Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology
View / Open Files
Authors
Barrow, JD
Scherrer, RJ
Publication Date
2018Journal Title
Physical Review D
ISSN
2470-0010
Publisher
American Physical Society (APS)
Volume
98
Issue
4
Type
Article
Metadata
Show full item recordCitation
Barrow, J., & Scherrer, R. (2018). Constraining density fluctuations with big bang nucleosynthesis in the era of precision cosmology. Physical Review D, 98 (4) https://doi.org/10.1103/PhysRevD.98.043534
Abstract
We reexamine big bang nucleosynthesis with large-scale baryon density inhomogeneities when the length scale of the density fluctuations exceeds the neutron diffusion length (∼10⁷-10⁸ cm at BBN), and the amplitude of the fluctuations is sufficiently small to prevent gravitational collapse. In this limit, the final light element abundances can be determined by simply mixing the abundances from regions with different baryon/photon ratios without interactions. We examine gaussian, lognormal, and gamma distributions for the baryon/photon ratio, η. We find that the deuterium and lithium-7 abundances increase with the RMS fluctuation in η, while the effect on helium-4 is much smaller. We show that these increases in the deuterium and lithium-7 abundances are a consequence of Jensen's inequality, and we derive analytic approximations for these abundances in the limit of small RMS fluctuations. Observational upper limits on the primordial deuterium abundance constrain the RMS fluctuation in η to be less than 17% of the mean value of η. This provides us with a new limit on the graininess of the early universe.
Sponsorship
Science and Technology Facilities Council (ST/P000673/1)
Science and Technology Facilities Council (ST/L000636/1)
Identifiers
External DOI: https://doi.org/10.1103/PhysRevD.98.043534
This record's URL: https://www.repository.cam.ac.uk/handle/1810/284991
Rights
Licence:
http://www.rioxx.net/licenses/all-rights-reserved
Statistics
Total file downloads (since January 2020). For more information on metrics see the
IRUS guide.
Recommended or similar items
The current recommendation prototype on the Apollo Repository will be turned off on 03 February 2023. Although the pilot has been fruitful for both parties, the service provider IKVA is focusing on horizon scanning products and so the recommender service can no longer be supported. We recognise the importance of recommender services in supporting research discovery and are evaluating offerings from other service providers. If you would like to offer feedback on this decision please contact us on: support@repository.cam.ac.uk