Chiral phase transition with primordial black holes: Distinct phase structure and catalysis

TL;DR

This paper investigates how primordial black holes influence the chiral phase transition, revealing novel phase structures and significantly affecting gravitational-wave signals, with implications for early universe cosmology.

Contribution

It introduces a new analysis of PBH effects on chiral symmetry breaking, showing catalysis of phase transitions and modifications to gravitational-wave signatures in a curved spacetime setting.

Findings

PBHs promote chiral symmetry restoration near the horizon.

A novel local phase structure with mixed second- and first-order transitions is found.

PBHs significantly alter the gravitational-wave spectrum from the phase transition.

Abstract

We study the impact of primordial black holes (PBHs) on the chiral phase transition and its associated stochastic gravitational-wave (GW) signals. Using the three-flavor Nambu-Jona-Lasinio model, we construct the chiral effective potential in a Schwarzschild spacetime background. We find that PBHs promote chiral symmetry restoration and induce a nontrivial local phase structure in the vicinity of the event horizon simultaneously. In particular, this structure exhibits a novel chiral symmetry breaking pattern involving both second- and first-order phase transitions, a feature absent in flat spacetime. We further demonstrate that PBHs act as genuine catalysts for the chiral phase transition by analyzing the bounce solution in curved spacetime. The presence of PBHs substantially enhances the inverse duration parameter $\beta/H$ while leaving the overall transition strength comparable to that in flat spacetime. As a consequence, even a small population of PBHs can induce $\mathcal{O}(1)$ shifts in both the peak frequency and the peak amplitude of the GW spectrum generated by the first-order dark chiral phase transition.