Frontiers of inflation in supergravity

• Project/Area Number: 17J00731
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: 寺田 隆広 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 特別研究員(PD)
• Project Period (FY): 2017-04-26 – 2020-03-31
• Project Status: Discontinued (Fiscal Year 2019)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2018: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: バウンス宇宙論 / サイクリック宇宙論 / インフレーション / 一般相対論 / 二次重力波 / 宇宙の再加熱 / 物質優勢期 / 原始ブラックホール / 重力波 / ユニタリティ / ケーラー曲率 / 超重力理論 / グラヴィティーノ / 非線形表現

Outline of Annual Research Achievements

超重力理論や超弦理論では、スカラーポテンシャルの極小点の値が負である事がよくある。スカラー場がその周辺を通ると、宇宙は膨張から収縮に転じる。過去又は将来の宇宙で収縮が起きた場合でも、再び宇宙が膨張に転じ、指数関数的な急膨張であるインフレーションを引き起こせる事を示した。先行研究ではエネルギー条件を破るといった強い仮定がおかれていたが、正の空間曲率を仮定すれば通常の一般相対論の枠組み内で再膨張を引き起こせる事を示した。しかも、再膨張の為に導入する仕組みがインフレーションを可能にするというエコノミカルな仕組みになっており、観測結果とも整合的である。
また、前年度の「初期曲率揺らぎから二次的に誘起される重力波」（二次重力波）の研究を発展・応用させる形で宇宙の再加熱前後における重力波生成について調べたところ、再加熱の時間スケールによって大幅に重力波の強さが変わる事が判明した。通常、 再加熱前に物質優勢期を形成している物質は固有の崩壊率で崩壊していくが、これに伴って曲率揺らぎも減少し、更には重力波が大きく減少する事が分かった。対照的に、仮に先行研究と同様に突然の再加熱遷移が起こった場合には、見落とされていた速い振動項の寄与によって非常に大きな重力波が生成されることを示した。この寄与は非常に大きく、再加熱温度や物質優勢期の長さによっては将来の重力波観測実験によって観測可能である。逆に言えば重力波が観測されなかったとしても再加熱温度の制限が可能であり、素粒子論的宇宙論において大きな意味を持つと共にインフレーション模型へのヒントにもなる。
これらの他に、宇宙の再加熱前（物質優勢期）に出来た原始ブラックホールの初期密集度について研究を行い、再加熱後（放射優勢期）と比べると密集しづらい事が分かった。超重力理論でも長い物質優勢期が実現される場合があり、その様な模型と観測の比較に貢献する結果である。

