Small-scale primordial fluctuations in the 21cm Dark Ages signal

Understand

Primordial black hole production in the mass range $10-10^4 \,{\rm M_\odot}$ is motivated respectively by interpretations of the LIGO/Virgo observations of binary black hole mergers and by their ability to seed intermediate black holes which would account for the presence of supermassive black holes at very high redshift.

• Their existence would imply a boost in the primordial power spectrum if they were produced by overdensities reentering the horizon and collapsing after single-field inflation.
• This, together with their associated Poisson fluctuations would cause a boost in the matter power spectrum on small scales.
• In fact, any evidence of extra power above that of an almost scale-invariant primordial power spectrum on small scales would suggest a non-single-field slow-roll model of inflation, whether or not primordial black holes were produced.