Primordial Black-Hole Dark Matter and Warm Natural Inflation
Prof. Grant Mathews
Department of Physics & Astronomy
University of Notre Dame
The prospect that the dark matter could be comprised in part or entirely of low mass primordial black holes has generated recent interest. This form of dark matter could account for the puzzling JWST observations of galaxies at high redshift and the existence of supermassive black holes shortly after the big bang. Neither of these observations are easily accounted for in current theories of cold dark matter cosmology. In this talk we describe our recent study of the warm natural inflationary (WNI) paradigm in which matter fields are generated during the early rapid expansion of the universe. We show two important new results arise in this model. One is that the observational constraints on the primordial power spectrum from the cosmic microwave background can be satisfied without going beyond the Planck scale of the effective field theory. The second is that WNI can inevitably provide perfect conditions for the production of primordial black holes (PBHs) and can account for all of the dark matter content of the universe while satisfying observational constraints. We also show that an interesting spectrum of gravitational waves can be generated by the induced spectrum of tensor fluctuation during warm natural inflation. Indeed, models that solve the dark-matter production also produce a contribution to the cosmic gravitational wave background that satisfies current constraints from pulsar timing and big bang nucleosynthesis. Indeed, there has been a recent exciting detection of a cosmic gravitational wave background. However, the cosmological gravitational wave background from WNI may be only observable in the next generation of space-based and ground-based gravitational wave interferometers.