2022 Fiscal Year Research-status Report
Formation of primordial black holes after inflation in modified gravity and supergravity
| Project/Area Number |
22K03624
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
Sergei V.Ketov 東京都立大学, 理学研究科, 准教授 (70347269)
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| Co-Investigator(Kenkyū-buntansha) |
藤田 裕 東京都立大学, 理学研究科, 教授 (10332165)
辻川 信二 早稲田大学, 理工学術院, 教授 (30318802)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | inflation / primordial black holes / modified gravity / supergravity / dark matter / gravitational waves |
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| Outline of Annual Research Achievements |
During the first year FY2022 of the project our research activities were focused on theoretical investigation of formation of primordial black holes (PBH) during inflation by constructing and investigating our original models in gravitational theory and supergravity theory. All our new models were consistent with recent measurements of the Cosmic Microwave Background (CMB) radiation, and predicted the formation of PBH of the asteroid size. Numerical calculations of the power spectrum of large scalar (curvature) perturbations were performed on computers in collaboration with other researchers in South Korea, Thailand, China, Germany and Russia. We achieved significant progress in our studies of new viable models of cosmological single-field and multi-field inflation, which have a large peak in the power spectrum of scalar perturbations leading to the PBH formation, by using the modified gravity theories. In supergravity, we extended our models by adding a mechanism of spontaneous supersymmetry breaking after inflation, which is important for reheating. Our new results were published in 8 original research papers in the high-ranked (Q1 and Q2 in the Web of Science rating) peer-reviewed international journals of physics, and presented by the Principal Investigator at the major international conference on high-energy particle physics, held in Greece in September 2022.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
We made significant advances in achieving several main objectives of the proposed research, namely, (i) using the manifestly supersymmetric supergravity techniques with a chiral matter added to supergravity, (ii) constructing several new single-field models of inflation leading to a high peak in the power spectrum required for PBH production, in agreement with CMB measurements, and (iii) computing the power spectrum of scalar perturbations and the spectrum of induced gravitational waves. We were able to derive some quantum (from string theory) corrections to the Starobinsky inflation due to contributions of dilaton and axion fields. Our new results were published in the international peer-reviewed journals of physics, while most of them were well cited.
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| Strategy for Future Research Activity |
Though our theoretical models were consistent with CMB measurements within two sigma, no perfect consistence (within one sigma) was achieved, as regards the value of the cosmological tilt of scalar perturbations. Therefore, our models have to be improved further. All our models are classical, so that possible impact of one-loop (quantum field theory) corrections still has to be studied. Ultra-violet completion of our inflationary models still has to be found in superstring theory, where impact of string theory corrections should be investigated. We are planning to use the powerful duality symmetry of string theory for these purposes. An important question about the maximal masses of primordial black holes formed during inflation remains unanswered.
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| Causes of Carryover |
The unused amount of financial support during the first year of the project took place because two business trips overseas planned for 2022 were postponed to the next fiscal year 2023 due to the corona virus epidemics and related COVID travel restrictions. The usage plan for the fiscal year 2023 includes two business trips to Europe for participation in the scientific conferences related to our research project.
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