nbodykit.cosmology.background¶
Classes
|
Perturbation with matter dominated initial condition. |
|
Perturbation Growth coefficients at several orders. |
|
Perturbation with Radiation dominated initial condition |
- class nbodykit.cosmology.background.MatterDominated(Omega0_m, Omega0_lambda=None, Omega0_k=0, a=None, a_normalize=1.0)[source]¶
Perturbation with matter dominated initial condition.
This is usually referred to the single fluid approximation as well.
The result here is accurate upto numerical precision. If Omega0_m
- Parameters
Omega0_m – matter density at redshift 0
Omega0_lambda – Lambda density at redshift 0, default None; set to ensure flat universe.
Omega0_k – Curvature density at redshift 0, default : 0
a (array_like) – a list of time steps where the factors are exact. other a values are interpolated.
Methods
D1(a[, order])Linear order growth function.
D2(a[, order])Second order growth function.
E(a[, order])Hubble function and derivatives against log a.
Gf(a)FastPM growth factor function, eq, 20
Gf2(a)Gf but for second order LPT
Gp(a)FastPM growth factor function, eq, 19
Gp2(a)Gp for second order LPT FastPM growth factor function, eq, 19
f1(a)Linear order growth rate
f2(a)Second order growth rate.
gf(a)Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a
gf2(a)gf but for second order LPT
gp(a)Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a
gp2(a)gp for second order LPT
Hfac
Om
efunc
efunc_prime
get_initial_condition
ode
- D1(a, order=0)¶
Linear order growth function.
- D2(a, order=0)¶
Second order growth function.
- E(a, order=0)¶
Hubble function and derivatives against log a.
- Gf(a)¶
FastPM growth factor function, eq, 20
- Gf2(a)¶
Gf but for second order LPT
- Gp(a)¶
FastPM growth factor function, eq, 19
- Gp2(a)¶
Gp for second order LPT FastPM growth factor function, eq, 19
- f1(a)¶
Linear order growth rate
- f2(a)¶
Second order growth rate.
- gf(a)¶
Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a
- gf2(a)¶
gf but for second order LPT
- gp(a)¶
Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a
- gp2(a)¶
gp for second order LPT
- class nbodykit.cosmology.background.Perturbation(a, a_normalize=1.0)[source]¶
Perturbation Growth coefficients at several orders.
2-LPT is implemented. This implements the single fluid model of Boltamann equations. Therefore it is accurate only in a matter dominated universe.
All derivatives are against
lna.Note
Formulas are derived from Yin Li’s notes on 2LPT.
Methods
D1(a[, order])Linear order growth function.
D2(a[, order])Second order growth function.
E(a[, order])Hubble function and derivatives against log a.
Gf(a)FastPM growth factor function, eq, 20
Gf2(a)Gf but for second order LPT
Gp(a)FastPM growth factor function, eq, 19
Gp2(a)Gp for second order LPT FastPM growth factor function, eq, 19
f1(a)Linear order growth rate
f2(a)Second order growth rate.
gf(a)Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a
gf2(a)gf but for second order LPT
gp(a)Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a
gp2(a)gp for second order LPT
Hfac
ode
- class nbodykit.cosmology.background.RadiationDominated(cosmo, a=None, a_normalize=1.0)[source]¶
Perturbation with Radiation dominated initial condition
This is approximated because the single fluid scale independent solution will need an initial condition that comes from a true Boltzmann code.
Here, the first order result is tuned to agree at sub-percent level comparing to a true multi-fluid boltzmann code under Planck15 cosmology.
- 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])Linear order growth function.
D2(a[, order])Second order growth function.
E(a[, order])Hubble function and derivatives against log a.
Gf(a)FastPM growth factor function, eq, 20
Gf2(a)Gf but for second order LPT
Gp(a)FastPM growth factor function, eq, 19
Gp2(a)Gp for second order LPT FastPM growth factor function, eq, 19
f1(a)Linear order growth rate
f2(a)Second order growth rate.
gf(a)Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a
gf2(a)gf but for second order LPT
gp(a)Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a
gp2(a)gp for second order LPT
Hfac
Om
efunc
efunc_prime
get_initial_condition
ode
- D1(a, order=0)¶
Linear order growth function.
- D2(a, order=0)¶
Second order growth function.
- E(a, order=0)¶
Hubble function and derivatives against log a.
- Gf(a)¶
FastPM growth factor function, eq, 20
- Gf2(a)¶
Gf but for second order LPT
- Gp(a)¶
FastPM growth factor function, eq, 19
- Gp2(a)¶
Gp for second order LPT FastPM growth factor function, eq, 19
- f1(a)¶
Linear order growth rate
- f2(a)¶
Second order growth rate.
- gf(a)¶
Similarly, the derivative is against ln a, so gf = Gf(a, order=1) / a
- gf2(a)¶
gf but for second order LPT
- gp(a)¶
Notice the derivative of D1 is against ln a but gp is d D1 / da, so gp = D1(a, order=1) / a
- gp2(a)¶
gp for second order LPT