Precision Predictions for the Primordial Power Spectra from f(R) Models of Inflation

Understand

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.