# Input parameter model¶

class camb.model.CAMBparams(**kwargs)[source]

Object storing the parameters for a CAMB calculation, including cosmological parameters and settings for what to calculate. When a new object is instantiated, default parameters are set automatically.

To add a new parameter, add it to the CAMBparams type in model.f90, then edit the _fields_ list in the CAMBparams class in model.py to add the new parameter in the corresponding location of the member list. After rebuilding the python version you can then access the parameter by using params.new_parameter_name where params is a CAMBparams instance. You could also modify the wrapper functions to set the field value less directly.

You can view the set of underlying parameters used by the Fortran code by printing the CAMBparams instance. In python, to set cosmology parameters it is usually best to use set_cosmology() and equivalent methods for most other parameters. Alternatively the convenience function camb.set_params() can construct a complete instance from a dictionary of relevant parameters.

Variables: WantCls – (boolean) Calculate C_L WantTransfer – (boolean) Calculate matter transfer functions and matter power spectrum WantScalars – (boolean) Calculates scalar modes WantTensors – (boolean) Calculate tensor modes WantVectors – (boolean) Calculate vector modes WantDerivedParameters – (boolean) Calculate derived parameters Want_cl_2D_array – (boolean) For the C_L, include NxN matrix of all possible cross-spectra between sources Want_CMB – (boolean) Calculate the temperature and polarization power spectra Want_CMB_lensing – (boolean) Calculate the lensing potential power spectrum DoLensing – (boolean) Include CMB lensing NonLinear – (integer/string, one of: NonLinear_none, NonLinear_pk, NonLinear_lens, NonLinear_both) Transfer – camb.model.TransferParams want_zstar – (boolean) want_zdrag – (boolean) min_l – (integer) l_min for the scalar C_L (1 or 2, L=1 dipoles are Newtonian Gauge) max_l – (integer) l_max for the scalar C_L max_l_tensor – (integer) l_max for the tensor C_L max_eta_k – (float64) Maximum k*eta_0 for scalar C_L, where eta_0 is the conformal time today max_eta_k_tensor – (float64) Maximum k*eta_0 for tensor C_L, where eta_0 is the conformal time today ombh2 – (float64) Omega_baryon h^2 omch2 – (float64) Omega_cdm h^2 omk – (float64) Omega_K omnuh2 – (float64) Omega_massive_neutrino h^2 H0 – (float64) Hubble parameter is km/s/Mpc units TCMB – (float64) CMB temperature today in Kelvin YHe – (float64) Helium mass fraction num_nu_massless – (float64) Effective number of massless neutrinos num_nu_massive – (integer) Total physical (integer) number of massive neutrino species nu_mass_eigenstates – (integer) Number of non-degenerate mass eigenstates share_delta_neff – (boolean) Share the non-integer part of num_nu_massless between the eigenstates nu_mass_degeneracies – (float64 array) Degeneracy of each distinct eigenstate nu_mass_fractions – (float64 array) Mass fraction in each distinct eigenstate nu_mass_numbers – (integer array) Number of physical neutrinos per distinct eigenstate InitPower – camb.initialpower.InitialPower Recomb – camb.recombination.RecombinationModel Reion – camb.reionization.ReionizationModel DarkEnergy – camb.dark_energy.DarkEnergyModel NonLinearModel – camb.nonlinear.NonLinearModel Accuracy – camb.model.AccuracyParams SourceTerms – camb.model.SourceTermParams z_outputs – (float64 array) redshifts to always calculate BAO output parameters scalar_initial_condition – (integer/string, one of: initial_vector, initial_adiabatic, initial_iso_CDM, initial_iso_baryon, initial_iso_neutrino, initial_iso_neutrino_vel) InitialConditionVector – (float64 array) if scalar_initial_condition is initial_vector, the vector of initial condition amplitudes OutputNormalization – (integer) If non-zero, multipole to normalize the C_L at Alens – (float64) non-physical scaling amplitude for the CMB lensing spectrum power MassiveNuMethod – (integer/string, one of: Nu_int, Nu_trunc, Nu_approx, Nu_best) DoLateRadTruncation – (boolean) If true, use smooth approx to radiation perturbations after decoupling on small scales, saving evolution of irrelevant oscillatory multipole equations Evolve_baryon_cs – (boolean) Evolve a separate equation for the baryon sound speed rather than using background approximation Evolve_delta_xe – (boolean) Evolve ionization fraction perturbations Evolve_delta_Ts – (boolean) Evolve the spin temperature perturbation (for 21cm) Do21cm – (boolean) 21cm is not yet implemented via the python wrapper transfer_21cm_cl – (boolean) Get 21cm C_L at a given fixed redshift Log_lvalues – (boolean) Use log spacing for sampling in L use_cl_spline_template – (boolean) When interpolating use a fiducial spectrum shape to define ratio to spline SourceWindows – array of camb.sources.SourceWindow CustomSources – camb.model.CustomSources
N_eff
Returns: Effective number of degrees of freedom in relativistic species at early times.
copy()

Make independent copy of this object.

