Secondary gravitational waves induced by primordial curvature perturbations
Speaker: Takahiro Terada (Nagoya University)
Abstract:
The direct detection of gravitational waves (GWs) marked the beginning of the era of GW and multi-messenger astronomy. In addition to astrophysical sources, we can consider the stochastic GW background as a powerful probe of the early Universe, thereby promoting the development of GW cosmology. In this talk, I will focus on secondary GWs induced by primordial curvature perturbations, which are generated at second order in cosmological perturbation theory. These GWs carry information about small-scale primordial fluctuations that are inaccessible to cosmic microwave background and large-scale structure observations. I will explain their physical origin and cosmological significance. For instance, such GWs can probe inflationary models—especially those predicting primordial black holes—as well as the thermal history of the Universe. I will also discuss the relevance of secondary GWs in light of recent results from pulsar timing arrays and highlight prospects for future observations.