Dark Spiky Primordial Black Holes

Abstract: Recent observations of two nearby black hole low-mass X-ray binaries have suggested possible indication of dark matter density spikes. While the evidence is compelling, one issue with this interpretation is that light black holes formed from stellar collapse are not expected to form dark matter spikes, and so it is unclear how the stellar-mass black holes in these binaries could have acquired such features. Since primordial black holes are expected to form ultra-dense dark matter mini-spikes, in this article we explore the possibility of a primordial origin for these light black holes.