Cosmological Density Perturbations from a Quantum Gravitational Model of Inflation

We derive the implications for anisotropies in the cosmic microwave background following from a model of inflation in which a bare cosmological constant is gradually screened by an infrared process in quantum gravity. The model predicts that the amplitude of scalar perturbations is AS = (2.0 ± 0.2) · 10—5, that the tensor-to-scalar ratio is r ≈︂ 1.7 · 10—3, and that the scalar and tensor spectral indices are n ≈︂ 0.97 and nT ≈︂ —2.8 · 10—4, respectively. By comparing the model's power spectrum with the COBE 4-year RMS quadrupole, the mass scale of inflation is determined to be M = (0.72 ± 0.03) · 1016 GeV. At this scale the model produces about 108 e-foldings of inflation, so another prediction is Ω = 1. PACS numbers: 04.60.-m, 98.80.Cq