Model-independent constraints in inflationary magnetogenesis
  We derive a simple model-independent upper bound on the strength of magnetic
fields obtained in inflationary and post-inflationary magnetogenesis taking
into account the constraints imposed by the condition of weak coupling,
back-reaction and Schwinger effect. This bound turns out to be rather low for
cosmologically interesting spatial scales. Somewhat higher upper bound is
obtained if one assumes that some unknown mechanism suppresses the Schwinger
effect in the early universe. Incidentally, we correct our previous estimates
for this case.
