The discovery of cosmic acceleration is believed to be the first observational evidence for new physics beyond the domain of the Standard Model of Particle Physics.  In spite of its fundamental importance for an actual understanding of the evolution of the Universe, the physical mechanism behind this phenomenon constitutes one of the greatest mysteries of modern Cosmology. In the “I CosmoSul: Cosmology and Gravitation of the Southern Cone”, several experts on Cosmology discussed alternative mechanisms of acceleration (including modifications in Gravity theory) and  as well as theoretical and observational constraints on the current theories.