Theoretical foundation of higher order cosmological perturbation

2018 Fiscal Year Final Research Report

• Project/Area Number: 26287044
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Kyoto University
• Principal Investigator: Tanaka Takahiro 京都大学, 理学研究科, 教授 (40281117)
• Research Collaborator: Urakawa Yuko
• Project Period (FY): 2014-04-01 – 2019-03-31
• Keywords: 宇宙物理学 / インフレーション / 曲がった時空の場の理論 / 赤外発散

Outline of Final Research Achievements

The invariance under spacial scale transformation plays an important role in the conservation of curvature perturbation on super horizon scales.The effective action that received the loop correction is also proved to maintain this invariance. Besides the conservation of curvature perturbation, there are also universal properties such as consistency relations. Although these are often claimed to be related to the large gauge transformation, we show that locality conditions are further needed. It was also shown that the conditions for the observable physical quantities not to have infrared divergences are the same locality conditions. On the other hand, in collaboration with a graduate student, Mr. Junsei Tokuda, we formulated a systematic method to derive an effective equation of motion for long wavelength modes of a scalar field on a De Sitter background spacetime, and we showed that the dynamics governed by this equation can be interpreted as a classical stochastic process.

Free Research Field

宇宙物理学

Academic Significance and Societal Importance of the Research Achievements

インフレーション宇宙論は宇宙の初期条件に関わる諸問題の多くを解決することに成功した。しかし、インフレーション宇宙論の成功は、それ以前の宇宙を探索することを難しくしている。我々の研究は、その状況を打破する突破口を見出すべく、インフレーション宇宙論の基礎付けの脆弱な部分にメスを入れ、ほころびが生じないかを確かめる試みである。結果としては、これまでの理論予想の正しさを補強する、より強固な理論的枠組みを与えることに貢献したことになる。