The First Particles

After cosmic inflation, the universe is cold and almost empty. Thus, the inflation field should decay to the particles for BBN through the so-called reheating process. Later, the matter-antimatter asymmetry and dark matter are produced. In this chapter, the ``first particle" production between the inflation phase and BBN phase is introduced. We focus on the reheating, electroweak baryogenesis, and leptogenesis.