hmf.alternatives.wdm.MassFunctionWDM.sigma_8_species

property MassFunctionWDM.sigma_8_species

"tot", "cb" or None.

The default, "tot", means sigma_8 is the r.m.s. of the total matter field (including massive neutrinos), which is how experiments such as Planck quote it, and how the default sigma_8 is defined. When the transfer model computes the CDM+baryon field (matter_species="cb", the default), its power spectrum is normalised so that the total matter field from the same model has r.m.s. sigma_8. "cb" means sigma_8 is that of the CDM+baryon field, and None means whichever field the transfer model computes.

This has no effect with massless neutrinos (the fields are then identical) or for transfer models that don’t distinguish the two fields (i.e. have no matter_species parameter, like EH or BBKS). Otherwise, normalising a field other than the computed one needs that field’s transfer function too. With CAMB or CLASS this reuses the same run, which gives both fields. See Massive neutrinos: which matter field to use.

Type:

str or None

Type:

Parameter

Type:

Which matter field sigma_8 describes