CMB Power Asymmetry from Primordial Sound Speed Parameter

TL;DR

This paper proposes a mechanism where primordial sound speed modulation during inflation explains the cosmic microwave background power asymmetry, predicting observable effects in polarization and non-Gaussianity.

Contribution

It introduces a novel inflationary model linking sound speed modulation to CMB asymmetry, consistent with observations and testable in future experiments.

Findings

The model reproduces observed hemispherical power asymmetry.

Predicts asymmetry in temperature-polarization and polarization autocorrelation.

Forecasts specific non-Gaussianity signatures for upcoming observations.

Abstract

The hemispherical power asymmetry in the cosmic microwave background may be explained by the modulation of some primordial cosmological parameter, such as the sound speed of the inflaton. This modulation can be achieved by the perturbation of a light field during inflation. We numerically examine this mechanism and show it can be consistent with current observations. Further, this model predicts that the power asymmetry also exists in the temperature-polarization correlation and polarization autocorrelation with the same shape, and in primordial non-gaussianity of equilateral type with a particular shape. Therefore, our mechanism is observationally detectable in forthcoming experiments.