Cosmology with massive neutrinos coupled to dark energy

TL;DR

It is found that mass-varying neutrinos can leave a significant imprint on the anisotropies in the cosmic microwave background and even lead to a reduction of power on large angular scales.

Abstract

Cosmological consequences of a coupling between massive neutrinos and dark energy are investigated. In such models, the neutrino mass is a function of a scalar field, which plays the role of dark energy. The background evolution, as well as the evolution of cosmological perturbations is discussed. We find that mass-varying neutrinos can leave a significant imprint on the anisotropies in the cosmic microwave background radiation and even lead to a reduction of power on large angular scales.

Figures (4)

• Figure 1: Background evolution: In the upper panel, we plot the evolution of the density parameters for a model with $\beta=0$, $\lambda=1$. In the lower panel the corresponding plot with $\beta=1$ is shown. (Neutrinos: solid line, CDM: dot-dashed line, scalar field: dotted line and radiation: dashed line.) In all cases, the mass of the neutrinos is $m_\nu = 0.314$ eV today. We are considering a flat universe with $\Omega_b h^2 = 0.022$, $\Omega_c h^2 = 0.12$, $\Omega_\nu h^2 = 0.01$ and $h=0.7$.
• Figure 2: The upper plot is the same as Figure 1, but choosing $\beta=-0.79$ and $\lambda = 1$. The cosmological parameters are chosen as in Figure 1. The lower plot shows the evolution of the neutrino mass in the different models (solid line: $\beta=0$, $\lambda=1$; short dashed line: $\beta=1$, $\lambda = 1$; dotted line: $\beta=-0.79$, $\lambda = 1$; long dashed line $\beta = 1$, $\lambda = 0.5$.)
• Figure 3: Upper panel: the CMB anisotropy spectrum (unnormalized). Solid line: $\beta=0$, $\lambda = 1$; short--dashed line: $\beta = 1$, $\lambda=1$; dotted line: $\beta=-0.79$, $\lambda = 1$; long--dashed line: $\beta=1$, $\lambda=0.5$. The lower panel shows the matter power spectrum. From the top curve to the bottom curve: ($\beta=0$, $\lambda=1$), ($\beta=1$, $\lambda=0.5$), ($\beta=-0.79$, $\lambda=1$). The matter power spectrum for ($\beta=1$, $\lambda=1$) is indistinguishable from the ($\beta=0$, $\lambda=1$) curve.
• Figure 4: Evolution of the sum of the metric perturbations $\Phi+\Psi$. Solid line: $\beta=0$, $\lambda = 1$; short--dashed line: $\beta = 1$, $\lambda=1$; dotted line: $\beta=-0.79$, $\lambda = 1$; long--dashed line: $\beta=1$, $\lambda=0.5$. The scale is $k=10^{-3}$Mpc$^{-1}$.