Probing non-Gaussianities with the high frequency tail of induced gravitational waves

We investigate in detail the spectrum of gravitational waves induced by a peaked primordial curvature power spectrum generated in single-field inflationary models. We argue that the f(NL) parameter can be inferred by measuring the high frequency spectral tilt of the induced gravitational waves. We also show that the intrinsically non-Gaussian impact of f(NL) in Omega(GW) is to broaden its peak, although at a negligible level in order not to overproduce primordial black holes. We discuss possible degeneracies in the high frequency spectral tilt between f(NL) and a general equation of state of the universe w. Finally, we discuss the constraints on the amplitude, peak and slope (or equivalently, f(NL)) of the primordial power spectrum by combining current and future gravitational wave experiments with limits on mu distortions from the cosmic microwave background.

Automated summary

In this study, we explore the spectrum of gravitational waves induced by a peaked primordial curvature power spectrum from single-field inflationary models. We suggest that the f(NL) parameter can be determined by measuring the high frequency spectral tilt of induced gravitational waves. It is found that the non-Gaussian impact of f(NL) on Omega(GW) is to broaden its peak, albeit at a negligible level to avoid overproducing primordial black holes. We also discuss potential degeneracies in the high frequency spectral tilt between f(NL) and the universe's general equation of state w. Finally, constraints on the amplitude, peak, and slope of the primordial power spectrum are discussed in relation to current and future gravitational wave experiments combined with limits on mu distortions from the cosmic microwave background.