Description
With the next generation of cosmological surveys about to commence, it is important to
understand how one can use the information obtained from such surveys to constrain the
space of dark energy and modified gravity theories. The effective field theory (EFT) of dark
energy has proven to be a useful approach in this regard, allowing an efficient exploration of
the parameter space. However, in order to gain a deeper understanding of the mechanism
underlying cosmic acceleration one would like to interpret constraints on the EFT parameters
in terms of fundamental covariant theories. In this talk I will discuss a method to reconstruct
the class of covariant Horndeski theories that reproduce the same background dynamics and
linear perturbations as a given EFT action. I will then present a number of examples and
applications. The work was done in collaboration with Lucas Lombriser and Andy Taylor.