Exploring the spectral shape of gravitational waves induced by primordial scalar perturbations and connection with the primordial black hole scenarios

There is a growing expectation that the gravitational wave detectors will start probing the stochastic gravitational wave backgrounds in the following years. We explore the spectral shapes of gravitational waves induced to second order by scalar perturbations and presumably have been produced in the early Universe. We calculate the gravitational wave spectra generated during radiation and kination eras together with the associated primordial black hole counterpart. We employ power spectra for the primordial curvature perturbation generated by alpha-attractors and nonminimal derivative coupling inflation models as well as Gaussian and delta-type shapes. We demonstrate the ability of the tensor modes to constrain the spectrum of the primordial curvature perturbations and discriminate among inflationary models. Gravitational wave production during kination and radiation eras can also be distinguished by their spectral shapes and amplitudes.

Automated summary

In this study, the spectral shapes of gravitational waves induced by scalar perturbations in the early Universe are explored, and their ability to constrain and discriminate among inflationary models is demonstrated. The production of gravitational waves during kination and radiation eras can be distinguished by their spectral shapes and amplitudes.