2020-04-13

UTAPwiki/セミナー/初期宇宙・相対論速報

Deformation of the gravitational wave spectrum by density perturbations †

Ryusuke Jinno †

Abstract:
We study the effect of primordial scalar perturbations on the propagation of cosmological gravitational waves (GWs). We point out that such scalar perturbations deform the power spectrum of any stochastic GWs of the early-Universe origin. We first show that, adopting linear order results in scalar perturbations, this deformation is described by the convolution of the original GW spectrum and a linearly biased Gaussian kernel, and then discuss how large this effect can be, taking the latest bounds on primordial black holes (PBHs). We also point out that full understanding of this effect requires calculations of second order in scalar perturbations.