[论文解读] The Effects of Temperature Related Viscosity on Cosmological Evolution

Jiaxin Wang, Xinhe Meng|arXiv (Cornell University)|Mar 20, 2013

Cosmology and Gravitation Theories被引用 1

一句话总结

本文提出了一种具有温度依赖性体积黏滞系数的修正$Λ$CDM模型，采用Chapman和Sutherland的黏滞系数公式来研究宇宙学演化。研究发现，$Λ$CDM-V模型延长了宇宙年龄，避免了未来的奇点，并实现了从非理想流体到理想流体宇宙学模型的平滑过渡，为标准模型提供了物理解释的拓展。

ABSTRACT

Bulk viscosity has been intrinsically existing in the observational cosmos evolution with various effects for different cosmological evolution stages endowed with complicated cosmic media. Normally in the idealized cosmology the physical viscosity effect is often negligent in some extent by assumptions, except for galaxies formation and evolution or the like astrophysics phenomena. Actually we have not fully understood the physical origin and effects of cosmic viscosity, including its functions for the universe evolution in reality. In this present article we extend the concept of temperature-dependent viscosity from classical statistical physics to observational cosmology, especially we examine the cosmological effects with possibility of the existence for two kinds of viscosity forms, which are described by the Chapman's relation and Sutherland's formula respectively. By considering that a modification of standard model with viscosity named as $\Lambda$CDM-V model is constructed, which is supported by data fitting. In addition to the enhancement to cosmic age value, the $\Lambda$CDM-V model possesses other two pleasing features: the prediction about the no-rip/singularity future and the mechanism of smooth transition from imperfect cosmological models to perfect ones.

研究动机与目标

• 研究温度依赖性体积黏滞系数在宇宙学演化中的物理作用。
• 通过引入经典统计物理中的黏滞效应，扩展标准$Λ$CDM模型。
• 评估黏滞系数是否能够解决宇宙年龄低估和未来奇点等问题。
• 研究宇宙学模型中从非理想流体到理想流体行为的过渡。

提出的方法

• 采用Chapman关系式和Sutherland公式，对宇宙介质中的温度依赖性体积黏滞系数进行建模。
• 通过将黏滞效应嵌入有效能量-动量张量，构建修正的$Λ$CDM-V模型。
• 将$Λ$CDM-V模型拟合至观测数据，以约束黏滞参数。
• 分析在黏滞效应作用下宇宙的动力学演化，评估宇宙年龄和未来奇点条件。
• 通过黏滞系数的衰减行为，评估从非理想流体到理想流体区域过渡的平滑性。

实验结果

研究问题

• RQ1 温度依赖性体积黏滞系数如何影响宇宙年龄的预测？
• RQ2 黏滞系数能否防止诸如'撕裂'（rip）等未来宇宙奇点？
• RQ3 黏滞系数的引入如何实现从非理想流体到理想流体宇宙学模型的平滑过渡？
• RQ4 通过数据拟合得到的黏滞参数具有哪些观测约束？

主要发现

• $Λ$CDM-V模型相比标准$Λ$CDM模型，提高了宇宙年龄的预测值。
• 由于黏滞系数的阻尼效应，该模型避免了诸如'撕裂'或有限时间奇点等未来奇点。
• 黏滞系数使得宇宙演化过程中从非理想流体行为向理想流体行为的过渡变得平滑。
• 该模型通过数据拟合得到支持，表明其与观测约束一致。