Different Aspects of Entropic Cosmology

IF 2.5 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Universe Pub Date : 2024-09-03 DOI:10.3390/universe10090352
Shin’ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul
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Abstract

We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon during the cosmic evolution of the universe; in particular, it is expressed by TdS=−d(ρV)+WdV (where W is the work density and other quantities have their usual meanings). In this way, the first law actually links various theories of gravity with the entropy of the apparent horizon. This leads to a natural question—“What is the form of the horizon entropy corresponding to a general modified theory of gravity?”. The second law of horizon thermodynamics states that the change in total entropy (the sum of horizon entropy + matter fields’ entropy) with respect to cosmic time must be positive, where the matter fields behave like an open system characterised by a non-zero chemical potential. The second law of horizon thermodynamics importantly provides model-independent constraints on entropic parameters. Finally, we discuss the standpoint of entropic cosmology on inflation (or bounce), reheating and primordial gravitational waves from the perspective of a generalised entropy function.
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熵宇宙学的不同方面
我们简要回顾了基于两个视界热力学定律(即热力学第一定律和第二定律)的熵宇宙学的最新发展。第一定律基本上提供了宇宙演化过程中视地平线的熵的变化;特别是,它用 TdS=-d(ρV)+WdV 表示(其中 W 是功密度,其他量具有通常的含义)。这样,第一定律实际上将各种引力理论与视界熵联系在了一起。这就自然引出了一个问题--"与一般修正引力理论相对应的视界熵的形式是什么?视界热力学第二定律指出,相对于宇宙时间,总熵(视界熵+物质场熵之和)的变化必须为正,其中物质场的行为就像一个开放系统,其特征是化学势不为零。地平线热力学第二定律为熵参数提供了与模型无关的重要约束。最后,我们从广义熵函数的角度,讨论了熵宇宙学关于暴胀(或反弹)、再热和原始引力波的观点。
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来源期刊
Universe
Universe Physics and Astronomy-General Physics and Astronomy
CiteScore
4.30
自引率
17.20%
发文量
562
审稿时长
24.38 days
期刊介绍: Universe (ISSN 2218-1997) is an international peer-reviewed open access journal focused on fundamental principles in physics. It publishes reviews, research papers, communications, conference reports and short notes. Our aim is to encourage scientists to publish their research results in as much detail as possible. There is no restriction on the length of the papers.
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