Exploring the early Universe phenomena through cosmological magnetic fields

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03842
• 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: The University of Tokyo
• Principal Investigator: Kamada Kohei 東京大学, 大学院理学系研究科(理学部), 助教 (60835362)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: カイラル量子異常 / バリオン数生成 / 初期宇宙磁場 / アクシオン

Outline of Final Research Achievements

I obtained several important results on the evolution of primordial magnetic fields and baryon/chiral asymmetry. The most important result is that I have shown that the baryon isocurvature fluctuation is inevitably produced by the magnetic fields at the electroweak symmetry breaking (EWSB) which gives the strong upper bound on its abundance to avoid spoiling the success of Big Bang Nucleosynthesis. As a result, intergalactic magnetic fields suggested by gamma-ray observation should be generated after EWSB. Other important results include that I have obtained the comprehensive understanding the evolution of the magnetic field and matter in the axion inflationary scenario and that I achieved pioneering studies on the similar effect of the gravitational waves to the magnetic field on the evolution of the matter.

Free Research Field

宇宙論

Academic Significance and Societal Importance of the Research Achievements

現在の宇宙のバリオン非対称の起源は、宇宙論研究の中でも最も重要な課題の一つである。磁場によるバリオン数生成は理論的整備や検証方法の提案が近年進んでいる興味深い機構である。本研究の成果により、この機構が働くためのシナリオ構築が進み、また、この機構が働いた後の宇宙の磁場や物質の発展に関する理解が深まった。観測的検証においては、宇宙の熱史全体のシナリオ依存性がありうるが、それを含めて将来の検証にむけて大きな前進が得られたといえる。