# Primordial Black Holes and Slow-Roll Violation

## TL;DR

This paper discusses how violating the slow-roll approximation in single-field inflation is necessary for primordial black holes to account for dark matter, and how to accurately predict the power spectrum in such scenarios.

## Contribution

It demonstrates that an optimized second-order evaluation of Hubble slow-roll parameters accurately models PBH formation even with large power spectrum amplification.

## Key findings

- Slow-roll violation is essential for PBH dark matter models.
- Second-order Hubble slow-roll parameters effectively predict power spectrum.
- Accurate modeling remains valid for large amplification over multiple e-folds.

## Abstract

For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least ${\cal O}(1)$ in order to enhance the curvature power spectrum within the required number of efolds between CMB scales and PBH mass scales. Power spectrum predictions which rely on the inflaton remaining on the slow-roll attractor can fail dramatically leading to qualitatively incorrect conclusions in models like an inflection potential and misestimate the mass scale in a running mass model. We show that an optimized temporal evaluation of the Hubble slow-roll parameters to second order remains a good description for a wide range of PBH formation models where up to a $10^7$ amplification of power occurs in $10$ efolds or more.