Broad primordial power spectrum and $\mu$-distortion constraints on primordial black holes

TL;DR

This paper explores how non-Gaussianity in broad primordial power spectra can weaken $0$-distortion constraints, potentially allowing for the formation of supermassive primordial black holes, challenging previous limitations.

Contribution

It demonstrates that non-Gaussianity can relax $0$-distortion constraints on broad power spectra, opening new possibilities for primordial black hole formation.

Findings

Non-Gaussianity weakens $0$-distortion constraints.

Broad power spectra can produce supermassive PBHs.

Constraints are less stringent under large non-Gaussianity.

Abstract

Supermassive black holes (SMBHs) might originate from supermassive primordial black holes (PBHs). However, the hypothesis that these PBHs formed through the enhancement of the primordial curvature perturbations has consistently faced significant challenges due to the stringent constraints imposed by $\mu$-distortion in the cosmic microwave background (CMB). In this work, we investigate the impact of non-Gaussianity on $\mu$-distortion constraint in the context of broad power spectra. Our results show that, under the assumption of non-Gaussian curvature perturbations, a broad power spectrum may lead to weaker $\mu$-distortion constraints compared to the Gaussian cases. Our findings highlight the potential of the broad power spectrum to alleviate the $\mu$-distortion constraints on supermassive PBHs under large non-Gaussianity.