Induced gravitational waves from ultra slow-roll inflation and pulsar timing arrays observations

The stochastic gravitational wave background (SGWB) detected recently by the pulsar timing arrays (PTAs) observations may have cosmological origins. In this work we consider a model of single field inflation containing an intermediate phase of ultra slow-roll. Fixing the amplitude of the peak of curvature perturbations by the PBHs bounds we calculate the gravitational waves (GWs) induced from the curvature perturbations enhanced during USR. The spectrum of the induced GWs depends on the sharpness of the transition from the USR phase to the final attractor phase as well as to the duration of the USR period. While the model can accommodate the current PTAs data but it has non-trivial predictions for the induced GWs on higher frequency ranges which can be tested by future observations.

Automated summary

We considered a model of single field inflation containing an intermediate phase of ultra slow-roll and calculated the induced gravitational waves from the enhanced curvature perturbations during this period. The model can accommodate the current observations but has non-trivial predictions for higher frequency ranges that can be tested in future observations.