On gravitational waves generated during inflation under the influence of a dynamical cosmological "constant"

TL;DR

This paper investigates how a dynamic, decaying cosmological constant influences the generation and spectrum of gravitational waves during inflation, revealing scale invariance conditions and the impact on wave amplitude decay.

Contribution

It introduces a non-perturbative approach to include a dynamical cosmological constant in tensor mode analysis during inflation, exploring specific models and their spectral implications.

Findings

The spectrum is scale invariant for bctb7=c2 Hb7^2 but not for bctb7=c1 H.

Non-perturbative bctb7 contributions accelerate amplitude decay.

Results suggest new bctb7(H, H^2) models for inflation compatibility.

Abstract

We study cosmological gravitational waves generated during inflation under the influence of a decaying cosmological "constant", in the Transverse-Traceless (TT) gauge. In our approach we consider a non-perturbative contribution of the dynamical cosmological "constant" to the tensor modes. As an application of the model we study the well-known cases $\Lambda(t)=\sigma H^2$ and $\Lambda(t) =\vartheta H$. The spectrum of gravitational waves for the first case results scale invariant at the end of inflation, whereas for the second case scale invariance is not achieved, leaving this to new proposals of the form: $\Lambda(t)=f(H,H^2)$, in order to include inflation in some $\Lambda(t)$CDM models. We also found that the non-perturbative contributions of $\Lambda(t)$, accelerate the decreasing of the amplitude of gravitational waves during a power-law inflationary stage, by an exponential factor.