Returns: deep copy of self
diff(params)[source]

Print differences between this set of parameters and params

Parameters: params – another CAMBparams instance
get_DH(ombh2=None, delta_neff=None)[source]

Get deuterium ration D/H by intepolation using the bbn.BBNPredictor instance passed to set_cosmology() (or the default one, if Y_He has not been set).

Parameters: ombh2 – $$\Omega_b h^2$$ (default: value passed to set_cosmology()) delta_neff – additional $$N_{\rm eff}$$ relative to standard value (of 3.046) (default: from values passed to set_cosmology()) BBN helium nucleon fraction D/H
get_Y_p(ombh2=None, delta_neff=None)[source]

Get BBN helium nucleon fraction (NOT the same as the mass fraction Y_He) by intepolation using the bbn.BBNPredictor instance passed to set_cosmology() (or the default one, if Y_He has not been set).

Parameters: ombh2 – $$\Omega_b h^2$$ (default: value passed to set_cosmology()) delta_neff – additional $$N_{\rm eff}$$ relative to standard value (of 3.046) (default: from values passed to set_cosmology()) $$Y_p^{\rm BBN}$$ helium nucleon fraction predicted by BBN.
replace(instance)

Replace the content of this class with another instance, doing a deep copy (in Fortran)

Parameters: instance – instance of the same class to replace this instance with
scalar_power(k)[source]

Get the primordial scalar curvature power spectrum at $$k$$

Parameters: k – wavenumber $$k$$ (in $${\rm Mpc}^{-1}$$ units) power spectrum at $$k$$
set_H0_for_theta(theta, cosmomc_approx=False, theta_H0_range=(10, 100), est_H0=67.0, iteration_threshold=8)[source]

Set H0 to give a specified value of the acoustic angular scale parameter theta.

Parameters: theta – value of $$r_s/D_M$$ at redshift $$z_\star$$ cosmomc_approx – if true, use approximate fitting formula for $$z_\star$$, if false do full numerical calculation theta_H0_range – min, max iterval to search for H0 (in km/s/Mpc) est_H0 – an initial guess for H0 in km/s/Mpc, used in the case comsomc_approx=False. iteration_threshold – differnce in H0 from est_H0 for which to iterate, used for cosmomc_approx=False
set_accuracy(AccuracyBoost=1.0, lSampleBoost=1.0, lAccuracyBoost=1.0, DoLateRadTruncation=True)[source]

Set parameters determining overall calculation accuracy (large values may give big slow down). For finer control you can set individual accuracy parameters by changing CAMBParams.Accuracy (model.AccuracyParams) .

Parameters: AccuracyBoost – increase AccuracyBoost to decrease integration step size, increase density of k sampling, etc. lSampleBoost – increase lSampleBoost to increase density of L sampling for CMB lAccuracyBoost – increase lAccuracyBoost to increase the maximum L included in the Boltzmann hierarchies DoLateRadTruncation – If True, use approximation to radiation perturbation evolution at late times self
set_classes(dark_energy_model=None, initial_power_model=None, non_linear_model=None, recombination_model=None)[source]

Change the classes used to implement parts of the model.

Parameters: dark_energy_model – ‘fluid’, ‘ppf’, or name of a DarkEnergyModel class initial_power_model – name of an InitialPower class non_linear_model – name of a NonLinearModel class recombination_model – name of recombination_model class
set_cosmology(H0: Optional[float] = None, ombh2=0.022, omch2=0.12, omk=0.0, cosmomc_theta: Optional[float] = None, thetastar: Optional[float] = None, neutrino_hierarchy: Union[str, int] = 'degenerate', num_massive_neutrinos=1, mnu=0.06, nnu=3.046, YHe: Optional[float] = None, meffsterile=0.0, standard_neutrino_neff=3.046, TCMB=2.7255, tau: Optional[float] = None, zrei: Optional[float] = None, deltazrei: Optional[float] = None, Alens=1.0, bbn_predictor: Union[None, str, camb.bbn.BBNPredictor] = None, theta_H0_range=(10, 100))[source]

Sets cosmological parameters in terms of physical densities and parameters (e.g. as used in Planck analyses). Default settings give a single distinct neutrino mass eigenstate, by default one neutrino with mnu = 0.06eV. Set the neutrino_hierarchy parameter to normal or inverted to use a two-eigenstate model that is a good approximation to the known mass splittings seen in oscillation measurements. For more fine-grained control can set the neutrino parameters directly rather than using this function.

