Uncovering the history of cosmic inflation from anomalies in cosmic microwave background spectra

Abstract

We propose an inflationary primordial feature model that can explain both the large and small-scale anomalies in the currently measured cosmic microwave background anisotropy spectra, revealing a clip of adventurous history of the Universe during its primordial epoch. Although the model is currently statistically indistinguishable from the Standard Model, we show that planned observations such as the Simons Observatory, LiteBIRD and CMB-S4 will complement each other in distinguishing the model differences due to their accurate E-mode polarization measurements, offering very optimistic prospects for a detection or exclusion. The model predicts a signal of classical primordial standard clock, which can also be used to distinguish the inflation and alternative scenarios in a model-independent fashion.