非保守单模引力中的全息Ricci暗能量
Holographic Ricci dark energy in Nonconservative Unimodular Gravity
AI总结：
本文在非保守单模引力框架下构建了基于Ricci标量截断的全息暗能量宇宙学模型，引入物质与暗能量相互作用项求解参数，统计表明其虽不及ΛCDM模型但具竞争力。
摘要：
由于单模条件（$\sqrt{-g}=ε=cte$），单模引力（UG）的结构对微分同胚的一个子类（即横向微分同胚）保持不变。因此，在宇宙学背景下，可以自由定义单模引力中能量动量张量的守恒定律。在UG中描述宇宙学动力学的完整方程系统的一个主要特征是，如果其结构中不使用能量动量张量的通常守恒定律，它们就构成一个欠定系统，也就是说，必须向系统中注入额外信息才能求解完整的方程组。在本文中，我们提出在非保守UG中构建一个基于具有Ricci标量量级截断的全息暗能量分量描述的背景宇宙学模型。尽管这一选择确实为宇宙学系统新增了信息，但完整的方程组仍然是欠定的，然而，该宇宙学模型的新特征是出现了物质与暗能量之间的相互作用。事实上，这是存在全息暗能量密度的宇宙学模型的一个众所周知特征。因此，我们针对相互作用项提出一个假设$Q=βH ρ_{m}$，并求得了我们模型的宇宙学参数。我们发现了一个具有与$Λ\mathrm{CDM}$模型相似特征的可行宇宙模型。我们使用$H(z)$的“宇宙计时器”（CC）数据对背景模型进行了统计分析，并使用赤池信息准则（AIC）和贝叶斯信息准则（BIC）作为模型选择标准，结果得出$Λ\mathrm{CDM}$仍然是最优模型。然而，与宇宙学模型$ω\mathrm{CDM}$相比，所提出的模型具有竞争力。
英文摘要：
The structure of unimodular gravity (UG) is invariant to a subclass of diffeomorphism, the transverse diffeomorphism, due to the unimodular condition ($\sqrt{-g}=ε=cte$). Consequently, there is a freedom to define how the conservation laws of the energy-momentum tensor in unimodular gravity in the cosmological context. One of the main characteristics of the complete system of equations that describe cosmological dynamics in UG is that they form an underdetermined system if the usual conservation law of the energy-momentum tensor is not used in your structure, that is, it is necessary to insert extra information into the system to solve the complete set of equations. In this article, we propose the construction of a background cosmological model based on the description of a holographic dark energy component with a cutoff of the order of Ricci scalar in non-conservative UG. Although this choice is indeed a new addition of information to the cosmological system, the complete set of equations remains underdetermined, however, the new feature of this cosmological model is the appearance of an interaction between matter and dark energy. Indeed, this is a well-known characteristic of cosmological models in which we have holographic dark energy density. Consequently, we propose an ansatz to the interaction term $Q=βH ρ_{m}$, and obtain the cosmological parameters of our model. We found a viable universe model with similar characteristics to the $Λ\mathrm{CDM}$ model. We performed statistical analysis of the background model using the "Cosmic Chronometer" (CC) data for $H(z)$, and obtain as a result using Akaike Information Criterion (AIC), and the Bayesian Information Criterion (BIC) as model selection criteria that $Λ\mathrm{CDM}$ prevails as the best model. However, the proposed model is competitive when compared to the cosmological model $ω\mathrm{CDM}$.
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