Axion Miniclusters Made Easy

Abstract

We use a modified version of the Peak Patch excursion set formalism to compute the mass and size distribution of QCD axion miniclusters from a fully non-Gaussian initial density field obtained from numerical simulations of axion string decay. We find strong agreement with N-Body simulations at a significantly lower computational cost. We employ a spherical collapse model and provide fitting functions for the modified barrier in the radiation era. The halo mass function at $z=629$ has a power-law distribution $M^{-0.6}$ for masses within the range $10^{-15}\lesssim M\lesssim 10^{-10}{M}_{\odot }$, with all masses scaling as $(m_a/50\mu \mathrm{eV}{)}^{-0.5}$. We construct merger trees to estimate the collapse redshift and concentration mass relation, $C(M)$, which is well described using analytical results from the initial power spectrum and linear growth. Using the calibrated analytic results to extrapolate to $z=0$, our method predicts a mean concentration $C\sim \mathcal{O}(\text{few})\times 10^4$. The low computational cost of our method makes future investigation of the statistics of rare, dense miniclusters easy to achieve.

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• Stellar Disruption of Axion Miniclusters in the Milky Way
• Simulations of axion-like particles in the post-inflationary scenario
• Structure of Axion Miniclusters
• Axion minivoids and implications for direct detection
• ALP Dark Matter Mini-Clusters from Kinetic Fragmentation
• Detecting Dark Matter Substructures on Small Scales with Fast Radio Bursts
• Post-inflationary axions: a minimal target for axion haloscopes
• ALP dark matter with non-periodic potentials: parametric resonance, halo formation and gravitational signatures
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• Axions in Andromeda: Searching for Minicluster -- Neutron Star Encounters with the Green Bank Telescope
• Astrophysical Searches and Constraints on Ultralight Bosonic Dark Matter
• On the Galactic radio signal from stimulated decay of axion dark matter
• Evidence for axion miniclusters with an increased central density
• A self-consistent wave description of axion miniclusters and their survival in the galaxy
• Self-similar kinetics for gravitational Bose-Einstein condensation