[c]RECFAST: Calculate the Recombination History of the Universe[/c][/b]
Abstract: RECFAST calculates the recombination of H, HeI, and HeII in the early Universe; this involves a line-by-line treatment of each atomic level. It differs in comparison to previous calculations in two major ways: firstly, the ionization fraction x_e is approximately 10% smaller for redshifts <~800, due to non-equilibrium processes in the excited states of H, and secondly, HeI recombination is much slower than previously thought, and is delayed until just before H recombines. RECFAST enables fast computation of the ionization history (and quantities such as the power spectrum of CMB anisotropies which depend on it) for arbitrary cosmologies.
Credit: Seager, Sara; Sasselov, Dimitar D.; Scott, Douglas
Site: https://www.cfa.harvard.edu/~sasselov/rec/
http://adsabs.harvard.edu/abs/1999ApJ...523L...1S
Bibcode: 2011ascl.soft06026S
ID: ascl:1106.026
RECFAST: Calculate the Recombination History of the Universe
RECFAST: Calculate the Recombination History of the Universe
Last edited by Ada Coda on Tue Nov 06, 2018 10:39 pm, edited 1 time in total.
Reason: Updated code entry.
Reason: Updated code entry.
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Re: RECFAST: Calculate the Recombination History of the Universe
Replaced non-working site link http://www.astro.ubc.ca/people/scott/recfast.html with https://www.cfa.harvard.edu/~sasselov/rec/ and edited abstract; original abstract appears below.
We have developed an improved recombination calculation of H, HeI, and HeII in the early Universe which involves a line-by-line treatment of each atomic level. We find two major differences compared with previous calculations. Firstly, the ionization fraction x_e is approximately 10% smaller for redshifts <~800, due to non-equilibrium processes in the excited states of H. Secondly, HeI recombination is much slower than previously thought, and is delayed until just before H recombines. We describe the basic physics behind the new results and present a simple way to reproduce our calculation. This should enable fast computation of the ionization history (and quantities such as the power spectrum of CMB anisotropies which depend on it) for arbitrary cosmologies, without the need to consider the hundreds of atomic levels used in our complete model.
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