Effective Field Theory Constraints on Primordial Black Holes from the High-Redshift Lyman-$\alpha$ Forest

TL;DR

This paper uses an effective field theory approach to analyze high-redshift Lyman-$\alpha$ forest data, providing new constraints on primordial black hole abundance across a wide mass range, especially for very massive black holes.

Contribution

It introduces an EFT-based likelihood for Lyman-$\alpha$ flux power spectrum analysis, enabling robust constraints on PBH dark matter over previously unexplored scales and redshifts.

Findings

Excluded PBH fractions $f_{\text{PBH}} \gtrsim 10^{-3}$ for masses $10^{4}-10^{16} M_{\odot}$

Provided leading constraints for PBHs heavier than $10^{9} M_{\odot}$

Demonstrated the Lyman-$\alpha$ forest as a sensitive probe of structure formation modifications

Abstract

We present updated constraints on the abundance of primordial black holes (PBHs) dark matter from the high-redshift Lyman-$\alpha$ forest data from MIKE/HIRES experiments. Our analysis leverages an effective field theory (EFT) description of the 1D flux power spectrum, allowing us to analytically predict the Lyman-$\alpha$ fluctuations on quasi-linear scales from first principles. Our EFT-based likelihood enables robust inference across redshifts $z = 4.2-5.4$ and down to scales of 100 kpc, within previously unexplored regions of parameter space for this dataset. We derive new bounds on the PBH fraction with respect to the total dark matter $f_{\text{PBH}}$, excluding populations with $f_{\text{PBH}} \gtrsim 10^{-3}$ for masses $M_{\text{PBH}} \sim 10^{4}-10^{16} M_{\odot}$. This offers the leading constraint for PBHs heavier than $10^{9} M_{\odot}$ and highlights the Lyman-$\alpha$ forest as a uniquely sensitive probe of new physics models that modify the structure formation history of our universe.