标题： 争议$τ$可行：低光学深度的高成本 显示英文标题

标题： Dispu$τ$able: the high cost of a low optical depth

摘要： Recent Baryonic Acoustic Oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) are mildly discrepant ($2.2\sigma$) with the Cosmic Microwave Background (CMB) when interpreted within $\Lambda$CDM. When analyzing these data with extended cosmologies this inconsistency manifests as a $\simeq3\sigma$ preference for sub-minimal neutrino mass or evolving dark energy. It is known that the preference for sub-minimal neutrino mass from the suppression of structure growth could be alleviated by increasing the optical depth to reionization $\tau$. We show that, because the CMB-inferred $\tau$ is negatively correlated with the matter fraction, a larger optical depth resolves a similar preference from geometric constraints. 光学深度足够大，可以解决中微子质量的矛盾（$\tau\sim0.09)$），也减少了对演化暗能量的偏好，从$\simeq3\sigma$到$\simeq1.5\sigma$。 相反，在$\Lambda$CDM中，DESI BAO、高$\ell$CMB和CMB透镜的组合得到$\tau = 0.090 \pm 0.012$。 所需增加的$\tau$是在$\simeq3-5\sigma$张力与普朗克低-$\ell$极化数据相冲突，当以字面意义看待时。 虽然在大尺度普朗克数据中没有系统性的证据，$\tau$仍然是约束最差的$\Lambda$冷暗物质参数，并远未达到其宇宙方差极限。 $\tau$对几种宇宙学测量的重要性加强了未来大尺度宇宙微波背景实验以及再电离时期直接探测的必要性。 显示英文摘要

摘要： Recent Baryonic Acoustic Oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) are mildly discrepant ($2.2\sigma$) with the Cosmic Microwave Background (CMB) when interpreted within $\Lambda$CDM. When analyzing these data with extended cosmologies this inconsistency manifests as a $\simeq3\sigma$ preference for sub-minimal neutrino mass or evolving dark energy. It is known that the preference for sub-minimal neutrino mass from the suppression of structure growth could be alleviated by increasing the optical depth to reionization $\tau$. We show that, because the CMB-inferred $\tau$ is negatively correlated with the matter fraction, a larger optical depth resolves a similar preference from geometric constraints. Optical depths large enough to resolve the neutrino mass tension ($\tau\sim0.09)$ also reduce the preference for evolving dark energy from $\simeq3\sigma$ to $\simeq1.5\sigma$. Conversely, within $\Lambda$CDM the combination of DESI BAO, high-$\ell$ CMB and CMB lensing yields $\tau = 0.090 \pm 0.012$. The required increase in $\tau$ is in $\simeq3-5\sigma$ tension with Planck low-$\ell$ polarization data when taken at face value. While there is no evidence for systematics in the large-scale Planck data, $\tau$ remains the least well-constrained $\Lambda$CDM parameter and is far from its cosmic variance limit. The importance of $\tau$ for several cosmological measurements strengthens the case for future large-scale CMB experiments as well as direct probes of the epoch of reionization.