Mild Non-Gaussianities under Perturbative Control from Rapid-Turn Inflation Models

Understand

Inflation can be supported in very steep potentials if it is generated by rapidly turning fields, which can be natural in negatively curved field spaces.

• The curvature perturbation, $\zeta$, of these models undergoes an exponential, transient amplification around the time of horizon crossing, but can still be compatible with observations at the level of the power spectrum.
• However, a recent analysis (based on a proposed single-field effective theory with an imaginary speed of sound) found that the trispectrum and other higher-order, non-Gaussian correlators also undergo similar exponential enhancements.
• This arguably leads to `hyper-large' non-Gaussianities in stark conflict with observations, and even to the loss of perturbative control of the calculations.