Insight into primordial magnetic fields from 21-cm line observation with
  EDGES experiment
  The recent observation of the 21-cm global absorption signal by EDGES
suggests that the intergalactic medium (IGM) gas has been cooler than the
cosmic microwave background during $15 \lesssim z \lesssim 20$. This result can
provide a strong constraint on heating sources for the IGM gas at these
redshifts. In this paper we study the constraint on the primordial magnetic
fields (PMFs) by the EDGES result. The PMFs can heat the IGM gas through their
energy dissipation due to the magnetohydrodynamic effects. By numerically
solving the thermal evolution of the IGM gas with the PMFs, we find that the
EDGES result gives a stringent limit on the PMFs as $B_{1\mathrm{Mpc}} \lesssim
10^{-10}$ G.