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] IAS, HKUST(中国)
• [Int'l Joint Research] IPARCOS, Madrid(スペイン)
• [Int'l Joint Research] U. Complutense Madrid(スペイン)
• [Int'l Joint Research] スタンフォード大学(米国)
• [Journal Article] Prospective constraints on the primordial black hole abundance from the stochastic gravitational-wave backgrounds produced by coalescing events and curvature perturbations (2019)
  • Author(s): Wang Sai、Terada Takahiro、Kohri Kazunori
  • Journal Title: Physical Review D Volume: 99 Issue: 10 Pages: 103531-103531
  • DOI: 10.1103/physrevd.99.103531
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Non-singular bouncing cosmology with positive spatial curvature and flat scalar potential (2019)
  • Author(s): Matsui Hiroki、Takahashi Fuminobu、Terada Takahiro
  • Journal Title: Physics Letters B Volume: 795 Pages: 152-159
  • DOI: 10.1016/j.physletb.2019.06.013
  • Peer Reviewed / Open Access
• [Journal Article] Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era (2019)
  • Author(s): Inomata Keisuke、Kohri Kazunori、Nakama Tomohiro、Terada Takahiro
  • Journal Title: Journal of Cosmology and Astroparticle Physics Volume: 2019 Issue: 10 Pages: 071-071
  • DOI: 10.1088/1475-7516/2019/10/071
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Enhancement of gravitational waves induced by scalar perturbations due to a sudden transition from an early matter era to the radiation era (2019)
  • Author(s): Inomata Keisuke、Kohri Kazunori、Nakama Tomohiro、Terada Takahiro
  • Journal Title: Physical Review D Volume: 100 Issue: 4 Pages: 043532-043532
  • DOI: 10.1103/physrevd.100.043532
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Primordial black hole dark matter and LIGO/Virgo merger rate from inflation with running spectral indices: formation in the matter- and/or radiation-dominated universe (2018)
  • Author(s): Kohri Kazunori、Terada Takahiro
  • Journal Title: Classical and Quantum Gravity Volume: 35 Issue: 23 Pages: 235017-235017
  • DOI: 10.1088/1361-6382/aaea18
  • Peer Reviewed / Open Access
• [Journal Article] Semianalytic calculation of gravitational wave spectrum nonlinearly induced from primordial curvature perturbations (2018)
  • Author(s): Kohri Kazunori、Terada Takahiro
  • Journal Title: Physical Review D Volume: 97 Issue: 12 Pages: 1-1
  • DOI: 10.1103/physrevd.97.123532
  • Peer Reviewed / Open Access
• [Journal Article] Unitarity constraint on the K?hler curvature (2018)
  • Author(s): Ema Yohei、Kitano Ryuichiro、Terada Takahiro
  • Journal Title: Journal of High Energy Physics Volume: 2018 Issue: 9 Pages: 075-075
  • DOI: 10.1007/jhep09(2018)075
  • Peer Reviewed / Open Access
• [Journal Article] Gravitino problem in inflation driven by inflaton-polonyi Kahler coupling (2018)
  • Author(s): Hasegawa Fuminori , Nakayama Kazunori , Terada Takahiro , Yamada Yusuke
  • Journal Title: Physics Letters B Volume: 777 Pages: 270-274
  • DOI: 10.1016/j.physletb.2017.12.038
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Suppression/Enhancement of the Gravitational Waves induced by Curvature Perturbations after Reheating (2019)
  • Author(s): Takahiro Terada
  • Organizer: Future Perspective in Cosmology and Gravity (KMI workshop)
  • Int'l Joint Research
• [Presentation] Primordial Black Hole Dark Matter and Gravitational Waves from Binary Mergers and from Curvature Perturbations (2019)
  • Author(s): Takahiro Terada
  • Organizer: Focus session "Frontier in Study on Dark Matter" at 2019 Korean Physical Society Spring Meeting
  • Invited
• [Presentation] Bouncing Universe from Nothing (2019)
  • Author(s): Takahiro Terada
  • Organizer: 43rd Johns Hopkins Workshop
  • Int'l Joint Research
• [Presentation] Bouncing Universe from Nothing (2019)
  • Author(s): Takahiro Terada
  • Organizer: XXV International Symposium: Particle physics, String theory and Cosmology (PASCOS 2019)
  • Int'l Joint Research
• [Presentation] Enhancement of gravitational waves induced by scalar perturbations due to a sudden transition from an early matter era to the radiation era (2019)
  • Author(s): Takahiro Terada
  • Organizer: COSMO19
  • Int'l Joint Research
• [Presentation] Enhancement of gravitational waves induced by scalar perturbations due to a sudden transition from an early matter era to the radiation era (2019)
  • Author(s): Takahiro Terada
  • Organizer: 16th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2019)
  • Int'l Joint Research
• [Presentation] Bouncing Universe from Nothing ー膨張・収縮・再膨張する宇宙ー (2019)
  • Author(s): 寺田 隆広
  • Organizer: 基研研究会 素粒子物理学の進展２０１９
• [Presentation] Sign of Kahler Curvature and Unitarity (2018)
  • Author(s): 寺田隆広
  • Organizer: 素粒子物理学の進展 2018
• [Presentation] Semi-Analytic Calculation of Gravitational Wave Spectrum Induced from Primordial Curvature Perturbations (2018)
  • Author(s): Takahiro Terada
  • Organizer: KEK Theory Meeting on Particle Physics Phenomenology and 3rd KIAS-NCTS-KEK workshop on Particle Physics Phenomenology
  • Int'l Joint Research
• [Presentation] Unitarity constraint on the Kahler curvature (2018)
  • Author(s): Takahiro Terada
  • Organizer: KEK Theory Workshop 2018
  • Int'l Joint Research
• [Presentation] Semi-Analytic Calculation of Gravitational Wave Spectrum Induced from Primordial Curvature Perturbations (2018)
  • Author(s): 寺田隆広
  • Organizer: 理論懇シンポジウム
• [Presentation] Analytic Calculation of Gravitational Wave Spectrum Induced from Primordial Curvature Perturbations (2018)
  • Author(s): Takahiro Terada
  • Organizer: COSMO-18
  • Int'l Joint Research
• [Presentation] Non-thermal Gravitino Production after Large-Field Inflation (2017)
  • Author(s): Takahiro Terada
  • Organizer: PASCOS 2017
  • Int'l Joint Research
• [Presentation] Constraints on running inflation with primordial black holes (2017)
  • Author(s): Takahiro Terada
  • Organizer: The 7th KIAS Workshop on Particle Physics and Cosmology and The 2nd KEK-NCTS-KIAS Workshop on Particle Physics Phenomenology
  • Int'l Joint Research / Invited