Probing the QCD axion dark matter (DM) hypothesis is extremely challenging as the axion interacts very weakly with Standard Model particles. We propose a new avenue to test the QCD axion DM via transient radio signatures coming from encounters between neutron stars (NSs) and axion minihalos around primordial black holes (PBHs). We consider a general QCD axion scenario in which the PQ symmetry breaking occurs before (or during) inflation coexisting with a small fraction of DM in the form of PBHs. The PBHs will unavoidably acquire around them axion minihalos with the typical length scale of parsecs. The axion density in the minihalos may be much higher than the local DM density, and the presence of these compact objects in the Milky Way today provides a novel chance for testing the axion DM hypothesis. We study the evolution of the minihalo mass distribution in the Galaxy accounting for tidal forces and estimate the encounter rate between NSs and the dressed PBHs. We find that the encounters give rise to transient line-like emission of radio frequency photons produced by the resonant axion-photon conversion in the NS magnetosphere and the characteristic signal could be detectable with the sensitivity of current and prospective radio telescopes. It would be important to investigate in detail search strategies for such signals which would provide a novel pathway for QCD axion detection.
Multi-messenger signal from QCD-Axion Ultracompact Minihalos
Institut de Fìsica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology（高能物理研究所，巴塞罗那科技研究院）；Facultad de Ingeniería, Universidad San Sebastián（圣塞巴斯蒂安大学工程学院）；Departamento de Ciencias Físicas, Universidad Andrés Bello（安德斯贝略大学物理科学系）
Transient axion streams from disrupted miniclusters
Università degli Studi di Salerno（萨莱诺大学）；Sofia University（索非亚大学）；Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati（意大利国家核物理研究所，弗拉斯卡蒂国家实验室）
Observable signatures of enhanced axion emission from protoneutron stars
利用广义相对论一维超新星（SN）模拟方法，研究了质子中子星（PNS）内部π介子诱导反应$π^- + p \rightarrow n + a$引起的轴子辐射增强的可观测特征，重点研究了超新星爆发后的早期演化，预测了前10 s中微子和轴子辐射的时间和光谱特征.π介子作为新的自由度被包含在热的和稠密的物质中。它们的热布居和它们在轴子产生中的作用都被一致地确定为包括由于它们与核子的相互作用而产生的影响。对于广泛的环境条件内遇到的PNS，我们发现，介子诱导的轴子生产占主导地位的核子核子韧致辐射过程。通过不断包括介子的作用，致密物质的状态方程和能量损失，我们的模拟预测强大的可辨别的特征中微子和轴子发射从银河系超新星，可以观察到在地面探测器。对于轴子耦合与当前的界限兼容，我们发现一个显着的抑制与时间的中微子光度在第一个10秒。这表明，从SN 1987 A的中微子信号得出的当前边界可以得到改善，未来的银河系超新星可能会提供更严格的约束。
A MeV-Scale Dark QCD Solution to the Axion Domain Wall Problem
College of Physics, Jiangxi Normal University（江西师范大学物理学院）；School of physics, Huazhong University of Science and Technology（华中科技大学物理学院）；Tsung-Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学李政道理论与粒子物理研究所及物理与天文学院）；Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (MOE), Shanghai Jiao Tong University（上海交通大学粒子物理与宇宙学上海市重点实验室及粒子天体物理教育部重点实验室）
