Can Primordial Black Holes form in the Standard Model ?

TL;DR

This paper examines whether primordial black holes could form within the Standard Model through Higgs field fluctuations, concluding that standard scenarios are unlikely but alternative gravity formulations might allow PBH formation.

Contribution

It demonstrates that standard Higgs field fluctuations in the SM cannot produce PBHs without conflicting with CMB constraints, but Palatini gravity offers a potential alternative.

Findings

Standard Higgs fluctuations produce too large curvature on cosmological scales.

PBH formation in the SM requires fine-tuning of the top-quark mass.

Palatini gravity may enable PBH formation without CMB conflicts.

Abstract

We investigate the viability of primordial black hole (PBH) formation in the Standard Model (SM) in a scenario that does not rely on specific inflationary features or any exotic physics such as phase transitions or non-minimal coupling to gravity. If the Brout-Englert-Higgs (BEH) field lies exactly at the transition between metastability and stability, its potential exhibits an inflexion point due to radiative corrections. The BEH can act like a stochastic curvaton field, leading to a non-Gaussian tail of large curvature fluctuations that later collapse into PBHs when they re-enter inside the horizon. This scenario would require a precise value of the top-quark mas to ensure the Higgs stability, which is disfavored but still consistent with the most recent measurements. However, we also find that large curvature fluctuations are also generated on cosmological scales that are inconsistent with cosmic microwave background (CMB) observations. We therefore conclude that the SM cannot have led to the formation of PBHs based on this mechanism. Nevertheless, a variation of the scenario based on the Palatini formulation of gravity may have provided the conditions to produce stellar-mass PBHs with an abundance comparable to dark matter, without producing too large curvature fluctuations on cosmological scales.