A plausible model of inflation driven by strong gravitational wave turbulence

TL;DR

This paper proposes a novel inflation model driven by strong gravitational wave turbulence, suggesting that nonlinearities in Einstein's equations can cause exponential expansion consistent with cosmic microwave background observations.

Contribution

It introduces a new inflation mechanism based on gravitational wave turbulence and demonstrates its compatibility with observational data, diverging from scalar field models.

Findings

Gravitational wave turbulence can induce exponential expansion.

The model's fossil spectrum aligns with Planck CMB data.

Inverse cascade leads to condensate formation, driving inflation.

Abstract

It is widely accepted that the primordial universe experienced a brief period of accelerated expansion called inflation. This scenario provides a plausible solution to the horizon and flatness problems. However, the particle physics mechanism responsible for inflation remains speculative with, in particular , the assumption of a scalar field called inflaton. Furthermore, the comparison with the most recent data raises new questions that encourage the consideration of alternative hypotheses. Here, we propose a completely different scenario based on a mechanism whose origins lie in the nonlin-earities of the Einstein field equations. We use the analytical results of weak gravitational wave turbulence to develop a phenomenological theory of strong gravitational wave turbulence where the inverse cascade of wave action plays a key role. In this scenario, the space-time metric excitation triggers an explosive inverse cascade followed by the formation of a condensate in Fourier space whose growth is interpreted as an expansion of the universe. Contrary to the idea that gravitation can only produce a decelerating expansion, our study reveals that gravitational wave turbulence could be a source of inflation. The fossil spectrum that emerges from this scenario is shown to be in agreement with the cosmic microwave background radiation measured by the Planck mission.