A cosmological study of the second-order gravitational waves induced by the coupling of primordial tensor and scalar (curvature) perturbations on small scales, and whether they can dominate the stochastic signal detected by pulsar timing arrays. Computes the induced energy-density spectrum, confronts it with CMB, BAO and PTA data and LISA sensitivity forecasts to constrain the parameter space of primordial gravitational waves and curvature perturbations, and uses a Bayes-factor model comparison to argue that induced plus primordial gravitational waves may explain the PTA signal better than a supermassive-black-hole-binary population.
A cosmology research paper (astro-ph.CO; published in JCAP, 2025) by Wu, Zhou, Kuang, Li, Chang and Huang investigating whether second-order tensor-scalar induced gravitational waves (TSIGWs) can dom…