Axion cosmology on the lattice QCD(Fostering Joint International Research)

2019 Fiscal Year Final Research Report

• Project/Area Number: 15KK0176
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: Kitano Ryuichiro 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 教授 (50543451)
• Project Period (FY): 2016 – 2019
• Keywords: 素粒子論

Outline of Final Research Achievements

Interactions of the elementary particles are described by the gauge theories. The gauge fields, which are the fundamental object in the gauge theories, are obeyed by the principle that the gauge transformed gauge fields describe the same physics. This property leads to the topologically rich nature of the theory. In this research project, we investigated the topological properties of the strong interactions, and obtained new knowledge on the axion, which is the hypothetical particle to explain dark matter of the Universe. In particular, by the simulation of the lattice gauge theory, we published the results on how the axion mass changes in the early Universe. Also, the theoretical research on the topology in the gauge theory has been conducted, and obtained new results such as the relation between the topology and the quark confinement, and the relation to the duality among three dimensional gauge theories.

Free Research Field

素粒子論

Academic Significance and Societal Importance of the Research Achievements

宇宙や素粒子の世界は謎だらけである。現在最大の謎の一つが、宇宙の暗黒物質の正体であろう。強い相互作用のトポロジーに関連した仮想粒子アクシオンはその候補であるが、その性質はあまりよく理解されてはいなかった。特に、初期宇宙の高温の環境においてどのような性質を持つか、特に質量の変化は現在の存在量を見積もる上で必要な情報となる。本研究では、質量の温度変化を格子シミュレーションにより計算し、新しい結果を発表した。また、一般にゲージ理論のトポロジー的性質に関するミステリーを理論的に考察し、興味深い結果を得た。