Probing Beyond-Horndeski Gravity on Ultra-Large Scales

In this book we explore the well-grounded models of DE-given a lack of fundamental understand of the DE the alternative might be the an idea that DE is not real with the exception that the relative weakening of gravity at late-time is the key factor for the acceleration. In particular we look into the so-called ’Horndeski theories’ and their extensions dubbed ’beyond-Horndeski gravity’ as the satisfactory alternative to concordance model Λ. The beyond-Horndeski gravity are characterized by the scalar field -which introduces the degree of freedom in addition to the GR tensor modes—which could result by minimizing the symmetry of the theories. This have recently gained exponential interest; e.g. of this method is the effective field theory of inflation EFT and unified dark energy.