Section cosmology

One can define the cosmological parameters in this optional section. The default values are taken from Planck 2018 and corresponds to a flat ΛCDM cosmology. The accepted cosmological parameters (with aliases) are:

• h₀ (with alias h_0): the reduced Hubble's constant, i.e. h₀ = H / 100 Mpc km⁻¹ s⁻¹ [0.6766];

• Ωₘ (with alias Omega_m): the matter density [0.3111];

• Ωᵥ (with alias Omega_v): the vacuum (dark) energy density (if unspecified, it is computed as Ωᵥ = 1 - Ωₘ - Ωᵣ, so to have a flat cosmology);

• Ωᵣ (with alias Omega_r): the radiation density (if unspecified, it is computed from Tᵧ and Nₑ);

• Ωₖ (with alias Omega_k): the curvature density Ωₖ = 1 - Ωₘ - Ωᵥ - Ωᵣ, [0.0, corresponding to a flat cosmology];

• Nₑ (with aliasN_e): the effective number of massless neutrino families [3.046];

• Tᵧ (with alias T_gamma): the CMB temperature in Kelvin [2.7255];

• w₀ (with alias w_0): the first term of the linearized equation of state, $w(a) = w_0 + w_\mathrm{a} (1 - a)$ [-1, corresponding to the equation of state of a cosmological constant];

• wₐ (with alias w_a): the second term of the linearized equation of state, $w(a) = w_0 + w_\mathrm{a} (1 - a)$ [0, no evolution for the equation of state].

Similarly to the definitions in the parameters section, any cosmological parameter can be set to a constant or to a distribution, so that one can use gravitational lensing as a cosmological probe. If one set a cosmological parameter as a distribution, a new free parameter with an appropriate name will be created. For example, if one defines h₀: 0.6 .. 0.8, then the free parameter cosmology_h₀ will be created for the user.