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Title: On the proper use of the reduced speed of light approximation

I show that the Reduced Speed of Light (RSL) approximation, when used properly (i.e. as originally designed - only for the local sources but not for the cosmic background), remains a highly accurate numerical method for modeling cosmic reionization. Simulated ionization and star formation histories from the "Cosmic Reionization On Computers" (CROC) project are insensitive to the adopted value of the reduced speed of light for as long as that value does not fall below about 10% of the true speed of light. Here, a recent claim of the failure of the RSL approximation in the Illustris reionization model appears to be due to the effective speed of light being reduced in the equation for the cosmic background too, and, hence, illustrates the importance of maintaining the correct speed of light in modeling the cosmic background.
Authors:
 [1]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); The Univ. of Chicago, Chicago, IL (United States)
Publication Date:
Report Number(s):
FERMILAB-PUB-16-290-A; arXiv:1607.07869
Journal ID: ISSN 1538-4357; 1478145
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 833; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmology: theory; galaxies: formation; large-scale structure of universe
OSTI Identifier:
1322155

Gnedin, Nickolay Y. On the proper use of the reduced speed of light approximation. United States: N. p., Web. doi:10.3847/1538-4357/833/1/66.
Gnedin, Nickolay Y. On the proper use of the reduced speed of light approximation. United States. doi:10.3847/1538-4357/833/1/66.
Gnedin, Nickolay Y. 2016. "On the proper use of the reduced speed of light approximation". United States. doi:10.3847/1538-4357/833/1/66. https://www.osti.gov/servlets/purl/1322155.
@article{osti_1322155,
title = {On the proper use of the reduced speed of light approximation},
author = {Gnedin, Nickolay Y.},
abstractNote = {I show that the Reduced Speed of Light (RSL) approximation, when used properly (i.e. as originally designed - only for the local sources but not for the cosmic background), remains a highly accurate numerical method for modeling cosmic reionization. Simulated ionization and star formation histories from the "Cosmic Reionization On Computers" (CROC) project are insensitive to the adopted value of the reduced speed of light for as long as that value does not fall below about 10% of the true speed of light. Here, a recent claim of the failure of the RSL approximation in the Illustris reionization model appears to be due to the effective speed of light being reduced in the equation for the cosmic background too, and, hence, illustrates the importance of maintaining the correct speed of light in modeling the cosmic background.},
doi = {10.3847/1538-4357/833/1/66},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 833,
place = {United States},
year = {2016},
month = {12}
}