Antimatter and anti-gravitation

This discussion between 2 physicists G. Chardin and L. Blanchet sheds light on a model of anti-gravitation for antimatter. According to the equivalence principle of general relativity, any body falls the same way in a gravitational field whatever its nature: matter or antimatter. This new model studies the consequences of a different behavior of antimatter when submitted to gravitation. A negative mass for antimatter could explain the acceleration of universe expansion without the need for a cosmological constant or black energy. This model gives the right age for the universe and can explain primordial nucleosynthesis on a longer time period: 40 years instead of 3 minutes for the standard model. The future experiments Gbar, Alpha-g and Aegis that will be performed at CERN, will clarify the behaviour of anti-hydrogen toward gravity, and will be a test of this new model. (A.C.)