LITP Wine & Cheese Seminar: Axion Stars with No Cosmic Strings Attached

Speaker: Henry Stubbs (Oxford). The talk will be held over zoom, but we will broadcast it in Varian 312.

We show that an era of early matter domination, such as the moduli-dominated epochs predicted in string theory, can lead to the formation of solitonic QCD axion stars. Crucially, this mechanism does not rely on the production of axion strings and therefore can apply to pre-inflationary axions. Across a broad, string-theory-motivated parameter space, an order-one fraction of the dark matter may become bound into axion stars and their surrounding halos. This would suppress the sensitivity of direct searches for QCD axion dark matter that assume a smooth dark matter distribution, while opening new routes to indirect detection in astrophysics. A discovery of pre-inflationary QCD axion stars would provide striking evidence for a non-standard cosmological history.