English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Inflation can be supported in very steep potentials if it is generated byrapidly 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 becompatible with observations at the level of the power spectrum. However, arecent analysis (based on a proposed single-field effective theory with animaginary speed of sound) found that the trispectrum and other higher-order,non-Gaussian correlators also undergo similar exponential enhancements. Thisarguably leads to `hyper-large' non-Gaussianities in stark conflict withobservations, and even to the loss of perturbative control of the calculations.In this paper, we provide the first analytic solution of the growth of theperturbations in two-field rapid-turn models, and find it in good agreementwith previous numerical and single-field EFT estimates. We also show that thenested structure of commutators of the in-in formalism has subtle and crucialconsequences: accounting for these commutators, we show analytically that thenaively leading-order piece (which indeed is exponentially large) cancelsexactly in all relevant correlators. The remaining non-Gaussianities of thesemodels are modest, and there is no problem with perturbative control from theexponential enhancement of $\zeta$. Thus, rapid-turn inflation with negativelycurved field spaces remains a viable and interesting class of candidatetheories of the early universe.

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