Cosmology

This page lists the high-level cosmology protocol. This is a fully-featured interface to describe the cosmological background of a physical universe.

At a lower level of abstraction, a cosmology consists of individual components.

class Cosmology

Bases: Protocol[Array, InputT]

Cosmology API Protocol.

Attributes

constants	The constants namespace for this cosmology object.
name	The name of the cosmology instance.

property __cosmology_namespace__: CosmologyNamespace

The cosmology namespace for this cosmology object.

property constants: CosmologyConstantsNamespace

The constants namespace for this cosmology object.

property name: str | None

The name of the cosmology instance.

This is a human-friendly label for the cosmology instance. It is optional, and may be None. If set, it should be a string. The name is useful for identifying the cosmology instance, for example logging the name in an analysis pipeline, presenting helpful error messages, and for plotting.

class StandardCosmology

Bases: NeutrinoComponent[Array, InputT], BaryonComponent[Array, InputT], PhotonComponent[Array, InputT], DarkMatterComponent[Array, InputT], MatterComponent[Array, InputT], DarkEnergyComponent[Array, InputT], CurvatureComponent[Array, InputT], TotalComponent[Array, InputT], HubbleParameter[Array, InputT], CriticalDensity[Array, InputT], DistanceMeasures[Array, InputT], Cosmology[Array, InputT], Protocol

API Protocol for the standard cosmology and expected set of components.

This is a protocol class that defines the standard API for the standard (FLRW-like) cosmology cosmology. It is not intended to be instantiaed. Instead, it should be used for isinstance checks or as an ABC for libraries that wish to define a compatible cosmology class.

Attributes

H0	Hubble parameter at redshift 0 in km s-1 Mpc-1.
Neff	Effective number of neutrino species.
Omega_b0	Omega baryon; the baryon density/critical density at z=0.
Omega_de0	Omega dark energy; the dark energy density/critical density at z=0.
Omega_dm0	Omega dark matter; the dark matter density/critical density at z=0.
Omega_gamma0	Omega gamma; the photon density/critical density at z=0.
Omega_k0	Omega curvature; the effective curvature density/critical density at z=0.
Omega_m0	Omega matter; the matter density/critical density at z=0.
Omega_nu0	Omega neutrino; the neutrino density/critical density at z=0.
Omega_tot0	Omega total; the total density/critical density at z=0.
T_cmb0	CMB temperature in K at z=0.
constants	The constants namespace for this cosmology object.
critical_density0	Critical density at z = 0 in Msol Mpc-3.
hubble_distance	Hubble distance in Mpc.
hubble_time	Hubble time in Gyr.
m_nu	Neutrino mass(es) in eV.
name	The name of the cosmology instance.
scale_factor0	Scale factor at z=0.

Methods

H(z, /)	Hubble parameter \(H(z)\) in km s-1 Mpc-1.
H_over_H0(z, /)	Standardised Hubble function \(E(z) = H(z)/H_0\).
Omega_b(z, /)	Redshift-dependent baryon density parameter.
Omega_de(z, /)	Redshift-dependent dark energy density parameter.
Omega_dm(z, /)	Redshift-dependent dark matter density parameter.
Omega_gamma(z, /)	Redshift-dependent photon density parameter.
Omega_k(z, /)	Redshift-dependent curvature density parameter.
Omega_m(z, /)	Redshift-dependent matter density parameter.
Omega_nu(z, /)	Redshift-dependent neutrino density parameter.
Omega_tot(z, /)	Redshift-dependent total density parameter.
T_cmb(z, /)	CMB temperature in K at redshift z.
age(z, /)	Age of the universe at redshift z in Gyr.
angular_diameter_distance(...)	Angular diameter distance \(d_A\) in Mpc.
comoving_distance(...)	Comoving line-of-sight distance \(d_c\) in Mpc.
comoving_volume(...)	Comoving volume \(V_c\) in Mpc3.
critical_density(z, /)	Redshift-dependent critical density in Msol Mpc-3.
differential_comoving_volume(z, /)	Differential comoving volume in Mpc3 per steradian.
lookback_distance(...)	Lookback distance \(d_T\) in Mpc.
lookback_time(-> ~cosmology.api._array_api.Array)	Lookback time in Gyr.
luminosity_distance(...)	Redshift-dependent luminosity distance \(d_L\) in Mpc.
proper_distance(...)	Proper distance \(d\) in Mpc.
proper_time(-> ~cosmology.api._array_api.Array)	Proper time \(t\) in Gyr.
scale_factor(z, /)	Redshift-dependenct scale factor.
transverse_comoving_distance(...)	Transverse comoving distance \(d_M\) in Mpc.

property __cosmology_namespace__: CosmologyNamespace

The cosmology namespace for this cosmology object.

property constants: CosmologyConstantsNamespace

The constants namespace for this cosmology object.

property name: str | None

The name of the cosmology instance.

