2020 Fiscal Year Final Research Report
Cosmological model from the holographic equipartition law with a nonadditive entropy
| Project/Area Number |
18K03613
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
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| Research Institution | Kanazawa University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | 加速膨張宇宙 / 宇宙論 / ホログラフィー原理 / エントロピー / 宇宙項 |
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| Outline of Final Research Achievements |
A cosmological model is derived from the holographic equipartition law with a nonadditive entropy, in order to understand an accelerated expansion of the late universe from viewpoints of thermodynamics and statistical mechanics. The second law of thermodynamics should constrain the upper limit of an extra driving term of the acceleration equation in the present model. The upper limit implies that the order of the driving term is likely consistent with the order of the cosmological constant measured by observations.
In addition, a power-law term is applied to the present model, in order to systematically examine dissipative and nondissipative universes from a thermodynamics viewpoint. Consequently, a nondissipative model is found to be consistent with observations and satisfy the thermodynamic constraints related to the maximization of entropy. This result shows that the nondissipative universe is likely favored.
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| Free Research Field |
宇宙物理にする理論，数理物理，物性基礎，流体工学，航空宇宙工学
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| Academic Significance and Societal Importance of the Research Achievements |
宇宙の加速膨張を説明するため，「ダークエネルギーを仮定した宇宙論モデル」が，標準モデルとして提案されている。しかし，標準モデルは，観測データと合うようにダークエネルギーの密度パラメータをチューニングする。本研究では，熱力学的な視点から，加速膨張宇宙のメカニズムを解明するため，新しい宇宙論モデルを構築し，このモデルの熱力学的制約条件を導出した。その結果，加速膨張に寄与する‘加速度方程式の駆動項’（ダークエネルギーに相当）の上限値は熱力学的に制約され，その上限値は観測データとほぼ一致することが判明した。加速膨張宇宙のメカニズムを理解する上で，熱力学的アプローチが重要な役割を果たすことが示された。
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