The propagation of intense laser light in plasmas is studied theoretically in this US/USSR collaboration. Of paramount importance is the investigation of physical conditions in which the electric field large compared to the atomic interactions and where relativistic motions are prominent. Present theoretical understanding of this regime is primitive and the computational tools required for the analysis are just beginning to be developed. Parallel experimental efforts will allow a direct comparison of theory and experiment and should result in a significant advance in our understanding of laser-matter interactions in ultra-intense fields.
