论文标题
超轻标量衰减和哈勃张力
Ultralight Scalar Decay and the Hubble Tension
论文作者
论文摘要
我们检查了哈勃张力，早期和晚期测量$ H_0 $之间的不匹配是否可以通过早期宇宙中的超轻标量场来减轻，我们评估了其在紫外线物理学中的合理性。由于它们的能量密度需要迅速地进行红移，因此我们探索了物质辐射平等时代的无质量领域。我们重点介绍了超轻伪量表，轴的具体实现，轴是衰减到阿贝里亚黑暗部门的衰变。这种情况避免了早期宇宙标量模型的其他流行实现的主要问题，因为它使用了规则的标量电势，该标量电势是二次的最小值，而不是许多现有模型的极端微调。这个想法是，标量最初是在其潜力中冻结的，直到$ h \ sim m $为止，然后有效的能量转移从标量向无质量场转移到了由于共振引起的振荡开始后不久就会发生。我们引入了一个有效的流体模型，该模型捕获了从冷冻标量相到辐射暗扇形相的过渡。我们对合并的Planck 2018，BAO，SH $ _0 $ ES和Pantheon Supernovae数据集进行了适合，发现该型号给出$ H_0 = 69.9 _ { - 0.86}^{+0.84} {+0.84} $ km/s/s/s/mpc，带有$Δχ^2 \ $Δ2\ 9 $ to $ $ cdm;虽然其他数据集的包含可能会使拟合度恶化。重要的是，我们发现足够快速衰减需要大量字段的耦合值：对于轴承量字段型号$ ϕf \ tilde {f}/λ$，它需要$λ\ lessim f/80 $，其中$2πf$是场范围。我们发现了标量 - 标准模型$ \ sim ϕ \，χ^2 $的相关结论以及利用扰动衰变的模型。我们得出的结论是，这些旨在减轻哈勃张力的超轻型标量模型，同时是合理的有效现场理论，需要难以嵌入紫外线物理学中的特征。
We examine whether the Hubble tension, the mismatch between early and late measurements of $H_0$, can be alleviated by ultralight scalar fields in the early universe, and we assess its plausibility within UV physics. Since their energy density needs to rapidly redshift away, we explore decays to massless fields around the era of matter-radiation equality. We highlight a concrete implementation of ultralight pseudo-scalars, axions, that decay to an abelian dark sector. This scenario circumvents major problems of other popular realizations of early universe scalar models in that it uses a regular scalar potential that is quadratic around the minimum, instead of the extreme fine-tuning of many existing models. The idea is that the scalar is initially frozen in its potential until $H\sim m$, then efficient energy transfer from the scalar to the massless field can occur shortly after the beginning of oscillations due to resonance. We introduce an effective fluid model which captures the transition from the frozen scalar phase to the radiation dark sector phase. We perform a fit to a combined Planck 2018, BAO, SH$_0$ES and Pantheon supernovae dataset and find that the model gives $H_0=69.9_{-0.86}^{+0.84}$ km/s/Mpc with $Δχ^2 \approx -9$ compared to $Λ$CDM; while inclusions of other data sets may worsen the fit. Importantly, we find that large values of the coupling between fields is required for sufficiently rapid decay: For axion-gauge field models $ϕF\tilde{F}/Λ$ it requires $Λ\lesssim f/80$, where $2πf$ is the field range. We find related conclusions for scalar-scalar models $\simϕ\,χ^2$ and for models that utilize perturbative decays. We conclude that these sorts of ultralight scalar models that purport to alleviate the Hubble tension, while being reasonable effective field theories, require features that are difficult to embed within UV physics.
