Non-linear fluctuating hydrodynamics based on fluctuation theorem

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K21881
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 15:Particle-, nuclear-, astro-physics, and related fields
• Research Institution: Sophia University
• Principal Investigator: Hirano Tetsufumi 上智大学, 理工学部, 教授 (40318803)
• Co-Investigator(Kenkyū-buntansha): 藤井 宏次 東京大学, 大学院総合文化研究科, 助教 (10313173) ; 村瀬 功一 上智大学, 理工学部, 研究員 (00834095)
• Project Period (FY): 2019-06-28 – 2024-03-31
• Keywords: 揺らぎの定理 / 相対論的揺動流体力学 / 一般化された揺動散逸関係 / クォークグルーオンプラズマ / 因果律

Outline of Final Research Achievements

We applied the ``fluctuation theorem'', one of the milestone in non-equilibrium statistical physics, to a system in which local thermal equilibrium is maintained while the background expands. We aimed to apply the results to high-energy nuclear collision. First, we analyzed the Langevin system, which includes a simpler memory effect, and the LCR circuit system, which includes thermal fluctuations, as the same equation system. In particular, we formulated hydrodynamic fluctuations and critical fluctuations in a one-dimensional expanding system, and described their causal dynamics. We also discussed the limitations caused by hydrodynamic fluctuations for generalized relativistic fluid equations. It was suggested that a generalized fluctuation dissipation relation that includes the effect of expansion is necessary to satisfy the "fluctuation theorem" in these systems.

Free Research Field

ハドロン物理学

Academic Significance and Societal Importance of the Research Achievements

非平衡統計物理学の揺らぎの定理において揺動流体を扱う例はそれほど多くない。研究代表者らは高エネルギー原子核衝突反応におけるクォークグルーオンプラズマ流体を扱う中で、この系における揺らぎの定理の適用可能性に先鞭をつけ、学際的な領域の研究を進めた。今後、相対論的揺動流体力学が高エネルギー原子核衝突反応のダイナミクスを記述するうえで中心になるにあたり、その基礎的な土台の一部を築いたという意味で意義がある。