BBN

Simple prior on Omega_b h^2 from light element abundances

File	likelihood/bbn/bbn_ombh2.py
Attribution	B.D Fields
	Molaro
	Sarkar
URL	http://pdg.lbl.gov/2013/reviews/rpp2013-rev-bbang-nucleosynthesis.pdf
Citations	Beringer et al. (Particle Data Group), Phys. Rev. D86, 010001 (2012)
	Cooke, R et al. ApJ, 830, 2 (2016)
	Pitrou, C. et al, MNRAS, 502, 2, 2474–2481, (2021)

This small module was written for CosmoSIS.

Measurements of the abundances of light elements D, 3He, 4He, and 7Li constrain the density budget at the epoch of nucleosynthesis in the first three minutes after the big bang.

There are various measurements of the light element abundance, and this module can select between different papers.

Assumptions

• Standard model of Big-Bang nucleosynthesis

Setup Parameters

Name	Type	Default	Description
paper	str	beringer_2012	Choice of which paper to use, beringer_2012, cooke_2016_i, cooke_2016_ii, cooke_2016_combined, pitrou_cooke_combined
mean	real	0.023	Replace the standard value measurement omega_b h^2 = 0.023 with a custom one
sigma	real	0.002	Replace the standard value error 0.002 with a custom one

Input values

Section	Name	Type	Default	Description
cosmological_parameters	omega_b	real		Baryon density fraction today
	h0	real		Hubble parameter H0/(100 km/s/Mpc)

Output values

Output values

Section	Name	Type	Description
likelihoods	BBN_LIKE	real	Gaussian likelihood value of supplied parameters