Institut de recherche sur les lois fondamentales de l'Univers

Motivated by the wish to find alternatives to dark energy or even dark matter, several relativistic theories of gravity have been constructed which deviate from Einstein relativity at large distances. In this talk I will illustrate such an approach with "massive gravity" where ones gives a (very small) mass to the graviton. The talk will be at introductory level, focusing on some general features of theories with large distance deviations from General Relativity but also discussing some nice  properties proper to "massive gravity" such as the so-called vDVZ discontinuity or the "Boulware-Deser ghost".