The paper explores the formation of axion stars in the post-inflationary scenario, where dark matter is composed of QCD axions. The authors argue that a significant fraction of the axion dark matter, up to one-fifth, can collapse into axion stars at the time of matter-radiation equality. This conclusion is robust against uncertainties in the axion mass and is supported by numerical simulations. The formation of axion stars is influenced by the time-dependent nature of the axion potential and the non-linear dynamics of axions, which affect the evolution of the axion energy spectrum. The paper also discusses the implications of these findings for phenomenology and experimental searches, suggesting that a large population of axion stars could exist and have interesting observational signatures.The paper explores the formation of axion stars in the post-inflationary scenario, where dark matter is composed of QCD axions. The authors argue that a significant fraction of the axion dark matter, up to one-fifth, can collapse into axion stars at the time of matter-radiation equality. This conclusion is robust against uncertainties in the axion mass and is supported by numerical simulations. The formation of axion stars is influenced by the time-dependent nature of the axion potential and the non-linear dynamics of axions, which affect the evolution of the axion energy spectrum. The paper also discusses the implications of these findings for phenomenology and experimental searches, suggesting that a large population of axion stars could exist and have interesting observational signatures.