Schwinger mechanism in dS_2 and AdS_2 revisited
  Recalculating the Bogoliubov coefficients from the solutions in Phys. Rev. D
78, 103517 (2008), we obtain the mean number of boson pairs in a uniform
electric field in the global coordinates dS_2 and AdS_2, which have the correct
zero-field and zero-curvature limits, and study the vacuum persistence at
one-loop. The mean number in AdS_2 gives the lowest limit to the
Breitenloher-Freedman bound in the uniform electric field, and the mean numbers
in dS_2 and AdS_2 satisfy the reciprocal relation N_{dS} (R, E) N_{AdS} (R, E)
= 1 under the analytical continuation of the scalar curvature R.
