2018 Fiscal Year Final Research Report

Testing Gaussianity of primordial gravitational waves toward understanding the inflationary Universe

Research Project

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Project/Area Number	17H07319
Research Category	Grant-in-Aid for Research Activity Start-up
Allocation Type	Single-year Grants
Research Field	Particle/Nuclear/Cosmic ray/Astro physics
Research Institution	Kagawa National College of Technology
Principal Investigator	Shiraishi Maresuke 香川高等専門学校, 一般教育科(高松キャンパス), 助教 (00803446)
Research Collaborator	Bartolo Nicola Orlando Giorgio Franciolini Gabriele Kehagias Alex Riotto Antonio Thorne Ben Fujita Tomohiro Hazumi Masashi Katayama Nobuhiko Komatsu Eiichiro Liguori Michele Fergusson James R. Tansella Vittorio Sugiyama Naonori S. Okumura Teppei Ravenni Andrea Domenech Guillem Hiramatsu Takashi Lin Chunshan Sasaki Misao Wang Yi
Project Period (FY)	2017-08-25 – 2019-03-31
Keywords	原始重力波 / 非ガウス性 / インフレーション / CMB / アクシオン / Chern-Simons修正重力 / 超弦理論 / パリティの破れ
Outline of Final Research Achievements	A main goal of this project is to understand the origin of our universe more deeply by determining the inflationary particle content through tests for Gaussianity of primordial gravitational waves (GWs). We therefore examined for inflationary gravitons and axions by means of both theoretical and observational approaches. The graviton mass was then constrained from the observed data of the cosmic microwave background (CMB) anisotropies, and a massless scenario is accordingly preferred. Our forecast analysis on axions indicates that unknown information on some fundamental properties (e.g. a coupling strength) could be obtained from future CMB and interferometric GW experiments such as LiteBIRD and LISA.
Free Research Field	宇宙論
Academic Significance and Societal Importance of the Research Achievements	今回の研究で得た重力子の質量の上限値は世界初のものであり、観測される宇宙像と無矛盾なインフレーションモデルを構築する上で貴重な情報となっている。一方で、将来的に高解像度のCMBデータ解析が実現すれば、微小な質量を持つ重力子も見つかるかもしれない。また、アクシオンの性質に関しても、宇宙観測技術の精度向上とともに新たな情報にアクセスできる可能性がある。本研究は、宇宙開闢に関する最新の理解を提供するとともに、将来研究の道筋を示す役割も担っている。