Strong Laser Field Physics

Part (A) of the project deals with the interaction of atoms and electrons with relativistic laser pulses. The influence of such fields on complex matter (molecules, solid states, plasmas) is investigated. in part (B). Recent technological advances in ultra-fast optics have permitted the realization of laser pulses that open the possibility to investigate light-matter interaction on a novel time scale and in unprecedented wavelength and intensity regimes. "Light and matter" is therefore the catchword which is superior to the topic of the project. Although the chosen theme therefore belongs to on of the oldest branches of theoretical physics there are many un-answered questions which are important for both pure research and for applications. A Atoms and electrons in relativistic electromagnetic fields In the first part the interaction of atoms and electrons with relativistic laser pulses is investigated. Numerical solution of the three-dimensional Dirac equation for atoms in intense laser pulses is beyond the capacity of the fastest parallel computers. This is mainly due to a lack of efficient numerical algorithms for the solution of the Dirac equation. We plan to develop analytical tools as well as significantly improved numerical algorithms for this purpose. This for the first time will make possible the accurate calculation of relativistic ionization rates and of the electron dynamics after relativistic field ionization. The ionization data will present an essential improvement for the realistic description of ultra-relativistic laser-plasma interaction, as it is, e.g., encountered in nuclear physics and astro-physics plasma applications. Finally, we will investigate the influence of vacuum polarization on light propagation and radiation reaction effects during the evolution of free electrons in high-intensity radiation fields. As a result of the electronic quiver-motion in the laser field, electrons start to emit radiation, which in turn affects the electron motion. As radiation reaction effects are intimately connected with singularities and with the renormalization in quantum electrodynamics (QED), this is a very difficult problem that has defied solution so far. B Complex matter in electromagnetic fields The focus of the second project part will be on the interaction of strong laser pulses with complex matter. So far the interaction of strong radiation fields with matter was treated in the single-active-electron approximation (SAEA). The SAEA means that only the valence electron interacts with the laser field and the other electrons remain unchanged. However, many interesting phenomena take place in parameter regimes where the SAEA breaks down. This can be the case e.g. in more complex systems where the laser induced polarization of the target modifies the ionization dynamics; or it may happen for short wavelengths where the electron correlation plays a significant role. The difficulty in the theoretical description of such effects lies in the fact that the interaction of complex matter with intense laser fields combines two of the most complicated areas in theoretical physics: many-body theory and nonperturbative phenomena. In part (B) we will develop different approaches that will be pursued towards development of a many-body theory in strong laser fields.