Gravitational waves from a dilaton-induced, first-order QCD phase transition

TL;DR

This paper proposes that a dilaton field can cause the QCD confinement transition to be first-order, producing gravitational waves detectable by pulsar timing arrays, linking cosmology, particle physics, and gravitational wave observations.

Contribution

It introduces a novel mechanism where a QCD dilaton induces a first-order phase transition, leading to observable gravitational wave signals.

Findings

First-order QCD transition can produce detectable gravitational waves.

Dilaton field dynamics influence early universe phase transitions.

Potential collider signatures of the dilaton field.

Abstract

We show that a `QCD dilaton' field, whose vacuum expectation value sets the strong coupling, can render the Quantum Chromodynamic (QCD) confinement transition first-order. The QCD dilaton is cosmologically attracted to a false vacuum at weak coupling in the early universe. Quantum tunnelling towards the true vacuum triggers prompt chiral symmetry breaking and confinement of QCD, leading to detonating bubbles of the hadronic phase. We find that plasma sound waves produced by this dilaton-induced, first-order QCD phase transition generate a stochastic gravitational wave signal strikingly similar to the recently detected gravitational wave background from Pulsar Timing Arrays. We briefly comment on how this theory can be probed through collider experiments and cosmology.