ANTIMATTER IN THE UNIVERSE

In this paper, the present knowledge on the study of antimatter in the universe is summarized. From the theoretical point of view, both bary on symmetric and asymmetric cosmologies are possible in the framework of big-bang theories. With the three ''Sakharov's conditions,'' it is possible to imagine an evolution from the big bang toward a universe w ith ''all matter'' inside or toward a symmetric universe with matter a nd antimatter separated in domains. Measurement of the gamma ray cosmi c background implies only a local asymmetry and does not rule out the possibility of a symmetry on a large scale. Observations of the antipr oton spectrum and antinuclei in cosmic rays are useful tools for study ing the possible existence of an antigalaxy. The number and quality of the present data are poor, and no data are available at high energy, where the presence of an antigalaxy must be revealable owing to a larg e amount of antiprotons and antinuclei. In this paper, the future expe rimental projects to measure the antiproton flux at high energies and to search for antinuclei in cosmic rays are briefly presented.