2023 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 |
The E-type alpha-attractor models of inflation were generalized in order to accommodate production of primordial black holes via adding a near-inflection point to the inflaton scalar potential, in good (within 1 sigma) agreement with the latest measurements of the cosmic microwave background radiation. The minimal number of new parameters was used but their fine-tuning was maximized in order to increase possible masses of primordial black holes formed during the ultra-slow-roll phase of inflation and representing part of the current dark matter.
An improved model of inflation and primordial black hole formation was also proposed in modified gravity by combining the Appleby-Battye-Starobinsky model and the quantum correction given by the term quartic in the spacetime scalar curvature. The relationship between active galactic nuclei power and molecular gas mass in elliptic galaxies was clarified, and the origin of the continuum emission was explained by synchrotron radiation.
An invited review about cosmological inflation, primordial black holes and dark matter in the supergravity framework was prepared and published by the PI as a book chapter in the global project "Handbook of Quantum Gravity" (Living Edition) by the Springer Publishers (2023).
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The progress of this research was according to the plan, though it was slower than expected. Our new results were essentially limited to the classical models without supersymmetry. Quantum corrections are expected to lead to the perturbative upper bound on the amplitude of large scalar perturbations responsible for primordial black hole production and, hence, may overrule the classical results. Therefore, calculations of quantum (loop) corrections to our classical models are necessary. Next, our results still need to be extended to supergravity, which is highly constrained by supersymmetry. Observational signatures of our models of inflation and primordial black hole production should also be explored.
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| Strategy for Future Research Activity |
We are going to further proceed with our research project according to the original plan by focusing on the unsolved problems in our research. Amongst them are (i) calculations of one-loop and two-loop quantum corrections to our classical model in modified gravity, (ii) extending our models of viable inflation to supergravity motivated by superstring theory and/or extending the Starobinsky model of inflation to the superstring-motivated supergravity, and (iii) calculating the spectrum and frequencies of the gravitational waves induced by production of primordial black holes in our models.
We expect to extend our international research collaboration for those purposes and attract more graduate students to our research.
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| Causes of Carryover |
The incurring amount of 21 yen was difficult to spend at the end of the fiscal year. This amount will be used in the following fiscal year.
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| Remarks |
This is the Homepage of the PI (Ketov) at Tokyo Metropolitan University
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