标题： 脉冲星测时阵列 显示英文标题

标题： Pulsar Timing Arrays

摘要： 脉冲星计时阵列 (PTA) 最近发现了纳赫兹频率范围内低频引力波 (GW) 的强有力证据。当引力波经过时，它们会在测量的长度和光传播时间上产生偏差。 PTA 实验利用分布于本星系群的毫秒脉冲星发出的高度一致的射电爆发，来识别指示引力波的微小计时偏差。为了区分引力波与噪声，PTA 会寻找不同脉冲星之间一种称为赫林斯-唐斯相关性的特定关联模式。最近发现的引力波信号类型是随机引力波背景 (GWB)，它在较低的引力波频率下观测到的功率更大。长期以来，人们一直预测超大质量黑洞 (SMBH) 双星会出现与这些观测结果相匹配的引力波背景。已知超大质量黑洞存在于星系中心，当两个超大质量黑洞在星系合并后聚集在一起时，星系中心就会形成双星。迄今为止，尚未发现任何超大质量黑洞双星的可靠实例，其形成和演化仍然存在巨大的不确定性。基于新的基础物理模型，尤其是在早期宇宙中，也提出了引力波爆的其他来源。提高粒子加速器（PTA）的灵敏度最终将能够表征引力波爆的各向异性，并对来自单个超大质量黑洞双星的引力波进行约束，这两者都可以最终揭示引力波爆的真正起源。如果源头是超大质量黑洞双星，则可能存在多种电磁对应体，从而允许利用低频引力波进行多信使天体物理学研究。 显示英文摘要

摘要： Pulsar Timing Arrays (PTAs) have recently found strong evidence for low-frequency gravitational waves (GWs) in the nanohertz frequency regime. As GWs pass, they produce deviations in measured lengths and light-travel times. PTA experiments utilize the highly-consistent radio bursts from millisecond pulsars, distributed throughout the local galaxy, to identify miniscule timing deviations indicative of GWs. To distinguish GWs from noise, PTAs search for a particular correlation pattern between different pulsars called Hellings & Downs correlations. The type of GW signal that has recently been identified is a stochastic GW background (GWB), which is observed to have more power at lower GW frequencies. A GWB matching these observations has long been predicted from super-massive black-hole (SMBH) binaries. SMBHs are known to exist in the centers of galaxies, which can then form binaries when two SMBHs are brought together following the merger of galaxies. No example of an SMBH binary has confidently been identified to date, and tremendous uncertainties about their formation and evolution remain. Alternative sources of the GWB have also been proposed, based on models for new fundamental physics, particularly in the early Universe. Improved sensitivity of PTAs will eventual lead to the characterization of GWB anisotropy and constraints on GWs from individual SMBH binaries, either of which could definitively demonstrate the true origin of the GWB. If the source is SMBH binaries, a variety of electromagnetic counterparts are possible, allowing for multimessenger astrophysics with low-frequency GWs.