Difference between CAMB and WMAP3 (Pt. II)

Post Reply
A Stewart
Posts: 5
Joined: September 27 2007
Affiliation: McGill University

Difference between CAMB and WMAP3 (Pt. II)

Post by A Stewart » October 12 2007

Hi all,

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 k0_scalar and k0_tensor to 0.002 in power_tilt.f90. I am taking nT = -r / 8.

Image

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 l4 Cl&;#123;pp&#125; and l3 Cl&;#123;pT&#125;
#where p is the projected potential. Output lensed CMB Cls &#40;without tensors&#41; are in lensed_output_file below.
do_lensing     = F

# 0&#58; linear, 1&#58; non-linear matter power &#40;HALOFIT&#41;, 2&#58; non-linear CMB lensing &#40;HALOFIT&#41;
do_nonlinear = 0

#Maximum multipole and k*eta. 
#  Note that Cls near lmax are inaccurate &#40;about 5%&#41;, go to 50 more than you need
#  Lensed power spectra are computed to lmax_scalar−250 where accurate at %-level
#  For high accuracy lensed spectra set lmax_scalar = &#40;l you need&#41; + 500
#  To get accurate lensed BB need to have lmax_scalar>2000, k_eta_max_scalar > 10000
#  Otherwise k_eta_max_scalar=2*lmax_scalar usually suffices
lmax_scalar      = 2000
k_eta_max_scalar  = 4000

#  Tensor settings should be less than or equal to the above
lmax_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 &#40;1=quintessence&#41;
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 &#40;for QED + non-instantaneous decoupling&#41;
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 h2 accounted for by each eigenstate, eg. 0.5 0.5
nu_mass_fractions = 1


#Reionization &#40;assumed sharp&#41;, 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&#40;1&#41;             = 21.0e−10
scalar_spectral_index&#40;1&#41;  = 0.984
scalar_nrun&#40;1&#41;            = 0
tensor_spectral_index&#40;1&#41;  = −0.081
#ratio is that of the initial tens/scal power spectrum amplitudes
initial_ratio&#40;1&#41;          = 0.65
#note vector modes use the scalar settings above

#Initial scalar perturbation mode &#40;adiabatic=1, CDM iso=2, Baryon iso=3, 
# neutrino density iso =4, neutrino velocity iso = 5&#41; 
initial_condition   = 1
#If above is zero, use modes in the following &#40;totally correlated&#41; proportions
#Note&#58; we assume all modes have the same initial power spectrum
initial_vector = −1 0 0 0 0

#For vector modes&#58; 0 for regular &#40;neutrino vorticity mode&#41;, 1 for magnetic
vector_mode = 0

#Normalization
COBE_normalize = F
##CMB_outputscale scales the output Cls
#To get MuK2 set realistic initial amplitude &#40;e.g. scalar_amp&#40;1&#41; = 2.3e−9 above&#41; and
#otherwise for dimensionless transfer functions set scalar_amp&#40;1&#41;=1 and use
#CMB_outputscale = 1
CMB_outputscale = 7.4311e12

#Transfer function settings, transfer_kmax=0.5 is enough for sigma_8
#transfer_kper_logint=0 sets sensible non-even sampling; 
#transfer_kper_logint=5 samples fixed spacing in log-k
transfer_high_precision = F
transfer_kmax           = 2
transfer_kper_logint   = 0
transfer_num_redshifts  = 1
transfer_redshift&#40;1&#41;    = 0
transfer_filename&#40;1&#41;    = transfer_out.dat
#Matter power spectrum output against k/h in units of h&;#123;−3&#125; Mpc3
transfer_matterpower&#40;1&#41; = 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&#58; curved correlation function, 2&#58; flat correlation function, 3&#58; inaccurate harmonic method
lensing_method = 1
accurate_BB = F

#Recombination calculation&#58; 1&#58; RECFAST, 2&#58; RECFAST+astro-ph/0501672 corrections
recombination = 1

#massive_nu_approx&#58; 0 - integrate distribution function
#                   1 - switch to series in velocity weight once non-relativistic
#                   2 - use fast approximate scheme &#40;CMB only- accurate for light neutrinos&#41;
#                   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 &#40;save time,v. accurate&#41;
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% &#40;except lensed BB&#41;. 
#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 Cl 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

Ben Gold
Posts: 81
Joined: September 25 2004
Affiliation: University of Minnesota
Contact:

Difference between CAMB and WMAP3 (Pt. II)

Post by Ben Gold » October 14 2007

The parameters given in the table aren't for the "best-fit" [tex]C_\ell[/tex], they're the means over the chain. For LCDM+tens the best-fit model has a slightly smaller [tex]\Omega_\Lambda[/tex], closer to 0.777 (not 0.803, which is the mean), which explains the difference at low [tex]\ell[/tex].

If you really want the "best-fit" parameters you'll need to download the chain files.

A Stewart
Posts: 5
Joined: September 27 2007
Affiliation: McGill University

Difference between CAMB and WMAP3 (Pt. II)

Post by A Stewart » October 15 2007

So, I guess that will involve running getdist from the COSMOMC package on those chain files. Is there anywhere that the actual "best-fit" parameters used are summarzied without having to install COSMOMC?

Sorry I think I should have posted this in the software thread.

Ben Gold
Posts: 81
Joined: September 25 2004
Affiliation: University of Minnesota
Contact:

Difference between CAMB and WMAP3 (Pt. II)

Post by Ben Gold » October 23 2007

The best-fit isn't hard to find from the chain files, just look for the line with the lowest -ln(L) and read off the parameters. From the command line you can do something like

Code: Select allp>

sort -n -k 2 chainfile.txt | head −1
I'll make the suggestion that in the future the best-fit params be summarized somewhere more obvious.

Post Reply