Theory HEP Seminar

Dark photon (and axion) stars

Edward Hardy

Liverpool

I will argue that many theories in which dark matter is light (with a mass < eV) lead to theoretically and observationally interesting dark matter substructure. As a particular, directly calculable, example I will show that this is the case for a new vector boson with non-zero mass (a ‘dark photon’ or ‘Proca boson’) that is present during inflation, at which time a relic abundance is automatically produced from vacuum fluctuations. Due to a remarkable parametric coincidence between the size of the primordial density perturbations and the scale at which quantum pressure is relevant, a substantial fraction of the dark matter inevitably collapses into gravitationally bound solitons, which are fully quantum coherent objects. The central densities of these ‘dark photon star’, or ‘Proca star’, solitons are typically a factor 10⁶ larger than the local background dark matter density today. I will also mention some possible observational consequences and directions for future work.