Primeval Corrections to the CMB Anisotropies

TL;DR

This paper explores how deviations in the inflaton's quantum state from the thermal vacuum could leave observable imprints in the CMB anisotropies, providing insights into the duration and features of inflation.

Contribution

It introduces the concept that initial quantum state deviations can produce observable IR effects in the CMB, acting as a quantum analogue of the cosmic no-hair theorem.

Findings

Deviations from the thermal vacuum can leave observable imprints in the CMB.

Inflation tends to erase initial deviations, aligning the quantum state with the thermal vacuum.

Absence of such imprints suggests a prolonged inflationary period exceeding 100 e-folds.

Abstract

We show that deviations of the quantum state of the inflaton from the thermal vacuum of inflation may leave an imprint in the CMB anisotropies. The quantum dynamics of the inflaton in such a state produces corrections to the inflationary fluctuations, which may be observable. Because these effects originate from IR physics below the Planck scale, they will dominate over any trans-Planckian imprints in any theory which obeys decoupling. Inflation sweeps away these initial deviations and forces its quantum state closer to the thermal vacuum. We view this as the quantum version of the cosmic no-hair theorem. Such imprints in the CMB may be a useful, independent test of the duration of inflation, or of significant features in the inflaton potential about 60 e-folds before inflation ended, instead of an unlikely discovery of the signatures of quantum gravity. The absence of any such substructure would suggest that inflation lasted uninterrupted much longer than ${\cal O}(100)$ e-folds.