Neutron diffusion and nucleosynthesis

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SUMMARY

The discussion centers on the article "Neutron Diffusion and Nucleosynthesis in an Inhomogeneous Big Bang Model" by Juan F. Lara, which introduces a novel computational code for analyzing Big Bang Nucleosynthesis (BBN) in a baryon inhomogeneous universe. The code simultaneously calculates neutron diffusion and nuclear reactions, revealing that the timing of neutron diffusion significantly influences the final abundances of helium-4 (He4), deuterium, and lithium-7 (Li7). The study finds that the baryon to photon ratio (η) ranges from (4.3 - 12.3) X 10^{-10}, with a depletion factor for Li7 as high as 5.9, indicating a departure from the Standard BBN model assumptions.

PREREQUISITES
  • Understanding of Big Bang Nucleosynthesis (BBN)
  • Familiarity with baryon density and photon ratios
  • Knowledge of neutron diffusion processes
  • Basic principles of nuclear reactions and weak decays
NEXT STEPS
  • Research the implications of baryon inhomogeneity in cosmological models
  • Study the Standard Big Bang Nucleosynthesis model for comparison
  • Explore computational methods for simulating nucleosynthesis
  • Investigate observational constraints on He4, deuterium, and Li7 abundances
USEFUL FOR

Astronomers, cosmologists, and researchers in theoretical physics focusing on the early universe and nucleosynthesis processes.

wolram
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http://arxiv.org/abs/astro-ph/0506364

Title: Neutron Diffusion and Nucleosynthesis in an Inhomogeneous Big Bang Model
Authors: Juan F. Lara
Comments: accepted for publication in Physical Review D

This article presents an original code for Big Bang Nucleosynthesis in a baryon inhomogeneous model of the universe. In this code neutron diffusion between high and low baryon density regions is calculated simultaneously with the nuclear reactions and weak decays that compose the nucleosynthesis process. The size of the model determines the time when neutron diffusion becomes significant. This article describes in detail how the time of neutron diffusion relative to the time of nucleosynthesis affects the final abundances of He4, deuterium and Li7. These results will be compared with the most recent observational constraints of He4, deuterium and Li7. This inhomogeneous model has He4 and deuterium constraints in concordance for baryon to photon ratio eta = (4.3 - 12.3) X 10^{-10} Li7 constraints are brought into concordance with the other isotope constraints by including a depletion factor as high as 5.9. These ranges for the baryon to photon ratio and for the depletion factor are larger than the ranges from a Standard Big Bang Nucleosynthesis model.
 
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wolram said:
http://arxiv.org/abs/astro-ph/0506364

Title: Neutron Diffusion and Nucleosynthesis in an Inhomogeneous Big Bang Model
Authors: Juan F. Lara
Comments: accepted for publication in Physical Review D
......
These ranges for the baryon to photon ratio and for the depletion factor are larger than the ranges from a Standard Big Bang Nucleosynthesis model.
Does that mean the standard BBN model has to be baryon homogeneous?

Garth
 
I think yes, but I am not sure. The universe is homogeneous after inflation. Why should it be 'baryon inhomogeneous'?
 

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