Inflection Points and the Power Spectrum

TL;DR

This paper investigates how inflection points in inflation models cause deviations from slow-roll, affecting the power spectrum and potentially explaining the low large-scale CMB power, with implications for inflation likelihood.

Contribution

It introduces a universal framework for understanding power spectrum effects near inflection points, linking deviations to basin of attraction and observable CMB anomalies.

Findings

Deviations from slow-roll are caused by transitions between singular trajectories.

Power spectrum effects scale with universality parameters.

Low large-scale power in CMB can be explained by inflection point dynamics.

Abstract

Inflection point inflation generically includes a deviation from slow-roll when the inflaton approaches the inflection point. Such deviations are shown to be generated by transitions between singular trajectories. The effects on the power spectrum are studied within the context of universality classes for small-field models. These effects are shown to scale with universality parameters, and can explain the anomalously low power at large scales observed in the CMB. The reduction of power is related to the inflection point's basin of attraction. Implications for the likelihood of inflation are discussed.