修正重力理論におけるコンパクト天体からの重力波

• Project Area: New development in astrophysics through multimessenger observations of gravitational wave sources
• Project/Area Number: 15H00777
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: The University of Tokyo
• Principal Investigator: 須山 輝明 東京大学, 大学院理学系研究科(理学部), 助教 (20456198)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000); Fiscal Year 2016: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2015: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
• Keywords: ブラックホール / 重力波 / 修正重力理論 / 中性子星 / 宇宙物理

Outline of Annual Research Achievements

昨年度はLIGOによる重力波の初の直接検出がなされ、重力波研究の状況が一変した。特に、重いブラックホールの連星合体という未知の現象が明らかにされ、その起源の解明が重要なテーマとして躍り出た。この歴史的発見に際してまずやるべきことは、可能性として考えられるシナリオを提唱することが急務だという立場に立ち、検出された重力波イベントGW150914は、原始ブラックホール連星の合体で生じたものであるというシナリオを提唱した。９０年代に中村らによって指摘された連星形成のメカニズムに基づき、３０倍太陽質量の原始ブラックホールの連星形成率及び宇宙年齢で連星が合体するイベント率を評価した。そして、原始ブラックホールの存在量がダークマターの0.1％程度であれば、LIGOによって見積もられたイベント率が説明できることを示した。この研究によって、同時に全ダークマターとしての３０倍太陽質量の原始ブラックホールの可能性が、重力波の観測だけから初めて棄却された。この研究成果は、多くの新聞や科学雑誌に取り上げられ、宇宙物理サイエンスの社会への普及にも貢献した。

この緊急性を要する研究に加え、従来のコンパクト天体における修正重力理論の研究も行なった。具体的には、原子核密度ほど以上の物質密度ではスカラー場の期待値が変化し、それに伴って重力定数も減少する割と単純なスカラー・テンソル理論において、修正されたTOV方程式を解くことで、中性子星の質量・半径関係が一般相対論の予言からどれだけずれるかを求めた。特に、最近の観測で存在が明らかになった２倍太陽質量の中性子星が実現できるパラメータ領域の探索を、様々な核物質の状態方程式に対して行なった。

