Mirror QCD phase transition as the origin of the nanohertz Stochastic Gravitational-Wave Background

Lei Zu; Chi Zhang; Yao-Yu Li; Yuchao Gu; Yue-Lin Sming Tsai; Yi-Zhong Fan

doi:10.1016/j.scib.2024.01.037

Mirror QCD phase transition as the origin of the nanohertz Stochastic Gravitational-Wave Background

Sci Bull (Beijing). 2024 Mar 30;69(6):741-746. doi: 10.1016/j.scib.2024.01.037. Epub 2024 Jan 30.

Authors

Lei Zu¹, Chi Zhang², Yao-Yu Li², Yuchao Gu¹, Yue-Lin Sming Tsai³, Yi-Zhong Fan⁴

Affiliations

¹ Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China.
² Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China; School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China.
³ Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China; School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China. Electronic address: smingtsai@pmo.ac.cn.
⁴ Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China; School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China. Electronic address: yzfan@pmo.ac.cn.

PMID: 38320899
DOI: 10.1016/j.scib.2024.01.037

Abstract

Several Pulsar Timing Array (PTA) Collaborations have recently provided strong evidence for a nHz Stochastic Gravitational-Wave Background (SGWB). Here we investigate the implications of a first-order phase transition occurring within the early Universe's dark quantum chromodynamics epoch, specifically within the framework of the mirror twin Higgs dark sector model. Our analysis indicates a distinguishable SGWB signal originating from this phase transition, which can explain the measurements obtained by PTAs. Remarkably, a significant portion of the parameter space for the SGWB signal also effectively resolves the existing tensions in both the H₀ and S₈ measurements in Cosmology. This intriguing correlation suggests a possible common origin of these three phenomena for 0.2<ΔN_eff<0.5, where the mirror dark matter component constitutes less than 30% of the total dark matter abundance. Next-generation CMB experiments such as CMB-S4 can test this parameter region.

Keywords: Dark matter; Gravitational wave; Mirror twin Higgs; Phase transition; Pulsar timing array.