2025/05/25 by Wang, Xin, Huang, Zhiqi
#83F05 #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th) #J.2
paper · doi:10.48550/arxiv.2505.19055
Recent observational analyses have revealed potential evidence for a preferred spatial direction in cosmological data. Such directional parameterization inherently places observers at a privileged spatial position, thereby conflicting with the Copernican principle and suffering from the look-elsewhere effect. To restore the Copernican principle which is the foundation of modern astronomy, we propose a stochastic framework for cosmological principle violations. The almost uniform temperature of cosmic microwave background suggests that the deviation of isotropy is negligible (\lesssim 10-5 level) on the last scattering surface, which can be used as a zero boundary condition to construct an orthogonal basis below the redshift of recombination. The relative deviation from Hubble diagram of isotropic (ΛCDM or w0waCDM) models is expanded with the orthogonal basis with a hierarchy of increasing resolution. Using this new approach, we test cosmological principle with type Ia supernovae, strong lens time delay, and gravitational-wave standard siren. The data sets are consistent with statistical isotropy on large scales.