Preheating with the Brakes On: The Effects of a Speed Limit

TL;DR

This paper investigates how non-canonical kinetic terms in the inflaton field affect preheating, revealing that a speed limit suppresses resonance and makes preheating less efficient compared to canonical models.

Contribution

It demonstrates that non-canonical kinetic terms lengthen oscillation periods and suppress resonance, reducing preheating efficiency in inflationary models.

Findings

Non-canonical kinetic terms create a speed limit on inflaton motion.

The lengthening of oscillation periods suppresses parametric resonance.

Expansion of the universe further diminishes preheating effectiveness.

Abstract

We study preheating in models where the inflaton has a non-canonical kinetic term, containing powers of the usual kinetic energy. The inflaton field oscillating about its potential minimum acts as a driving force for particle production through parametric resonance. Non-canonical kinetic terms can impose a speed limit on the motion of the inflaton, modifying the oscillating inflaton profile. This has two important effects: it turns a smooth sinusoidal profile into a sharp saw-tooth, enhancing resonance, and it lengthens the period of oscillations, suppressing resonance. We show that the second effect dominates over the first, so that preheating with a non-canonical inflaton field is less efficient than with canonical kinetic terms, and that the expansion of the Universe suppresses resonance even further.