Nonlinear X-ray Matter Interaction Processes

High-intensity laser-matter interaction experiments in the optical regime using lasers with intensities in excess of 1021 W/cm2 have revealed an abundance of exotic nonlinear processes.  Since x-ray free-electron lasers have become available in Germany, in the USA, and, more recently, in Japan, there has been an extensive quest for discovering and characterizing nonlinear processes in the x-ray regime. In this seminar we review some of these processes, focussing specifically on the electron dynamics in x-ray-irradiated materials and the transition dynamics to warm-dense matter.