Recurrent Axinovae and their Cosmological Constraints

Understand

Axion-like dark matter whose symmetry breaking occurs after the end of inflation predicts enhanced primordial density fluctuations at small scales.

• This leads to dense axion minihalos (or miniclusters) forming early in the history of the Universe.
• Condensation of axions in the minihalos leads to the formation and subsequent growth of axion stars at the cores of these halos.
• If, like the QCD axion, the axion-like particle has attractive self-interactions there is a maximal mass for these stars, above which the star rapidly shrinks and converts an $\mathcal{O}(1)$ fraction of its mass into unbound relativistic axions.