journal club on aspects of information, quantum theory, and gravity
27 Nov 2025
Primordial black holes (PBHs) offer a distinctive link between gravitational physics and particle phenomenology. Formed in the early Universe through mechanisms such as large primordial inhomogeneities, phase transitions, topological defects, or bubble collisions, they can span masses from sub-planetary scales to many solar masses—far beyond the range produced by stellar collapse. Their Hawking evaporation provides a concrete manifestation of gravitational particle production, generating a thermal spectrum of all kinematically accessible species and probing high-energy physics beyond laboratory reach. PBHs with initial masses near $10^{15}$ g are of particular interest, as they would be completing their evaporation today in a brief, explosive phase marked by rapidly rising temperatures and intense emission of high-energy particles.
Neutrinos furnish two complementary avenues to investigate such objects: they serve as direct messengers of Hawking radiation, still unverified experimentally, and they allow PBH evaporation to be considered as a potential explanation for rare ultra-high-energy neutrino events. In this context, the hypothesis that the ~220 PeV KM3NeT event arose from a nearby PBH burst has been quantitatively assessed. Incorporating multi-messenger constraints, including expected gamma-ray and neutrino coincident signals, indicates that such an interpretation is strongly disfavored within minimal four-dimensional evaporation scenarios. These studies nevertheless establish how evaporating PBHs provide a quantitative and testable interface between gravitational particle production and high-energy neutrino phenomenology.