camb.bbn

class camb.bbn.BBNPredictor[source]

The base class for making BBN predictions for Helium abundance

Y_He(ombh2, delta_neff=0.0)[source]

Get BBN helium mass fraction for CMB code.

Parameters:
  • ombh2 – Omega_b h^2
  • delta_neff – additional N_eff relative to standard value (of 3.046)
Returns:

Y_He helium mass fraction predicted by BBN

Y_p(ombh2, delta_neff=0.0)[source]

Get BBN helium nucleon fraction. Must be implemented by extensions.

Parameters:
  • ombh2 – Omega_b h^2
  • delta_neff – additional N_eff relative to standard value (of 3.046)
Returns:

Y_p helium nucleon fraction predicted by BBN

class camb.bbn.BBN_fitting_parthenope(tau_neutron=None)[source]

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)
  • tau_neutron – neutron lifetime
Returns:

Y_p helium nucleon fraction predicted by BBN

class camb.bbn.BBN_table_interpolator(interpolation_table='PArthENoPE_880.2_standard.dat')[source]

BBN predictor based on interpolation on a table calculated from BBN code

DH(ombh2, delta_neff=0.0)[source]

Get deuterium ration D/H by interpolation in table

Parameters:
  • ombh2 – Omega_b h^2
  • delta_neff – additional N_eff relative to standard value (of 3.046)
Returns:

D/H

Y_p(ombh2, delta_neff=0.0)[source]

Get BBN helium nucleon fraction by intepolation in table.

Parameters:
  • ombh2 – Omega_b h^2
  • delta_neff – additional N_eff relative to standard value (of 3.046)
Returns:

Y_p helium nucleon fraction predicted by BBN. Call Y_He() to get mass fraction instead.

camb.bbn.get_default_predictor()[source]

Get instance of default BBNPredictor class. Currently fitting formula to match Planck 2015 analysis.