Model-independent reconstruction of the primordial curvature power spectrum from  PTA  data

Yi, Zhu; You, Zhi-Qiang; Wu, You

doi:10.1088/1475-7516/2024/01/066

Cited by 16 publications

(1 citation statement)

References 126 publications

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“…7 −0.6 × 10 −15 at a reference frequency of 1 yr −1 [86]. While supermassive black hole binaries are considered as an explanation [93][94][95][96][97][98][99], alternative interpretations include cosmic inflation [94,95], first-order phase transitions [100][101][102][103][104][105][106][107], cosmic strings [108][109][110][111][112][113][114][115], domain walls [116][117][118], or scalar-induced gravitational waves [4,[119][120][121][122][123][124][125][126][127][128][129][130][131]. For more about the physical explanation of signals in the PTA band, please refer to the references [132][133][134]…”

Section: Introductionmentioning

confidence: 99%

The Pulsar Timing Array Signal from Infrared Regions of Scalar-Induced Gravitational Waves

Fei

2024

Universe

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The common-spectrum process, characterized by the Hellings–Downs angular correlation and observed by pulsar timing array collaborations, such as NANOGrav, PPTA, EPTA, and CPTA, can be explained by the scalar-induced gravitational waves (SIGWs). The energy density of SIGWs exhibits universal behavior in the infrared regions. Utilizing a broken power law parameterization for the primordial curvature power spectrum, we clarify the PTA signal through the infrared characteristics of the SIGWs, using Bayesian analysis to provide posterior distributions. Bayesian factors emphasize the statistical preference for the SIGW model over explanations involving supermassive black hole binaries.

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Section: Introductionmentioning

confidence: 99%

The Pulsar Timing Array Signal from Infrared Regions of Scalar-Induced Gravitational Waves

Fei

2024

Universe

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Prospects for Taiji to detect a gravitational-wave background from cosmic strings

Chen,

Huang,

Liu

et al. 2024

J. Cosmol. Astropart. Phys.

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Recently, multiple pulsar timing array collaborations have presented compelling evidence for a stochastic signal at nanohertz frequencies, potentially originating from cosmic strings. Cosmic strings are linear topological defects that can arise during phase transitions in the early Universe or as fundamental strings in superstring theory. This paper focuses on investigating the detection capabilities of Taiji, a planned space-based gravitational wave detector, for the gravitational wave background generated by cosmic strings. By analyzing simulated Taiji data and utilizing comprehensive Bayesian parameter estimation techniques, we demonstrate a significant improvement in precision compared to the NANOGrav 15-year data set, surpassing it by an order of magnitude. This highlights the enhanced measurement capabilities of Taiji. Consequently, Taiji can serve as a valuable complementary tool to pulsar timing arrays in validating and exploring the physics of cosmic strings in the early Universe.

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Simultaneously probing the sound speed and equation of state of the early Universe with pulsar timing arrays

Liu,

Wu,

Chen

2024

J. Cosmol. Astropart. Phys.

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Recently, several major pulsar timing array (PTA) collaborations have assembled strong evidence for the existence of a gravitational-wave background at frequencies around the nanohertz regime. Assuming that the PTA signal is attributed to scalar-induced gravitational waves, we jointly employ the PTA data from the NANOGrav 15-year data set, PPTA DR3, and EPTA DR2 to probe the conditions of the early Universe. Specifically, we explore the equation of state parameter (w), the reheating temperature (T rh), and the sound speed (cs ), finding w = 0.59+0.36 -0.40 (median + 90% credible interval), and T rh ≲ 0.2 GeV at the 95% credible interval for a lognormal power spectrum of the curvature perturbation. Furthermore, we compute Bayes factors to compare different models against the power-law spectrum model, effectively excluding the pressure-less fluid domination model. Our study underscores the significance of scalar-induced gravitational waves as a powerful tool to explore the nature of the early Universe.

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Model-independent reconstruction of the primordial curvature power spectrum from PTA data

Cited by 16 publications

References 126 publications

The Pulsar Timing Array Signal from Infrared Regions of Scalar-Induced Gravitational Waves

The Pulsar Timing Array Signal from Infrared Regions of Scalar-Induced Gravitational Waves

Prospects for Taiji to detect a gravitational-wave background from cosmic strings

Simultaneously probing the sound speed and equation of state of the early Universe with pulsar timing arrays

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