Determination of neutrino mass hierarchy by 21 cm line and CMB B-mode
  polarization observations
  We focus on the ongoing and future observations for both the 21 cm line and
the CMB B-mode polarization produced by a CMB lensing, and study their
sensitivities to the effective number of neutrino species, the total neutrino
mass, and the neutrino mass hierarchy. We find that combining the CMB
observations with future square kilometer arrays optimized for 21 cm line such
as Omniscope can determine the neutrino mass hierarchy at 2 sigma. We also show
that a more feasible combination of Planck + POLARBEAR and SKA can strongly
improve errors of the bounds on the total neutrino mass and the effective
number of neutrino species to be Delta Sigma m_nu ~ 0.12 eV and Delta N_nu ~
0.38 at 2 sigma.
