Hubble deep field
As inferred from the large velocities of matter within the galaxies,gravity has to be stronger than expected there. As inferred from themotion between galaxies, gravity most be reversed in this vast emptyspace. Image: Part of the Hubble Ultra Deep Field (NASA, ESA,S. Beckwith (STScI) and the HUDF Team).


My work mainly aims at developing theoretical and phenomenological aspects of cosmological theories and to test them against observational data. The accumulation of high quality astronomical data have brought about a paradigm shift in cosmology. We can now make precise quantitative statements about the history and content of our Universe, and to much surprise, data tells us that it has an accelerating expansion, currently being dominated by dark matter and dark energy. Today, few doubt the overwhelming evidence of these, or similar, dark entities.  However, the precise nature of dark matter and energy is much more elusive and they remain two of the biggest mysteries in Science. Only recently have data allowed not only for their detection, but also to discriminate between explanations.

An interesting fact is that the dark sectors have so far only been probed gravitationally. In the last years, a consistent generalization of general relativity have been found where a massive particle is added to the massless graviton mediating the gravitational force. Being a
natural extension of massless gravity, bimetric massive gravity is a theoretically sound and observationally testable theory. It is currently subject to large interest after not only being proved to be theoretically consistent, but also to agree with observations of the background expansion. In other respects, the theory has been shown to differ from the dark entity model. Being a new theory, and having a more complex structure than massless gravity, much work is needed to develop its rich phenomenology.