Testing primordial black hole scenario from their rotations

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K03864
• 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: Tokyo Institute of Technology
• Principal Investigator: Suyama Teruaki 東京工業大学, 理学院, 教授 (20456198)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 原始ブラックホール / 重力波

Outline of Final Research Achievements

I determined the threshold for the size of primordial density fluctuations required for the formation of primordial black holes. The threshold increases with the square of the angular momentum, indicating that primordial black holes with higher rotation speeds are less likely to form. Consequently, it was found that the distribution function of fluctuations, rather than the threshold, primarily determines the angular momentum distribution of primordial black holes, at least for Gaussian-type primordial fluctuations. Based on these results, a methodology was developed to verify primordial black hole scenarios through gravitational wave observations using merger rate distributions, which was then applied to actual data from the LIGO-Virgo O3 observations. It was demonstrated that the current data volume is insufficient, highlighting the need for data accumulation through future observations.

Free Research Field

宇宙論

Academic Significance and Societal Importance of the Research Achievements

LIGOによるブラックホール(BH)連星の発見以降、原始BHが注目を集めています。原始BHが本当に宇宙に存在するかどうかを明らかにすることで、初期宇宙の解明が一段と進みます。原始BHは、重力波だけでなく他にも遠方の星を重力レンズで増光させたり、宇宙マイクロ波背景放射を歪めたりと、様々な電磁的観測シグナルを生み出します。これまでにもそのような電磁観測から原始BHの存在量に制限が与えられてきましたが、LIGO以降、重力波を用いた原始BHの検証という新しい潮流が生まれています。本研究は原始BHの新しい検証方法を構築し、原始BHの存在可能性に対する知見を拡げるものです。