Seeds of Large Scale Anisotropy in Pre-Big-Bang Cosmology

TL;DR

This paper investigates how electromagnetic and axion seeds in string cosmology can generate large-scale temperature anisotropies, with light axions producing spectra consistent with current observational data.

Contribution

It demonstrates that massless or very light axions can produce a flat or slightly tilted blue spectrum fitting observational data, highlighting a novel seed mechanism in string cosmology.

Findings

Light axions lead to a flat or slightly tilted blue spectrum.

Electromagnetic and axion seeds can account for large-scale anisotropies.

Results align with current cosmological observations.

Abstract

Within a string cosmology context, the large scale temperature anisotropies may arise from the contribution of seeds to the metric fluctuations. We study the cases of electromagnetic and axion seeds. We find that massless or very light axions can lead to a flat or slightly tilted blue spectrum, that fits current data.