CosmoCoffee

[Loison Hoi]

Has anyone tried to comapre the values of ln(L) of the new WMAP3 code (version 2.2.1) with previous versions?

Here are the best fit likelihoods I got from version 2.1 WMAP3 code (May 2006 CosmoMC):

~~~~~~~~~LambdaCDM~~~lcdm+run+tens~~Δ χ²
-log(Like)~~~5626.133~~~~~~~5624.566~~~~~3.134

If I evaluate the above best fit models with the new code (version 2.2.1, Oct 2006 CosmoMC), I will have
~~~~~~~~~LambdaCDM~~~lcdm+run+tens~~Δ χ²
-log(Like)~~~~2676.319~~~~~~2675.306~~~~~2.026

The evidence for the running model becomes smaller, but this is not my question. The WMAP_3yr_options.f90 says

! If you'd like to compare the values of ln(L) returned by this version
! of the code with previous versions, use the following:
!
!! double precision, parameter :: tt_pixlike_lndet_offset(3:4) &
!! = (/5476.3672001139175d0,29467.570953238155d0/)
!! double precision, parameter :: teeebb_pixlike_lndet_offset = 0d0
!! double precision, parameter :: te_lndet_offset = 0d0

I used the above settings and got
~~~~~~~~~LambdaCDM~~~lcdm+run+tens~~Δ χ²
-log(Like)~~~~−18057.50~~~~~−18058.51~~~~~~2.020

The Δ χ² are almost the same, as I would have expected. However,

1. The values of χ² are negative, is it a problem?
2. I would expect that I will have a number like -log(like)=5626 so that the new value of likelihood is comparable to the old value. However, I got a number like −18057 instead. I also tried to use

!! integer :: lowl_tt_res = 3
!! integer :: lowl_max = 12

And the numbers are -log(like)=1668.8 for the default offset settings, and -log(like)=4580.6 for the above offset settings. So, does anyone know why I did not have the numbers which are comparable to the old likelihoods? Thanks.

Loison Hoi
31 Oct 2006