Dark radiation from a unified dark fluid model

Abstract

We present a unified dark fluid model to describe the possible evolutionary behavior of $\Delta N_{{\mathrm {eff}}}$ in dark radiation. This model can be viewed as an interacting model for the dark sectors, in which dark matter interacts with dark radiation. We show that the evolution of $\Delta N_{{\mathrm {eff}}}$ can be nicely explained without some drawbacks, such as the blowup of $\Delta N_{{\mathrm {eff}}}$ and the non-vanishing interaction at the late time.