Talk detail

Participant	Akrami, Yashar
Institution	Institute of Theoretical Astrophysics, University of Oslo - P.O. Box 1029 Blindern - Oslo - - Norway

Session	AT4	Accepted	Yes	Order	3	Time	15'
Talk	Oral abstract	Title	Accelerated expansion from massive gravity: a Bayesian analysis with improved generality
Co-authors	Tomi Sebastian Koivisto, Marit Sandstad
Abstract	After the remarkable progress in building theories of massive gravity that happened only over the last two years, the field has undergone a significant boost in both purely theoretical aspects and its applications in cosmology. The recent discovery of a ghost-free, non-linear extension of Fierz and Pauli's linearized theory of massive gravity, and its bigravity generalization, has opened a new door for cosmologists to interpret the observed late-time accelerated expansion of the Universe without any need to introduce an explicit cosmological constant (or dark energy) into the Einstein's field equations. In this talk, I describe a generalized version of bimetric theory of massive gravity where matter is coupled to both metrics in a consistent way. This leads to a theory that behaves as a cosmological constant at both late and early epochs of the cosmic evolution with a transition region in between. I demonstrate the possibility of obtaining cosmic acceleration in this framework through a best-fit analysis of the theory where background dynamics of the Universe given by this model is compared with real cosmological data. I present the results of an extensive Bayesian estimation of the parameters of the theory in comparison with the concordance model of cosmology. The best-fit analysis is performed using MultiNest, a state-of-the-art scanning algorithm based on nested sampling. Our results illustrate that the model can yield perfect fits but there are a few caveats that should be taken into account when interpreting the results.