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] 国立台湾大学(台湾)
• [Journal Article] Linear perturbation analysis of hairy black holes in shift-symmetric Horndeski theories: odd-parity perturbations (2017)
  • Author(s): Kazufumi Takahashi, Teruaki Suyama
  • Journal Title: Physical Review D Volume: 95 Issue: 2 Pages: 1-8
  • DOI: 10.1103/physrevd.95.024034
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Primordial black hole scenario for the gravitational-wave event GW150914 (2016)
  • Author(s): Misao Sasaki, Teruaki Suyama, Takahiro Tanaka, Shuichiro Yokoyama
  • Journal Title: Physical Review Letters Volume: 117 Issue: 6 Pages: 1-5
  • DOI: 10.1103/physrevlett.117.061101
  • NAID: 120005825908
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Healthy degenerate theories with higher derivatives (2016)
  • Author(s): Hayato Motohashi, Karim Noui, Teruaki Suyama, Masahide Yamaguchi, Lavid Langlois
  • Journal Title: JCAP Volume: 1607 Issue: 07 Pages: 1-29
  • DOI: 10.1088/1475-7516/2016/07/033
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Primordial black holes as a novel probe of primordial gravitational waves II: detailed analysis (2016)
  • Author(s): Tomohiro Nakama, Teruaki Suyama
  • Journal Title: Physical Review D Volume: 94 Issue: 4 Pages: 1-20
  • DOI: 10.1103/physrevd.94.043507
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Fundamental theorem on gauge fixing at the action level (2016)
  • Author(s): Hayato Motohashi, Teruaki Suyama, Kazufumi Takahashi
  • Journal Title: Physical Review D Volume: 94 Issue: 12 Pages: 1-21
  • DOI: 10.1103/physrevd.94.124021
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Supermassive black holes formed by direct collapse of inflationary perturbations (2016)
  • Author(s): Tomohiro Nakama, Teruaki Suyama, Jun'ichi Yokoyama
  • Journal Title: Physical Review D Volume: 94 Issue: 10 Pages: 1-15
  • DOI: 10.1103/physrevd.94.103522
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Instability of hairy black holes in shift-symmetric Horndeski theories (2016)
  • Author(s): Hiromu Ogawa, Tsutomu Kobayashi, Teruaki Suyama
  • Journal Title: Physical Review D Volume: 93 Issue: 6 Pages: 1-9
  • DOI: 10.1103/physrevd.93.064078
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Universal instability of hairy black holes in Lovelock-Galileon theories in D dimensions (2016)
  • Author(s): Kazufumi Takahashi, Teruaki Suyama, Tsutomu Kobayashi
  • Journal Title: Physical Review D Volume: 93 Issue: 6 Pages: 1-9
  • DOI: 10.1103/physrevd.93.064068
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Large tensor mode, field range bound and consistency in generalized G-inflation (2015)
  • Author(s): Taro Kunimitsu, Teruaki Suyama, Yuki Watanabe, Jun'ichi Yokoyama
  • Journal Title: Journal of Cosmology and Astroparticle Physics Volume: 1508 Issue: 08 Pages: 1-27
  • DOI: 10.1088/1475-7516/2015/08/044
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Primordial black holes as a novel probe of primordial gravitational waves (2015)
  • Author(s): Tomohiro Nakama, Teruaki Suyama
  • Journal Title: Physical Review D Volume: 92 Issue: 12 Pages: 1-6
  • DOI: 10.1103/physrevd.92.121304
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Spontaneous scalarization-induced dark matter and variation of the gravitational constant (2015)
  • Author(s): Pisin Chen, Teruaki Suyama, Jun'ichi Yokoyama
  • Journal Title: Physical Reivew D Volume: 92 Issue: 12 Pages: 1-15
  • DOI: 10.1103/physrevd.92.124016
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Presentation] LIGOと原始ブラックホールからの重力波 (2017)
  • Author(s): 須山輝明
  • Organizer: 日本物理学会第７２回年次大会
  • Place of Presentation: 大阪大学(大阪府豊中市)
  • Year and Date: 2017-03-17
• [Presentation] Primordial Black Hole Scenario for the Gravitational-Wave Event GW150914 (2017)
  • Author(s): 須山輝明
  • Organizer: Workshop on primordial black hole
  • Place of Presentation: 台北(台湾)
  • Int'l Joint Research / Invited
• [Presentation] Primordial Black Hole Scenario for the Gravitational-Wave Event GW150914 (2016)
  • Author(s): 須山輝明
  • Organizer: Symposium on New development in astrophysics through multimessenger observations of gravitational wave sources
  • Place of Presentation: 京都大学(京都府京都市)
  • Year and Date: 2016-12-26
  • Int'l Joint Research
• [Presentation] Primordial Black Hole Scenario for the Gravitational-Wave Event GW150914 (2016)
  • Author(s): 須山輝明
  • Organizer: Spanish-Portuguese relativity meeting
  • Place of Presentation: リスボン(ポルトガル)
  • Year and Date: 2016-09-12
  • Int'l Joint Research
• [Presentation] 自発的スカラー化を伴うスカラー・テンソル理論と暗黒物質 (2016)
  • Author(s): 須山輝明
  • Organizer: 日本物理学会第７１回年次大会
  • Place of Presentation: 東北学院大学(宮城県仙台市)
  • Year and Date: 2016-03-19
• [Presentation] Probing primordial perturbation on small scales (2016)
  • Author(s): Teruaki Suyama
  • Organizer: Mini-workshop on inflation
  • Place of Presentation: 京都大学(京都府京都市)
  • Year and Date: 2016-03-10
  • Int'l Joint Research
• [Presentation] Neutron stars in scalar-tensor theories (2016)
  • Author(s): Teruaki Suyama
  • Organizer: 4th Annual Symposium of the Innovative Area on Multi-messenger Study of Gravitational Wave Sources
  • Place of Presentation: 東京大学(千葉県柏市)
  • Year and Date: 2016-02-18
  • Int'l Joint Research
• [Presentation] 自発的スカラー化、修正重力、暗黒物質 (2016)
  • Author(s): 須山輝明
  • Organizer: 新学術領域「重力波天体」A05合宿
  • Place of Presentation: KKR伊豆長岡千歳荘(静岡県伊豆の国市)
  • Year and Date: 2016-01-07
• [Presentation] 原始ブラックホールと重力波 (2016)
  • Author(s): 須山輝明
  • Organizer: 秋の学校「理論と観測から迫るダークマターの正体とその分布」
  • Place of Presentation: 国立天文台(東京都三鷹市)
  • Invited
• [Presentation] Primordial black holes as a novel probe of primordial gravitational waves (2015)
  • Author(s): Teruaki Suyama
  • Organizer: Second LeCosPA symposium
  • Place of Presentation: 台北(中華民国)
  • Year and Date: 2015-12-14
  • Int'l Joint Research / Invited
• [Presentation] Spontaneous scalarization-induced dark matter and variation of the gravitational constant (2015)
  • Author(s): Teruaki Suyama
  • Organizer: The 25th Workshop on General Relativity and Gravitation in Japan
  • Place of Presentation: 京都大学(京都府京都市)
  • Year and Date: 2015-12-07
  • Int'l Joint Research
• [Presentation] Spontaneous scalarization : asymmetron as dark matter (2015)
  • Author(s): Teruaki Suyama
  • Organizer: Exploring Theories of Modified Gravity
  • Place of Presentation: シカゴ(アメリカ合衆国)
  • Year and Date: 2015-10-12
  • Int'l Joint Research / Invited
• [Presentation] Generation of sparse and localized curvature perturbation from inflation (2015)
  • Author(s): Teruaki Suyama
  • Organizer: COSMO15
  • Place of Presentation: ワルシャワ(ポーランド共和国)
  • Year and Date: 2015-09-07
  • Int'l Joint Research