sigma8_rescale¶
Rescale structure measures to use a specified sigma_8
File |
utility/sample_sigma8/sigma8_rescale.py |
Attribution |
Susana Fernandez |
Jack Elvin-Poole |
|
URL |
Boltzmann codes like CAMB and CLASS typically take a primordial power spectrum amplitude A_s as an input parameter defining the amplitude of cosmic structure fluctutations.
Late-time data sets more naturally measure a late-time amplitude, and the measure sigma_8 is usually instead for these data. If all other cosmological parameters are fixed A_s ~ sigma_8^2, but when other parameters can vary they are not perfectly equivalent.
This module enables you to sample over sigma_8 while still passing A_s into a Boltzmann code. It does this by using an input value sigma8_input, which can be sampled over, and a fixed fiducial A_s value. After the Boltzmann code is run and sigma_8 for the fiducial amplitude calculated, the CMB and matter power spectra are scaled by (sigma8_input**2)/(sigma8_boltzmann**2), and sigma_8 is overwritten.
Assumptions¶
Spectra scale quadratically with sigma_8
Setup Parameters¶
None
Input values¶
Section |
Name |
Type |
Default |
Description |
|---|---|---|---|---|
cosmological_parameters |
sigma_8 |
real |
Late time amplitude sigma_8 as output from CAMB or another Boltzmann code |
|
sigma8_input |
real |
The desired sigma_8, usually from the sampler |
||
A_s |
real |
The fixed fiducial primordial amplitude |
||
cmb_cl |
TT |
real 1d |
CMB TT power spectrum |
|
EE |
real 1d |
CMB EE power spectrum |
||
BB |
real 1d |
CMB BB power spectrum |
||
TE |
real 1d |
CMB TE power spectrum |
||
matter_power_lin |
P_K |
real 2d |
Matter power spectrum P(k,z) |
Output values¶
Section |
Name |
Type |
Description |
|---|---|---|---|
cosmological_parameters |
sigma_8 |
real |
Re-scaled sigma_8, set to sigma_8_input |
A_s |
real |
Rescaled A_s |
|
cmb_cl |
TT |
real 1d |
Rescaled CMB TT power spectrum |
EE |
real 1d |
Rescaled CMB EE power spectrum |
|
BB |
real 1d |
Rescaled CMB BB power spectrum |
|
TE |
real 1d |
Rescaled CMB TE power spectrum |
|
matter_power_lin |
P_K |
real 1d |
Rescaled matter power spectrum P(k,z) |