equation. Explicit expressions for steady state fluxes are given in terms of electromagnetic field quantities. The results can also be applied to anomalous transport phenomena in weakly turbulent plasmas.     

Quantum kinetic theory of confined electrons in a strong time dependent field

A gauge-invariant Green’s function approach to the quantum transport of spatially confined electrons in strong electromagnetic fields is presented. The theory includes mean field and exchange effects, as well as collisions and initial correlations. It allows for a self-consistent treatment of spectral properties and collective effects (plasmons), on one hand, and nonlinear field phenomena, such as harmonic generation and multiphoton absorption, on the other. It is equally applicable to electrons in quantum dots, ultracold ions in traps and valence electrons of metal clusters.     

Multicomponent transport algorithms for partially ionized mixtures

We investigate iterative methods for solving linear systems arising from the kinetic theory of gases and providing multicomponent transport coefficients of partially ionized plasmas. We consider the situations of weak and strong magnetic fields as well as electron temperature nonequilibrium and the linear systems are investigated in their natural constrained singular symmetric form. Stationary iterative techniques are considered with new more singular formulations of the transport linear systems as well as orthogonal residuals algorithms. The new formulations are derived by considering generalized inverses with nullspaces of increasing dimension. Numerical tests are performed with high temperature air and iterative techniques lead to fast and accurate evaluation of the transport coefficients for all ionization levels and magnetic field intensities.     

Nonequilibrium perturbation theory in Liouville-Fock space for inelastic electron transport

We use a superoperator representation of the quantum kinetic equation to develop nonequilibrium perturbation theory for an inelastic electron current through a quantum dot. We derive a Lindblad-type kinetic equation for an embedded quantum dot (i.e. a quantum dot connected to Lindblad dissipators through a buffer zone). The kinetic equation is converted to non-Hermitian field theory in Liouville-Fock space. The general nonequilibrium many-body perturbation theory is developed and applied to the quantum dot with electron-vibronic and electron-electron interactions. Our perturbation theory becomes equivalent to a Keldysh nonequilibrium Green's function perturbative treatment provided that the buffer zone is large enough to alleviate the problems associated with approximations of the Lindblad kinetic equation.     

Redshift modification of pulsars and magnetars by relativistic plasmas and vacuum polarization

The redshifts of emissions from pulsars and magnetars consist of two components: gravitational and non-gravitational redshifts. The latter results from the electromagnetic and kinetic effects of relativistic plasmas, characterized by refractive indices and streaming velocities of the media, respectively. The vacuum polarization effect induced by strong magnetic fields can modify the refractive indices of the media, and thus leads to a modification to the redshifts. The Gordon effective metric is introduced to study the redshifts of emissions. The modification of the gravitational redshift, caused by the effects of relativistic plasmas and vacuum polarization, is obtained.     

The Boltzmann equation from quantum field theory

We show from first principles the emergence of classical Boltzmann equations from relativistic nonequilibrium quantum field theory as described by the Kadanoff–Baym equations. Our method applies to a generic quantum field, coupled to a collection of background fields and sources, in a homogeneous and isotropic spacetime. The analysis is based on analytical solutions to the full Kadanoff–Baym equations, using the WKB approximation. This is in contrast to previous derivations of kinetic equations that rely on similar physical assumptions, but obtain approximate equations of motion from a gradient expansion in momentum space. We show that the system follows a generalized Boltzmann equation whenever the WKB approximation holds. The generalized Boltzmann equation, which includes off-shell transport, is valid far from equilibrium and in a time dependent background, such as the expanding universe.     

