Cosmological dynamics of viable f(R) theories of gravity
  A complete analysis of the dynamics of the Hu-Sawicki modification to General
Relativity is presented. In particular, the full phase-space is given for the
case in which the model parameters are taken to be n=1, c1=1, and several
stable de Sitter equilibrium points together with an unstable "matter-like"
point are identified. We find that if the cosmological parameters are chosen to
take on their Lambda CDM values today, this results in a universe which, until
very low redshifts, is dominated by an equation of state parameter equal t1/3,
leading to an expansion history very different from Lambda CDM. We demonstrate
that this problem can be resolved by choosing Lambda CDM initial conditions at
high redshifts and integrating the equations to the present day.
