Scalar induced gravity waves from ultra slow-roll Galileon inflation

Understand

We consider the production of secondary gravity waves in Galileon inflation with an ultra-slow roll (USR) phase and show that the spectrum of scalar-induced gravitational waves (SIGWs) in this case is consistent with the recent NANOGrav 15-year data and with sensitivities of other ground and space-based missions, LISA, BBO, DECIGO, CE, ET, HLVK (consists of aLIGO, aVirgo, and KAGRA), and HLV(03).

• Thanks to the non-renormalization property of Galileon theory, the amplitude of the large fluctuation is controllable at the sharp transitions between SR and USR regions.
• We show that the behaviour of the GW spectrum, when one-loop effects are included in the scalar power spectrum, is preserved under a shift of the sharp transition scale with peak amplitude $\Omega_{\rm GW}h^2\sim {\cal O}(10^{-6})$, and hence it can cover a wide range of frequencies within ${\cal O}(10^{-9}{\rm Hz} - 10^{7}{\rm Hz})$.
• An analysis of the allowed mass range for primordial black holes (PBHs) is also performed, where we find that mass values ranging from ${\cal O}(1M_{\odot} - 10^{-18}M_{\odot})$ can be generated over the corresponding allowed range of low and high frequencies.