On the Suppression of Parametric Resonance and the Viability of
  Tachyonic Preheating after Multi-Field Inflation
  We investigate the feasibility of explosive particle production via
parametric resonance or tachyonic preheating in multi-field inflationary models
by means of lattice simulations. We observe a strong suppression of resonances
in the presence of four-leg interactions between the inflaton fields and a
scalar matter field, leading to insufficient preheating when more than two
inflatons couple to the same matter field. This suppression is caused by a
dephasing of the inflatons that increases the effective mass of the matter
field.
  Including three-leg interactions leads to tachyonic preheating, which is not
suppressed by an increase in the number of fields. If four-leg interactions are
sub-dominant, we observe a slight enhancement of tachyonic preheating. Thus, in
order for preheating after multi-field inflation to be efficient, one needs to
ensure that three-leg interactions are present. If no tachyonic contributions
exist, we expect the old theory of reheating to be applicable.
