Cosmology of the proxy theory to massive gravity
  In this paper, we scrutinize very closely the cosmology in the proxy theory
to massive gravity obtained in Phys. Rev. D84 (2011) 043503. This proxy theory
was constructed by covariantizing the decoupling limit Lagrangian of massive
gravity and represents a subclass of Horndeski scalar-tensor theory. Thus, this
covariantization unifies two important classes of modified gravity theories,
namely massive gravity and Horndeski theories. We go beyond the regime which
was studied in Phys. Rev. D84 (2011) 043503 and show that the theory does not
admit any homogeneous and isotropic self-accelerated solutions. We illustrate
that the only attractor solution is flat Minkowski solution, hence this theory
is less appealing as a dark energy model. We also show that the absence of de
Sitter solutions is tightly related to the presence of shift symmetry breaking
interactions.
