The origin of matter

The author presents the issue of how matter triumphed over anti-matter in the formation of the universe. Theories focus on the nature of asymmetry that might have created an excess of matter over anti-matter. Sakharov and Kuzmin listed 3 conditions that must be met for baryogenesis to take place. First the baryon number must not be conserved: there must be some interactions that change the number of baryons, baryon-number violation can rise from an interaction between quarks and leptons. Secondly, 2 symmetries that relate particles to antiparticles must be violated. The CP violation in Kaon decay is too weak to create enough baryon asymmetry, so physicists believe that larger sources of CP violation await discovery. Thirdly, there must be the loss of thermal equilibrium of the universe. In thermal equilibrium, baryons are decaying but inverse processes are also taking place, quarks are fusing to form baryons, rates being equal no baryon asymmetry is generated. But if thermal equilibrium is broken, to say temperature is decreasing, at a certain temperature a pair of quarks will no longer have enough energy to produce a heavy particle which generates baryon asymmetry. (A.C.)