Despite the tremendous advance of observational cosmology, the value of the Hubble constant ($H_0$) is still controversial (the so called ``Hubble tension'') because of the inconsistency between local/late-time measurements and those derived from the cosmic microwave background. As the age of the Universe is very sensitive to $H_0$, we explored whether the present-day oldest stars could place independent constraints on the Hubble constant. To this purpose, we selected from the literature the oldest objects (globular clusters, stars, white dwarfs, ultra-faint and dwarf spheroidal galaxies) with accurate age estimates. Adopting a conservative prior on their formation redshifts ($11 \leq z_{\rm f} \leq 30$) and assuming $Ω_{\rm M} = 0.3 \pm 0.02$, we developed a method based on Bayesian statistics to estimate the Hubble constant. We selected the oldest objects ($>13.3$ Gyr) and estimated $H_0$ both for each of them individually and for the average ages of homogeneous subsamples. Statistical and systematic uncertainties were properly taken into account. The constraints based on individual ages indicate that $H_0<70.6$ km/s/Mpc when selecting the most accurate estimates. If the ages are averaged and analyzed independently for each subsample, the most stringent constraints imply $H_0<73.0$ with a probability of 90.3% and errors around 2.5 km/s/Mpc. We also constructed an ``accuracy matrix'' to assess how the constraints on $H_0$ become more stringent with further improvements in the accuracy of stellar ages and $Ω_{\rm M}$. The results show the high potential of the oldest stars as independent and competitive cosmological probes not only limited to the Hubble constant.
Revisiting the Matter Creation Process: Observational Constraints on Gravitationally Induced Dark Energy and the Hubble Tension
SISSA-International School for Advanced Studies（国际高等研究学院）；INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；Institute of Space Sciences (ICE,CSIC)（空间科学研究所）；Universidad Complutense de Madrid（马德里康普顿斯大学）；Istanbul Technical University（伊斯坦布尔理工大学）；ENEA, Nuclear Department（意大利国家新能源与可再生能源署核能部）；Sapienza University of Rome（罗马智慧大学）；University of Sheffield（谢菲尔德大学）
Revisiting the Hubble sequence in the SDSS DR7 spectroscopic sample: a publicly available bayesian automated classification
我们提出了一个自动形态分类的4种类型（E，S 0，Sab，Scd）的~700.000星系SDSS DR 7光谱样本的基础上支持向量机。分类的主要新属性是，我们将每个星系关联到四个形态类中的概率，而不是分配一个单一的类。因此，分类更好地适应自然，我们期望不同形态类型之间的连续过渡。该算法使用视觉分类进行训练，然后与几个独立的视觉分类进行比较，包括Galaxy Zoo首次发布的目录。我们发现自动分类和经典的视觉之间有很好的相关性。编译的目录旨在用于不同的应用程序，可以在http://gepicom04.obspm.fr/sdss_morphology/Morphology_2010.html下载，很快就可以从CasJobs数据库下载。
The oldest Milky Way stars: New constraints on the age of the Universe and the Hubble constant
Università di Bologna（博洛尼亚大学）；INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文台）；Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Universität Potsdam（波茨坦大学）
Revisiting the cosmic distance duality relation with machine learning reconstruction methods: the combination of HII galaxies and ultra-compact radio quasars
The age of the Universe from a large sample of the oldest Galactic stars
Institute of Cosmology and Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）；Scottish Universities Physics Alliance, University of Saint Andrews（圣安德鲁斯大学苏格兰大学物理联盟）
Revisiting GW170817 at milliarcsecond scale: high-precision constraints on jet geometry and $H_0$
CSIRO, Space and Astronomy（CSIRO空间与天文）；Centre for Astrophysics and Supercomputing, Swinburne University of Technology（斯威本科技大学天体物理与超级计算中心）；ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)（ARC引力波发现卓越中心（OzGrav））；School of Physics and Astronomy, Tel Aviv University（特拉维夫大学物理与天文学学院）；School of Mathematics and Physics, University of Queensland（昆士兰大学数学与物理学院）；Indian Institute Of Technology Kanpur（坎普尔印度理工学院）；Caltech（加州理工学院）
Revisiting model-independent constraints on spatial curvature and cosmic ladders calibration: updated and forecast analyses
Università di Roma Tor Vergata（罗马托尔维加塔大学）；INFN, Sezione di Roma 2（意大利国家核物理研究所罗马第二分部）；Università di Roma La Sapienza（罗马第一大学）；Universitat de Barcelona (UB)（巴塞罗那大学）；Institut de Ciències del Cosmos (ICCUB)（宇宙科学研究所）
