脉冲星计时阵列观测的随机背景信号对标量诱导引力波的限制

Limits on scalar-induced gravitational waves from the stochastic background by pulsar timing array observations

最近,NANOGrav、PPTA、EPTA和CPTA合作组各自独立报告了关于随机引力波背景的观测证据.尽管根据观测推断的引力波背景(幅度、频谱)与超大质量双黑洞并合的预言相一致,但这一观测也为搜寻宇宙早期的新物理现象提供了新的窗口.本文探讨了用早期宇宙中的标量诱导引力波来解释这一信号的可能性.作者采用参数化的拐折幂律谱作为随机引力波背景能谱的普适性描述,利用NANOGrav、PPTA和EPTA的新数据和贝叶斯推断的方法进行研究.本研究结果可以约束诱导引力波能谱的相关参数,并进一步对可能在早期宇宙中产生原初黑洞的各种暴胀模型给出限制,这些模型有望在未来的空间引力波观测实验中得到检验.

Recently,the NANOGrav,PPTA,EPTA,and CPTA Collaborations independently reported their evidence of the Stochastic Gravitational Waves Background(SGWB).While the inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from the population of supermassive black-hole binaries(SMBHBs),the search for new physics remains plausible in this observational window.In this work,we explore the possibility of explaining such a signal by the scalar-induced gravitational waves(IGWs)in the very early universe.We use a parameterized broken power-law function as a general description of the energy spectrum of the SGWB and fit it to the new results of NANOGrav,PPTA and EPTA.We find that this approach can put constraints on the parameters of IGW energy spectrum and further yield restrictions on various inflation models that may produce primordial black holes(PBHs)in the early universe,which is also expected to be examined by the forthcoming space-based GW experiments.