A Consistency Relation for Single-Field Inflation with Power Spectrum Oscillations

Understand

We derive a theoretical upper bound on the oscillation frequency in the scalar perturbation power spectrum of single-field inflation.

• Oscillations are most naturally produced by modified vacua with varying phase.
• When this phase changes rapidly, it induces strong interactions between the scalar fluctuations.
• If the interactions are sufficiently strong the theory cannot be evaluated using perturbation theory, hence imposing a limit on the oscillation frequency.