Exploring neutrino mass and mass hierarchy in interacting dark energy models

We investigate how the dark energy properties impact the constraints on the total neutrino mass in interacting dark energy (IDE) models. In this study, we focus on two typical interacting dynamical dark energy models, i.e., the interacting w cold dark matter (IwCDM) model and the interacting holographic dark energy (IHDE) model. To avoid the large-scale instability problem in IDE models, we apply the parameterized post-Friedmann approach to calculate the perturbation of dark energy. We employ the Planck 2015 cosmic microwave background temperature and polarization data, combined with low-redshift measurements on baryon acoustic oscillation distance scales, type Ia supernovae, and the Hubble constant, to constrain the cosmological parameters. We find that the dark energy properties could influence the constraint limits on the total neutrino mass. Once dynamical dark energy is considered in the IDE models, the upper bounds of n-ary sumation m(v) will be changed. By considering the values of chi(2)(min), we find that in these IDE models the normal hierarchy case is slightly preferred over the inverted hierarchy case; for example, Delta chi(2) = 2.720 is given in the IHDE+ n-ary sumation m(v) model. In addition, we also find that in the IwCDM+ n-ary sumation m(v) model beta = 0 is consistent with current observational data inside the 1 sigma range, and in the IHDE+ n-ary sumation m(v) model beta > 0 is favored at more than 2 sigma level.