BBN models¶
- class camb.bbn.BBNPredictor[source]¶
The base class for making BBN predictions for Helium abundance
- class camb.bbn.BBN_fitting_parthenope(tau_neutron=None)[source]¶
Old BBN predictions for Helium abundance using fitting formulae based on Parthenope (pre 2015).
- Y_p(ombh2, delta_neff=0.0, tau_neutron=None)[source]¶
Get BBN helium nucleon fraction. # Parthenope fits, as in Planck 2015 papers
- Parameters:
ombh2 – \(\Omega_b h^2\)
delta_neff – additional N_eff relative to standard value (of 3.046 for consistency with Planck)
tau_neutron – neutron lifetime
- Returns:
\(Y_p^{\rm BBN}\) helium nucleon fraction predicted by BBN
- class camb.bbn.BBN_table_interpolator(interpolation_table='PRIMAT_Yp_DH_ErrorMC_2021.dat', function_of=('ombh2', 'DeltaN'))[source]¶
BBN predictor based on interpolation from a numerical table calculated by a BBN code.
Tables are supplied for Parthenope 2017 (PArthENoPE_880.2_standard.dat, default), similar but with Marucci rates (PArthENoPE_880.2_marcucci.dat), PRIMAT (PRIMAT_Yp_DH_Error.dat, PRIMAT_Yp_DH_ErrorMC_2021.dat).
- Parameters:
interpolation_table – filename of interpolation table to use.
function_of – two variables that determine the interpolation grid (x,y) in the table, matching top column label comment. By default ombh2, DeltaN, and function argument names reflect that, but can also be used more generally.
- DH(ombh2, delta_neff=0.0, grid=False)[source]¶
Get deuterium ratio D/H by interpolation in table
- Parameters:
ombh2 – \(\Omega_b h^2\) (or, more generally, value of function_of[0])
delta_neff – additional N_eff relative to standard value (of 3.044) (or value of function_of[1])
grid – parameter for
RectBivariateSpline
(whether to evaluate the results on a grid spanned by the input arrays, or at points specified by the input arrays)
- Returns:
D/H
- Y_p(ombh2, delta_neff=0.0, grid=False)[source]¶
Get BBN helium nucleon fraction by intepolation in table.
- Parameters:
ombh2 – \(\Omega_b h^2\) (or, more generally, value of function_of[0])
delta_neff – additional N_eff relative to standard value (of 3.044) (or value of function_of[1])
grid – parameter for
RectBivariateSpline
(whether to evaluate the results on a grid spanned by the input arrays, or at points specified by the input arrays)
- Returns:
Y_p helium nucleon fraction predicted by BBN. Call Y_He() to get mass fraction instead.
- get(name, ombh2, delta_neff=0.0, grid=False)[source]¶
Get value for variable “name” by intepolation from table (where name is given in the column header comment) For example get(‘sig(D/H)’,0.0222,0) to get the error on D/H
- Parameters:
name – string name of the parameter, as given in header of interpolation table
ombh2 – \(\Omega_b h^2\) (or, more generally, value of function_of[0])
delta_neff – additional N_eff relative to standard value (of 3.044) (or value of function_of[1])
grid – parameter for
RectBivariateSpline
(whether to evaluate the results on a grid spanned by the input arrays, or at points specified by the input arrays)
- Returns:
Interpolated value (or grid)