Quantum radiative corrections to slow-roll inflation

We consider the nonminimally coupled lambda phi^4 scalar field theory in de Sitter space and construct the renormalization group improved renormalized effective theory at the one-loop level. Based on the corresponding quantum Friedmann equation and the scalar field equation of motion, we calculate the quantum radiative corrections to the scalar spectral index n_s, gravitational wave spectral index n_g and the ratio r of tensor to scalar perturbations. When compared with the standard (tree-level) values, we find that the quantum contributions are suppressed by lambda N^2 where N denotes the number of e-foldings. Hence there is an N^2 enhancement with respect to the naive expectation, which is due to the infrared enhancement of scalar vacuum fluctuations characterising de Sitter space. Since observations constrain lambda to be very small lambda ~ 10^(-12) and N ~ 50-60, the quantum corrections in this inflationary model are unobservably small.