Theoretical research on gravitational wave phenomena caused by string axions

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03654
• 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: Osaka City University
• Principal Investigator: Hirotaka Yoshino 大阪市立大学, 数学研究所, 特別研究員 (20377972)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: ブラックホール / 強重力 / アクシオン / 重力波

Outline of Final Research Achievements

The original aim of this research project was to clarify the behavior of axion field around a black hole, in particular, at the stage where the self-interaction effects become important after the growth of the superradiant instability. However, the time scale of the superradinat instability is extremely long, and it was difficult to proceed with this project by numerical simulations. For this reason, I included the clarification of the properties of gravitational field around black holes and observable phenomena into the plan. As a result, I have accomplished the research in the following issues: The optical image of a star under gravitational collapse, proposition a new concept to characterize the strength of gravity around a black hole, clarification of photon behavior at the distant region from a black hole, and the observability of gravitons generated by the photon-graviton conversion in black hole magnetospheres.

Free Research Field

一般相対論

Academic Significance and Societal Importance of the Research Achievements

ブラックホール周辺の観測が可能になってきた中で、それに関わる理論の基本的な概念の整備、将来観測にかかわる基礎的な研究成果を出すことができた。また、もともとのアクシオンのテーマでは成果が思うように出なかったが、次につながるステップを踏むことができた。