Description
Scalar-induced gravitational waves (SIGWs), produced nonlinearly by enhanced curvature perturbations, offer a promising probe of primordial non-Gaussianity (PNG) in the early Universe. In this talk, I will present our recent work on the imprints of local-type PNG on the SIGW background. I will introduce a “renormalized” diagrammatic approach we developed, which simplifies calculations of the SIGW energy-density spectrum in the presence of high-order PNG and enables systematic analysis up to arbitrary order. This work includes the energy-density fraction spectrum of the isotropic background, the angular power spectrum describing anisotropies, and the angular bispectrum and trispectrum characterizing non-Gaussianity. Specifically, using this framework, we perform numerical calculations for PNG up to quartic order. Our results show that PNG can significantly enhance the SIGW energy density and generate distinctive anisotropic and non-Gaussian signatures. These findings highlight the potential of the SIGW background as a sensitive probe of primordial non-Gaussianity.
