Constraints on ultraslow-roll inflation from the third LIGO-Virgo observing run

The nonattractor evolution in ultraslow-roll (USR) inflation results in the amplification of superhorizon curvature perturbations and then induces a strong and detectable stochastic gravitational wave background. In this paper, we search for such a stochastic gravitational wave background in data from the third LIGO-Virgo observing run and place constraints on the USR inflationary models. The e-folding number of the USR phase are constrained to be Delta N less than or similar to 2.9 at the 95% confidence level and the power spectrum of curvature perturbations amplified during the USR phase is constrained to be log(10)P(Rp) < -1.7 at the scales 2.9 x 10(5) pc(-1) less than or similar to k less than or similar to 1.7 x 10(11) pc(-1). Besides, we forecast the ability of future experiments to constrain USR inflation, and find P-Rp less than or similar to 10-3.6 for LISA and Taiji, P-Rp less than or similar to 10(-3).3 for Cosmic Explore and Einstein Telescope, P-Rp less than or similar to 10(-5.5) for DECIGO and Big Bang Observer, and P-Rp less than or similar to 10(-5.2) for Square Kilometre Array.