Primordial Black Holes Are True Vacuum Nurseries (2311.01869v1)

Abstract: The Hawking evaporation of primordial black holes (PBH) reheats the Universe locally, forming hot spots that survive throughout their lifetime. We propose to use the temperature profile of such hot spots to calculate the decay rate of metastable vacua in cosmology, avoiding inconsistencies inherent to the Hartle-Hawking or Unruh vacuum. We apply our formalism to the case of the electroweak vacuum stability and find that a PBH energy fraction $\beta > 7\times 10^{-80} (M/g)^{3/2}$ is ruled out for black holes with masses $0.8 g < M < 10^{15} g$.

• The paper demonstrates that Hawking radiation from PBHs produces hot spots that trigger localized electroweak vacuum decay.
• It employs numerical analysis to rule out an energy fraction β > 7×10⁻⁸⁰ (M/g)^(3/2) for PBHs between 0.8 g and 10¹⁵ g.
• The study offers new constraints on early Universe cosmology, challenging conventional models of cosmic phase transitions.

Primordial Black Holes as Agents in Vacuum Stability: Insights and Implications

The paper "Primordial Black Holes Are True Vacuum Nurseries" by Hamaide et al. explores a novel approach to understanding the decay of metastable vacua in cosmology, elucidating the role of primordial black holes (PBHs) in this context. Specifically, the paper investigates the influence of Hawking radiation from PBHs on the electroweak vacuum's stability, offering new insights into the early Universe's conditions.

Overview of the Study

The authors propose that PBHs, through their Hawking radiation, create localized hot spots rather than achieving thermal equilibrium as traditionally assumed in the Hartle-Hawking or Unruh vacuum states. This deviation provides a new mechanism to analyze the decay rates of false vacua in cosmology. By focusing on the electroweak vacuum's metastability, the paper presents evidence that PBHs can form true vacuum bubbles, consequently imposing new constraints on the mass range and abundance of PBHs during the early Universe.

Numerical Results and Analysis

A key quantitative result from the paper is the assertion that an energy fraction $\beta > 7\times 10^{-80} (M/\mathrm{g})^{3/2}$ is ruled out for black holes with masses between $0.8 \,{\rm g}$ and $10^{15} \,{\rm g}$. This finding significantly constrains models where PBHs could dominate the universe's early density or where their presence could notably affect electroweak vacuum stability.

The paper's methodological advancements are grounded in an innovative treatment of the temperature profiles around PBHs. By considering the dynamic interactions between Hawking radiation and the surrounding thermal plasma, the authors extend previous work on vacuum decay rates. They demonstrate that the Hawking radiation forms enduring hot spots, subsequently allowing the electroweak vacuum to decay at rates influenced by the local temperature rather than global idealized assumptions.

Theoretical Implications

The results have profound theoretical implications, particularly concerning our understanding of phase transitions in the early Universe. The insights on false-vacuum decay prompt reconsideration of the potential role of PBHs in triggering or mediating such transitions. Moreover, the findings necessitate revisiting current inflationary models and scenarios of PBH formation and evaporation.

Future Directions in AI and Cosmology

Moving forward, this research opens avenues for more sophisticated AI and computational models to simulate early-universe conditions with greater accuracy. Future studies might explore the interplay between different types of cosmic relics and phase transitions, utilizing AI to parse vast datasets for patterns or evidence supporting hypotheses like those discussed.

Conclusion

In conclusion, this paper contributes a pivotal understanding of how PBHs, through their thermal interactions and Hawking evaporation, potentially influence cosmic vacuum stability. These results offer stringent constraints on primordial black hole abundance and provide a novel perspective for examining the early universe's phase transitions. Such insights will be invaluable as the community continues challenging and refining theoretical models of the cosmos's birth and evolution.