Speaker
Description
Cosmic strings formed after Peccei–Quinn symmetry breaking are expected to radiate axions throughout their evolution, playing a central role in determining the axion relic abundance and guiding experimental searches. A precise understanding of the string network dynamics and the resulting axion spectrum is therefore essential.
In previous work, we established that axion string networks exhibit standard scaling, with an approximately constant number of strings per horizon volume. Here, we focus on the axion emission spectrum, analyzing all components of the axion current and their unequal-time correlators. This allows us to disentangle the contributions from propagating axions and string-bound fields, showing that earlier estimates based solely on the timelike current component overestimate the radiated spectrum by about 30%.
Our results indicate that axion emission from a scaling string network is close to scale-invariant, with the spectrum approaching a universal form. We will also present a determination of the axion number density produced from strings. These findings provide improved theoretical input for axion dark matter predictions and help refine the interpretation of experimental searches.