CosmoCoffee Forum Index CosmoCoffee

 FAQFAQ   SearchSearch  MemberlistSmartFeed   MemberlistMemberlist    RegisterRegister 
   ProfileProfile   Log inLog in 
Arxiv New Filter | Bookmarks & clubs | Arxiv ref/author:

Difference between CAMB and WMAP3 (Pt. II)
Post new topic   Reply to topic    CosmoCoffee Forum Index -> Cosmological Observations
View previous topic :: View next topic  
Author Message
A Stewart

Joined: 27 Sep 2007
Posts: 5
Affiliation: McGill University

PostPosted: October 12 2007  Reply with quote

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 k_0_scalar and k_0_tensor to 0.002 in power_tilt.f90. I am taking nT = -r / 8.

Here is my params.ini file:


#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^{pp} and l^3 C_l^{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

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^{-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
Back to top
View user's profile  
Ben Gold

Joined: 25 Sep 2004
Posts: 97
Affiliation: University of Minnesota

PostPosted: October 14 2007  Reply with quote

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

If you really want the "best-fit" parameters you'll need to download the chain files.
Back to top
View user's profile [ Hidden ] Visit poster's website
A Stewart

Joined: 27 Sep 2007
Posts: 5
Affiliation: McGill University

PostPosted: October 15 2007  Reply with quote

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.
Back to top
View user's profile  
Ben Gold

Joined: 25 Sep 2004
Posts: 97
Affiliation: University of Minnesota

PostPosted: October 23 2007  Reply with quote

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

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.
Back to top
View user's profile [ Hidden ] Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    CosmoCoffee Forum Index -> Cosmological Observations All times are GMT + 5 Hours
Page 1 of 1

Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB © 2001, 2005 phpBB Group. Sponsored by WordWeb online dictionary and dictionary software.