Cosmology in f(R) exponential gravity
  Using an approach that treats the Ricci scalar itself as a degree of freedom, we analyze the cosmological evolution within an f(R) model that has been proposed recently (exponential gravity) and that can be viable for explaining the accelerated expansion and other features of the Universe. This approach differs from the usual scalar-tensor method and, among other things, it spares us from dealing with unnecessary discussions about frames. It also leads to a simple system of equations which is particularly suited for a numerical analysis. 
Luisa Jaime, Marcelo Salgado and Leonardo Patino
gr-qc astro-ph.CO