Preheating in an Asymptotically Safe Quantum Field Theory
  We consider reheating in a class of asymptotically safe quantum field
theories recently studied in \cite{Litim:2014uca, Litim:2015iea}. These
theories allow for an inflationary phase in the very early universe. Inflation
ends with a period of reheating. Since the models contain many scalar fields
which are intrinsically coupled to the inflaton there is the possibility of
parametric resonance instability in the production of these fields, and the
danger that the induced curvature fluctuations will become too large. Here we
show that the parametric instability indeed arises, and that hence the energy
transfer from the inflaton condensate to fluctuating fields is rapid. Demanding
that the curvature fluctuations induced by the parametrically amplified entropy
modes do not exceed the upper observational bounds puts a lower bound on the
number of fields which the model of Ref.~\cite{Litim:2014uca, Litim:2015iea}
must contain. This bound also depends on the total number of e-foldings of the
inflationary phase.
