Nanohertz gravitational waves and primordial quark nuggets from dense QCD matter in the early universe

TL;DR

This paper explores how a first-order QCD phase transition in the early universe could produce nanohertz gravitational waves and primordial quark nuggets, potentially explaining high-redshift galaxies and compact star formation.

Contribution

It introduces a novel connection between baryon density effects on QCD phase transitions, gravitational wave signals, and primordial quark nugget formation in the early universe.

Findings

Nanohertz gravitational waves can originate from high baryon chemical potential transitions.

Primordial quark nuggets may form and survive, acting as seeds for galaxy and star formation.

Transition rates vary with baryon chemical potential, affecting gravitational wave signals.

Abstract

The first-order QCD phase transition at high temperature features a large transition rate in the magnitude of $\beta/H \sim 10^4$ with induced stochastic gravitational waves typically lying in the LISA range. High baryon density in the early universe can be generated through Affleck-Dine baryogenesis. The baryon chemical potential enhances the potential barrier and significantly reduces the transition rate, which decreases from infinity at the critical end point (CEP) to zero at the critical nucleation point (CNP). Nanohertz gravitational waves can be produced in a narrow window of high baryon chemical potential with transition rate in the order of $\beta/H \sim 10^1$. When the phase transition rate reaches zero, the false vacuum of high baryon density quark matter is unlikely to decay and can persist over cosmological time scales. Therefore the primordial quark nuggets (PQN) can form and survive in the early universe as the seeds of compact stars, thereby dramatically accelerating the evolution of compact stars and the formation of galaxies, which may explain the high red-shift massive galaxies observed by the James Webb Space Telescope.