nbodykit.cosmology.background module¶

class nbodykit.cosmology.background.PerturbationGrowth(cosmo, a=None)[source]¶

Bases: object

Perturbation Growth coefficients at several orders.

2-LPT is implemented.

All derivatives are against lna. (order).

Note

Formulas are derived from Yin Li’s notes on 2LPT.

Parameters:	cosmo (Cosmology) – a astropy Cosmology like object. a (array_like) – a list of time steps where the factors are exact. other a values are interpolated.

Methods

D1(a[, order])
D2(a[, order])
E(a[, order])
Gf(a)	FastPM growth factor function, eq, 20
Gp(a)	FastPM growth factor function, eq, 19
Hfac(a)
Om(a)
f1(a)
f2(a)
gf(a)	Similarly, the derivative is against ln a, so
gp(a)	Notice the derivative of D1 is against ln a but gp is d D1 / da, so
ode(y, lna)

D1(a, order=0)[source]¶

D2(a, order=0)[source]¶

E(a, order=0)[source]¶

Gf(a)[source]¶

FastPM growth factor function, eq, 20

Gp(a)[source]¶

FastPM growth factor function, eq, 19

Hfac(a)[source]¶

Om(a)[source]¶

f1(a)[source]¶

f2(a)[source]¶

gf(a)[source]¶

Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a

gp(a)[source]¶

Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a

ode(y, lna)[source]¶