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Article
Report number arXiv:1303.5086 ; CERN-PH-TH-2013-139 ; CERN-PH-TH-2013-139
Title Planck 2013 results. XXVI. Background geometry and topology of the Universe
Author(s) Planck Collaboration  Visa alla 225 författare
Publication 2014-10-29
Imprint 22 Mar 2013
Number of pages 23
Note Comments: 23 Pages, 23 Figures
24 Pages, 22 Figures
In: Astron. Astrophys. 571 (2014) A26
DOI 10.1051/0004-6361/201321546
Subject category Astrophysics and Astronomy
Accelerator/Facility, Experiment PLANCK RE24
Abstract Planck CMB temperature maps allow detection of large-scale departures from homogeneity and isotropy. We search for topology with a fundamental domain nearly intersecting the last scattering surface (comoving distance χr). For most topologies studied the likelihood maximized over orientation shows some preference for multi-connected models just larger than χr. This effect is also present in simulated realizations of isotropic maps and we interpret it as the alignment of mild anisotropic correlations with chance features in a single realization; such a feature can also exist, in milder form, when the likelihood is marginalized over orientations. Thus marginalized, the limits on the radius Ri of the largest sphere inscribed in a topological domain (at log-likelihood-ratio -5) are: in a flat Universe, Ri>0.9χr for the cubic torus (cf. Ri>0.9χr at 99% CL for a matched-circles search); Ri>0.7χr for the chimney; Ri>0.5χr for the slab; in a positively curved Universe, Ri>1.0χr for the dodecahedron; Ri>1.0χr for the truncated cube; Ri>0.9χr for the octahedron. Similar limits apply to alternate topologies. We perform a Bayesian search for an anisotropic Bianchi VIIh geometry. In a non-physical setting where the Bianchi parameters are decoupled from cosmology, Planck data favour a Bianchi component with a Bayes factor of at least 1.5 units of log-evidence: a Bianchi pattern is efficient at accounting for some large-scale anomalies in Planck data. However, the cosmological parameters are in strong disagreement with those found from CMB anisotropy data alone. In the physically motivated setting where the Bianchi parameters are fitted simultaneously with standard cosmological parameters, we find no evidence for a Bianchi VIIh cosmology and constrain the vorticity of such models: (ω/H)0<8×1010 (95% CL). [Abridged]
Copyright/License Preprint: © 2013-2025 CERN (License: CC-BY-3.0)



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 Journalen skapades 2013-03-23, och modifierades senast 2024-05-03


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