No abstract

A kinetic theory for quantum many-particle systems in time-dependent electromagnetic fields is developed based on a gauge-invariant formulation. The resulting kinetic equation generalizes previous results to quantum systems and includes many-body effects. It is, in particular, applicable to the interaction of strong laser fields with dense correlated plasmas.

No abstract

In this paper, nonequilibrium properties of strongly coupled plasmas are considered. Usually, such problems are dealt with using Boltzmann– or Lenard–Balescu-type equations. However, for the application to strongly coupled plasmas, these equations exhibit several shortcomings. So, it is not possible (i), to describe the short time kinetics, (ii), to recover the correct (energy) conservation laws and thermodynamics, and, (iii), to account for the formation or destruction of bound states. Therefore, the kinetics of strongly coupled plasmas is considered starting from the Kadanoff–Baym equations, which are known to overcome the above limitations. This is demonstrated by a numerical solution of the two-time Kadanoff–Baym equations in second Born approximation. To be able to discuss approximations which are physically more interesting, it is advantageous to proceed to the time diagonal Kadanoff–Baym equations. In first order gradient expansion, generalizations of the Boltzmann and of the Lenard–Balescu kinetic equations are derived accounting for the bound state problem, too. Thus, the shortcomings (i)–(iii) mentioned above are overcome. Finally, the kinetic equations are applied to the problem of ionization kinetics.

The non-Markovian carrier-carrier scattering dynamics in a dense electron gas is investigated. Within the framework of quantum kinetic equations in the second Born approximation we study the relevance of retardation (memory) effects, energy broadening and correlation build-up for femtosecond relaxation processes. Furthermore, the important issue of total energy conservation, within various well-established approximation schemes, is analysed. The most important non-Markovian effect is shown to be the broadening of the energy delta function leading to an increase of kinetic energy with time. Our numerical analysis includes both the single-time kinetic equation and the full two-time Kadanoff-Baym equations. Our results are expected to correctly reproduce qualitative features of non-Markovian dynamics in plasmas, fluids, nuclear matter and in the intraband relaxation of semiconductors. The comparison of the exact solutions for different approximations allows suggestions for simplifications that make this kind of calculation and their extension, especially to realistic semiconductor situations, more feasible.