Abstract: Cosmological measurements are affected by the energy density of massive neutrinos. We extend here a recent analysis of current cosmological data to nonminimal cosmologies. Several possible scenarios are examined: a constant w not equal -1 dark energy equation of state, a nonflat universe, a time-varying dark energy component and coupled dark matter-dark energy universes or modified gravity scenarios. When considering cosmological data only, (3 + 2) massive neutrino models with similar to 0.5 eV sterile species are allowed at 95% confidence level. This scenario has been shown to reconcile reactor, LSND and MiniBooNE positive signals with null results from other searches. Big bang nucleosynthesis bounds could compromise the viability of (3 + 2) models if the two sterile species are fully thermalized states at decoupling.

Abstract: Recent cosmological data have provided evidence for a “dark” relativistic background at high statistical significance. Parameterized in terms of the number of relativistic degrees of freedom N-eff, however, the current data seem to indicate a higher value than the one expected in the standard scenario based on three active neutrinos. This dark radiation component can be characterized not only by its abundance but also by its clustering properties, as its effective sound speed and its viscosity parameter. It is therefore crucial to study the correlations among the dark radiation properties and key cosmological parameters, as the dark energy equation of state or the running of the scalar spectral index, with current and future cosmic microwave background data. We find that dark radiation with viscosity parameters different from their standard values may be misinterpreted as an evolving dark energy component or as a running spectral index in the power spectrum of primordial fluctuations.

Abstract: Recent cosmic microwave background measurements at high multipoles from the South Pole Telescope and from the Atacama Cosmology Telescope seem to disagree in their conclusions for the neutrino and dark radiation properties. In this paper we set new bounds on the dark radiation and neutrino properties in different cosmological scenarios combining the ACT and SPT data with the nine-year data release of the Wilkinson Microwave Anisotropy Probe (WMAP-9), baryon acoustic oscillation data, Hubble Telescope measurements of the Hubble constant, and supernovae Ia luminosity distance data. In the standard three massive neutrino case, the two high multipole probes give similar results if baryon acoustic oscillation data are removed from the analyses and Hubble Telescope measurements are also exploited. A similar result is obtained within a standard cosmology with N-eff massless neutrinos, although in this case the agreement between these two measurements is also improved when considering simultaneously baryon acoustic oscillation data and Hubble Space Telescope measurements. In the N-eff massive neutrino case the two high multipole probes give very different results regardless of the external data sets used in the combined analyses. When considering extended cosmological scenarios with a dark energy equation of state or with a running of the scalar spectral index, the evidence for neutrino masses found for the South Pole Telescope in the three neutrino scenario disappears for all the data combinations explored here. Again, adding Hubble Telescope data seems to improve the agreement between the two high multipole cosmic microwave background measurements considered here. In the case in which a dark radiation background with unknown clustering properties is also considered, SPT data seem to exclude the standard value for the dark radiation viscosity c(vis)(2) = 1/3 at the 2 sigma C.L., finding evidence for massive neutrinos only when combining SPT data with baryon acoustic oscillation measurements.