A Little Inflation in the Early Universe at the QCD Phase Transition

We explore a scenario that allows for a strong first order phase transition of QCD at a non-negligible baryon number in the early Universe and its possible observable consequences. The main assumption is a quasistable QCD-vacuum state that leads to a short period of inflation, consequently diluting the net baryon to photon ratio to today’s observed value. A strong mechanism for baryogenesis is needed to start out with a baryon asymmetry of order unity, e.g., as provided by Affleck-Dine baryogenesis. The cosmological implications are direct effects on primordial density fluctuations up to dark matter mass scales of $M_{\max }\sim 1–10M_{\odot }$, change in the spectral slope up to $M_{\max }\sim {10}^6–{10}^8{M}_{\odot }$, production of strong primordial magnetic fields and a gravitational wave spectrum with present day peak strain amplitude of up to $h_c({\nu }_{\mathrm{peak}})\sim 5\times {10}^{-15}$ around ${\nu }_{\mathrm{peak}}\sim 4\times {10}^{-8}\mathrm{Hz}$.