Relation between the isotropy of the CMB and the geometry of the universe

2009/03/31 by Syksy Rasanen, Syksy Räsänen · 2 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Relativity and Gravitational Theory #astro-ph.CO #gr-qc

paper · pdf · doi:10.1103/physrevd.79.123522

published as Phys.Rev.D79:123522,2009 · 5 pages. v2: Corrected an error in the proof, added references and clarifications

arxiv created 2009/04/21 · openalex publication_date 2009/06/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01

Abstract

The near isotropy of the cosmic microwave background (CMB) is considered to be the strongest indication for the homogeneity and isotropy of the Universe, a cornerstone of most cosmological analysis. We derive new theorems which extend the Ehlers-Geren-Sachs result that an isotropic CMB implies that the Universe is either stationary or homogeneous and isotropic, and its generalization to the almost isotropic case. We discuss why the theorems do not apply to the real Universe, and why the CMB observations do not imply that the Universe would be nearly homogeneous and isotropic.

Citations

• An Almost Isotropic Cosmic Microwave Temperature Does Not Imply an Almost Isotropic Universe

Cited by

• Applicability of the linearly perturbed FRW metric and Newtonian cosmology
• The isotropic blackbody CMB as evidence for a homogeneous universe