论文标题
低$ z $万神殿中的当地物质不足或修改重力的提示
Hints of a Local Matter Underdensity or Modified Gravity in the Low $z$ Pantheon data
论文作者
论文摘要
Pantheon型IA Supernovae（SNIA）数据的红移层析成像侧重于$λ$ CDM的绝对幅度$ m $和/或Hubble常数$ h_0 $的最佳拟合价值，表示局部变化（$ z \ simsim 0.2 $），以$2σ$ $2σ$，相对于最佳的满足级别的满足。如果这种变化是物理的，则可以将其解释为$ h_0 $的局部值，对应于局部物质$Δρ_0/ρ_0/ρ_0\ simeq -0.10 \ pm 0.04 $，或者是牛顿常数的时间变化，这意味着将不断发展的Chandrasekhar质量和绝对的绝对巨大$ $ $ $ m $ m $ m $ m。局部空间方案将预测最佳拟合值$ H_0 $的各向异性，因为我们不太可能位于局部球形不足的局部。使用半球比较方法，我们发现与模拟各向同性数据集一致的各向异性水平。但是，我们表明，即使在在各向同性$λ$ CDM的上下文中获得的模拟万神殿数据中，Pantheon SNIA数据的各向异性天空分布也会引起首选的方向范围。因此，我们构建了Pantheon SNIA的更多各向同性分布的子集，并表明优选的方向范围消失了。使用此子集，我们再次使用半球比较方法或偶极拟合方法找到了各向异性的证据。在修改后的重力场景的上下文中，我们允许在早期和晚期的一般相对论（gr）$μ（z）= 1+g_a z^2/（1+z）^2-g_a z^4/（1+z）^4 $，适合$ g_a $ $ g_a $ sim $ l \ sim $ sim $ sim for。对于以前的研究指示的$ b = -3/2 $，我们发现$ g_a = -0.47 \ pm 0.36 $，距$ g_a = 0 $的GR值超过$1.5σ$。低$ z $的重力较弱的暗示与增长和镜头数据弱的证据一致。
A redshift tomography of the Pantheon type Ia supernovae (SnIa) data focusing on the best fit value of the absolute magnitude $M$ and/or Hubble constant $H_0$ in the context of $Λ$CDM indicates a local variation ($z\lesssim 0.2$) at $2σ$ level, with respect to the best fit of the full dataset. If this variation is physical, it can be interpreted either as a locally higher value of $H_0$, corresponding to a local matter underdensity $δρ_0/ρ_0 \simeq -0.10 \pm 0.04$ or as a time variation of Newton's constant which implies an evolving Chandrasekhar mass and thus an evolving absolute magnitude $M$ of SnIa. The local void scenario would predict an anisotropy in the best fit value of $H_0$ since it is unlikely that we are located at the center of a local spherical underdensity. Using a hemisphere comparison method we find an anisotropy level consistent with simulated isotropic datasets. We show however, that the anisotropic sky distribution of the Pantheon SnIa data induces a preferred range of directions even in simulated Pantheon data obtained in the context of isotropic $Λ$CDM. We thus construct a more isotropically distributed subset of the Pantheon SnIa and show that the preferred range of directions disappears. Using this subset we again find no evidence for anisotropy using either the hemisphere comparison method or the dipole fit method. In the context of the modified gravity scenario, we allow for an evolving normalized Newton's constant consistent with General Relativity (GR) at early and late times $μ(z)=1+g_a z^2/(1+z)^2-g_a z^4/(1+z)^4$ and fit for $g_a$ assuming $L\sim G_{\rm{eff}}^b$. For $b=-3/2$ indicated by previous studies we find $g_a=-0.47 \pm 0.36$ which is more than $1.5σ$ away from the GR value of $g_a=0$. This weak hint for weaker gravity at low $z$ is consistent with similar evidence from growth and weak lensing data.
