Miniclusters from axion string simulations

TL;DR

This paper investigates the properties of axion miniclusters through various simulation methods, revealing similarities in energy distribution despite differences in mass and density profiles, which impacts dark matter detection strategies.

Contribution

It compares different simulation approaches for axion miniclusters, highlighting their effects on mass distribution and internal structure, advancing understanding of axion dark matter.

Findings

Similar energy distribution between minicluster halos and voids

Differences in mass distribution and density profiles across methods

Implications for axion dark matter detection

Abstract

The properties of axion miniclusters and of the voids between them can have very strong implications for the discovery of axions and the dark matter of the Universe. These properties can be strongly affected by axion dynamics in the early Universe, such as the axion string network and the non-linear dynamics around the QCD phase transition. Recently, improvements in numerical simulation techniques have allowed us to calculate the dark matter axion field from axion strings and QCD effects using different methods: directly with low-tension strings but high resolution, directly with effective high-tension strings, or indirectly by extrapolating an attractor solution. In this work, we study the properties of miniclusters in the different approaches used in the literature. We find that, while there are substantial differences in the mass distribution and internal density profiles, globally there is a similar energy distribution between minicluster halos and voids.