Speaker
Description
General Relativity (GR) is currently the established theory for describing gravity. However, there are certain unresolved theoretical issues (such as the vacuum energy problem) and observational ones (cosmological tensions) that point to the need to consider modifications or extensions of the theory. On the other hand, observations indicate that the universe is undergoing accelerated expansion, which is commonly explained as a consequence of the dominance of a dark energy component whose nature remains unknown. Similarly, it is also known that most of the matter in the universe is present in the form of dark matter, whose nature is likewise unknown. In GR, the fundamental symmetry of the theory is invariance under diffeomorphisms (Diff), which translates into the invariance of physical laws under coordinate transformations. In this talk, we focus on breaking Diff invariance down to the subgroup of transverse diffeomorphisms (TDiff) in the matter sector, specifically studying the cosmological implications that this may have and the possible consequences regarding the description of the dark sector. In particular, we study models with multiple TDiff scalar fields as a possible description of interacting dark matter and dark energy, carrying out an analysis of these models from a phenomenological perspective.