Exploring higher-derivative theories of gravity
| Project/Area Number |
18K13565
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
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| Research Institution | Kogakuin University (2020-2021)
Kyoto University (2018-2019) |
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Principal Investigator |
Motohashi Hayato 工学院大学, 教育推進機構(公私立大学の部局等), 准教授 (00708563)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2021)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2021: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2020: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
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| Keywords | 重力 / 相対論 / 宇宙論 / ブラックホール / インフレーション / ダークエネルギー / 摂動論 / ホイン関数 / 原始ブラックホール / 修正重力理論 / 可逆変換 / 修正重力 / 高階微分 / オストログラドスキー・ゴースト / 重力理論 |
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| Outline of Final Research Achievements |
Recently, various scalar-tensor theories with higher-order derivatives are proposed as extensions of general relativity. Such theories are prone to suffer from pathological degrees of freedom known as the Ostrogradsky ghosts. We propose a systematic algorithm where we impose a set of degeneracy conditions to eliminate the ghosts from generic theories involving arbitrarily higher-order derivatives. We also find a generalization of the disformal transformation to include higher derivatives, and applying it to construct a novel class of scalar-tensor theory. Further, we explore the higher-derivative theories of gravity from multiple viewpoints: find novel black hole exact solutions, establish the black hole perturbation theory, resolve the strong coupling by scordatura mechanism, and clarify its role in dark energy and inflationary models.
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| Academic Significance and Societal Importance of the Research Achievements |
米国の重力波干渉計LIGOによる2016年の重力波初検出の報告以来、ブラックホールの理論・観測の研究者によるノーベル賞受賞が相次いでおり、現在ブラックホール研究は国際的に大きな注目を集めている。このような状況において重力理論検証の枠組みとしてゴーストを持たない高階微分重力理論を構築したことは大きな意義を持つ。また、ブラックホール厳密解の発見及び摂動論の定式化は準固有振動等の観測量につながるものであり、後続研究も進行中である。我が国の重力波干渉計KAGRAも2020年から観測を開始しており、本研究成果と将来的な観測データを合わせることで新しい物理法則の糸口がつかめるか、今後の進展が期待される。
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Report
(5 results)
Research Products
(76 results)
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[Journal Article] On Rotating Black Holes in DHOST Theories2020
Author(s)
Jibril Ben Achour, Hongguang Liu, Hayato Motohashi, Shinji Mukohyama, Karim Noui
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Journal Title
Journal of Cosmology and Astroparticle Physics
Volume: 11
Issue: 11
Pages: 1-21
DOI
Related Report
Peer Reviewed / Open Access / Int'l Joint Research
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[Presentation] Black holes in modified gravity2020
Author(s)
Hayato Motohashi
Organizer
AAPPS-DACG Workshop on Astrophysics, Cosmology and Gravitation, Asia Pacific Center for Theoretical Physics (APCTP), Pohang, South Korea (online)
Related Report
Int'l Joint Research
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