QCD-induced Electroweak Phase Transition

TL;DR

This paper demonstrates that QCD condensates can facilitate the completion of a first-order electroweak phase transition in models with supercooling, impacting cosmological evolution and potential observational signatures.

Contribution

It introduces the effect of QCD condensates on radion/dilaton potential, enabling phase transition completion in scenarios previously thought trapped in false vacuum.

Findings

QCD condensates lower the potential barrier for phase transition.

Electroweak symmetry breaking can occur at or below QCD temperatures.

The model predicts observable cosmological signatures.

Abstract

Phase transitions associated with nearly conformal dynamics are known to lead to significant supercooling. A notorious example is the phase transition in Randall-Sundrum models or their CFT duals. In fact, it was found that the phase transition in this case is first-order and the tunneling probability for the radion/dilaton is so small that the system typically remains trapped in the false vacuum and the phase transition never completes. The universe then keeps expanding and cooling. Eventually the temperature drops below the QCD scale. We show that the QCD condensates which subsequently form give an additional contribution to the radion/dilaton potential, an effect which had been ignored so far. This significantly reduces the barrier in the potential and allows the phase transition to complete in a substantially larger region of parameter space. Due to the supercooling, electroweak symmetry is then broken simultaneously. This class of models therefore naturally leads to an electroweak phase transition taking place at or below QCD temperatures, with interesting cosmological implications and signatures.