Primordial Gravitational Waves Enhancement

TL;DR

This paper investigates how a quantum gravitational inflation model can enhance primordial gravitational waves, focusing on the effects of oscillatory phases and resonance on the wave spectrum.

Contribution

It introduces a new method for evolving the graviton mode functions directly and provides reliable initial conditions, improving the analysis of gravitational wave enhancement during inflation.

Findings

Enhanced gravitational wave signals depend on the number of oscillatory periods.

Resonant effects significantly influence specific wave numbers.

The energy density spectrum shows notable amplification due to the model's dynamics.

Abstract

We reconsider the enhancement of primordial gravitational waves that arises from a quantum gravitational model of inflation. A distinctive feature of this model is that the end of inflation witnesses a brief phase during which the Hubble parameter oscillates in sign, changing the usual Hubble friction to anti-friction. An earlier analysis of this model was based on numerically evolving the graviton mode functions after guessing their initial conditions near the end of inflation. The current study is based on an equation which directly evolves the normalized square of the magnitude. We are also able to make a very reliable estimate for the initial condition using a rapidly converging expansion for the sub-horizon regime. Results are obtained for the energy density per logarithmic wave number as a fraction of the critical density. These results exhibit how the enhanced signal depends upon the number of oscillatory periods; they also show the resonant effects associated with particular wave numbers.