The nonextensive parameter for nonequilibrium electron gas in an electromagnetic field

The nonextensive parameter for nonequilibrium electron gas of the plasma in an electromagnetic field is studied. We exactly obtained an expression of the q$q$-parameter based on Boltzmann kinetic theories for plasmas, where Coulombian interactions and Lorentz forces play dominant roles. We show that the q$q$-parameter different from unity is related by an equation to temperature gradient, electric field strength, magnetic induction as well as overall bulk velocity of the gas. The effect of the magnetic field on the q$q$-parameter depends on the overall bulk velocity. Thus the q$q$-parameter for the electron gas in an electromagnetic field represents the nonequilibrium nature or nonisothermal configurations of the plasma with electromagnetic interactions.     

Beam-plasma coupling effects on the stopping power of dense plasmas

The stopping power for ion beams in dense plasmas is investigated on the basis of quantum kinetic equations. Strong correlations between the beam ions and the plasma particles which occur for high ion charge numbers and strongly coupled plasmas are treated on the level of the statically screened T-matrix (binary collision) approximation. Dynamic screening effects are included using a combined scheme which considers both close collisions and collective effects. Applying this approach, the ion charge number dependence of the stopping power is determined. The result is a modification of the Z(2)(b) scaling law. In particular, the stopping power is reduced for strong beam-plasma coupling. Good agreement is found between T-matrix results and simulation data (particle-in-cell and molecular dynamics) for low beam velocities.     

Dielectric breakdown of Mott insulators in dynamical mean-field theory

Using nonequilibrium dynamical mean-field theory, we compute the time evolution of the current in a Mott insulator after a strong electric field is turned on. We observe the formation of a quasistationary state in which the current is almost time independent although the system is constantly excited. At moderately strong fields this state is stable for quite long times. The stationary current exhibits a threshold behavior as a function of the field, in which the threshold increases with the Coulomb interaction and vanishes as the metal-insulator transition is approached.     

Geometric phase contribution to quantum nonequilibrium many-body dynamics

We study the influence of geometry of quantum systems underlying space of states on its quantum many-body dynamics. We observe an interplay between dynamical and topological ingredients of quantum nonequilibrium dynamics revealed by the geometrical structure of the quantum space of states. As a primary example we use the anisotropic XY ring in a transverse magnetic field with an additional time-dependent flux. In particular, if the flux insertion is slow, nonadiabatic transitions in the dynamics are dominated by the dynamical phase. In the opposite limit geometric phase strongly affects transition probabilities. This interplay can lead to a nonequilibrium phase transition between these two regimes. We also analyze the effect of geometric phase on defect generation during crossing a quantum-critical point.     

A Spin-Statistics Theorem for Quantum Fields¶on Curved Spacetime Manifolds¶in a Generally Covariant Framework

A model-independent, locally generally covariant formulation of quantum field theory over four-dimensional, globally hyperbolic spacetimes will be given which generalizes similar, previous approaches. Here, a generally covariant quantum field theory is an assignment of quantum fields to globally hyperbolic spacetimes with spin-structure where each quantum field propagates on the spacetime to which it is assigned. Imposing very natural conditions such as local general covariance, existence of a causal dynamical law, fixed spinor- or tensor type for all quantum fields of the theory, and that the quantum field on Minkowski spacetime satisfies the usual conditions, it will be shown that a spin-statistics theorem holds: If for some of the spacetimes the corresponding quantum field obeys the “wrong” connection between spin and statistics, then all quantum fields of the theory, on each spacetime, are trivial. Received: 1 March 2001 / Accepted: 28 May 2001     

Simulating nonequilibrium quantum fields with stochastic quantization techniques

We present lattice simulations of nonequilibrium quantum fields in Minkowskian space-time. Starting from a nonthermal initial state, the real-time quantum ensemble in (3 + 1) dimensions is constructed by a stochastic process in an additional (5th) "Langevin-time." For the example of a self-interacting scalar field, we show how to resolve apparent unstable Langevin dynamics and compare our quantum results with those obtained in classical field theory. Such a direct simulation method is crucial for our understanding of collision experiments of heavy nuclei or other nonequilibrium phenomena in strongly coupled quantum many-body systems.