Instead of setting the Hubble parameter directly, you can instead set the acoustic scale parameter (cosmomc_theta, which is based on a fitting forumula for simple models, or thetastar, which is numerically calculated more generally). Note that you must have already set the dark energy model, you can’t use set_cosmology with theta and then change the background evolution (which would change theta at the calculated H0 value).Likewise the dark energy model cannot depend explicitly on H0.

Parameters: H0 – Hubble parameter today in km/s/Mpc. Can leave unset and instead set thetastar or cosmomc_theta (which solves for the required H0). ombh2 – physical density in baryons omch2 – physical density in cold dark matter omk – Omega_K curvature parameter cosmomc_theta – The approximate CosmoMC theta parameter $$\theta_{\rm MC}$$. The angular diamter distance is calculated numerically, but the redshift $$z_\star$$ is calculated using an approximate (quite accurate but non-general) fitting formula. Leave unset to use H0 or thetastar. thetastar – The angular acoustic scale parameter $$\theta_\star = r_s(z_*)/D_M(z_*)$$, defined as the ratio of the photon-baryon sound horizon $$r_s$$ to the angular diameter distance $$D_M$$, where both quantities are evaluated at $$z_*$$, the redshift at which the optical depth (excluding reionization) is unity. Leave unset to use H0 or cosmomc_theta. neutrino_hierarchy – ‘degenerate’, ‘normal’, or ‘inverted’ (1 or 2 eigenstate approximation) num_massive_neutrinos – number of massive neutrinos mnu – sum of neutrino masses (in eV). Omega_nu is calculated approximately from this assuming neutrinos non-relativistic today; i.e. here is defined as a direct proxy for Omega_nu. Internally the actual physical mass is calculated from the Omega_nu accounting for small mass-dependent velocity corrections but neglecting spectral distortions to the neutrino distribution. Set the neutrino field values directly if you need finer control or more complex neutrino models. nnu – N_eff, effective relativistic degrees of freedom YHe – Helium mass fraction. If None, set from BBN consistency. meffsterile – effective mass of sterile neutrinos standard_neutrino_neff – default value for N_eff in standard cosmology (non-integer to allow for partial heating of neutrinos at electron-positron annihilation and QED effects) TCMB – CMB temperature (in Kelvin) tau – optical depth; if None and zrei is None, current Reion settings are not changed zrei – reionization mid-point optical depth (set tau=None to use this) deltazrei – redshift width of reionization; if None, uses default Alens – (non-physical) scaling of the lensing potential compared to prediction bbn_predictor – bbn.BBNPredictor instance used to get YHe from BBN consistency if YHe is None, or name of a BBN predictor class, or file name of an interpolation table theta_H0_range – if thetastar or cosmomc_theta is specified, the min, max interval of H0 values to map to; if H0 is outside this range it will raise an exception.
set_custom_scalar_sources(custom_sources, source_names=None, source_ell_scales=None, frame='CDM', code_path=None)[source]

Set custom sources for angular power spectrum using camb.symbolic sympy expressions.

Parameters: custom_sources – list of sympy expressions for the angular power spectrum sources source_names – optional list of string naes for the sources source_ell_scales – list or dictionary of scalings for each source name, where for integer entry n, the source for multipole $$\ell$$ is scalled by $$\sqrt{(\ell+n)!/(\ell-n)!}$$, i.e. $$n=2$$ for a new polarization-like source. frame – if the source is not gauge invariant, frame in which to interpret result code_path – optional path for output of source code for CAMB f90 source function
set_dark_energy(w=-1.0, cs2=1.0, wa=0, dark_energy_model='fluid')[source]

Set dark energy parameters (use set_dark_energy_w_a to set w(a) from numerical table instead) To use a custom dark energy model, assign the class instance to the DarkEnergy field instead.

