CSN4 coordinates theoretical physics research, which is concerned with developing hypotheses, models and physical theories to explain the results of experiments and to open up new scenarios for physics. Theoretical physicists from CSN4 are currently mainly engaged in research into the origin of the mass of fundamental particles, the nature and characteristics of the dark matter, the explanation of the matter-antimatter asymmetry in the universe and the fundamental quantum unification of all interactions, including gravity. Other research projects address the nature and intrinsic structure of space-time, physics of the nucleus and of the constituent particles, including the processes that occurred at the time of the Big-Bang and the subsequent evolution of the universe. These theoretical studies are based on the results of experiments using particle accelerators and of astroparticle physics experiments, and also on mathematical methods and formal and numerical techniques.