Dark radiation from a unified dark fluid model

Understand

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.