Figure 1

Evolution of the energy density as a function of the scale factor $a$. Heavy curves at the top are total energy density including matter, photons, and neutrinos; light curves at the bottom are energy density in the neutrino sector (including $\varphi$’s in the interacting case). Three different scenarios are depicted, differing in neutrino content: three massless neutrinos (solid line ), three degenerate standard model neutrinos with $\sum _{}^{}{m}_{\nu }=1\mathrm{e}\mathrm{V}$ (dotted line), and three interacting degenerate neutrinos plus massless $\varphi$ (dashed line). We use the same total matter density, ${\Omega }_m=0.3$, throughout; ${\rho }_{\mathrm{c}r}$ denotes the critical density today.Reuse & Permissions

Figure 2

The ratio of power spectra $P/P(m_{\nu }=0)$ where $P(m_{\nu }=0)$ is the power spectrum for the standard scenario with massless neutrinos. The solid curves show this ratio for various (degenerate) neutrino masses in the interacting scenario. Dashed curves show the ratio in the standard scenario, for which the current limit is $\sum _{}^{}{m}_{\nu }<1–2\mathrm{e}\mathrm{V}$. Note that the tritium bound, $\sum _{}^{}{m}_{\nu }<6.6\mathrm{e}\mathrm{V}$, always applies.Reuse & Permissions