Precision Predictions for the Primordial Power Spectra from f(R) Models   of Inflation
  We study the power spectra of f(R) inflation using a new technique in which the norm-squared of the mode functions is evolved. Our technique results in excellent analytic approximations for how the spectra depend upon the function $f(R)$. Although the spectra are numerically the same in the Jordan and Einstein frames for the same wave number $k$, they depend upon the geometries of these frames in quite different ways. For example, the power spectra in the two frames are different functions of the number of e-foldings until end of inflation. We discuss how future data on reheating can be used to distinguish f(R) inflation from scalar-driven inflation. 
D. J. Brooker (Florida), S. D. Odintsov (Barcelona) and R. P. Woodard   (Florida)
gr-qc astro-ph.CO