A little inflation at the cosmological QCD phase transition

TL;DR

This paper reexamines the 'little inflation' scenario during the QCD phase transition, exploring its effects on primordial fluctuations, magnetic field seeds, and gravitational waves, with implications for early universe cosmology.

Contribution

It provides a detailed analysis of the cosmological consequences of a strong first order QCD phase transition with little inflation, using a chiral effective model.

Findings

Potential primordial density fluctuation effects up to 1 solar mass

Altered spectral slope for fluctuations up to 10^6 solar masses

Predicted gravitational wave peak at ~4 x 10^{-8} Hz

Abstract

We reexamine the recently proposed "little inflation" scenario that allows for a strong first order phase-transition of QCD at non-negligible baryon number in the early universe and its possible observable consequences. The scenario is based on the assumptions of a strong mechanism for baryogenesis and a quasistable QCD-medium state which triggers a short inflationary period of inflation diluting the baryon asymmetry to the value observed today. The cosmological implications are reexamined, namely effects on primordial density fluctuations up to dark matter mass scales of $M_{max} \sim 1 M_{\astrosun}$, change in the spectral slope up to $M_{max} \sim 10^6 M_{\astrosun}$, production of seeds for the present galactic and extragalactic magnetic fields and a gravitational wave spectrum with a peak frequency around $\nu_{peak} \sim 4 \cdot 10^{-8} Hz$. We discuss the issue of nucleation in more detail and employ a chiral effective model of QCD to study the impact on small scale structure formation.