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arXiv · 2306.16769

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

Lei Zu·Chi Zhang·Yao-Yu Li·Yu-Chao Gu·Yue-Lin Sming Tsai·Yi-Zhong Fan
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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 (dQCD) 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 $H_0$ and $S_8$ measurements in Cosmology. This intriguing correlation suggests a possible common origin of these three phenomena for $0.2 < \Delta N_{\rm eff} < 0.5$, where the mirror dark matter component constitutes about $30\%$ of the total dark matter abundance. Next generation CMB experiment such as CMB-S4 is able to test this parameter region.

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Lei Zu, Chi Zhang, Yao-Yu Li, Yu-Chao Gu, Yue-Lin Sming Tsai, Yi-Zhong Fan. 2023-06-29. Mirror QCD phase transition as the origin of the nanohertz Stochastic Gravitational-Wave Background. https://doi.org/10.1016/j.scib.2024.01.037

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