Preheating in an Asymptotically Safe Quantum Field Theory

TL;DR

This paper investigates reheating in asymptotically safe quantum field theories, showing parametric resonance leads to rapid energy transfer and establishing bounds on the number of scalar fields to match observational constraints.

Contribution

It demonstrates the occurrence of parametric resonance during reheating in these theories and derives bounds on the number of scalar fields based on curvature fluctuation limits.

Findings

Parametric resonance causes rapid energy transfer from inflaton to scalar fields.

A lower bound on the number of scalar fields is established to keep curvature fluctuations within observational bounds.

Reheating dynamics are significantly influenced by the number of coupled scalar fields.

Abstract

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.