2010/03/31 by Peter W. Graham, Roni Harnik, Surjeet Rajendran · 32 citations
Mathematics · Physics and Astronomy · #Anisotropy #Astrophysics #Cosmic background radiation #Cosmic microwave background #Cosmic variance #Cosmology and Gravitation Theories #Curse of dimensionality #Curvature #Galaxies: Formation, Evolution, Phenomena #Geometry #Inflation (cosmology) #Isotropy #Mathematics #Observable #Observable universe #Physics #Quantum mechanics #Relativity and Gravitational Theory #Sky #Statistical physics #Statistics #Theoretical physics #Universe #astro-ph.CO #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1103/physrevd.82.063524
published in Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields 82(6) (American Physical Society) · 30 pages, 2 figures. v2: minor changes to agree with published version
openalex publication_date 2010/09/20 · arxiv created 2010/09/28 · arxiv updated 2010/09/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
It seems generic to have vacua with lower dimensionality than ours. We consider the possibility that the observable universe originated in a transition from one of these vacua. Such a universe has anisotropic spatial curvature. This may be directly observable through its late-time effects on the CMB if the last period of slow-roll inflation was not too long. These affect the entire sky, leading to correlations which persist up to the highest CMB multipoles, thus allowing a conclusive detection above cosmic variance. Further, this anisotropic curvature causes different dimensions to expand at different rates. This leads to other potentially observable signals including a quadrupolar anisotropy in the CMB which limits the size of the curvature. Conversely, if isotropic curvature is observed it may be evidence that our parent vacuum was at least 3+1 dimensional. Such signals could reveal our history of decompactification, providing evidence for the existence of vastly different vacua.