arXiv 2012.052822020-12astro-ph.COgr-qc

修正引力的有效流体方法的宇宙学约束

Cosmological constraints with the Effective Fluid approach for Modified Gravity

Wilmar Cardona, Rubén Arjona, Alejandro Estrada, Savvas Nesseris

备注：: 21 pages, 3 figures, 4 tables. References added. Matches published version in JCAP
发表信息：: JCAP05(2021)064
DOI：: 10.1088/1475-7516/2021/05/064

摘要：

修正引力模型的宇宙学约束很少得到严格的执行。首先，即使一般的MG模型发展不同（即，背景和微扰），通常假设一个$Λ$ CDM背景。这种处理是不正确的，在精确宇宙学的时代，可能会导致宇宙学参数的不希望的偏差。第二，中微子质量在分析中通常是固定的，这可能会模糊它与MG参数的关系。在之前的几篇论文中，我们证明了通过使用有效流体方法，我们可以准确地计算相当一般的MG模型中的观测值。我们的方法的一个吸引人的优点是，它允许在玻尔兹曼解算器中非常容易地实现这种模型（即，更少的错误倾向），同时具有有效流体的有用的分析描述以理解基础物理。本文阐述了如何有效的流体方法可以用来进行适当的分析宇宙学的限制MG模型。我们研究了三个MG模型，包括中微子质量的总和作为一个变化的参数，在我们的马尔可夫链蒙特卡罗分析。两个模型（即，设计者$f(R)$ [DES-fR]和设计者Horndeski [HDES]）具有背景匹配$Λ$ CDM，而在第三模型（即，Hu $\&$ Sawicki $f(R)$模型[HS]），背景与标准模型不同。通过这种方式，我们估计如何相关的背景时，约束MG参数随着中微子的质量。我们在流行的玻尔兹曼求解器类中实现模型，并使用最近的可用数据（即，Planck 2018，CMB透镜，BAO，SNIa Pantheon编译，来自SHOES的$H_0$，以及RSD Gold-18编译）来计算MG参数中的严格宇宙学约束，这些约束解释了与$Λ$ CDM模型的偏差。[删节]

英文摘要：

Cosmological constraints of Modified Gravity (MG) models are seldom carried out rigorously. First, even though general MG models evolve differently (i.e., background and perturbations) to the standard cosmological model, it is usual to assume a $Λ$CDM background. This treatment is not correct and in the era of precision cosmology could induce undesired biases in cosmological parameters. Second, neutrino mass is usually held fixed in the analyses which could obscure its relation to MG parameters. In a couple of previous papers we showed that by using the Effective Fluid Approach we can accurately compute observables in fairly general MG models. An appealing advantage of our approach is that it allows a pretty easy implementation of this kinds of models in Boltzmann solvers (i.e., less error--prone) while having a useful analytical description of the effective fluid to understand the underlying physics. This paper illustrates how an effective fluid approach can be used to carry out proper analyses of cosmological constraints in MG models. We investigated three MG models including the sum of neutrino masses as a varying parameter in our Markov Chain Monte Carlo analyses. Two models (i.e., Designer $f(R)$ [DES-fR] and Designer Horndeski [HDES]) have a background matching $Λ$CDM, while in a third model (i.e., Hu $\&$ Sawicki $f(R)$ model [HS]) the background differs from the standard model. In this way we estimate how relevant the background is when constraining MG parameters along with neutrinos' masses. We implement the models in the popular Boltzmann solver CLASS and use recent, available data (i.e., Planck 2018, CMB lensing, BAO, SNIa Pantheon compilation, $H_0$ from SHOES, and RSD Gold-18 compilation) to compute tight cosmological constraints in the MG parameters that account for deviation from the $Λ$CDM model. [abridged]

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