I am new to CAMB and as a test I am just trying to reproduce the WMAP3 results for lcdm+tens model using the parameters given here.

When I plot the

*totCls.dat*file output by CAMB along with the one given on the LAMBDA website I see a large difference around l<100. Can anyone explain whether this is normal or suggest a fix?

I have changed both

*k*and

_{0_scalar}*k*to 0.002 in

_{0_tensor}*power_tilt.f90*. I am taking n

_{T}= -r / 8.

Here is my params.ini file:

Code: Select allp>

```
#Parameters for CAMB
#output_root is prefixed to output file names
output_root = test_lcdm_tens
#What to do
get_scalar_cls = T
get_vector_cls = F
get_tensor_cls = T
get_transfer = F
#if do_lensing then scalar_output_file contains additional columns of l
```^{4} C_{l}^{&};#123;pp} and l^{3} C_{l}^{&};#123;pT}
#where p is the projected potential. Output lensed CMB Cls (without tensors) are in lensed_output_file below.
do_lensing = F
# 0: linear, 1: non-linear matter power (HALOFIT), 2: non-linear CMB lensing (HALOFIT)
do_nonlinear = 0
#Maximum multipole and k*eta.
# Note that C_{ls} near l_{max} are inaccurate (about 5%), go to 50 more than you need
# Lensed power spectra are computed to l_{max_scalar}−250 where accurate at %-level
# For high accuracy lensed spectra set l_{max_scalar} = (l you need) + 500
# To get accurate lensed BB need to have l_{max_scalar}>2000, k_eta_max_scalar > 10000
# Otherwise k_eta_max_scalar=2*l_{max_scalar} usually suffices
l_{max_scalar} = 2000
k_eta_max_scalar = 4000
# Tensor settings should be less than or equal to the above
l_{max_tensor} = 1500
k_eta_max_tensor = 3000
#Main cosmological parameters, neutrino masses are assumed degenerate
# If use_phyical set phyiscal densities in baryone, CDM and neutrinos + Omega_k
use_physical = T
ombh2 = 0.0233
omch2 = 0.0962
omnuh2 = 0
omk = 0
hubble = 78.7
#effective equation of state parameter for dark energy, assumed constant
w = −1
#constant comoving sound speed of the dark energy (1=quintessence)
cs2_lam = 1
#if use_physical = F set parameters as here
#omega_baryon = 0.0376
#omega_cdm = 0.1594
#omega_lambda = 0.803
#omega_neutrino = 0
#massless_neutrinos is the effective number (for QED + non-instantaneous decoupling)
temp_cmb = 2.726
helium_fraction = 0.24
massless_neutrinos = 3.04
massive_neutrinos = 0
#Neutrino mass splittings
nu_mass_eigenstates = 1
#nu_mass_degeneracies = 0 sets nu_mass_degeneracies = massive_neutrinos
#otherwise should be an array
#e.g. for 3 neutrinos with 2 non-degenerate eigenstates, nu_mass_degeneracies = 2 1
nu_mass_degeneracies = 0
#Fraction of total omega_nu h^{2} accounted for by each eigenstate, eg. 0.5 0.5
nu_mass_fractions = 1
#Reionization (assumed sharp), ignored unless reionization = T
reionization = T
re_use_optical_depth = T
re_optical_depth = 0.090
#If re_use_optical_depth = F then use following, otherwise ignored
re_redshift = 10.5
re_ionization_frac = 1
#Initial power spectrum, amplitude, spectral index and running
initial_power_num = 1
scalar_amp(1) = 21.0e−10
scalar_spectral_index(1) = 0.984
scalar_nrun(1) = 0
tensor_spectral_index(1) = −0.081
#ratio is that of the initial tens/scal power spectrum amplitudes
initial_ratio(1) = 0.65
#note vector modes use the scalar settings above
#Initial scalar perturbation mode (adiabatic=1, CDM iso=2, Baryon iso=3,
# neutrino density iso =4, neutrino velocity iso = 5)
initial_condition = 1
#If above is zero, use modes in the following (totally correlated) proportions
#Note: we assume all modes have the same initial power spectrum
initial_vector = −1 0 0 0 0
#For vector modes: 0 for regular (neutrino vorticity mode), 1 for magnetic
vector_mode = 0
#Normalization
COBE_normalize = F
##CMB_outputscale scales the output Cls
#To get MuK^{2} set realistic initial amplitude (e.g. scalar_amp(1) = 2.3e−9 above) and
#otherwise for dimensionless transfer functions set scalar_amp(1)=1 and use
#CMB_outputscale = 1
CMB_outputscale = 7.4311e12
#Transfer function settings, transfer_kmax=0.5 is enough for sigma_8
#transfer_k_{per_logint}=0 sets sensible non-even sampling;
#transfer_k_{per_logint}=5 samples fixed spacing in log-k
transfer_high_precision = F
transfer_kmax = 2
transfer_k_{per_logint} = 0
transfer_num_redshifts = 1
transfer_redshift(1) = 0
transfer_filename(1) = transfer_out.dat
#Matter power spectrum output against k/h in units of h^{&};#123;−3} Mpc^{3}
transfer_matterpower(1) = matterpower.dat
#Output files not produced if blank. make camb_fits to use use the FITS setting.
scalar_output_file = scalCls.dat
vector_output_file = vecCls.dat
tensor_output_file = tensCls.dat
total_output_file = totCls.dat
lensed_output_file = lensedCls.dat
FITS_filename = scalCls.fits
##Optional parameters to control the computation speed,accuracy and feedback
#If feedback_level > 0 print out useful information computed about the model
feedback_level = 1
# 1: curved correlation function, 2: flat correlation function, 3: inaccurate harmonic method
lensing_method = 1
accurate_BB = F
#Recombination calculation: 1: RECFAST, 2: RECFAST+astro-ph/0501672 corrections
recombination = 1
#massive_nu_approx: 0 - integrate distribution function
# 1 - switch to series in velocity weight once non-relativistic
# 2 - use fast approximate scheme (CMB only- accurate for light neutrinos)
# 3 - intelligently use the best accurate method
massive_nu_approx = 3
#Whether you are bothered about polarization.
accurate_polarization = T
#Whether you are bothered about percent accuracy on EE from reionization
accurate_reionization = F
#whether or not to include neutrinos in the tensor evolution equations
do_tensor_neutrinos = F
#Whether to turn off small-scale late time radiation hierarchies (save time,v. accurate)
do_late_rad_truncation = T
#Computation parameters
#if number_of_threads=0 assigned automatically
number_of_threads = 0
#Default scalar accuracy is about 0.3% (except lensed BB).
#For 0.1%-level try accuracy_boost=2, l_accuracy_boost=2.
#Increase accuracy_boost to decrease time steps, use more k values, etc.
#Decrease to speed up at cost of worse accuracy. Suggest 0.8 to 3.
accuracy_boost = 2
#Larger to keep more terms in the hierarchy evolution.
l_accuracy_boost = 2
#Increase to use more C_{l} values for interpolation.
#Increasing a bit will improve the polarization accuracy at l up to 200 -
#interpolation errors may be up to 3%
#Decrease to speed up non-flat models a bit
l_sample_boost = 1