Gravitational waves and primordial black holes from axion domain walls in level crossing  

作　　者：Hai-Jun Li Yu-Feng Zhou 李海军;周宇峰(Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190,China;School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;School of Fundamental Physics and Mathematical Sciences,Hangzhou Institute for Advanced Study,University of Chinese Academy of Sciences,Hangzhou 310024,China;International Centre for Theoretical Physics Asia-Pacific,Beijing/Hangzhou,China)

机构地区：[1]Key Laboratory of Theoretical Physics,Institute of Theoretical Physics,Chinese Academy of Sciences,Beijing 100190,China [2]School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China [3]School of Fundamental Physics and Mathematical Sciences,Hangzhou Institute for Advanced Study,University of Chinese Academy of Sciences,Hangzhou 310024,China [4]International Centre for Theoretical Physics Asia-Pacific,Beijing/Hangzhou,China

出　　处：《Chinese Physics C》2025年第3期171-180,共10页中国物理C(英文版)

基　　金：Supported by the CAS Project for Young Scientists in Basic Research(YSBR-006);the National Key R&D Program of China(2017YFA0402204);the National Natural Science Foundation of China(11821505,11825506,12047503)。

摘　　要：In this paper,we investigate the nano-Hertz gravitational wave(GW)emission and massive primordial black hole(PBH)formation from the light QCD axion scenario.We consider the axion domain wall formation from the level crossing induced by the mass mixing between the light Z_(N)QCD axion and axion-like particle.A general mixing case in which the heavy and light mass eigenvalues do not necessarily have to coincide with the axion masses is considered.To form the domain walls,the axions should start to oscillate slightly before the level crossing.The domain walls must annihilate before dominating the Universe to avoid cosmological catastrophe.Then,we focus our attention on the GW emission from the domain wall annihilation and the PBH formation from the domain wall collapse.We show the predicted GW spectra with a peak frequency~0.2 nHz and peak amplitude~5×10^(-9),which can be tested by future pulsar timing array projects.In addition,during the domain wall annihilation,the closed walls could shrink to the Schwarzschild radius and collapse into the PBH.We find that PBHs in the mass range of O(10^(5)-10^(8))M_(⊙)could potentially form in this scenario and account for a small fraction(~10^(-5))of the cold dark matter.

关 键 词：gravitational waves primordial black holes QCD axion 

分 类 号：O57[理学—粒子物理与原子核物理]