A numerical study of primordial magnetic field amplification by
  inflation-produced gravitational waves
  We numerically study the interaction of inflation-produced magnetic fields
with gravitational waves, both of which originate from quantum fluctuations
during inflation. The resonance between the magnetic field perturbations and
the gravitational waves has been suggested as a possible mechanism for magnetic
field amplification. However, some analytical studies suggest that the effect
of the inflationary gravitational waves is too small to provide significant
amplification. Our numerical study shows more clearly how the interaction
affects the magnetic fields and confirms the weakness of the influence of the
gravitational waves. We present an investigation based on the
magnetohydrodynamic approximation and take into account the differences of the
Alfven speed.
