We investigate the apparent power-law scaling of the pseudo phase space density (PPSD) in CDM halos. We study fluid collapse, using the close analogy between the gas entropy and the PPSD in the fluid approximation. Our hydrodynamic calculations allow for a precise evaluation of logarithmic derivatives. For scale-free initial conditions, entropy is a power law in Lagrangian (mass) coordinates, but not in Eulerian (radial) coordinates. The deviation from a radial power law arises from incomplete hydrostatic equilibrium (HSE), linked to bulk inflow and mass accretion, and the convergence to the asymptotic central power-law slope is very slow. For more realistic collapse, entropy is not a power law with either radius or mass due to deviations from HSE and scale-dependent initial conditions. Instead, it is a slowly rolling power law that appears approximately linear on a log-log plot. Our fluid calculations recover PPSD power-law slopes and residual amplitudes similar to N-body simulations, indicating that deviations from a power law are not numerical artefacts. In addition, we find that realistic collapse is not self-similar: scale lengths such as the shock radius and the turnaround radius are not power-law functions of time. We therefore argue that the apparent power-law PPSD cannot be used to make detailed dynamical inferences or extrapolate halo profiles inward, and that it does not indicate any hidden integrals of motion. We also suggest that the apparent agreement between the PPSD and the asymptotic Bertschinger slope is purely coincidental.
Characterising galaxy cluster scaling relations as cosmic isotropy tracers using FLAMINGO simulations
Leiden University（莱顿大学）；SRON Netherlands Institute for Space Research（荷兰空间研究所）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；Lorentz Institute for Theoretical Physics, Leiden University（莱顿大学洛伦兹理论物理研究所）
Apparent horizon and gravitational thermodynamics of the Universe: Solutions to the temperature and entropy confusions, and extensions to modified gravity
Kruglov-entropy cosmology from apparent-horizon thermodynamics: background dynamics and observational constraints
The Institute for Fundamental Study “The Tah Poe Academia Institute”, Naresuan University（那莱苏安大学基础研究院“塔波学术院”）；NAS, Centre for Theoretical Physics & Natural Philosophy, Mahidol University（马希隆大学自然与科学研究中心理论物理与自然哲学中心）；Department of Physics, Naresuan University（那莱苏安大学物理系）
Probing the Hubble Tension with an Infinite-Future Condition on the Hubble Parameter
Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与前沿科学研究院）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Department of Astronomy, University of Science and Technology of China（中国科学技术大学天文学系）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）
本文研究了在37个宇宙钟测量数据上对高斯过程（GP）重构H(z)时施加无限未来的条件的影响，结果表明H0值从68.71±6.08降低到约64.67-65.86±4.45-4.85 km s^{-1} Mpc^{-1}，同时H0与Planck ΛCDM值的偏离较小，但与局部距离阶梯测量的偏离增大。
Supermassive black hole seeds from direct collapse of CDM-curvature peaks
University of Canterbury（坎特伯雷大学）；Institute of Cosmology & Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）；INFN Sezione di Trieste（的里雅斯特意大利国家核物理研究所）；Rikkyo University（立教大学）；iCLA, Yamanashi Gakuin University（山梨学院大学国际基督教学习中心）；Centre for Theoretical Physics, Jamia Millia Islamia（贾米亚米利亚伊斯兰大学理论物理中心）
Physical Implications and Updated Observational Constraints of the PAge-like Unified Dark Fluid Model
School of Physics and Astronomy, Sun Yat-sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area, Sun Yat-sen University（中山大学粤港澳大湾区空间望远镜科学中心）
