Speaker
Description
We show that a secondary period of warm inflation (lukewarm inflation) may dilute unwanted relics while enhancing the power spectrum of primordial curvature perturbations on small scales. At temperatures parametrically below the GUT scale, this enhancement is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-solar mass primordial black holes (PBHs). We then consider a later stage, just above the QCD scale, which damps the coherent oscillations of the QCD axion, avoiding the need to fine-tune the initial misalignment angle for a decay constant close to the GUT scale, and may dilute a large pre-existing baryon asymmetry. This realization involves right-handed neutrinos in the 0.1–1 GeV mass range and is followed by an early-matter era, which may modify the resulting small-scale signatures.