hmf.growth_factor

Module defining calculations of the cosmological growth factor and growth rate.

The primary class, GrowthFactor, intelligently dispatches to a number of different methods for calculating the growth factor, depending on the cosmology and the parameters. The most general method, which is applicable for any FLRW cosmology, is ODEGrowthFactor, which solves the full ODE for the growth factor. This is the most general method, but also the slowest. For cosmologies with negligible radiation density, the growth factor can be calculated using the integral form defined in IntegralGrowthFactor. If the cosmology is also flat, then the growth factor can be calculated using the analytical formulae implemented in Eisenstein97GrowthFactor, which is the fastest method. Various other limiting cases and assumptions are also implemented. If using the base GrowthFactor class, the appropriate method will be chosen automatically such that it uses the fastest available correct method.

In addition, a couple of approximate formulae are included, for example Carroll1992 and GenMFGrowth, which are not exact for any cosmology but are very fast to compute and quite accurate across a broad range of cosmologies.

Full details of the formulae, their assumptions and limitations, and derivations, are given in the technical documentation.

The main two functions that the model component provides are growth_factor and growth_rate. The growth rate is the logarithmic derivative of the growth factor. In all classes, the growth rate will be internally consistent with the growth factor (i.e. any approximations made to one will also be made to the other).

Base Component(s)

BaseGrowthFactor(cosmo, **model_parameters)

General class for a growth factor calculation.

Models

CambGrowth(*args, **kwargs)	Growth factor computed using CAMB at k/h = 1.0.
Carroll1992(*args, **kwargs)	Analytic approximation for the growth factor from Carroll et al. 1992.
Eisenstein97GrowthFactor(cosmo, ...)	Growth factor calculated using the formulae in Eisenstein 1997.
FromArray(cosmo, **model_parameters)	Use a spline over a given array to define the growth factor.
FromFile(cosmo, **model_parameters)	Import a growth factor from file.
GenMFGrowth(cosmo, **model_parameters)	Port of growth factor routines found in the genmf code.
GrowthFactor(*args, **kwargs)	Growth factor calculation that intelligently chooses which method to use.
Heath77GrowthFactor(cosmo, **model_parameters)	Growth factor calculated using the analytic formula in Heath 1977.
IntegralGrowthFactor(cosmo, **model_parameters)	Growth factor computed using the integral of Heath 1977.
ODEGrowthFactor(cosmo, **model_parameters)	Growth factor calculation that solves the full ODE.