Quantum radiative corrections to slow-roll inflation

We consider the nonminimally coupled λφ⁴ 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 nₛ, gravitational wave spectral index ng, 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 λN², where N denotes the number of e-foldings. Hence, there is an N² enhancement with respect to the naive expectation, which is due to the infrared enhancement of scalar vacuum fluctuations characterizing de Sitter space. Since observations constrain λ to be very small λ~10^-12 and N~50--60, the quantum corrections in this inflationary model are unobservably small.