标量$ε$ -场暗能量的贝叶斯模型选择
Bayesian model selection on Scalar $ε$-Field Dark Energy
摘要：
本文的主要目的是分析最小耦合标量场-- quintessence和phantom --作为解释宇宙加速膨胀的主要候选者，并将其观测值与当前的宇宙学观测值进行比较;作为副产品，我们介绍了它的Python模块。这项工作包括一个参数$ε$，它允许在同一分析中合并精华和幻影字段。到目前为止所包括的势的例子是$V(ϕ)=V_0ϕ^μe^{βϕ^α}$和$V(ϕ)=V_0(\cosh(αϕ)+β)$，其中$α$、$μ$和$β$是自由参数，但是该分析可以容易地扩展到任何其他标量场势。除了场分量和物质的标准含量之外，该研究还结合了空间曲率（$Ω_k$）的贡献，因为它一直是最近研究的焦点。该分析包含最新的数据集以及嵌套采样器，以生成后验分布以及贝叶斯证据，从而允许执行模型选择。在这项工作中，我们约束参数空间描述的两个通用的潜力，并在几个组合中，我们发现，最适合目前的数据集是由一个模型稍微有利于与潜在的$V(ϕ)=V_0ϕ^μe^{βϕ}$与$β=0.22\pm 1.56$，$μ= -0.41\pm 1.90$，和轻微的负曲率$Ω_{k,0}=-0.0016\pm0.0018$，它提出了$1.6σ$从标准的$Λ$ CDM模型的偏差的精华字段。尽管该势能包含三个额外参数，但贝叶斯证据$\mathcal{B}_{Λ, ϕ} =2.0$无法区分该模型与具有曲率的$Λ$ CDM（$Ω_{k,0}=0.0013\pm0.0018$）。提供最小贝叶斯证据的电位对应于具有$α=-0.61\pm 1.36$的$V(ϕ)=V_0 \cosh(αϕ)$。
英文摘要：
The main aim of this paper is to analyse minimally-coupled scalar-fields -- quintessence and phantom -- as the main candidates to explain the accelerated expansion of the universe and compare its observables to current cosmological observations; as a byproduct we present its python module. This work includes a parameter $ε$ which allows to incorporate both quintessence and phantom fields within the same analysis. Examples of the potentials, so far included, are $V(ϕ)=V_0ϕ^μe^{βϕ^α}$ and $V(ϕ)=V_0(\cosh(αϕ)+β)$ with $α$, $μ$ and $β$ being free parameters, but the analysis can be easily extended to any other scalar field potential. Additional to the field component and the standard content of matter, the study also incorporates the contribution from spatial curvature ($Ω_k$), as it has been the focus in recent studies. The analysis contains the most up-to-date datasets along with a nested sampler to produce posterior distributions along with the Bayesian evidence, that allows to perform a model selection. In this work we constrain the parameter-space describing the two generic potentials, and among several combinations, we found that the best-fit to current datasets is given by a model slightly favouring the quintessence field with potential $V(ϕ)=V_0ϕ^μe^{βϕ}$ with $β=0.22\pm 1.56$, $μ= -0.41\pm 1.90$, and slightly negative curvature $Ω_{k,0}=-0.0016\pm0.0018$, which presents deviations of $1.6σ$ from the standard $Λ$CDM model. Even though this potential contains three extra parameters, the Bayesian evidence $\mathcal{B}_{Λ, ϕ} =2.0$ is unable to distinguish this model compared to the $Λ$CDM with curvature ($Ω_{k,0}=0.0013\pm0.0018$). The potential that provides the minimal Bayesian evidence corresponds to $V(ϕ)=V_0 \cosh(αϕ)$ with $α=-0.61\pm 1.36$.
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