We study the inflation process of the Universe based on the renormalizable quantum gravity formulated as a conformal field theory. We show that the power-law conformal field theory spectrum approaches that of the Harrison-Zel’dovich-Peebles–type as the amplitude of gravitational potential gradually reduces during the inflation. The non-Gaussanity parameter is preserved within an order of unity due to the diffeomorphism invariance. Sharp falloff of the angular power spectrum of cosmic microwave background at large scale is understood as a consequence of the existence of dynamical scale of the quantum gravity ${\Lambda }_{\mathrm{QG}}(\simeq {10}^{17}\mathrm{GeV})$. The angular power spectra are computed and compared with the WMAP5 and ACBAR data with a quality of ${\chi }^2/\mathrm{dof}\simeq 1.1$.

• Received 3 August 2009

DOI:https://doi.org/10.1103/PhysRevD.81.083533