Probing the primordial universe with gravitational waves detectors

TL;DR

This paper analyzes how current and future gravitational wave detectors can constrain the primordial universe's properties, especially the tilt of the gravitational wave spectrum, and tests early universe models against observational data.

Contribution

It combines recent observational data with theoretical models to improve constraints on the primordial gravitational wave spectrum and assesses future detector capabilities.

Findings

Current limit on tilt n_T: 0.016^{+0.614}_{-0.989} at 95% C.L.

Future detectors like Einstein Telescope and LISA can tighten constraints on n_T.

Some early universe models with blue-tilted spectra are tested against datasets.

Abstract

The spectrum of primordial gravitational waves (GWs), especially its tilt $n_T$, carries significant information about the primordial universe. Combining recent aLIGO and Planck2015+BK14 data, we find that the current limit is $n_T=0.016^{+0.614}_{-0.989}$ at 95% C.L. We also estimate the impacts of Einstein Telescope and LISA on constraining $n_T$. Moreover, based on the effective field theory of cosmological perturbations, we make an attempt to confront some models of early universe scenarios, which produce blue-tilted GWs spectrum ($n_T>0$), with the corresponding datasets.