| 研究開始時の研究の概要 |
The discovery of gravitational wave in 2015 marks the dawn of gravitational wave astronomy/cosmology. This is a new window to observe the beginning and evolution of our universe. In the next few decays, there will be many new gravitational-wave experiments, including the Japanese project KAGRA. This research is aimed to study the general and characteristic features of the stochastic gravitational-wave background originating from different sources in the early universe, which is helpful in both comprehending the physics of the early universe, and in seeking for such signals in the future.
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| 研究実績の概要 |
In the entire period of this program JP20K14461, I completed 13 papers (10 published, 3 in submission). Here is a summary of some representitive works.
1. Pi and Sasaki, Phys.Rev.Lett. 131 (2023) 1, 011002. We found a fully nonlinear expression for the curvature perturbation in single-field inflation models, which is very helpful in determining its statistical properties.
2. Cai, Pi, and Sasaki, Phys.Rev.D 102 (2020) 8, 083528. We show that under some general conditions, the GW spectra, no matter what sources they come from, has an universal infrared f^3 scaling.
3. Demenech and Pi, Sci.China Phys.Mech.Astron. 65 (2022) 3, 230411. We show that the nHz GW signal observed by pulsar timing arrays (NANOGrav, etc.) could indicate the presense of planet-mass PBHs.
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