Implications of the possible 21-cm line excess at cosmic dawn on
  dynamics of interacting dark energy
  In this paper we study implications of the possible excess of 21-cm line
global signal at the epoch of cosmic dawn on the evolutions of a class of
dynamically interacting dark energy (IDE) models. We firstly summarize two
dynamical mechanisms in which different background evolutions can exert
considerable effects on the 21-cm line global signal. One is the decoupling
time of Compton scattering heating, the other stems from the direct change of
optical depth due to the different expansion rate of the Universe. After that,
we investigate the IDE models to illustrate the tension between the results of
Experiment to Detect the Global Epoch of reionization Signature (EDGES) and
other experiments. To apply the analyses of these two mechanisms to IDE models,
we find that only the optical depth can be significantly changed. Accordingly,
in order to relieve the tension by including the effects of the decoupling time
of Compton scattering heating, we deduce a possible evolution form for the
Hubble parameter within IDE that begins at an early stage around $z\sim 100$
and then smoothly evolves to a value at $z\sim 17$ which is smaller than that
obtained in the standard paradigm. Eventually, we fulfill this scenario by
adding an early dark energy dominated stage to the cosmological paradigm
described by IDE models, which can alleviate the tension between EDGES and
other cosmological observations but cannot completely solve it.
