Fundamental study of vacuum decay towards the application to cosmology and particle physics

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20371
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0203:Particle-, nuclear-, astro-physics, and related fields
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Oshita Naritaka 国立研究開発法人理化学研究所, 数理創造プログラム, 基礎科学特別研究員 (50911632)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: 真空崩壊

Outline of Final Research Achievements

The vacuum decay or nucleation of vacuum bubble, which describes an important phenomenon in cosmology and particle physics, has been studied and the following three achievements were obtained: (i) The Lorentzian path integral was applied to the vacuum decay as a novel way to compute the vacuum decay rate. (ii) Based on the Wheeler-DeWitt equation, it was numerically discovered that there exists another bubble solution, which gives a higher decay rate than that of the common bubble solution discovered by Coleman and de Luccia. (iii) It was theoretically shown that an expanding bubble can be nucleated in the higher-dimensional AdS spacetime, compatible with the superstring theory, and mimics the expanding four-dimensional Universe on the bubble surface even if there exists a black hole in the AdS spacetime. This gives a supporting evidence of that the superstring theory, in which an expanding universe is difficult to be realized, can be compatible with cosmology.

Free Research Field

重力、宇宙論、場の量子論

Academic Significance and Societal Importance of the Research Achievements

本研究成果は、宇宙誕生直後などの初期宇宙において重要となる真空の安定性の理解に貢献する。従来まで用いられた真空崩壊率の計算法であるユークリッド経路積分には、幾らか問題点が指摘されており、それらを克服する新たな計算法の確立の第一歩となる研究成果である。また、素粒子論と重力理論を統合し得る有力な理論として超弦理論が知られているが、この理論では、我々の宇宙のように膨張する時空を包含し難いという性質が知られている。超弦理論で許される高次元空間が非一様な場合でも、そこで生成した真空泡の膨張が我々の宇宙の膨張を模倣することから、異なるスケールの物理が、一貫性を持ってこの宇宙を記述し得る理論的傍証も示した。