“…Therefore, most researchers have chosen to study dark energy by constraining w from observations. However, in a series of works [515,719,720,721,722,723,724], Wang and collaborators argued that, due to the smearing effect [712] arising from the multiple integrals relating w(z) to the luminosity distance of SN d L (z), it is difficult to constrain w using the SN data [711]. On the contrary, since using the dark energy density ρ de can minimize the smearing effect by removing one integral, ρ de can be constrained more tightly than w given the same observational data (see Fig.…”