2015/12/31 by Syksy Rasanen, Syksy Räsänen, Jussi Valiviita +2 · 2 citations
Physics and Astronomy · #Cosmic background radiation #Cosmic microwave background #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark matter #Dark radiation #Degeneracy (biology) #Multipole expansion #Particle physics theoretical and experimental studies #Perturbation theory (quantum mechanics) #Planck #Radiation #astro-ph.CO #gr-qc #hep-ph
paper · pdf · doi:10.1088/1475-7516/2016/04/050
published as JCAP 04 (2016) 050 · 22 pages, 5 figures, 2 tables, JCAP format. v2. Added the epsilon<0 case, one plot, clarifications, and 3 references. Published version
arxiv created 2016/04/26 · openalex publication_date 2016/04/26 · arxiv updated 2016/04/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We constrain deviations of the form T ∝ (1+ z ) 1+ from the standard redshift-temperature relation, corresponding to modifying distance duality as D L = (1+ z ) 2(1+ ) D A . We consider a consistent model, in which both the background and perturbation equations are changed. For this purpose, we introduce a species of dark radiation particles to which photon energy density is transferred, and assume ≥ 0. The Planck 2015 release high multipole temperature plus low multipole data give the limit < 4.5 × 10 −3 at 95% C.L. The main obstacle to improving this CMB-only result is strong degeneracy between and the physical matter densities ω b and ω c . A constraint on deuterium abundance improves the limit to < 1.8 × 10 −3 . Adding the Planck high-multipole CMB polarisation and BAO data leads to a small improvement; with this maximal dataset we obtain < 1.3 × 10 −3 . This dataset constrains the present dark radiation energy density to at most 12% of the total photon plus dark radiation density. Finally, we discuss the degeneracy between dark radiation and the effective number of relativistic species N eff , and consider the impact of dark radiation perturbations and allowing < 0 on the results.