Gravitinos, Reheating and the Matter-Antimatter Asymmetry of the Universe.

Astrophysical observations indicate that the Universe is made up primarily of matter rather than both matter and antimatter. This matter-antimatter asymmetry of the Universe can be explained by the asymmetric decay of some heavy particles if the early Universe is sufficiently hot after a phase called reheating. But these high temperatures also lead to an over- abundance of particles called gravitinos whose presence has very adverse cosmological consequences, which is referred to as the 'gravitino problem'.We shall discuss the matter-antimatter asymmetry of the Universe and the gravitino problem, and then examine whether or not the gravitino abundance can be suppressed in some new scenarios of gravitino production.