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arXiv 1212.4136astro-ph.COgr-qc
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Chaobergin气体有救赎吗?

Does Chaplygin gas have salvation?

Juliano Pereira Campos, Júlio César Fabris, Rafael Perez, Oliver F. Piattella, Hermano Velten

摘要:

我们研究了由广义Chaubergin气体模型(一种由状态方程p = -A/ρ^α表征的理想流体)提供的统一方案。我们的关注在于背景运动学测试和小扰动演化相关测试之间可能存在的紧张关系。我们分析了宇宙微分年龄、Ia型超新星、重子声学振荡和宇宙背景辐射角谱第一峰位置的观测数据。结果表明,这些检验有利于参数α取负值:在2σ水平上,α=-0.089 ^{+0.161}_{-0.128},α< 0,置信度为85%。这些将对应于从结构形成的观点来看不可接受的声速的平方声速的负值。我们讨论了一个可能的解决方案,这个问题时,广义Chaubergin气体的框架中提出的Rastall修改后的引力理论。我们表明,在这个理论中的流体描述不服务的目的,但它是必要的框架中的广义Chaubergin气体的标量场理论。最后,我们讨论了在α= 0的情况下广义Chaubergin气体提供的标准广义相对论统一图像:这通常被认为与标准的ΛCDM模型是不可区分的,但我们表明,由Mészáros方程控制的小扰动的演化确实是不同的,并且与ΛCDM方案相比,亚视界GCG物质晕的形成可能受到重要影响。

英文摘要:

We investigate the unification scenario provided by the generalised Chaplygin gas model (a perfect fluid characterized by an equation of state p = -A/ρ^α). Our concerns lie with a possible tension existing between background kinematic tests and those related to the evolution of small perturbations. We analyse data from the observation of the differential age of the universe, type Ia supernovae, baryon acoustic oscillations and the position of the first peak of the angular spectrum of the cosmic background radiation. We show that these tests favour negative values of the parameter α: we find α= - 0.089^{+0.161}_{-0.128} at the 2σ level and that α< 0 with 85% confidence. These would correspond to negative values of the square speed of sound which are unacceptable from the point of view of structure formation. We discuss a possible solution to this problem, when the generalised Chaplygin gas is framed in the modified theory of gravity proposed by Rastall. We show that a fluid description within this theory does not serve the purpose, but it is necessary to frame the generalised Chaplygin gas in a scalar field theory. Finally, we address the standard general relativistic unification picture provided by the generalised Chaplygin gas in the case α= 0: this is usually considered to be undistinguishable from the standard ΛCDM model, but we show that the evolution of small perturbations, governed by the Mészáros equation, is indeed different and the formation of sub-horizon GCG matter halos may be importantly affected in comparison with the ΛCDM scenario.

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