Parameters: w – $$w\equiv p_{\rm de}/\rho_{\rm de}$$, assumed constant wa – evolution of w (for dark_energy_model=ppf) cs2 – rest-frame sound speed squared of dark energy fluid dark_energy_model – model to use (‘fluid’ or ‘ppf’), default is ‘fluid’ self
set_dark_energy_w_a(a, w, dark_energy_model='fluid')[source]

Set the dark energy equation of state from tabulated values (which are cubic spline interpolated).

Parameters: a – array of sampled a = 1/(1+z) values w – array of w(a) dark_energy_model – model to use (‘fluid’ or ‘ppf’), default is ‘fluid’ self
set_for_lmax(lmax, max_eta_k=None, lens_potential_accuracy=0, lens_margin=150, k_eta_fac=2.5, lens_k_eta_reference=18000.0)[source]

Set parameters to get CMB power spectra accurate to specific a l_lmax. Note this does not fix the actual output L range, spectra may be calculated above l_max (but may not be accurate there). To fix the l_max for output arrays use the optional input argument to results.CAMBdata.get_cmb_power_spectra() etc.

Parameters: lmax – $$\ell_{\rm max}$$ you want max_eta_k – maximum value of $$k \eta_0\approx k\chi_*$$ to use, which indirectly sets k_max. If None, sensible value set automatically. lens_potential_accuracy – Set to 1 or higher if you want to get the lensing potential accurate (1 is only Planck-level accuracy) lens_margin – the $$\Delta \ell_{\rm max}$$ to use to ensure lensed $$C_\ell$$ are correct at $$\ell_{\rm max}$$ k_eta_fac – k_eta_fac default factor for setting max_eta_k = k_eta_fac*lmax if max_eta_k=None lens_k_eta_reference – value of max_eta_k to use when lens_potential_accuracy>0; use k_eta_max = lens_k_eta_reference*lens_potential_accuracy self
set_initial_power(initial_power_params)[source]

Set the InitialPower primordial power spectrum parameters

Parameters: initial_power_params – initialpower.InitialPowerLaw or initialpower.SplinedInitialPower instance self
set_initial_power_function(P_scalar, P_tensor=None, kmin=1e-06, kmax=100.0, N_min=200, rtol=5e-05, effective_ns_for_nonlinear=None, args=())[source]

Set the initial power spectrum from a function P_scalar(k, *args), and optionally also the tensor spectrum. The function is called to make a pre-computed array which is then interpolated inside CAMB. The sampling in k is set automatically so that the spline is accurate, but you may also need to increase other accuracy parameters.

Parameters: P_scalar – function returning normalized initial scalar curvature power as function of k (in Mpc^{-1}) P_tensor – optional function returning normalized initial tensor power spectrum kmin – minimum wavenumber to compute kmax – maximum wavenumber to compute N_min – minimum number of spline points for the pre-computation rtol – relative tolerance for deciding how many points are enough effective_ns_for_nonlinear – an effective n_s for use with approximate non-linear corrections args – optional list of arguments passed to P_scalar (and P_tensor) self
set_initial_power_table(k, pk=None, pk_tensor=None, effective_ns_for_nonlinear=None)[source]

Set a general intial power spectrum from tabulated values. It’s up to you to ensure the sampling of the k values is high enough that it can be interpolated accurately.

Parameters: k – array of k values (Mpc^{-1}) pk – array of primordial curvature perturbation power spectrum values P(k_i) pk_tensor – array of tensor spectrum values effective_ns_for_nonlinear – an effective n_s for use with approximate non-linear corrections
set_matter_power(redshifts=(0.0, ), kmax=1.2, k_per_logint=None, nonlinear=None, accurate_massive_neutrino_transfers=False, silent=False)[source]

Set parameters for calculating matter power spectra and transfer functions.

Parameters: redshifts – array of redshifts to calculate kmax – maximum k to calculate (where k is just k, not k/h) k_per_logint – minimum number of k steps per log k. Set to zero to use default optimized spacing. nonlinear – if None, uses existing setting, otherwise boolean for whether to use non-linear matter power. accurate_massive_neutrino_transfers – if you want the massive neutrino transfers accurately silent – if True, don’t give warnings about sort order self
set_nonlinear_lensing(nonlinear)[source]

Settings for whether or not to use non-linear corrections for the CMB lensing potential. Note that set_for_lmax also sets lensing to be non-linear if lens_potential_accuracy>0

Parameters: nonlinear – true to use non-linear corrections
tensor_power(k)[source]

Get the primordial tensor curvature power spectrum at $$k$$

Parameters: k – wavenumber $$k$$ (in $${\rm Mpc}^{-1}$$ units) tensor power spectrum at $$k$$
validate()[source]

Do some quick tests for sanity

Returns: True if OK
class camb.model.AccuracyParams[source]

Structure with parameters governing numerical accuracy. AccuracyBoost will also scale almost all the other parameters except for lSampleBoost (which is specific to the output interpolation) and lAccuracyBoost (which is specific to the multipole hierarchy evolution), e.g setting AccuracyBoost=2, IntTolBoost=1.5, means that internally the k sampling for integration will be boosed by AccuracyBoost*IntTolBoost = 3.

