Concluding remarks: Theoretical aspects

We summarize the theoretical aspects of the Conference on LiBeB, Cosmic Rays and Gamma-Ray Lines held in December 1998 in Paris. The meeting was aimed at the cross fertilization of different astrophysical fields and methods related to the these topics, including the astrophysical diagnostics of the involved processes. The main inquiries focused on the relationship between the origins of LiBeB and those of nonthermal nuclei in the Galaxy, specifically the cosmic rays and a possible distinct low energy cosmic-ray component. The relationship to nucleosynthesis in the Big Bang was also explored along with the other Galactic LiBeB producing processes that do not involve accelerated particles. It was emphasized that the key input data for future progress are elemental and isotopic abundances both in stars as functions of metallicity, and in the current epoch cosmic rays, where relatively short Lived radioisotopes can play a very important role. In addition, gamma-ray and X-ray lines, in particular those that carry clear signatures of accelerated particle interactions, are also of great importance.