Searching for high energy physics through reheating processes in the early Universe

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03609
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Tohoku University (2021-2022); The University of Tokyo (2018-2020)
• Principal Investigator: Nakayama Kazunori 東北大学, 理学研究科, 准教授 (90596652)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: インフレーション / 再加熱 / 暗黒物質

Outline of Final Research Achievements

(1)We found gravitational particle production processes in the reheating phase after inflation when the inflaton oscillates coherently. Due to this process, purely gravitational dark matter can be efficiently produced so that it accounts for the presend dark matter abundance. Gravitons are also produced, which constitute high frequency part of the stochastic gravitational wave background. (2) We point out that the well-known vector coherent oscillation dark matter model suffers from serious instability. We proposed an alternative model, which, however, also suffers from severe constraints from isocurvature perturbation and statistical anisotropy in the cosmic microwave background. (3) We proposed a new idea for light bosonic dark matter detection with the use of magnons in ferromagnetic material.

Free Research Field

素粒子論・宇宙論

Academic Significance and Societal Importance of the Research Achievements

現在の素粒子論・宇宙論の最大の目標の一つである暗黒物質の解明には、初期宇宙での暗黒物質生成過程の理解と、実験での検出方法の提案が必要である。本研究を通して、その両方において大きな進展があった。初期宇宙での再加熱過程における重力的粒子生成を提案し、世界的な潮流を生み出すことに成功した。また、固体物性を利用した軽いアクシオンなどの暗黒物質の新たな観測方法を提案した。