Cosmological density perturbations from a quantum gravitational model of inflation

We derive the implications for anisotropies in the cosmic microwave backgro und following from a model of inflation in which a bare cosmological consta nt is gradually screened by an infrared process in quantum gravity. The mod el predicts that the amplitude of scalar perturbations is A(S) = (2.0 +/- 0 .2) . 10(-5), that the tensor-to-scalar ratio is r approximate to 1.7 . 10( -3), and that the scalar and tensor spectral indices are n approximate to 0 .97 and n(T) approximate to -2.8 . 10(-4), respectively By comparing the mo del's power spectrum with the COBE 4-year RMS quadrupole, the mass scale of inflation is determined to be M = (0.72 +/- 0.03) . 10(16) GeV. At this sc ale the model produces about 10(8) e-foldings of inflation, so another pred iction is Ohm = 1.