This is a human-friendly label for the cosmology instance. It is optional, and may be None. If set, it should be a string. The name is useful for identifying the cosmology instance, for example logging the name in an analysis pipeline, presenting helpful error messages, and for plotting.

Wrappers

In order to provide a consistent interface, existing cosmology libraries can be wrapped to conform to the Cosmology API. The form of these wrappers is specified here.

Details of using these wrappers is upcoming. You can see the development of the Astropy and CAMB wrappers in the cosmology.api GitHub repo.

For details of how to write your own wrapper, see the developer documentation.

class CosmologyWrapper

Bases: Cosmology[Array, InputT], Protocol

The standard for Cosmology compatability wrappers.

This is a protocol class that defines an API standard. It is not intended to be used directly, and should not be instantiated. Instead, it should be used as a Protocol or ABC for libraries that wish to define a wrapper for the standard API.

Parameters:

cosmo: object

The object to wrap.

Attributes

constants	The constants namespace for this cosmology object.
name	The name of the cosmology instance.

class StandardCosmologyWrapper

Bases: CosmologyWrapper[Array, InputT], StandardCosmology[Array, InputT], Protocol

The standard for StandardCosmology compatability wrappers.

This is a protocol class that defines an API standard. It is not intended to be used directly, and should not be instantiated. Instead, it should be used as a Protocol or ABC for libraries that wish to define a wrapper for the standard API.

Parameters:

cosmo: object

The object to wrap.

Attributes

H0	Hubble parameter at redshift 0 in km s-1 Mpc-1.
Neff	Effective number of neutrino species.
Omega_b0	Omega baryon; the baryon density/critical density at z=0.
Omega_de0	Omega dark energy; the dark energy density/critical density at z=0.
Omega_dm0	Omega dark matter; the dark matter density/critical density at z=0.
Omega_gamma0	Omega gamma; the photon density/critical density at z=0.
Omega_k0	Omega curvature; the effective curvature density/critical density at z=0.
Omega_m0	Omega matter; the matter density/critical density at z=0.
Omega_nu0	Omega neutrino; the neutrino density/critical density at z=0.
Omega_tot0	Omega total; the total density/critical density at z=0.
T_cmb0	CMB temperature in K at z=0.
constants	The constants namespace for this cosmology object.
critical_density0	Critical density at z = 0 in Msol Mpc-3.
hubble_distance	Hubble distance in Mpc.
hubble_time	Hubble time in Gyr.
m_nu	Neutrino mass(es) in eV.
name	The name of the cosmology instance.
scale_factor0	Scale factor at z=0.

Methods

H(z, /)	Hubble parameter \(H(z)\) in km s-1 Mpc-1.
H_over_H0(z, /)	Standardised Hubble function \(E(z) = H(z)/H_0\).
Omega_b(z, /)	Redshift-dependent baryon density parameter.
Omega_de(z, /)	Redshift-dependent dark energy density parameter.
Omega_dm(z, /)	Redshift-dependent dark matter density parameter.
Omega_gamma(z, /)	Redshift-dependent photon density parameter.
Omega_k(z, /)	Redshift-dependent curvature density parameter.
Omega_m(z, /)	Redshift-dependent matter density parameter.
Omega_nu(z, /)	Redshift-dependent neutrino density parameter.
Omega_tot(z, /)	Redshift-dependent total density parameter.
T_cmb(z, /)	CMB temperature in K at redshift z.
age(z, /)	Age of the universe at redshift z in Gyr.
angular_diameter_distance(...)	Angular diameter distance \(d_A\) in Mpc.
comoving_distance(...)	Comoving line-of-sight distance \(d_c\) in Mpc.
comoving_volume(...)	Comoving volume \(V_c\) in Mpc3.
critical_density(z, /)	Redshift-dependent critical density in Msol Mpc-3.
differential_comoving_volume(z, /)	Differential comoving volume in Mpc3 per steradian.
lookback_distance(...)	Lookback distance \(d_T\) in Mpc.
lookback_time(-> ~cosmology.api._array_api.Array)	Lookback time in Gyr.
luminosity_distance(...)	Redshift-dependent luminosity distance \(d_L\) in Mpc.
proper_distance(...)	Proper distance \(d\) in Mpc.
proper_time(-> ~cosmology.api._array_api.Array)	Proper time \(t\) in Gyr.
scale_factor(z, /)	Redshift-dependenct scale factor.
transverse_comoving_distance(...)	Transverse comoving distance \(d_M\) in Mpc.