Constraints on neutrino density and velocity isocurvature modes from WMAP-9 data
| Autor: | Parampreet Walia, Jussi Valiviita, M. Savelainen, Hannu Kurki-Suonio, Stanislav Rusak |
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| Přispěvatelé: | Helsinki Institute of Physics, Department of Physics |
| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Mixed model
Nuclear and High Energy Physics Particle physics Cosmology and Nongalactic Astrophysics (astro-ph.CO) Cold dark matter POLARIZATION Cosmic microwave background education FOS: Physical sciences EFFICIENT General Relativity and Quantum Cosmology (gr-qc) Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics CMB 01 natural sciences 114 Physical sciences General Relativity and Quantum Cosmology Cosmology PARAMETERS High Energy Physics - Phenomenology (hep-ph) INFLATION 0103 physical sciences Adiabatic process 010303 astronomy & astrophysics Physics SPECTRUM 010308 nuclear & particles physics COSMOLOGICAL PERTURBATIONS CMB cold spot EVOLUTION High Energy Physics - Phenomenology Amplitude TENSOR PERTURBATIONS SCALAR FIELDS Neutrino Astrophysics - Cosmology and Nongalactic Astrophysics |
| Popis: | We use WMAP 9-year and other CMB data to constrain cosmological models where the primordial perturbations have both an adiabatic and a (possibly correlated) neutrino density (NDI), neutrino velocity (NVI), or cold dark matter density (CDI) isocurvature component. For NDI and CDI we use both a phenomenological approach, where primordial perturbations are parametrized in terms of amplitudes at two scales, and a slow-roll two-field inflation approach, where slow-roll parameters are used as primary parameters. For NVI we use only the phenomenological approach, since it is difficult to imagine a connection with inflation. We find that in the NDI and NVI cases larger isocurvature fractions are allowed than in the corresponding models with CDI. For uncorrelated perturbations, the upper limit to the primordial NDI (NVI) fraction is 24% (20%) at k = 0.002 Mpc^{-1} and 28% (16%) at k = 0.01 Mpc^{-1}. For maximally correlated (anticorrelated) perturbations, the upper limit to the NDI fraction is 3.0% (0.9%). The nonadiabatic contribution to the CMB temperature variance can be as large as 10% (-13%) for the NDI (NVI) modes. Bayesian model comparison favors pure adiabatic initial mode over the mixed primordial adiabatic and NDI, NVI, or CDI perturbations. At best, the betting odds for a mixed model (uncorrelated NDI) are 1:3.4 compared to the pure adiabatic model. For the phenomenological generally correlated mixed models the odds are about 1:100, whereas the slow-roll approach leads to 1:13 (NDI) and 1:51 (CDI). Comment: 17 pages, 11 figures, 5 tables. V2: 3 references added |
| Databáze: | OpenAIRE |
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