Variables: AccuracyBoost – (float64) general accuracy setting effecting everything related to step sizes etc. (including separate settings below except the next two) lSampleBoost – (float64) accuracy for sampling in ell for interpolation for the C_l (if >=50, all ell are calculated) lAccuracyBoost – (float64) Boosts number of multipoles integrated in Boltzman heirarchy AccuratePolarization – (boolean) Do you care about the accuracy of the polarization Cls? AccurateBB – (boolean) Do you care about BB accuracy (e.g. in lensing) AccurateReionization – (boolean) Do you care about pecent level accuracy on EE signal from reionization? TimeStepBoost – (float64) Sampling timesteps BackgroundTimeStepBoost – (float64) Number of time steps for background thermal history and source window interpolation IntTolBoost – (float64) Tolerances for integrating differential equations SourcekAccuracyBoost – (float64) Accuracy of k sampling for source time integration IntkAccuracyBoost – (float64) Accuracy of k sampling for integration TransferkBoost – (float64) Accuracy of k sampling for transfer functions NonFlatIntAccuracyBoost – (float64) Accuracy of non-flat time integration BessIntBoost – (float64) Accuracy of bessel integration truncation LensingBoost – (float64) Accuracy of the lensing of CMB power spectra NonlinSourceBoost – (float64) Accuracy of steps and kmax used for the non-linear correction BesselBoost – (float64) Accuracy of bessel pre-computation sampling LimberBoost – (float64) Accuracy of Limber approximation use SourceLimberBoost – (float64) Scales when to switch to Limber for source windows KmaxBoost – (float64) Boost max k for source window functions neutrino_q_boost – (float64) Number of momenta integrated for neutrino perturbations
class camb.model.TransferParams[source]

Object storing parameters for the matter power spectrum calculation.

Variables: high_precision – (boolean) True for more accuracy accurate_massive_neutrinos – (boolean) True if you want neutrino transfer functions accurate (false by default) kmax – (float64) k_max to output (no h in units) k_per_logint – (integer) number of points per log k interval. If zero, set an irregular optimized spacing PK_num_redshifts – (integer) number of redshifts to calculate PK_redshifts – (float64 array) redshifts to output for the matter transfer and power
class camb.model.SourceTermParams[source]

Structure with parameters determining how galaxy/lensing/21cm power spectra and transfer functions are calculated.

Variables: limber_windows – (boolean) Use Limber approximation where appropriate. CMB lensing uses Limber even if limber_window is false, but method is changed to be consistent with other sources if limber_windows is true limber_phi_lmin – (integer) When limber_windows=True, the minimum L to use Limber approximation for the lensing potential and other sources (which may use higher but not lower) counts_density – (boolean) Include the density perturbation source counts_redshift – (boolean) Include redshift distortions counts_lensing – (boolean) Include magnification bias for number counts counts_velocity – (boolean) Non-redshift distortion velocity terms counts_radial – (boolean) Radial displacement velocity term; does not include time delay; subset of counts_velocity, just 1 / (chi * H) term counts_timedelay – (boolean) Include time delay terms * 1 / (H * chi) counts_ISW – (boolean) Include tiny ISW terms counts_potential – (boolean) Include tiny terms in potentials at source counts_evolve – (boolean) Accout for source evolution line_phot_dipole – (boolean) Dipole sources for 21cm line_phot_quadrupole – (boolean) Quadrupole sources for 21cm line_basic – (boolean) Include main 21cm monopole density/spin temerature sources line_distortions – (boolean) Redshift distortions for 21cm line_extra – (boolean) Include other sources line_reionization – (boolean) Replace the E modes with 21cm polarization use_21cm_mK – (boolean) Use mK units for 21cm
class camb.model.CustomSources[source]

Structure containing symoblic-compiled custom CMB angular power spectrum source functions. Don’t change this directly, instead call model.CAMBparams.set_custom_scalar_sources().

Variables: num_custom_sources – (integer) number of sources set c_source_func – (pointer) Don’t directly change this custom_source_ell_scales – (integer array) scaling in L for outputs