TY - JOUR

T1 - Constraints on neutrino density and velocity isocurvature modes from WMAP-9 data

AU - Savelainen, Matti

AU - Väliviita, Jussi

AU - Walia, Parampreet

AU - Rusak, Stanislav

AU - Kurki-Suonio, Hannu

PY - 2013/9/27

Y1 - 2013/9/27

N2 - We use WMAP-9 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 the 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 1â̂3.4 compared to the pure adiabatic model. For the phenomenological generally correlated mixed models the odds are about 1â̂100, whereas the slow-roll approach leads to 1â̂13 (NDI) and 1â̂51 (CDI).

AB - We use WMAP-9 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 the 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 1â̂3.4 compared to the pure adiabatic model. For the phenomenological generally correlated mixed models the odds are about 1â̂100, whereas the slow-roll approach leads to 1â̂13 (NDI) and 1â̂51 (CDI).

UR - http://www.scopus.com/inward/record.url?scp=84885071293&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.88.063010

DO - 10.1103/PhysRevD.88.063010

M3 - Article

AN - SCOPUS:84885071293

SN - 1550-7998

VL - 88

SP - 1

EP - 18

JO - Physical Review D

JF - Physical Review D

IS - 6

M1 - 063010

ER -