通过最小和广义建模方法揭示动力学暗能量证据中的偏差
Uncovering the bias in the evidence for dynamical dark energy through minimal and generalized modeling approaches
AI总结：
本研究通过对比CPL、LZ和常数w模型，发现CPL参数化对动力学暗能量存在偏差，提出需采用最小或广义建模方法以更准确检验暗能量状态方程偏离LCDM的证据。
摘要：
在这封信中，我们认为CPL参数化对暗能量状态方程存在偏差，倾向于偏好该模型而非常数$w$模型，而后者给出的界限仍与LCDM相容。为此，我们使用CMB、超新星和来自DESI数据集的BAO数据，将状态方程参数$w_0$和早期类型$w_a$（CPL）的约束与晚期时间参数化$w_a$（LZ）以及常数$w$模型的约束进行比较。我们发现，与CPL模型的情况相同，LZ模型也偏好动力学暗能量，但其数值相对于LCDM极限几乎对称分布。这是因为$w_0$的存在使得每种参数化都能通过补偿对$w\sim -1$的偏好来重新调整方向。为进一步检验我们的假设，我们将$w_0$固定为-1，并采用最小方法考虑偏离一个自由参数的模型，或者扩展到更一般的模型，这些模型要么同时包含晚期和早期效应，要么允许存在两种暗能量流体（一种类似流体，一种类似常数分量）。我们发现，除原始CPL外，所有变体仍与LCDM相容，其似然峰值接近$w_0 = -1$、$w_a = 0$或$Ω_{\rm CC}$为0.68，其中常数$w$和晚期$w_a$具有最小的约束。尽管我们发现CPL的证据比更最小的情况更强，但对于更广义的参数化，偏好进一步增加，同时在显著性水平上仍与LCDM相容。我们得出结论，考虑CPL模型不足以检验对标准模型的偏离，有必要进行进一步的最小或更广义的方法，以更好地理解模型测试和推断方法的结果。（删节）
英文摘要：
In this letter we argue that the CPL parameterisation for the dark energy equation of state is biased towards preferring such model over the constant $w$ while the latter bounds are still compatible with LCDM. For that we compare constraints on the EoS parameters $w_0$ and early time type $w_a$ (CPL) against those with a late time parameterisation on $w_a$ (LZ) and the constant $w$ model, using CMB, Supernovae and BAO from DESI datasets. We found, the same as was the case with CPL model, preference for dynamical dark energy within the LZ model, but for values almost symmetrically distributed with respect to their LCDM limits. This is due to the fact that the presence of $w_0$ allows to recast each parametrisation into making it compensate the preference for $w\sim -1$ in the opposite direction. To further test our hypothesis, we fixed $w_0$ to -1 and followed a minimal approach by considering models that deviates by one free parameter, or we extend to more general models that either group both late and early effects, or allow the presence of two dark energy fluid alike and constant alike component. We found that all the variants, except the original CPL are still compatible with LCDM, with likelihoods peaking close to $w_0 = -1$, $w_a = 0$, or 0.68 for $Ω_{\rm CC}$, with the constant $w$ and the late time $w_a$ having the smallest constraints. Although we found that the evidence from CPL is stronger than those for the more minimal cases, however the preference increases further for the more generalized parameterizations, while still staying compatible with LCDM in terms of the significance levels. We conclude that considering CPL model is not sufficient to test deviation from the standard model and that it is necessary to conduct further minimal or more general approaches to better understand the outcomes from model testing and inference methods.(abridged)
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