The Cosmological QCD Phase Transition Revisited

TL;DR

This paper investigates how a first order QCD phase transition in the early universe could have led to phenomena like primordial black holes, magnetic fields, and gravitational waves, with potential detection by future observatories.

Contribution

It proposes a cosmological model where a QCD phase transition causes little inflation and predicts observable signatures like gravitational waves and primordial black holes.

Findings

Primordial black holes could originate from bubble nucleation during the transition.

The gravitational wave background may contain imprints of the QCD phase transition.

The power spectrum of cold dark matter could be affected up to billion solar mass scales.

Abstract

The QCD phase diagram might exhibit a first order phase transition for large baryochemical potentials. We explore the cosmological implications of such a QCD phase transition in the early universe. We propose that the large baryon-asymmetry is diluted by a little inflation where the universe is trapped in a false vacuum state of QCD. The little inflation is stopped by bubble nucleation which leads to primordial production of the seeds of extragalactic magnetic fields, primordial black holes and gravitational waves. In addition the power spectrum of cold dark matter can be affected up to mass scales of a billion solar masses. The imprints of the cosmological QCD phase transition on the gravitational wave background can be explored with the future gravitational wave detectors LISA and BBO and with pulsar timing.