consistency

Deduce missing cosmological parameters and check consistency

File	utility/consistency/consistency_interface.py
Attribution	CosmoSIS Team
URL

There are various ways of parameterizing cosmologies with different advantages in different contexts. This module takes a set of cosmological parameters and tries to use them to deduce the remaining parameters. For example, if you specify ombh2 and h then it computes omega_b. It has a fairly full set of relations to do this.

If you specify inconsistent parameters (e.g. omega values that do not add up to 1) then an error status is returned.

You can set an option to also calculate the Hubble parameter from the CosmoMC theta parameter, and vice versa. This is off by default as it’s a little slower. It uses the camb code directly so should match up.

The standard set of relations is in consistency.py and relates the standard LCDM parameters, including massive neutrinos.

It also converts log1e10As or A_s_1e9 to A_s, and (S_8, Omega_m) to (sigma_8, Omega_m).

Assumptions

• LCDM parameterization

• First pass: tries no assumptions

• Second pass: tries omega_nu=0

• Third pass: tries omega_nu=0 and omega_k=0

Setup Parameters

Name	Type	Default	Description
verbose	bool	False	Whether to print how derived parameters were calculated and what assumptions used
cosmomc_theta	bool	False	Whether to add relations that calculate H0 from the CosmoMC theta parameter
relations_file	str		Path to an alternative parameter relations file. Relations should be specified in the form ‘new_parameter=parameter_b*parameter_b’ with one per line.
extra_relations	str		Extra relations to be added to the default list. Relations should be specified in the form ‘new_parameter=parameter_b*parameter_b,new_parameter2=parameter_d/parameter_e’

Input values

Section	Name	Type	Default	Description
cosmological_parameters	omega_m	real		Matter density fraction of critical
	omega_b	real		Baryon density fraction of critical
	omega_c	real		CDM density fraction of critical
	omega_k	real		Curvature pseudo-density fraction of critical
	omega_nu	real		Massive neutrino density fraction of critical
	omega_lambda	real		Dark energy density fraction of critical
	ommh2	real		Physical density omega_m * h^2
	ombh2	real		Physical density omega_b * h^2
	omch2	real		Physical density omega_c * h^2
	omnuh2	real		Physical density omega_nu * h^2
	baryon_fraction	real		Ratio omega_b/omega_m
	hubble	real		Hubble parameter H_0 in km/s/Mpc
	h	real		Dimensionless Hubble h = H_0 / 100 km/s/Mpc
	log1e10As	real		log (10**10 * A_s) parameter. Ignored if not present
	A_s_1e9	real		10**9 * A_s parameter. Ignored if not present
	S_8	real		sigma_8 * (omega_m/0.3)**0.5 parameter. Ignored if not present.

Output values

Output values

Section	Name	Type	Description
cosmological_parameters	omega_m	real	Matter density fraction of critical
	omega_b	real	Baryon density fraction of critical
	omega_c	real	CDM density fraction of critical
	omega_k	real	Curvature pseudo-density fraction of critical
	omega_nu	real	Massive neutrino density fraction of critical
	omega_lambda	real	Dark energy density fraction of critical
	ommh2	real	Physical density omega_m * h^2
	ombh2	real	Physical density omega_b * h^2
	omch2	real	Physical density omega_c * h^2
	omnuh2	real	Physical density omega_nu * h^2
	baryon_fraction	real	Ratio omega_b/omega_m
	hubble	real	Hubble parameter H_0 in km/s/Mpc
	h	real	Dimensionless Hubble h = H_0 / 100 km/s/Mpc
	A_s	real	Amplitude of primordial fluctuations. Only if log1e10As or A_s_1e9 is present on input.
	sigma_8	real	RMS mass fluctuation in 8 Mpc/h spheres. Only if S_8 is present on input.