Primordial black hole hot spots and nucleosynthesis

Upon their evaporation via Hawking radiation, primordial black holes (PBHs) deposit energy in the ambient plasma on scales that can be smaller than the typical distance between two black holes, leading to the formation of hot spots around them. We investigate how such hot spots may act as a shield against the release of low-energy photons, affecting PBH’s capacity to dissociate light nuclei after big bang nucleosynthesis through photo-dissociation. We find that this shielding effect is particularly relevant for PBHs with masses between <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mn>10</a:mn> <a:mn>11</a:mn> </a:msup> <a:mtext> </a:mtext> <a:mtext> </a:mtext> <a:mi mathvariant="normal">g</a:mi> </a:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mn>4</d:mn> <d:mo>×</d:mo> <d:msup> <d:mn>10</d:mn> <d:mn>12</d:mn> </d:msup> <d:mtext> </d:mtext> <d:mtext> </d:mtext> <d:mi mathvariant="normal">g</d:mi> </d:math> . We emphasize that the magnitude of this effect is highly dependent on the specific shape of the temperature profile around PBHs and its time evolution, stressing the necessity for a comprehensive study of PBH hot spots and their dynamics in the future.