Preheating in an asymptotically safe quantum field theory

Abstract

We consider reheating in a class of asymptotically safe quantum field theories recently studied in [1, 2]. 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. [1, 2] must contain. This bound also depends on the total number of e-foldings of the inflationary phase.

Is asymptotically safe inflation eternal?

“…Hence, for every initial value of the field above 9.2 Planck Masses, there is a non-zero probability of eternal inflation. On the other hand, for φ 0 = 9.2 M P l and parameters given by (4.18), the inflation classically produces roughly 54 e-folds, depending on the reheating time [102], and is in the agreement with CMB data. This shows that the model is on a verge of being eternally inflating, which may point out to the interesting phenomenology.…”

“…The non-minimal coupled potential has one local maximum and two minima. The region to the left of the maximum is the region, where the inflation can be brought to an end and the reheating takes place [102]. To the right of the maximum, the inflation becomes classically eternal.…”

UV conformal window for asymptotic safety

“…General scenarios have been classified and conditions for cosmological fixed points with inflationary expansions in the early universe are known [59] (see [60,61] for settings where inflation arises purely quantum gravitationally). It has also been speculated that inflation may arise from asymptotically safe toy models [22,27], neglecting quantum gravity altogether [62,63]. Compatibility with the 2015 Planck data [64] at the 2σ-level requires a large conformal window up to ≈ 0.7 .…”

Is asymptotically safe inflation eternal?

“…The non-minimal coupled potential has one local maximum and two minima. The region to the left of the maximum is the region, where the inflation can be brought to an end and the reheating takes place [104]. To the right of the maximum, the inflation becomes classically eternal.…”