http://arxiv.org/abs/2003.04783
The detection of Primordial Gravitational Waves (PGWs) is one of the most important goals of modern cosmology since PGWs can both provide substantial evidence for primordial inflation and shed light on its physical nature. Small scale experiments on gravitational waves such as Ligo-Virgo and, in future, LISA and Einstein Telescope (ET), are sensitive to the stochastic background, $\Omega_{\rm{GW}}$. So they can be used to constrain the inflationary parameters. In performing this kind of analysis the primordial spectrum of gravitational waves is usually parametrized with a power law that includes only the amplitude and the spectral tilt. In this paper, we investigate the robustness of such constraints showing that the higher-order terms in the power law approximation (i.e. the runnings of the tensor tilt) can lead to non-negligible corrections on small scales. We start investigating these corrections in the simplest scenario of slow-roll inflation that predicts an almost scale-invariant, slightly red tilted primordial spectrum of gravitational waves. Nevertheless we estimate a correction on $\Omega_{\rm GW}$ of about 39\% on the Ligo-Virgo scales. Then we focus on blue models of inflation analyzing the robustness of the constraints that can be obtained using small scale measurements of the stochastic background. We prove that it is effectively possible to constrain the inflationary parameters on the CMB scales with the small scale data, but also that the higher-order corrections are non-negligible on small scales. We constrain a physical model of blue inflation that employs a pseudo scalar axion naturally coupled to gauge fields. We prove that, once the higher-order corrections are considered in the analysis, future experiments can tightly constraints the spectral tilt $n_{\rm t}$ improving at least of an order of magnitude the constraints.
W. Giarè and A. Melchiorri
Wed, 11 Mar 20
23/65
Comments: N/A