改变先验：非定域引力中的绝对中微子质量约束
Changing the prior: absolute neutrino mass constraints in nonlocal gravity
摘要：
在非局部修正引力的观测约束研究中，讨论了先验变化问题。在后者中，一个模型的特点是修改的形式$\sim m^2 R\Box^{-2}R$的爱因斯坦-希尔伯特作用进行了比较，对基础$Λ$ CDM一个贝叶斯的方式。结果发现，由于$H_0 \,$ - $\, Ω_M$计划中出现了一个占主导地位的张力，竞争性的修正重力模型与给定CMB+SNIa+BAO数据的$Λ$ CDM相比明显不受欢迎（在$22 \,$：$\, 1$的投注赔率方面）。我们确定了产生这种张力的基本机制，并表明它主要是由非局域模型描述的有效暗能量的后期，相当平滑，幻影性质引起的。我们找到了可能的解决方案，它被解决，并探讨了一个给定的，包括在扩展的初始基线从一个大质量中微子本征态到三个简并的，其绝对质量$\sum m_ν\, / \, 3$是允许采取的值在一个合理的事先间隔。作为一个净效应，绝对中微子质量被推断为在$2 σ$水平上是非零的，在$\sum m_ν\approx 0.21 {\, \rm eV}$上是最佳拟合的，并且贝叶斯张力消失，使得非定域引力模型在统计上等效于$Λ$ CDM，给出了最近的CMB+SNIa+BAO数据。我们还讨论了生长率测量$f σ_8$的约束，其适合被发现是改善了一个更大的质量中微子分数以及。$ν$扩展的非局部模型也比$Λ$ CDM更倾向于更高的$H_0$值，因此与局部测量结果更一致。
英文摘要：
Prior change is discussed in observational constraints studies of nonlocally modified gravity. In the latter, a model characterized by a modification of the form $\sim m^2 R\Box^{-2}R$ to the Einstein-Hilbert action was compared against the base $Λ$CDM one in a Bayesian way. It was found that the competing modified gravity model is significantly disfavored (at $22 \,$:$\, 1$ in terms of betting-odds) against $Λ$CDM given CMB+SNIa+BAO data, because of a dominant tension appearing in the $H_0 \,$-$\, Ω_M$ plan. We identify the underlying mechanism generating such a tension and show that it is mostly caused by the late-time, quite smooth, phantom nature of the effective dark energy described by the nonlocal model. We find possible solutions for it to be resolved and explore a given one that consists in extending the initial baseline from one massive neutrino eigenstate to three degenerate ones, whose absolute mass $\sum m_ν\, / \, 3$ is allowed to take values within a reasonable prior interval. As a net effect, the absolute neutrino mass is inferred to be non-vanishing at $2 σ$ level, best-fitting at $\sum m_ν\approx 0.21 {\, \rm eV}$, and the Bayesian tension disappears rendering the nonlocal gravity model statistically equivalent to $Λ$CDM, given recent CMB+SNIa+BAO data. We also discuss constraints from growth rate measurements $f σ_8$ whose fit is found to be improved by a larger massive neutrino fraction as well. The $ν$-extended nonlocal model also prefers a higher value of $H_0$ than $Λ$CDM, therefore in better agreement with local measurements.
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