CosmoFit.cosmology.GrowthCalculator

class CosmoFit.cosmology.GrowthCalculator(cosmology, k=0.1)

Bases: object

Fast evaluator for the linear growth factor D(z), growth rate f(z) = dlnD/dlna, and fsigma8(z), given a Cosmology.

Built lazily: the ODE solve only happens the first time D/f/ sigma8/fsigma8 is actually requested after construction or after rebuild() – most fits never touch growth-of- structure data, so this avoids paying for an ODE solve on every single MCMC step the way the (always-needed) DistanceIntegrator does.

Parameters:

• cosmology (Cosmology)

• k (float, optional) – Wavenumber [h/Mpc], forwarded to cosmology.mu(a, k). Irrelevant for every scale-independent mu (the default, and every modified-gravity model implemented here except FRHuSawicki), which ignores it. Default 0.1 h/Mpc, a representative galaxy-survey RSD scale.

__init__(cosmology, k=0.1)

Parameters:

k (float)

Methods

D(z)	Linear growth factor, normalized to D(z=0) = 1.
__init__(cosmology[, k])
fsigma8(z)	f(z) * sigma8(z), the RSD growth-rate observable.
growth_rate(z)	Linear growth rate f(z) = dlnD/dlna.
rebuild()	Invalidate the cached growth solution -- call whenever the cosmology's parameters change.
sigma8(z)	sigma8(z) = sigma8_0 * D(z).