A little inflation in the early universe at the QCD phase transition

TL;DR

This paper proposes a scenario where a brief inflation during the QCD phase transition in the early universe causes observable effects on density fluctuations, magnetic fields, and gravitational waves, with potential tests at upcoming facilities.

Contribution

It introduces a novel QCD inflation scenario with specific cosmological signatures and links it to upcoming experimental probes.

Findings

Primordial density fluctuations affected up to 10 solar masses

Spectral slope altered for mass scales 10^6 - 10^8 solar masses

Primordial magnetic fields up to 10^12 Gauss produced

Abstract

We explore a scenario that allows for a strong first order phase-transition of QCD at non-negligible baryon number in the early universe and its possible cosmological observable consequences. The main assumption is a quasi-stable QCD-vacuum state that leads to a short period of inflation, consequently diluting the net baryon to photon ratio to it's today 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 1 - 10 solar masses, change in the spectral slope up to mass scales of 10^6 - 10^8 solar masses, production of primordial magnetic fields with initial strength up to 10^12 Gauss and a gravitational wave spectrum with present day peak strain amplitude of at most h_c = 5 * 10^-15 around a frequency of 4*10^-8 Hz. The little QCD inflation scenario could be probed with the upcoming heavy ion research facility FAIR at GSI, Darmstadt.