How Primordial Black Holes Change BBN
Tianning Wang, Evan Grohs, Laura Mersini-Houghton

TL;DR
This paper investigates how primordial black holes with specific mass ranges influence Big Bang Nucleosynthesis through Hawking radiation, revealing a threshold mass that alters the BBN behavior and elemental abundances.
Contribution
The study introduces a detailed reaction-network simulation incorporating PBH evaporation effects, identifying a mass threshold that changes BBN dynamics and elemental yields.
Findings
PBH evaporation acts as an entropy injection, affecting initial conditions for BBN.
A mass threshold near 10^{10} g separates two regimes of BBN behavior.
For larger PBHs, helium-4 abundance increases monotonically with PBH abundance.
Abstract
Primordial Black Holes (PBHs) provide a powerful probe of early-universe physics, linking inflationary fluctuations to observable cosmological phenomena. In this work, we use a bottom-up approach to study how PBHs with masses in the range modify Big Bang Nucleosynthesis (BBN) through Hawking radiation. We incorporate PBH evaporation into a reaction-network code to evaluate its impact on light-element abundances. Our analysis shows that PBH evaporation acts as an entropy injection mechanism, increasing the comoving entropy density. To reproduce the observed comoving entropy density per baryon from the CMB, BBN simulations must therefore begin with a smaller initial entropy than in the standard scenario without PBHs. The results also reveal a threshold near that separates two distinct regimes of…
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Taxonomy
TopicsCosmology and Gravitation Theories · Noncommutative and Quantum Gravity Theories · Dark Matter and Cosmic Phenomena
