GenMFGrowth

class hmf.cosmology.growth_factor.GenMFGrowth(cosmo: FLRW, **model_parameters)

Port of growth factor routines found in the genmf code.

Parameters:

• cosmo (astropy.cosmology.FLRW instance) – Cosmological model.

• **model_parameters (unpack-dict) –

  Parameters specific to this model. In this case, available parameters are as follows.To see their default values, check the _defaults class attribute.

  dz:

  Step-size for redshift integration

  zmax:

  Maximum redshift to integrate to. Only used for growth_factor_fn().

Attributes

Or0

The fractional radiation density at redshift zero.

references: ClassVar[tuple[str, ...]] = ('Reed, D. S., et al., 2007. MNRAS 374, 2. https://ui.adsabs.harvard.edu/abs/2007MNRAS.374....2R',)

References to cite when this model is used, each a formatted citation string. Subclasses inherit their parent’s references unless they set their own.

Methods

dlne_dlna(z)

Compute the derivative of ln(E(a)) with respect to ln(a).

This is useful for the growth factor, which has terms \(E'(a)/E(a) \equiv (1/a)*dlnE/dlna\) in its definition.

This implementation simply uses the exact definition from astropy of E(a) and writes down the derivative analytically. The dark-energy density scales as \(\rho_{\rm DE}(a) \propto \exp(-3\int (1+w)\, d\ln a)\), so its logarithmic derivative is \(-3(1+w(a))\), which vanishes only for a cosmological constant. With massive neutrinos, the radiation term is \(\Omega_\gamma (1 + N(z)) a^{-4}\), where \(N(z)\) is astropy’s nu_relative_density. \(N\) varies with time as the neutrinos become non-relativistic, so its derivative is included, computed by central finite difference in \(\ln(1+z)\).

classmethod get_models() → Mapping[str, type]

Get a read-only mapping of all implemented models for this component.

The mapping is a live view of the registry, so it shows models registered later, but it can not be used to add or remove models.

growth_factor(z)

Compute the normalized growth factor, \(D(a) = D^+(a)/D^+(a=1)\).

Parameters:

z (array_like) – Redshift.

Returns:

gf – The growth factor at z.

Return type:

array_like

growth_rate(z) → float | ndarray

Compute the growth rate, \(f(a) = d\ln D^+ / d\ln a\).

Parameters:

z (array_like) – Redshift.

Returns:

gr – The growth rate at z.

Return type:

array_like

radiation_density(z)

The fractional radiation density as a function of redshift.