Inflation, Renormalization, and CMB Anisotropies

Understand

In single-field, slow-roll inflationary models, scalar and tensorial (Gaussian) perturbations are both characterized by a zero mean and a non-zero variance.

• In position space, the corresponding variance of those fields diverges in the ultraviolet.
• The requirement of a finite variance in position space forces its regularization via quantum field renormalization in an expanding universe.
• This has an important impact on the predicted scalar and tensorial power spectra for wavelengths that today are at observable scales.