1207.6414 (Cristiano Germani)

On the Covariant Galileon and a consistent self-accelerating Universe    [PDF]

Cristiano Germani

In this paper we show that the flat space Galilean theories with up to three scalars in the equation of motion (the quartic Galileons) are recovered in the decoupling limit of certain scalar theories non-minimally coupled to gravity, the so-called "Slotheonic" theories. These theories are also invariant under the generalized Galilean shifts in curved spacetime. While Galilean self-(derivative)couplings are not explicit in the action, they appear after integrating out gravity. In turn, we show that the quintic Galilean theory cannot be enhanced to be invariant under curved spacetime Galilean shifts. We then argue that Galilean supersymmetric theories up to the quartic, may only be found in the context of supergravity. Finally, we discuss on the possibility that Slotheonic theories are the effective four dimensional theories of consistent DGP-like models with self-accelerating cosmological solutions. Moreover, we show that the quartic and cubic Galileon in consistent DGP models cannot be decoupled.

View original: http://arxiv.org/abs/1207.6414